diff --git a/creusot/tests/should_fail/bug/01_resolve_unsoundness.coma b/creusot/tests/should_fail/bug/01_resolve_unsoundness.coma
index abad02a300..16cd216935 100644
--- a/creusot/tests/should_fail/bug/01_resolve_unsoundness.coma
+++ b/creusot/tests/should_fail/bug/01_resolve_unsoundness.coma
@@ -101,22 +101,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C01ResolveUnsoundness_MakeVecOfSize
   let%span s01_resolve_unsoundness0 = "../01_resolve_unsoundness.rs" 10 29 10 39
@@ -135,55 +120,39 @@ module C01ResolveUnsoundness_MakeVecOfSize
   
   let%span span7 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span19 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span20 = "" 0 0 0 0
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span21 = "" 0 0 0 0
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span27 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
-  let%span span28 = "" 0 0 0 0
-  
-  let%span span29 = "" 0 0 0 0
-  
-  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
-  
-  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
-  
-  let%span span32 = "" 0 0 0 0
+  let%span span24 = "" 0 0 0 0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
@@ -222,76 +191,61 @@ module C01ResolveUnsoundness_MakeVecOfSize
   
   constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq bool) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq bool . ([%#span8] inv'3 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq bool . [%#span8] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec bool (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec bool (Global'0.t_global)) : Seq'0.t_seq bool
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec bool (Global'0.t_global) . ([%#span10] inv'0 self)
-   -> ([%#span12] inv'3 (shallow_model'0 self))
-  && ([%#span11] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec bool (Global'0.t_global) . ([%#span9] inv'0 self)
+   -> ([%#span10] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec bool (Global'0.t_global)) =
-    [%#span13] inv'3 (shallow_model'0 self)
+    [%#span11] inv'3 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec bool (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq bool = [%#span14] ()
+  constant empty'0 : Seq'0.t_seq bool
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span16] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'0 (empty'0 : Seq'0.t_seq bool) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span12] len'0 (empty'0 : Seq'0.t_seq bool) = 0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq bool) (x : int) : bool
+  function index_logic'0 (self : Seq'0.t_seq bool) (_2 : int) : bool
   
   function concat'0 (self : Seq'0.t_seq bool) (other : Seq'0.t_seq bool) : Seq'0.t_seq bool
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq bool, other : Seq'0.t_seq bool . ([%#span17] inv'3 self)
-   -> ([%#span18] inv'3 other)
-   -> ([%#span21] inv'3 (concat'0 self other))
-  && ([%#span20] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq bool, other : Seq'0.t_seq bool . ([%#span14] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span19] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span13] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : bool) : Seq'0.t_seq bool
   
-  axiom singleton'0_spec : forall v : bool . ([%#span22] inv'2 v)
-   -> ([%#span25] inv'3 (singleton'0 v))
-  && ([%#span24] index_logic'0 (singleton'0 v) 0 = v) && ([%#span23] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : bool . ([%#span15] inv'2 v)
+   -> ([%#span17] index_logic'0 (singleton'0 v) 0 = v) && ([%#span16] len'0 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq bool) (v : bool) : Seq'0.t_seq bool =
-    [%#span26] concat'0 self (singleton'0 v)
+    [%#span18] concat'0 self (singleton'0 v)
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec bool (Global'0.t_global))) : Seq'0.t_seq bool =
-    [%#span27] shallow_model'0 ( * self)
+    [%#span19] shallow_model'0 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec bool (Global'0.t_global))) (value:bool) (return'  (ret:()))= {[@expl:precondition] [%#span29] inv'2 value}
-    {[@expl:precondition] [%#span28] inv'1 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec bool (Global'0.t_global))) (value:bool) (return'  (ret:()))= {[@expl:precondition] [%#span21] inv'2 value}
+    {[@expl:precondition] [%#span20] inv'1 self}
     any
-    [ return' (result:())-> {[%#span30] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
+    [ return' (result:())-> {[%#span22] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
       (! return' {result}) ]
     
   
   let rec new'0 (_1:()) (return'  (ret:Vec'0.t_vec bool (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec bool (Global'0.t_global))-> {[%#span32] inv'0 result}
-      {[%#span31] len'0 (shallow_model'0 result) = 0}
+    [ return' (result:Vec'0.t_vec bool (Global'0.t_global))-> {[%#span24] inv'0 result}
+      {[%#span23] len'0 (shallow_model'0 result) = 0}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_fail/bug/specialize.coma b/creusot/tests/should_fail/bug/specialize.coma
index 616485f2c9..fbbc128c22 100644
--- a/creusot/tests/should_fail/bug/specialize.coma
+++ b/creusot/tests/should_fail/bug/specialize.coma
@@ -128,22 +128,7 @@ module Specialize_F
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Specialize_G
   type t
@@ -152,51 +137,38 @@ module Specialize_G
   
   let%span sspecialize1 = "../specialize.rs" 27 8 27 9
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span7 = "" 0 0 0 0
+  let%span span4 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span12 = "../specialize.rs" 6 9 6 13
+  let%span span8 = "../specialize.rs" 6 9 6 13
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq t)
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'1 (self : Seq'0.t_seq t)
   
+  predicate inv'1 (_x : Seq'0.t_seq t)
+  
   axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
@@ -207,24 +179,23 @@ module Specialize_G
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span8] inv'0 self)
-   -> ([%#span10] inv'1 (shallow_model'0 self))
-  && ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span5] inv'0 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span11] inv'1 (shallow_model'0 self)
+    [%#span7] inv'1 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
   use prelude.prelude.Intrinsic
   
-  let rec x'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span12] inv'0 self}
+  let rec x'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span8] inv'0 self}
     any [ return' (result:())-> (! return' {result}) ] 
   
   let rec g (v:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:()))= {[%#sspecialize1] inv'0 v}
@@ -239,57 +210,44 @@ end
 module Specialize_H
   let%span sspecialize0 = "../specialize.rs" 37 20 37 25
   
-  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "" 0 0 0 0
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span7 = "" 0 0 0 0
-  
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span12 = "../specialize.rs" 12 17 12 21
+  let%span span8 = "../specialize.rs" 12 17 12 21
   
-  let%span span13 = "../specialize.rs" 11 14 11 19
+  let%span span9 = "../specialize.rs" 11 14 11 19
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   use prelude.prelude.Int32
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq int32)
-  
   function len'0 (self : Seq'0.t_seq int32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int32 . ([%#span1] inv'1 self)  -> ([%#span2] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int32 . [%#span1] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span3] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span5] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span2] len'0 (empty'0 : Seq'0.t_seq int32) = 0
   
   predicate invariant'1 (self : Seq'0.t_seq int32) =
-    [%#span6] true
+    [%#span3] true
+  
+  predicate inv'1 (_x : Seq'0.t_seq int32)
   
   axiom inv'1 : forall x : Seq'0.t_seq int32 . inv'1 x = true
   
@@ -301,25 +259,24 @@ module Specialize_H
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span8] inv'0 self)
-   -> ([%#span10] inv'1 (shallow_model'0 self))
-  && ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span5] inv'0 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span11] inv'1 (shallow_model'0 self)
+    [%#span7] inv'1 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
   use prelude.prelude.Intrinsic
   
-  let rec x'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span12] inv'0 self}
-    any [ return' (result:())-> {[%#span13] false} (! return' {result}) ] 
+  let rec x'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span8] inv'0 self}
+    any [ return' (result:())-> {[%#span9] false} (! return' {result}) ] 
   
   let rec h (v:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:()))= (! bb0
     [ bb0 = s0 [ s0 = x'0 {v} (fun (_ret':()) ->  [ &_2 <- _ret' ] s1) | s1 = bb1 ] 
@@ -336,17 +293,13 @@ module Specialize_Impl0
   
   let%span span1 = "" 0 0 0 0
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
@@ -368,24 +321,19 @@ module Specialize_Impl0
   
   constant max'0 : usize = [%#span1] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq u) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq u . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq u . [%#span2] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec u (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec u (Global'0.t_global)) : Seq'0.t_seq u
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec u (Global'0.t_global) . ([%#span4] inv'0 self)
-   -> ([%#span6] inv'1 (shallow_model'0 self))
-  && ([%#span5] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec u (Global'0.t_global) . ([%#span3] inv'0 self)
+   -> ([%#span4] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec u (Global'0.t_global)) =
-    [%#span7] inv'1 (shallow_model'0 self)
+    [%#span5] inv'1 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec u (Global'0.t_global) . inv'0 x = true
   
diff --git a/creusot/tests/should_fail/final_borrows.coma b/creusot/tests/should_fail/final_borrows.coma
index c5155cfb16..b4e58a917c 100644
--- a/creusot/tests/should_fail/final_borrows.coma
+++ b/creusot/tests/should_fail/final_borrows.coma
@@ -232,22 +232,7 @@ module FinalBorrows_UnnestingFails
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module FinalBorrows_Indexing
   type t
@@ -264,93 +249,63 @@ module FinalBorrows_Indexing
   
   let%span sfinal_borrows5 = "../final_borrows.rs" 37 35 37 41
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span8 = "" 0 0 0 0
   
-  let%span span11 = "" 0 0 0 0
+  let%span span9 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span12 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span10 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span13 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span11 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span14 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span12 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span13 = "../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
   
-  let%span span16 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span14 = "../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
   
-  let%span span17 = "../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
+  let%span span15 = "../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
   
-  let%span span18 = "../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
+  let%span span16 = "../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
   
-  let%span span19 = "../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
-  
-  let%span span20 = "../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
-  
-  let%span span21 = "../../../../creusot-contracts/src/std/slice.rs" 67 4 67 43
-  
-  let%span span22 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span17 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
   use prelude.prelude.Slice
   
-  predicate invariant'5 (self : slice t)
+  predicate invariant'3 (self : slice t)
   
-  predicate inv'5 (_x : slice t)
+  predicate inv'3 (_x : slice t)
   
-  axiom inv'5 : forall x : slice t . inv'5 x = true
-  
-  use prelude.prelude.Borrow
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'4 (self : Seq'0.t_seq (borrowed t))
-  
-  predicate inv'4 (_x : Seq'0.t_seq (borrowed t))
-  
-  axiom inv'4 : forall x : Seq'0.t_seq (borrowed t) . inv'4 x = true
+  axiom inv'3 : forall x : slice t . inv'3 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
+  use prelude.prelude.Borrow
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'1 (self : Seq'0.t_seq (borrowed t)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . ([%#span6] inv'4 self)  -> ([%#span7] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . [%#span6] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq (borrowed t) = [%#span8] ()
+  constant empty'1 : Seq'0.t_seq (borrowed t)
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span9] len'1 (empty'1 : Seq'0.t_seq (borrowed t)) = 0
-  
-  predicate invariant'3 (self : Seq'0.t_seq t)
-  
-  predicate inv'3 (_x : Seq'0.t_seq t)
-  
-  axiom inv'3 : forall x : Seq'0.t_seq t . inv'3 x = true
-  
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'1 (empty'1 : Seq'0.t_seq (borrowed t)) = 0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span6] inv'3 self)  -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span6] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span8] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'2 (self : borrowed (slice t))
   
@@ -370,49 +325,43 @@ module FinalBorrows_Indexing
   
   axiom inv'0 : forall x : t . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (x : int) : borrowed t
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (_2 : int) : borrowed t
   
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : slice t . ([%#span12] inv'5 self)
-   -> ([%#span14] inv'3 (shallow_model'1 self))
-  && ([%#span13] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice t . ([%#span9] inv'3 self)
+   -> ([%#span10] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'1 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span15] index_logic'2 (shallow_model'1 self) ix
+    [%#span11] index_logic'2 (shallow_model'1 self) ix
   
   function shallow_model'0 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span16] shallow_model'1 ( * self)
+    [%#span12] shallow_model'1 ( * self)
   
   function to_mut_seq'0 (self : borrowed (slice t)) : Seq'0.t_seq (borrowed t)
   
-  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span17] inv'2 self)
-   -> ([%#span21] inv'4 (to_mut_seq'0 self))
-  && ([%#span20] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span13] inv'2 self)
+   -> ([%#span16] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  ^ index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( ^ self) i)
-  && ([%#span19] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  && ([%#span15] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  * index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( * self) i)
-  && ([%#span18] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
+  && ([%#span14] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (slice t)) =
-    [%#span22]  ^ self =  * self
+    [%#span17]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed t) =
-    [%#span22]  ^ self =  * self
+    [%#span17]  ^ self =  * self
   
   let rec indexing (x:borrowed (slice t)) (return'  (ret:borrowed t))= {[%#sfinal_borrows3] inv'2 x}
     {[%#sfinal_borrows2] len'0 (shallow_model'0 x) >= 1}
diff --git a/creusot/tests/should_succeed/100doors.coma b/creusot/tests/should_succeed/100doors.coma
index 8dd27af1b9..4b2f8ca652 100644
--- a/creusot/tests/should_succeed/100doors.coma
+++ b/creusot/tests/should_succeed/100doors.coma
@@ -125,22 +125,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -191,209 +176,189 @@ module C100doors_F
   
   let%span span15 = "" 0 0 0 0
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span17 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span18 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span18 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span20 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span21 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span23 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span24 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span25 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span26 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span27 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span28 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span29 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span30 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span30 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span31 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span31 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span32 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span32 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span33 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span33 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span34 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span34 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span35 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span35 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span36 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span36 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span37 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span37 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span38 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span38 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span39 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span39 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span40 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span40 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span41 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span41 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span42 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span42 = "" 0 0 0 0
   
-  let%span span43 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span43 = "" 0 0 0 0
   
-  let%span span44 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span44 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span45 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span45 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span46 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span46 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span47 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span47 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span48 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span48 = "" 0 0 0 0
   
-  let%span span49 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span49 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
   let%span span51 = "" 0 0 0 0
   
   let%span span52 = "" 0 0 0 0
   
-  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span54 = "" 0 0 0 0
   
-  let%span span55 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span55 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span56 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span57 = "" 0 0 0 0
+  let%span span57 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span58 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span58 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span59 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span59 = "" 0 0 0 0
   
-  let%span span60 = "" 0 0 0 0
+  let%span span60 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
   let%span span61 = "" 0 0 0 0
   
-  let%span span62 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span62 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span63 = "" 0 0 0 0
+  let%span span63 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span64 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span64 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span65 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span65 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span66 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span66 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span67 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span67 = "" 0 0 0 0
   
-  let%span span68 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span68 = "" 0 0 0 0
   
   let%span span69 = "" 0 0 0 0
   
-  let%span span70 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span70 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span71 = "" 0 0 0 0
+  let%span span71 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
-  let%span span72 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span72 = "" 0 0 0 0
   
-  let%span span73 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span74 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span75 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span76 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span77 = "" 0 0 0 0
-  
-  let%span span78 = "" 0 0 0 0
-  
-  let%span span79 = "" 0 0 0 0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span80 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
+  predicate invariant'11 (self : Seq'0.t_seq bool) =
+    [%#span14] true
   
-  let%span span81 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
+  predicate inv'11 (_x : Seq'0.t_seq bool)
   
-  let%span span82 = "" 0 0 0 0
+  axiom inv'11 : forall x : Seq'0.t_seq bool . inv'11 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'11 (self : borrowed bool) =
+  predicate invariant'10 (self : borrowed bool) =
     [%#span14] true
   
-  predicate inv'11 (_x : borrowed bool)
+  predicate inv'10 (_x : borrowed bool)
   
-  axiom inv'11 : forall x : borrowed bool . inv'11 x = true
+  axiom inv'10 : forall x : borrowed bool . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
   use Alloc_Vec_Vec_Type as Vec'0
   
-  predicate invariant'10 (self : borrowed (Vec'0.t_vec bool (Global'0.t_global))) =
+  predicate invariant'9 (self : borrowed (Vec'0.t_vec bool (Global'0.t_global))) =
     [%#span14] true
   
-  predicate inv'10 (_x : borrowed (Vec'0.t_vec bool (Global'0.t_global)))
+  predicate inv'9 (_x : borrowed (Vec'0.t_vec bool (Global'0.t_global)))
   
-  axiom inv'10 : forall x : borrowed (Vec'0.t_vec bool (Global'0.t_global)) . inv'10 x = true
+  axiom inv'9 : forall x : borrowed (Vec'0.t_vec bool (Global'0.t_global)) . inv'9 x = true
   
-  predicate invariant'9 (self : bool) =
+  predicate invariant'8 (self : bool) =
     [%#span14] true
   
-  predicate inv'9 (_x : bool)
+  predicate inv'8 (_x : bool)
   
-  axiom inv'9 : forall x : bool . inv'9 x = true
+  axiom inv'8 : forall x : bool . inv'8 x = true
   
-  predicate invariant'8 (self : Vec'0.t_vec bool (Global'0.t_global)) =
+  predicate invariant'7 (self : Vec'0.t_vec bool (Global'0.t_global)) =
     [%#span14] true
   
-  predicate inv'8 (_x : Vec'0.t_vec bool (Global'0.t_global))
+  predicate inv'7 (_x : Vec'0.t_vec bool (Global'0.t_global))
   
-  axiom inv'8 : forall x : Vec'0.t_vec bool (Global'0.t_global) . inv'8 x = true
+  axiom inv'7 : forall x : Vec'0.t_vec bool (Global'0.t_global) . inv'7 x = true
   
   use prelude.prelude.UIntSize
   
-  predicate invariant'7 (self : usize) =
+  predicate invariant'6 (self : usize) =
     [%#span14] true
   
-  predicate inv'7 (_x : usize)
+  predicate inv'6 (_x : usize)
   
-  axiom inv'7 : forall x : usize . inv'7 x = true
+  axiom inv'6 : forall x : usize . inv'6 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'6 (self : Option'0.t_option usize) =
+  predicate invariant'5 (self : Option'0.t_option usize) =
     [%#span14] true
   
-  predicate inv'6 (_x : Option'0.t_option usize)
+  predicate inv'5 (_x : Option'0.t_option usize)
   
-  axiom inv'6 : forall x : Option'0.t_option usize . inv'6 x = true
+  axiom inv'5 : forall x : Option'0.t_option usize . inv'5 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
-  predicate invariant'5 (self : borrowed (Range'0.t_range usize)) =
-    [%#span14] true
-  
-  predicate inv'5 (_x : borrowed (Range'0.t_range usize))
-  
-  axiom inv'5 : forall x : borrowed (Range'0.t_range usize) . inv'5 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'4 (self : Seq'0.t_seq bool) =
+  predicate invariant'4 (self : borrowed (Range'0.t_range usize)) =
     [%#span14] true
   
-  predicate inv'4 (_x : Seq'0.t_seq bool)
+  predicate inv'4 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'4 : forall x : Seq'0.t_seq bool . inv'4 x = true
+  axiom inv'4 : forall x : borrowed (Range'0.t_range usize) . inv'4 x = true
   
   predicate invariant'3 (self : Seq'0.t_seq usize) =
     [%#span14] true
@@ -408,24 +373,19 @@ module C100doors_F
   
   constant max'0 : usize = [%#span15] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq bool) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq bool . ([%#span16] inv'4 self)  -> ([%#span17] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq bool . [%#span16] len'0 self >= 0
   
   predicate inv'2 (_x : Vec'0.t_vec bool (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec bool (Global'0.t_global)) : Seq'0.t_seq bool
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec bool (Global'0.t_global) . ([%#span18] inv'2 self)
-   -> ([%#span20] inv'4 (shallow_model'0 self))
-  && ([%#span19] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec bool (Global'0.t_global) . ([%#span17] inv'2 self)
+   -> ([%#span18] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'2 (self : Vec'0.t_vec bool (Global'0.t_global)) =
-    [%#span21] inv'4 (shallow_model'0 self)
+    [%#span19] inv'11 (shallow_model'0 self)
   
   axiom inv'2 : forall x : Vec'0.t_vec bool (Global'0.t_global) . inv'2 x = true
   
@@ -436,46 +396,37 @@ module C100doors_F
   
   axiom inv'1 : forall x : bool . inv'1 x = true
   
-  constant empty'1 : Seq'0.t_seq bool = [%#span22] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span24] ()
-  
-  axiom empty_len'1_spec : forall _1 : () . [%#span23] len'0 (empty'1 : Seq'0.t_seq bool) = 0
+  constant empty'1 : Seq'0.t_seq bool
   
-  use seq.Seq
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span20] len'0 (empty'1 : Seq'0.t_seq bool) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span16] inv'3 self)  -> ([%#span17] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span16] len'1 self >= 0
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span25] inv'3 self)
-   -> ([%#span26] inv'3 other)
-   -> ([%#span29] inv'3 (concat'0 self other))
-  && ([%#span28] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span22] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span27] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span21] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : Range'0.t_range usize)
   
   use prelude.prelude.Int
   
   function deep_model'0 (self : usize) : int =
-    [%#span30] UIntSize.to_int self
+    [%#span23] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span31] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span24] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'1 visited > 0
@@ -488,109 +439,101 @@ module C100doors_F
   function produces_trans'0 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span32] produces'0 a ab b)
-   -> ([%#span33] produces'0 b bc c)
-   -> ([%#span34] inv'0 a)
-   -> ([%#span35] inv'3 ab)
-   -> ([%#span36] inv'0 b)
-   -> ([%#span37] inv'3 bc)  -> ([%#span38] inv'0 c)  -> ([%#span39] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span25] produces'0 a ab b)
+   -> ([%#span26] produces'0 b bc c)
+   -> ([%#span27] inv'0 a)
+   -> ([%#span28] inv'0 b)  -> ([%#span29] inv'0 c)  -> ([%#span30] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span22] ()
+  constant empty'0 : Seq'0.t_seq usize
   
   function produces_refl'0 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span40] inv'0 self)
-   -> ([%#span41] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span31] inv'0 self)
+   -> ([%#span32] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
   
   predicate invariant'0 (self : Range'0.t_range usize) =
     [%#span14] true
   
   axiom inv'0 : forall x : Range'0.t_range usize . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span24] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'1 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'1 (empty'0 : Seq'0.t_seq usize) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'3 (self : bool) =
-    [%#span42] true
-  
-  use seq.Seq
+    [%#span33] true
   
-  function index_logic'2 (self : Seq'0.t_seq bool) (x : int) : bool
+  function index_logic'2 (self : Seq'0.t_seq bool) (_2 : int) : bool
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec bool (Global'0.t_global)) (ix : int) : bool =
-    [%#span43] index_logic'2 (shallow_model'0 self) ix
+    [%#span34] index_logic'2 (shallow_model'0 self) ix
   
   predicate resolve'2 (self : Vec'0.t_vec bool (Global'0.t_global)) =
-    [%#span44] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'3 (index_logic'0 self i)
+    [%#span35] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'3 (index_logic'0 self i)
   
   predicate resolve'1 (self : borrowed bool) =
-    [%#span45]  ^ self =  * self
+    [%#span36]  ^ self =  * self
   
   use prelude.prelude.Slice
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq bool) (fin : Seq'0.t_seq bool) =
-    [%#span46] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
+    [%#span37] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
      -> index_logic'2 old' i = index_logic'2 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq bool) (out : bool) =
-    [%#span47] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span38] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq bool) =
-    [%#span48] UIntSize.to_int self < len'0 seq
+    [%#span39] UIntSize.to_int self < len'0 seq
   
   function shallow_model'2 (self : borrowed (Vec'0.t_vec bool (Global'0.t_global))) : Seq'0.t_seq bool =
-    [%#span49] shallow_model'0 ( * self)
+    [%#span40] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec bool (Global'0.t_global))) (index:usize) (return'  (ret:borrowed bool))= {[@expl:precondition] [%#span52] inv'7 index}
-    {[@expl:precondition] [%#span51] inv'10 self}
-    {[@expl:precondition] [%#span50] in_bounds'0 index (shallow_model'2 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec bool (Global'0.t_global))) (index:usize) (return'  (ret:borrowed bool))= {[@expl:precondition] [%#span43] inv'6 index}
+    {[@expl:precondition] [%#span42] inv'9 self}
+    {[@expl:precondition] [%#span41] in_bounds'0 index (shallow_model'2 self)}
     any
-    [ return' (result:borrowed bool)-> {[%#span57] inv'11 result}
-      {[%#span56] len'0 (shallow_model'0 ( ^ self)) = len'0 (shallow_model'2 self)}
-      {[%#span55] resolve_elswhere'0 index (shallow_model'2 self) (shallow_model'0 ( ^ self))}
-      {[%#span54] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span53] has_value'0 index (shallow_model'2 self) ( * result)}
+    [ return' (result:borrowed bool)-> {[%#span48] inv'10 result}
+      {[%#span47] len'0 (shallow_model'0 ( ^ self)) = len'0 (shallow_model'2 self)}
+      {[%#span46] resolve_elswhere'0 index (shallow_model'2 self) (shallow_model'0 ( ^ self))}
+      {[%#span45] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span44] has_value'0 index (shallow_model'2 self) ( * result)}
       (! return' {result}) ]
     
   
   function shallow_model'1 (self : Vec'0.t_vec bool (Global'0.t_global)) : Seq'0.t_seq bool =
-    [%#span58] shallow_model'0 self
+    [%#span49] shallow_model'0 self
   
-  let rec index'0 (self:Vec'0.t_vec bool (Global'0.t_global)) (index:usize) (return'  (ret:bool))= {[@expl:precondition] [%#span61] inv'7 index}
-    {[@expl:precondition] [%#span60] inv'8 self}
-    {[@expl:precondition] [%#span59] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec bool (Global'0.t_global)) (index:usize) (return'  (ret:bool))= {[@expl:precondition] [%#span52] inv'6 index}
+    {[@expl:precondition] [%#span51] inv'7 self}
+    {[@expl:precondition] [%#span50] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:bool)-> {[%#span63] inv'9 result}
-      {[%#span62] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:bool)-> {[%#span54] inv'8 result}
+      {[%#span53] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span64] inv'7 v)
-   -> ([%#span67] inv'3 (singleton'0 v))
-  && ([%#span66] index_logic'1 (singleton'0 v) 0 = v) && ([%#span65] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span55] inv'6 v)
+   -> ([%#span57] index_logic'1 (singleton'0 v) 0 = v) && ([%#span56] len'1 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span45]  ^ self =  * self
+    [%#span36]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span68] resolve'0 self
+    [%#span58] resolve'0 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span69] inv'5 self}
+  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span59] inv'4 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span71] inv'6 result}
-      {[%#span70] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span61] inv'5 result}
+      {[%#span60] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -607,31 +550,31 @@ module C100doors_F
   
   function new'1 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq usize . ([%#span72] inv'3 x)  -> ([%#span73] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq usize . ([%#span62] inv'3 x)  -> ([%#span63] deref'1 (new'1 x) = x)
   
   function new'0 (x : Range'0.t_range usize) : Snapshot'0.t_snapshot (Range'0.t_range usize)
   
-  axiom new'0_spec : forall x : Range'0.t_range usize . ([%#span72] inv'0 x)  -> ([%#span73] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Range'0.t_range usize . ([%#span62] inv'0 x)  -> ([%#span63] deref'0 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span74] self = res
+    [%#span64] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range usize) =
-    [%#span75] true
+    [%#span65] true
   
-  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span77] inv'0 self}
-    {[@expl:precondition] [%#span76] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span67] inv'0 self}
+    {[@expl:precondition] [%#span66] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range usize)-> {[%#span78] inv'0 result}
-      {[%#span76] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range usize)-> {[%#span68] inv'0 result}
+      {[%#span66] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec from_elem'0 (elem:bool) (n:usize) (return'  (ret:Vec'0.t_vec bool (Global'0.t_global)))= {[@expl:precondition] [%#span79] inv'1 elem}
+  let rec from_elem'0 (elem:bool) (n:usize) (return'  (ret:Vec'0.t_vec bool (Global'0.t_global)))= {[@expl:precondition] [%#span69] inv'1 elem}
     any
-    [ return' (result:Vec'0.t_vec bool (Global'0.t_global))-> {[%#span82] inv'2 result}
-      {[%#span81] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
-      {[%#span80] len'0 (shallow_model'0 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec bool (Global'0.t_global))-> {[%#span72] inv'2 result}
+      {[%#span71] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
+      {[%#span70] len'0 (shallow_model'0 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/bug/206.coma b/creusot/tests/should_succeed/bug/206.coma
index baa8a3ead8..85a4177e79 100644
--- a/creusot/tests/should_succeed/bug/206.coma
+++ b/creusot/tests/should_succeed/bug/206.coma
@@ -125,47 +125,24 @@ module C206_A_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C206_U2_Impl
   let%span s2060 = "../206.rs" 8 10 8 22
   
   let%span span1 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span4 = "" 0 0 0 0
   
-  let%span span7 = "" 0 0 0 0
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
   use prelude.prelude.UIntSize
   
@@ -180,20 +157,15 @@ module C206_U2_Impl
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -201,18 +173,17 @@ module C206_U2_Impl
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'0 self)
-   -> ([%#span10] inv'1 (shallow_model'0 self))
-  && ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span5] inv'0 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span11] inv'1 (shallow_model'0 self)
+    [%#span7] inv'1 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'0 x = true
   
@@ -231,31 +202,23 @@ module C206_Ex
   
   let%span span1 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "" 0 0 0 0
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span7 = "" 0 0 0 0
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span8 = "../206.rs" 8 10 8 22
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span9 = "../206.rs" 7 0 7 8
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span12 = "../206.rs" 8 10 8 22
-  
-  let%span span13 = "../206.rs" 7 0 7 8
-  
-  let%span span14 = "../206.rs" 15 8 15 13
+  let%span span10 = "../206.rs" 15 8 15 13
   
   use prelude.prelude.UIntSize
   
@@ -270,20 +233,15 @@ module C206_Ex
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -291,18 +249,17 @@ module C206_Ex
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'0 self)
-   -> ([%#span10] inv'1 (shallow_model'0 self))
-  && ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span5] inv'0 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span11] inv'1 (shallow_model'0 self)
+    [%#span7] inv'1 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'0 x = true
   
@@ -313,13 +270,13 @@ module C206_Ex
   use C206_A_Type as C206_A_Type
   
   function u2'0 [#"../206.rs" 9 0 9 11] (a : A'0.t_a) : () =
-    [%#span13] ()
+    [%#span9] ()
   
-  axiom u2'0_spec : forall a : A'0.t_a . [%#span12] shallow_model'0 (C206_A_Type.a_0 a)
+  axiom u2'0_spec : forall a : A'0.t_a . [%#span8] shallow_model'0 (C206_A_Type.a_0 a)
   = shallow_model'0 (C206_A_Type.a_0 a)
   
   function u'0 [#"../206.rs" 13 0 13 14] (a : A'0.t_a) : () =
-    [%#span14] u2'0 a
+    [%#span10] u2'0 a
   
   use prelude.prelude.Intrinsic
   
diff --git a/creusot/tests/should_succeed/bug/217.coma b/creusot/tests/should_succeed/bug/217.coma
index b4e372bd24..d899bb0934 100644
--- a/creusot/tests/should_succeed/bug/217.coma
+++ b/creusot/tests/should_succeed/bug/217.coma
@@ -1,95 +1,50 @@
 
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C217_Ex_Impl
   let%span s2170 = "../217.rs" 10 10 10 17
   
-  let%span sseq21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span sseq22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span sseq21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 66 8 66 39
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 62 8 62 39
   
   use prelude.prelude.Int
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'0 (self : Seq'0.t_seq int) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq int)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq int . inv'0 x = true
-  
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq int) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int . ([%#sseq21] inv'0 self)  -> ([%#sseq22] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq int = [%#span4] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq int . [%#sseq21] len'0 self >= 0
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq int) = 0
+  constant empty'0 : Seq'0.t_seq int
   
-  use prelude.seq_ext.SeqExt
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span2] len'0 (empty'0 : Seq'0.t_seq int) = 0
   
-  function index_logic'0 (self : Seq'0.t_seq int) (x : int) : int
+  function index_logic'0 (self : Seq'0.t_seq int) (_2 : int) : int
   
   function subsequence'0 (self : Seq'0.t_seq int) (n : int) (m : int) : Seq'0.t_seq int
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq int, n : int, m : int . ([%#span7] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq int, n : int, m : int . ([%#span3] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span8] inv'0 self)
-   -> ([%#span11] inv'0 (subsequence'0 self n m))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span5] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#span9] len'0 (subsequence'0 self n m) = m - n)
+  && ([%#span4] len'0 (subsequence'0 self n m) = m - n)
   
   function tail'0 [@inline:trivial] (self : Seq'0.t_seq int) : Seq'0.t_seq int =
-    [%#span12] subsequence'0 self 1 (len'0 self)
+    [%#span6] subsequence'0 self 1 (len'0 self)
   
   constant c  : Seq'0.t_seq int
   
@@ -97,10 +52,9 @@ module C217_Ex_Impl
   
   function ex [#"../217.rs" 11 0 11 37] (c : Seq'0.t_seq int) (a : int) : int
   
-  goal vc_ex : ([%#sseq21] inv'0 c)
-  /\ (([%#sseq22] len'0 c >= 0)
+  goal vc_ex : ([%#sseq21] len'0 c >= 0)
    -> match len'0 c = 0 with
     | True -> true
     | False -> 0 <= ([%#s2170] len'0 c) /\ ([%#s2170] len'0 (tail'0 c)) < ([%#s2170] len'0 c)
-    end)
+    end
 end
diff --git a/creusot/tests/should_succeed/bug/874.coma b/creusot/tests/should_succeed/bug/874.coma
index 42b64b4655..813040c85f 100644
--- a/creusot/tests/should_succeed/bug/874.coma
+++ b/creusot/tests/should_succeed/bug/874.coma
@@ -101,22 +101,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Mem_ManuallyDrop_ManuallyDrop_Type
   type t_manuallydrop 't =
@@ -194,200 +179,164 @@ module C874_CanExtend
   
   let%span span13 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 268 31 268 33
+  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
+  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 268 52 268 54
+  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
+  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
+  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
+  let%span span28 = "" 0 0 0 0
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
+  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
+  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
+  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span35 = "" 0 0 0 0
+  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span35 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span36 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span37 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span38 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span39 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span40 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
   
-  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span41 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span42 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
   
-  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span43 = "../../../../../creusot-contracts/src/std/vec.rs" 134 27 134 47
   
-  let%span span46 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span44 = "" 0 0 0 0
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span45 = "" 0 0 0 0
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span46 = "../../../../../creusot-contracts/src/std/vec.rs" 135 16 138 18
   
-  let%span span49 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span47 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span50 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span48 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span51 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
+  let%span span49 = "../../../../../creusot-contracts/src/std/boxed.rs" 20 8 20 31
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
+  let%span span50 = "" 0 0 0 0
   
-  let%span span53 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
+  let%span span51 = "../../../../../creusot-contracts/src/std/slice.rs" 310 18 310 35
   
-  let%span span54 = "../../../../../creusot-contracts/src/std/vec.rs" 134 27 134 47
+  let%span span52 = "" 0 0 0 0
   
-  let%span span55 = "" 0 0 0 0
-  
-  let%span span56 = "" 0 0 0 0
-  
-  let%span span57 = "../../../../../creusot-contracts/src/std/vec.rs" 135 16 138 18
-  
-  let%span span58 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
-  
-  let%span span59 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
-  
-  let%span span60 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
-  
-  let%span span61 = "../../../../../creusot-contracts/src/std/boxed.rs" 20 8 20 31
+  use prelude.prelude.Int32
   
-  let%span span62 = "" 0 0 0 0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span63 = "../../../../../creusot-contracts/src/std/slice.rs" 310 18 310 35
+  predicate invariant'6 (self : Seq'0.t_seq int32) =
+    [%#span13] true
   
-  let%span span64 = "" 0 0 0 0
+  predicate inv'6 (_x : Seq'0.t_seq int32)
   
-  use prelude.prelude.Int32
+  axiom inv'6 : forall x : Seq'0.t_seq int32 . inv'6 x = true
   
   use prelude.prelude.Slice
   
-  predicate invariant'6 (self : slice int32) =
+  predicate invariant'5 (self : slice int32) =
     [%#span13] true
   
-  predicate inv'6 (_x : slice int32)
+  predicate inv'5 (_x : slice int32)
   
-  axiom inv'6 : forall x : slice int32 . inv'6 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'5 : forall x : slice int32 . inv'5 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
   use Alloc_Vec_IntoIter_IntoIter_Type as IntoIter'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
-  
-  use seq.Seq
-  
-  predicate inv'3 (_x : Seq'0.t_seq int32)
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function len'0 (self : Seq'0.t_seq int32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int32 . ([%#span14] inv'3 self)  -> ([%#span15] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int32 . [%#span14] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq int32) (other : Seq'0.t_seq int32) : Seq'0.t_seq int32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span16] inv'3 self)
-   -> ([%#span17] inv'3 other)
-   -> ([%#span20] inv'3 (concat'0 self other))
-  && ([%#span19] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span16] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span18] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  predicate inv'5 (_x : IntoIter'0.t_intoiter int32 (Global'0.t_global))
+  predicate inv'4 (_x : IntoIter'0.t_intoiter int32 (Global'0.t_global))
   
   function shallow_model'4 (self : IntoIter'0.t_intoiter int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
   predicate produces'0 (self : IntoIter'0.t_intoiter int32 (Global'0.t_global)) (visited : Seq'0.t_seq int32) (rhs : IntoIter'0.t_intoiter int32 (Global'0.t_global))
     
    =
-    [%#span21] shallow_model'4 self = concat'0 visited (shallow_model'4 rhs)
+    [%#span17] shallow_model'4 self = concat'0 visited (shallow_model'4 rhs)
   
   function produces_trans'0 (a : IntoIter'0.t_intoiter int32 (Global'0.t_global)) (ab : Seq'0.t_seq int32) (b : IntoIter'0.t_intoiter int32 (Global'0.t_global)) (bc : Seq'0.t_seq int32) (c : IntoIter'0.t_intoiter int32 (Global'0.t_global)) : ()
     
    =
-    [%#span30] ()
+    [%#span24] ()
   
-  axiom produces_trans'0_spec : forall a : IntoIter'0.t_intoiter int32 (Global'0.t_global), ab : Seq'0.t_seq int32, b : IntoIter'0.t_intoiter int32 (Global'0.t_global), bc : Seq'0.t_seq int32, c : IntoIter'0.t_intoiter int32 (Global'0.t_global) . ([%#span22] produces'0 a ab b)
-   -> ([%#span23] produces'0 b bc c)
-   -> ([%#span24] inv'5 a)
-   -> ([%#span25] inv'3 ab)
-   -> ([%#span26] inv'5 b)
-   -> ([%#span27] inv'3 bc)  -> ([%#span28] inv'5 c)  -> ([%#span29] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : IntoIter'0.t_intoiter int32 (Global'0.t_global), ab : Seq'0.t_seq int32, b : IntoIter'0.t_intoiter int32 (Global'0.t_global), bc : Seq'0.t_seq int32, c : IntoIter'0.t_intoiter int32 (Global'0.t_global) . ([%#span18] produces'0 a ab b)
+   -> ([%#span19] produces'0 b bc c)
+   -> ([%#span20] inv'4 a)
+   -> ([%#span21] inv'4 b)  -> ([%#span22] inv'4 c)  -> ([%#span23] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span31] ()
+  constant empty'0 : Seq'0.t_seq int32
   
   function produces_refl'0 (self : IntoIter'0.t_intoiter int32 (Global'0.t_global)) : () =
-    [%#span34] ()
+    [%#span27] ()
   
-  axiom produces_refl'0_spec : forall self : IntoIter'0.t_intoiter int32 (Global'0.t_global) . ([%#span32] inv'5 self)
-   -> ([%#span33] produces'0 self (empty'0 : Seq'0.t_seq int32) self)
+  axiom produces_refl'0_spec : forall self : IntoIter'0.t_intoiter int32 (Global'0.t_global) . ([%#span25] inv'4 self)
+   -> ([%#span26] produces'0 self (empty'0 : Seq'0.t_seq int32) self)
   
-  predicate invariant'5 (self : IntoIter'0.t_intoiter int32 (Global'0.t_global)) =
+  predicate invariant'4 (self : IntoIter'0.t_intoiter int32 (Global'0.t_global)) =
     [%#span13] true
   
-  axiom inv'5 : forall x : IntoIter'0.t_intoiter int32 (Global'0.t_global) . inv'5 x = true
+  axiom inv'4 : forall x : IntoIter'0.t_intoiter int32 (Global'0.t_global) . inv'4 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'4 (self : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global))) =
+  predicate invariant'3 (self : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global))) =
     [%#span13] true
   
-  predicate inv'4 (_x : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global)))
+  predicate inv'3 (_x : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global)))
   
-  axiom inv'4 : forall x : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global)) . inv'4 x = true
-  
-  predicate invariant'3 (self : Seq'0.t_seq int32) =
-    [%#span13] true
-  
-  axiom inv'3 : forall x : Seq'0.t_seq int32 . inv'3 x = true
+  axiom inv'3 : forall x : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global)) . inv'3 x = true
   
   use Alloc_Vec_Vec_Type as Vec'0
   
@@ -402,18 +351,17 @@ module C874_CanExtend
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span35] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span28] (18446744073709551615 : usize)
   
   predicate inv'1 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span36] inv'1 self)
-   -> ([%#span38] inv'3 (shallow_model'0 self))
-  && ([%#span37] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span29] inv'1 self)
+   -> ([%#span30] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span39] inv'3 (shallow_model'0 self)
+    [%#span31] inv'6 (shallow_model'0 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'1 x = true
   
@@ -424,59 +372,53 @@ module C874_CanExtend
   
   axiom inv'0 : forall x : slice int32 . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span41] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span40] len'0 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span32] len'0 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   predicate ext_eq'0 (self : Seq'0.t_seq int32) (oth : Seq'0.t_seq int32)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq int32, oth : Seq'0.t_seq int32 . ([%#span42] inv'3 self)
-   -> ([%#span43] inv'3 oth)
-   -> ([%#span45] len'0 self = len'0 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq int32, oth : Seq'0.t_seq int32 . ([%#span34] len'0 self = len'0 oth
   /\ (forall i : int . 0 <= i /\ i < len'0 self  -> index_logic'1 self i = index_logic'1 oth i)  -> ext_eq'0 self oth)
-  && ([%#span44] ext_eq'0 self oth  -> self = oth)
+  && ([%#span33] ext_eq'0 self oth  -> self = oth)
   
   predicate resolve'1 (self : int32) =
-    [%#span46] true
+    [%#span35] true
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span47] index_logic'1 (shallow_model'0 self) ix
+    [%#span36] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span48] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
+    [%#span37] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
   
   function shallow_model'2 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span49] shallow_model'0 ( * self)
+    [%#span38] shallow_model'0 ( * self)
   
   function shallow_model'5 (self : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span49] shallow_model'4 ( * self)
+    [%#span38] shallow_model'4 ( * self)
   
   predicate resolve'2 (self : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global))) =
-    [%#span50]  ^ self =  * self
+    [%#span39]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global))) =
-    [%#span51] resolve'2 self /\ shallow_model'5 self = (empty'0 : Seq'0.t_seq int32)
+    [%#span40] resolve'2 self /\ shallow_model'5 self = (empty'0 : Seq'0.t_seq int32)
   
   predicate into_iter_post'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) (res : IntoIter'0.t_intoiter int32 (Global'0.t_global))
     
    =
-    [%#span52] shallow_model'0 self = shallow_model'4 res
+    [%#span41] shallow_model'0 self = shallow_model'4 res
   
   predicate into_iter_pre'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span53] true
+    [%#span42] true
   
-  let rec extend'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (iter:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span56] inv'1 iter}
-    {[@expl:precondition] [%#span55] inv'2 self}
-    {[@expl:precondition] [%#span54] into_iter_pre'0 iter}
+  let rec extend'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (iter:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span45] inv'1 iter}
+    {[@expl:precondition] [%#span44] inv'2 self}
+    {[@expl:precondition] [%#span43] into_iter_pre'0 iter}
     any
-    [ return' (result:())-> {[%#span57] exists prod : Seq'0.t_seq int32 . exists done' : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global)) . exists start_ : IntoIter'0.t_intoiter int32 (Global'0.t_global) . inv'3 prod
-      /\ inv'4 done'
-      /\ inv'5 start_
+    [ return' (result:())-> {[%#span46] exists prod : Seq'0.t_seq int32 . exists done' : borrowed (IntoIter'0.t_intoiter int32 (Global'0.t_global)) . exists start_ : IntoIter'0.t_intoiter int32 (Global'0.t_global) . inv'3 done'
+      /\ inv'4 start_
       /\ into_iter_post'0 iter start_
       /\ completed'0 done'
       /\ produces'0 start_ prod ( * done') /\ shallow_model'0 ( ^ self) = concat'0 (shallow_model'2 self) prod}
@@ -485,17 +427,16 @@ module C874_CanExtend
   
   function shallow_model'3 (self : slice int32) : Seq'0.t_seq int32
   
-  axiom shallow_model'3_spec : forall self : slice int32 . ([%#span58] inv'6 self)
-   -> ([%#span60] inv'3 (shallow_model'3 self))
-  && ([%#span59] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : slice int32 . ([%#span47] inv'5 self)
+   -> ([%#span48] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   function shallow_model'1 (self : slice int32) : Seq'0.t_seq int32 =
-    [%#span61] shallow_model'3 self
+    [%#span49] shallow_model'3 self
   
-  let rec into_vec'0 (self:slice int32) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span62] inv'0 self}
+  let rec into_vec'0 (self:slice int32) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span50] inv'0 self}
     any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span64] inv'1 result}
-      {[%#span63] shallow_model'0 result = shallow_model'1 self}
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span52] inv'1 result}
+      {[%#span51] shallow_model'0 result = shallow_model'1 self}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/bug/991.coma b/creusot/tests/should_succeed/bug/991.coma
index dd0525faea..0e6752a4b9 100644
--- a/creusot/tests/should_succeed/bug/991.coma
+++ b/creusot/tests/should_succeed/bug/991.coma
@@ -130,51 +130,28 @@ module C991_Formula_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C991_Impl1_LoveAndHope
   let%span s9910 = "../991.rs" 21 14 21 28
   
   let%span span1 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span7 = "" 0 0 0 0
+  let%span span4 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span8 = "../991.rs" 16 8 16 42
   
-  let%span span12 = "../991.rs" 16 8 16 42
-  
-  let%span span13 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span9 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
   use prelude.prelude.UIntSize
   
@@ -189,20 +166,15 @@ module C991_Impl1_LoveAndHope
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -210,18 +182,17 @@ module C991_Impl1_LoveAndHope
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'0 self)
-   -> ([%#span10] inv'1 (shallow_model'2 self))
-  && ([%#span9] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span5] inv'0 self)
+   -> ([%#span6] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span11] inv'1 (shallow_model'2 self)
+    [%#span7] inv'1 (shallow_model'2 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'0 x = true
   
@@ -232,10 +203,10 @@ module C991_Impl1_LoveAndHope
   use C991_Formula_Type as C991_Formula_Type
   
   function shallow_model'1 [#"../991.rs" 15 4 15 50] (self : Formula'0.t_formula) : (Seq'0.t_seq usize, bool) =
-    [%#span12] (shallow_model'2 (C991_Formula_Type.formula_vec self), C991_Formula_Type.formula_b self)
+    [%#span8] (shallow_model'2 (C991_Formula_Type.formula_vec self), C991_Formula_Type.formula_b self)
   
   function shallow_model'0 (self : Formula'0.t_formula) : (Seq'0.t_seq usize, bool) =
-    [%#span13] shallow_model'1 self
+    [%#span9] shallow_model'1 self
   
   use prelude.prelude.Intrinsic
   
diff --git a/creusot/tests/should_succeed/bug/two_phase.coma b/creusot/tests/should_succeed/bug/two_phase.coma
index 15adbdd857..061b1aa928 100644
--- a/creusot/tests/should_succeed/bug/two_phase.coma
+++ b/creusot/tests/should_succeed/bug/two_phase.coma
@@ -101,91 +101,65 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module TwoPhase_Test
   let%span stwo_phase0 = "../two_phase.rs" 5 10 5 37
   
-  let%span span1 = "" 0 0 0 0
+  let%span span1 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span2 = "" 0 0 0 0
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span4 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span8 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span13 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span8 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span9 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span10 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span17 = "" 0 0 0 0
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span18 = "" 0 0 0 0
   
-  let%span span25 = "" 0 0 0 0
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span26 = "" 0 0 0 0
+  let%span span20 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span21 = "" 0 0 0 0
   
-  let%span span28 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span29 = "" 0 0 0 0
-  
-  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
   use prelude.prelude.UIntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'3 (_x : Seq'0.t_seq usize)
+  predicate invariant'4 (self : Seq'0.t_seq usize) =
+    [%#span1] true
+  
+  predicate inv'4 (_x : Seq'0.t_seq usize)
+  
+  axiom inv'4 : forall x : Seq'0.t_seq usize . inv'4 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -195,36 +169,26 @@ module TwoPhase_Test
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span1] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span2] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span2] inv'3 self)  -> ([%#span3] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span3] len'1 self >= 0
   
-  predicate inv'4 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'3 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span4] inv'4 self)
-   -> ([%#span6] inv'3 (shallow_model'2 self))
-  && ([%#span5] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span4] inv'3 self)
+   -> ([%#span5] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'4 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span7] inv'3 (shallow_model'2 self)
+  predicate invariant'3 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span6] inv'4 (shallow_model'2 self)
   
-  axiom inv'4 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'4 x = true
-  
-  predicate invariant'3 (self : Seq'0.t_seq usize) =
-    [%#span8] true
-  
-  axiom inv'3 : forall x : Seq'0.t_seq usize . inv'3 x = true
+  axiom inv'3 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'3 x = true
   
   predicate invariant'2 (self : usize) =
-    [%#span8] true
+    [%#span1] true
   
   predicate inv'2 (_x : usize)
   
@@ -233,77 +197,67 @@ module TwoPhase_Test
   use prelude.prelude.Borrow
   
   predicate invariant'1 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span8] true
+    [%#span1] true
   
   predicate inv'1 (_x : borrowed (Vec'0.t_vec usize (Global'0.t_global)))
   
   axiom inv'1 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'1 x = true
   
   predicate invariant'0 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span8] true
+    [%#span1] true
   
   predicate inv'0 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   axiom inv'0 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span9] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span11] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'1 (empty'0 : Seq'0.t_seq usize) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'1 (empty'0 : Seq'0.t_seq usize) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span12] index_logic'1 (shallow_model'2 self) ix
+    [%#span8] index_logic'1 (shallow_model'2 self) ix
   
   function shallow_model'0 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span13] shallow_model'2 ( * self)
+    [%#span9] shallow_model'2 ( * self)
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span14]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span10]  ^ self =  * self
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span15] inv'3 self)
-   -> ([%#span16] inv'3 other)
-   -> ([%#span19] inv'3 (concat'0 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span12] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span17] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span11] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span20] inv'2 v)
-   -> ([%#span23] inv'3 (singleton'0 v))
-  && ([%#span22] index_logic'1 (singleton'0 v) 0 = v) && ([%#span21] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span13] inv'2 v)
+   -> ([%#span15] index_logic'1 (singleton'0 v) 0 = v) && ([%#span14] len'1 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq usize) (v : usize) : Seq'0.t_seq usize =
-    [%#span24] concat'0 self (singleton'0 v)
+    [%#span16] concat'0 self (singleton'0 v)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (value:usize) (return'  (ret:()))= {[@expl:precondition] [%#span26] inv'2 value}
-    {[@expl:precondition] [%#span25] inv'1 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (value:usize) (return'  (ret:()))= {[@expl:precondition] [%#span18] inv'2 value}
+    {[@expl:precondition] [%#span17] inv'1 self}
     any
-    [ return' (result:())-> {[%#span27] shallow_model'2 ( ^ self) = push'1 (shallow_model'0 self) value}
+    [ return' (result:())-> {[%#span19] shallow_model'2 ( ^ self) = push'1 (shallow_model'0 self) value}
       (! return' {result}) ]
     
   
   function shallow_model'1 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize =
-    [%#span28] shallow_model'2 self
+    [%#span20] shallow_model'2 self
   
-  let rec len'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span29] inv'0 self}
+  let rec len'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span21] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span30] UIntSize.to_int result = len'1 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span22] UIntSize.to_int result = len'1 (shallow_model'1 self)} (! return' {result}) ]
     
   
   let rec test (v:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (return'  (ret:()))= (! bb0
diff --git a/creusot/tests/should_succeed/cell/02.coma b/creusot/tests/should_succeed/cell/02.coma
index dfd630fbb7..7548b38363 100644
--- a/creusot/tests/should_succeed/cell/02.coma
+++ b/creusot/tests/should_succeed/cell/02.coma
@@ -233,22 +233,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
@@ -282,81 +267,73 @@ module C02_FibMemo
   
   let%span s0213 = "../02.rs" 93 10 93 28
   
-  let%span span14 = "" 0 0 0 0
+  let%span span14 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span15 = "" 0 0 0 0
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span21 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span21 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span22 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span25 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span23 = "../02.rs" 85 4 87 5
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span24 = "../02.rs" 31 10 31 11
   
-  let%span span27 = "../02.rs" 85 4 87 5
+  let%span span25 = "../02.rs" 29 0 29 8
   
-  let%span span28 = "../02.rs" 31 10 31 11
+  let%span span26 = "../02.rs" 72 12 75 13
   
-  let%span span29 = "../02.rs" 29 0 29 8
+  let%span span27 = "../02.rs" 23 4 23 38
   
-  let%span span30 = "../02.rs" 72 12 75 13
+  let%span span28 = "../02.rs" 24 16 24 20
   
-  let%span span31 = "../02.rs" 23 4 23 38
+  let%span span29 = "../02.rs" 24 22 24 23
   
-  let%span span32 = "../02.rs" 24 16 24 20
+  let%span span30 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span33 = "../02.rs" 24 22 24 23
+  let%span span31 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span34 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span32 = "../02.rs" 44 11 44 17
   
-  let%span span35 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span33 = "../02.rs" 45 10 45 28
   
-  let%span span36 = "../02.rs" 44 11 44 17
+  let%span span34 = "../02.rs" 46 10 46 11
   
-  let%span span37 = "../02.rs" 45 10 45 28
+  let%span span35 = "../02.rs" 43 0 43 8
   
-  let%span span38 = "../02.rs" 46 10 46 11
+  let%span span36 = "../02.rs" 61 10 61 49
   
-  let%span span39 = "../02.rs" 43 0 43 8
+  let%span span37 = "../02.rs" 60 0 60 8
   
-  let%span span40 = "../02.rs" 61 10 61 49
+  let%span span38 = "../02.rs" 18 16 18 20
   
-  let%span span41 = "../02.rs" 60 0 60 8
+  let%span span39 = "../02.rs" 17 4 17 42
   
-  let%span span42 = "../02.rs" 18 16 18 20
+  let%span span40 = "../02.rs" 18 25 18 26
   
-  let%span span43 = "../02.rs" 17 4 17 42
+  let%span span41 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span44 = "../02.rs" 18 25 18 26
+  let%span span42 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span43 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span44 = "" 0 0 0 0
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span45 = "" 0 0 0 0
   
-  let%span span48 = "" 0 0 0 0
+  let%span span46 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span49 = "" 0 0 0 0
-  
-  let%span span50 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
-  
-  let%span span51 = "" 0 0 0 0
+  let%span span47 = "" 0 0 0 0
   
   use C02_Fib_Type as Fib'0
   
@@ -368,7 +345,12 @@ module C02_FibMemo
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'7 (_x : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)))
+  predicate invariant'7 (self : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))) =
+    [%#span14] true
+  
+  predicate inv'8 (_x : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)))
+  
+  axiom inv'8 : forall x : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) . inv'8 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -378,68 +360,58 @@ module C02_FibMemo
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span14] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span15] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) . ([%#span15] inv'7 self)
-   -> ([%#span16] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) . [%#span16] len'0 self
+  >= 0
   
-  predicate inv'8 (_x : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global))
+  predicate inv'7 (_x : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global)) : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))
     
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global) . ([%#span17] inv'8 self)
-   -> ([%#span19] inv'7 (shallow_model'1 self))
-  && ([%#span18] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global) . ([%#span17] inv'7 self)
+   -> ([%#span18] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'7 (self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global))
+  predicate invariant'6 (self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global))
    =
-    [%#span20] inv'7 (shallow_model'1 self)
+    [%#span19] inv'8 (shallow_model'1 self)
   
-  axiom inv'8 : forall x : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global) . inv'8 x
+  axiom inv'7 : forall x : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global) . inv'7 x
   = true
   
-  predicate invariant'6 (self : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))) =
-    [%#span21] true
-  
-  axiom inv'7 : forall x : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) . inv'7 x = true
-  
   predicate invariant'5 (self : ()) =
-    [%#span21] true
+    [%#span14] true
   
   predicate inv'6 (_x : ())
   
   axiom inv'6 : forall x : () . inv'6 x = true
   
   predicate invariant'4 (self : ()) =
-    [%#span21] true
+    [%#span14] true
   
   predicate inv'5 (_x : ())
   
   axiom inv'5 : forall x : () . inv'5 x = true
   
   predicate invariant'3 (self : Option'0.t_option usize) =
-    [%#span21] true
+    [%#span14] true
   
   predicate inv'4 (_x : Option'0.t_option usize)
   
   axiom inv'4 : forall x : Option'0.t_option usize . inv'4 x = true
   
   predicate invariant'2 (self : Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) =
-    [%#span21] true
+    [%#span14] true
   
   predicate inv'2 (_x : Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))
   
   axiom inv'2 : forall x : Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib) . inv'2 x = true
   
   predicate invariant'1 (self : usize) =
-    [%#span21] true
+    [%#span14] true
   
   predicate inv'1 (_x : usize)
   
@@ -447,19 +419,18 @@ module C02_FibMemo
   
   predicate invariant'0 (self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global))
    =
-    [%#span21] true
+    [%#span14] true
   
   predicate inv'0 (_x : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global))
   
   axiom inv'0 : forall x : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global) . inv'0 x
   = true
   
-  constant empty'0 : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) = [%#span22] ()
+  constant empty'0 : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span24] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'0 (empty'0 : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)))
+  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'0 (empty'0 : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)))
   = 0
   
   use prelude.prelude.Borrow
@@ -467,26 +438,24 @@ module C02_FibMemo
   function shallow_model'0 (self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global)) : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))
     
    =
-    [%#span25] shallow_model'1 self
+    [%#span21] shallow_model'1 self
   
   use C02_Fib_Type as C02_Fib_Type
   
   use C02_Cell_Type as C02_Cell_Type
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))) (x : int) : Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)
+  function index_logic'1 (self : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))) (_2 : int) : Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global)) (ix : int) : Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)
     
    =
-    [%#span26] index_logic'1 (shallow_model'1 self) ix
+    [%#span22] index_logic'1 (shallow_model'1 self) ix
   
   predicate fib_cell'0 [#"../02.rs" 84 0 84 32] (v : Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global))
     
    =
-    [%#span27] forall i : int . UIntSize.to_int (C02_Fib_Type.fib_ix (C02_Cell_Type.cell_ghost_inv (index_logic'0 v i)))
+    [%#span23] forall i : int . UIntSize.to_int (C02_Fib_Type.fib_ix (C02_Cell_Type.cell_ghost_inv (index_logic'0 v i)))
     = i
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
@@ -496,54 +465,54 @@ module C02_FibMemo
   function fib'0 [#"../02.rs" 32 0 32 25] (i : int) : int
   
   axiom fib'0_def : forall i : int . fib'0 i
-  = ([%#span29] if i <= 0 then 0 else if i = 1 then 1 else fib'0 (i - 1) + fib'0 (i - 2))
+  = ([%#span25] if i <= 0 then 0 else if i = 1 then 1 else fib'0 (i - 1) + fib'0 (i - 2))
   
   predicate inv'3 [#"../02.rs" 70 4 70 43] (self : Fib'0.t_fib) (v : Option'0.t_option usize) =
-    [%#span30] match v with
+    [%#span26] match v with
       | Option'0.C_None -> true
       | Option'0.C_Some i -> UIntSize.to_int i = fib'0 (UIntSize.to_int (C02_Fib_Type.fib_ix self))
       end
   
-  let rec set'0 (self:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (v:Option'0.t_option usize) (return'  (ret:()))= {[@expl:precondition] [%#span33] inv'4 v}
-    {[@expl:precondition] [%#span32] inv'2 self}
-    {[@expl:precondition] [%#span31] inv'3 (C02_Cell_Type.cell_ghost_inv self) v}
+  let rec set'0 (self:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (v:Option'0.t_option usize) (return'  (ret:()))= {[@expl:precondition] [%#span29] inv'4 v}
+    {[@expl:precondition] [%#span28] inv'2 self}
+    {[@expl:precondition] [%#span27] inv'3 (C02_Cell_Type.cell_ghost_inv self) v}
     any [ return' (result:())-> (! return' {result}) ] 
   
   function deref'1 (self : Snapshot'0.t_snapshot ()) : ()
   
   function new'1 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'1_spec : forall x : () . ([%#span34] inv'6 x)  -> ([%#span35] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : () . ([%#span30] inv'6 x)  -> ([%#span31] deref'1 (new'1 x) = x)
   
   use int.Power
   
   function lemma_fib_bound'0 [#"../02.rs" 47 0 47 30] (i : int) : ()
   
   axiom lemma_fib_bound'0_def : forall i : int . lemma_fib_bound'0 i
-  = ([%#span39] if i = 0 then
+  = ([%#span35] if i = 0 then
     ()
   else
     if i = 1 then () else let _ = lemma_fib_bound'0 (i - 2) in lemma_fib_bound'0 (i - 1)
   )
   
-  axiom lemma_fib_bound'0_spec : forall i : int . ([%#span36] 0 <= i)  -> ([%#span37] fib'0 i <= Power.power 2 i)
+  axiom lemma_fib_bound'0_spec : forall i : int . ([%#span32] 0 <= i)  -> ([%#span33] fib'0 i <= Power.power 2 i)
   
   function deref'0 (self : Snapshot'0.t_snapshot ()) : ()
   
   function new'0 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'0_spec : forall x : () . ([%#span34] inv'5 x)  -> ([%#span35] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : () . ([%#span30] inv'5 x)  -> ([%#span31] deref'0 (new'0 x) = x)
   
   function lemma_max_int'0 [#"../02.rs" 62 0 62 22] (_1 : ()) : () =
-    [%#span41] ()
+    [%#span37] ()
   
-  axiom lemma_max_int'0_spec : forall _1 : () . [%#span40] Power.power 2 63
+  axiom lemma_max_int'0_spec : forall _1 : () . [%#span36] Power.power 2 63
   < UIntSize.to_int (18446744073709551615 : usize)
   
-  let rec get'0 (self:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span42] inv'2 self}
+  let rec get'0 (self:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span38] inv'2 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span44] inv'4 result}
-      {[%#span43] inv'3 (C02_Cell_Type.cell_ghost_inv self) result}
+    [ return' (result:Option'0.t_option usize)-> {[%#span40] inv'4 result}
+      {[%#span39] inv'3 (C02_Cell_Type.cell_ghost_inv self) result}
       (! return' {result}) ]
     
   
@@ -552,19 +521,19 @@ module C02_FibMemo
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))) (out : Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))
     
    =
-    [%#span45] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span41] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)))
     
    =
-    [%#span46] UIntSize.to_int self < len'0 seq
+    [%#span42] UIntSize.to_int self < len'0 seq
   
-  let rec index'0 (self:Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global)) (index:usize) (return'  (ret:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)))= {[@expl:precondition] [%#span49] inv'1 index}
-    {[@expl:precondition] [%#span48] inv'0 self}
-    {[@expl:precondition] [%#span47] in_bounds'0 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec (Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)) (Global'0.t_global)) (index:usize) (return'  (ret:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib)))= {[@expl:precondition] [%#span45] inv'1 index}
+    {[@expl:precondition] [%#span44] inv'0 self}
+    {[@expl:precondition] [%#span43] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))-> {[%#span51] inv'2 result}
-      {[%#span50] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:Cell'0.t_cell (Option'0.t_option usize) (Fib'0.t_fib))-> {[%#span47] inv'2 result}
+      {[%#span46] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/filter_positive.coma b/creusot/tests/should_succeed/filter_positive.coma
index 7eaad3bd76..fc694dbd0d 100644
--- a/creusot/tests/should_succeed/filter_positive.coma
+++ b/creusot/tests/should_succeed/filter_positive.coma
@@ -1,38 +1,19 @@
 
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module FilterPositive_NumOfPos_Impl
   let%span sfilter_positive0 = "../filter_positive.rs" 36 10 36 13
   
   use prelude.prelude.Int32
   
-  use seq.Seq
+  use prelude.prelude.Int
   
   use prelude.prelude.Int32
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use prelude.prelude.Int
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  function index_logic'0 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'0 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   constant i  : int
   
@@ -67,13 +48,9 @@ module FilterPositive_LemmaNumOfPosIncreasing_Impl
   
   use prelude.prelude.Int32
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'0 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function num_of_pos'0 [#"../filter_positive.rs" 37 0 37 49] (i : int) (j : int) (t : Seq'0.t_seq int32) : int
   
@@ -111,60 +88,38 @@ module FilterPositive_LemmaNumOfPosStrictlyIncreasing_Impl
   
   let%span sfilter_positive2 = "../filter_positive.rs" 78 10 78 49
   
-  let%span span3 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../filter_positive.rs" 36 10 36 13
   
-  let%span span9 = "../filter_positive.rs" 36 10 36 13
+  let%span span6 = "../filter_positive.rs" 38 4 46 5
   
-  let%span span10 = "../filter_positive.rs" 38 4 46 5
+  use prelude.prelude.Int
   
   use prelude.prelude.Int32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq int32) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq int32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq int32 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq int32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int32 . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int32 . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Int32
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'0 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function num_of_pos'0 [#"../filter_positive.rs" 37 0 37 49] (i : int) (j : int) (t : Seq'0.t_seq int32) : int
   
   axiom num_of_pos'0_def : forall i : int, j : int, t : Seq'0.t_seq int32 . num_of_pos'0 i j t
-  = ([%#span10] if i >= j then
+  = ([%#span6] if i >= j then
     0
   else
     if Int32.to_int (index_logic'0 t (j - 1)) > 0 then num_of_pos'0 i (j - 1) t + 1 else num_of_pos'0 i (j - 1) t
@@ -323,128 +278,122 @@ module FilterPositive_M
   
   let%span span19 = "" 0 0 0 0
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span21 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span25 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span26 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span28 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span29 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span29 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span30 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span31 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span31 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span32 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span32 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span33 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span34 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span34 = "" 0 0 0 0
   
-  let%span span35 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span35 = "" 0 0 0 0
   
-  let%span span36 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span36 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span37 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span37 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span38 = "" 0 0 0 0
+  let%span span38 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span39 = "" 0 0 0 0
+  let%span span39 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span40 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span40 = "" 0 0 0 0
   
-  let%span span41 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span41 = "../filter_positive.rs" 36 10 36 13
   
-  let%span span42 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span42 = "../filter_positive.rs" 38 4 46 5
   
-  let%span span43 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span43 = "../filter_positive.rs" 62 11 62 17
   
-  let%span span44 = "" 0 0 0 0
+  let%span span44 = "../filter_positive.rs" 63 10 63 48
   
-  let%span span45 = "../filter_positive.rs" 36 10 36 13
+  let%span span45 = "../filter_positive.rs" 64 10 64 13
   
-  let%span span46 = "../filter_positive.rs" 38 4 46 5
+  let%span span46 = "../filter_positive.rs" 67 8 69 9
   
-  let%span span47 = "../filter_positive.rs" 62 11 62 17
+  let%span span47 = "../filter_positive.rs" 76 11 76 32
   
-  let%span span48 = "../filter_positive.rs" 63 10 63 48
+  let%span span48 = "../filter_positive.rs" 77 11 77 20
   
-  let%span span49 = "../filter_positive.rs" 64 10 64 13
+  let%span span49 = "../filter_positive.rs" 78 10 78 49
   
-  let%span span50 = "../filter_positive.rs" 67 8 69 9
+  let%span span50 = "../filter_positive.rs" 75 0 75 8
   
-  let%span span51 = "../filter_positive.rs" 76 11 76 32
+  let%span span51 = "" 0 0 0 0
   
-  let%span span52 = "../filter_positive.rs" 77 11 77 20
+  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span53 = "../filter_positive.rs" 78 10 78 49
+  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
-  let%span span54 = "../filter_positive.rs" 75 0 75 8
+  let%span span54 = "" 0 0 0 0
   
-  let%span span55 = "" 0 0 0 0
+  let%span span55 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
+  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span57 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
+  let%span span57 = "" 0 0 0 0
   
   let%span span58 = "" 0 0 0 0
   
-  let%span span59 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span59 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span60 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span60 = "" 0 0 0 0
   
   let%span span61 = "" 0 0 0 0
   
-  let%span span62 = "" 0 0 0 0
+  let%span span62 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span63 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  use prelude.prelude.Int32
   
-  let%span span64 = "" 0 0 0 0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span65 = "" 0 0 0 0
+  predicate invariant'7 (self : Seq'0.t_seq int32) =
+    [%#span18] true
   
-  let%span span66 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  predicate inv'7 (_x : Seq'0.t_seq int32)
   
-  use prelude.prelude.Int32
+  axiom inv'7 : forall x : Seq'0.t_seq int32 . inv'7 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'7 (self : borrowed int32) =
+  predicate invariant'6 (self : borrowed int32) =
     [%#span18] true
   
-  predicate inv'7 (_x : borrowed int32)
+  predicate inv'6 (_x : borrowed int32)
   
-  axiom inv'7 : forall x : borrowed int32 . inv'7 x = true
+  axiom inv'6 : forall x : borrowed int32 . inv'6 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
   use Alloc_Vec_Vec_Type as Vec'0
   
-  predicate invariant'6 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) =
+  predicate invariant'5 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) =
     [%#span18] true
   
-  predicate inv'6 (_x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)))
-  
-  axiom inv'6 : forall x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)) . inv'6 x = true
-  
-  predicate invariant'5 (self : int32) =
-    [%#span18] true
+  predicate inv'5 (_x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)))
   
-  predicate inv'5 (_x : int32)
-  
-  axiom inv'5 : forall x : int32 . inv'5 x = true
+  axiom inv'5 : forall x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)) . inv'5 x = true
   
   predicate invariant'4 (self : int32) =
     [%#span18] true
@@ -453,30 +402,28 @@ module FilterPositive_M
   
   axiom inv'4 : forall x : int32 . inv'4 x = true
   
-  use prelude.prelude.UIntSize
-  
-  predicate invariant'3 (self : usize) =
+  predicate invariant'3 (self : int32) =
     [%#span18] true
   
-  predicate inv'3 (_x : usize)
+  predicate inv'3 (_x : int32)
   
-  axiom inv'3 : forall x : usize . inv'3 x = true
+  axiom inv'3 : forall x : int32 . inv'3 x = true
   
-  predicate invariant'2 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span18] true
+  use prelude.prelude.UIntSize
   
-  predicate inv'2 (_x : Vec'0.t_vec int32 (Global'0.t_global))
+  predicate invariant'2 (self : usize) =
+    [%#span18] true
   
-  axiom inv'2 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'2 x = true
+  predicate inv'2 (_x : usize)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'2 : forall x : usize . inv'2 x = true
   
-  predicate invariant'1 (self : Seq'0.t_seq int32) =
+  predicate invariant'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
     [%#span18] true
   
-  predicate inv'1 (_x : Seq'0.t_seq int32)
+  predicate inv'1 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
-  axiom inv'1 : forall x : Seq'0.t_seq int32 . inv'1 x = true
+  axiom inv'1 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'1 x = true
   
   use prelude.prelude.UIntSize
   
@@ -484,76 +431,68 @@ module FilterPositive_M
   
   constant max'0 : usize = [%#span19] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq int32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int32 . ([%#span20] inv'1 self)  -> ([%#span21] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int32 . [%#span20] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span22] inv'0 self)
-   -> ([%#span24] inv'1 (shallow_model'0 self))
-  && ([%#span23] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span21] inv'0 self)
+   -> ([%#span22] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span25] inv'1 (shallow_model'0 self)
+    [%#span23] inv'7 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span26] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span28] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span27] len'0 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span24] len'0 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : int32) =
-    [%#span29] true
-  
-  use seq.Seq
+    [%#span25] true
   
-  function index_logic'0 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'0 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span30] index_logic'0 (shallow_model'0 self) ix
+    [%#span26] index_logic'0 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span31] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'1 self i)
+    [%#span27] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'1 self i)
   
   predicate resolve'0 (self : borrowed int32) =
-    [%#span32]  ^ self =  * self
+    [%#span28]  ^ self =  * self
   
   use prelude.prelude.Slice
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq int32) (fin : Seq'0.t_seq int32) =
-    [%#span33] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
+    [%#span29] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
      -> index_logic'0 old' i = index_logic'0 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) (out : int32) =
-    [%#span34] index_logic'0 seq (UIntSize.to_int self) = out
+    [%#span30] index_logic'0 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) =
-    [%#span35] UIntSize.to_int self < len'0 seq
+    [%#span31] UIntSize.to_int self < len'0 seq
   
   function shallow_model'2 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span36] shallow_model'0 ( * self)
+    [%#span32] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:usize) (return'  (ret:borrowed int32))= {[@expl:precondition] [%#span39] inv'3 index}
-    {[@expl:precondition] [%#span38] inv'6 self}
-    {[@expl:precondition] [%#span37] in_bounds'0 index (shallow_model'2 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:usize) (return'  (ret:borrowed int32))= {[@expl:precondition] [%#span35] inv'2 index}
+    {[@expl:precondition] [%#span34] inv'5 self}
+    {[@expl:precondition] [%#span33] in_bounds'0 index (shallow_model'2 self)}
     any
-    [ return' (result:borrowed int32)-> {[%#span44] inv'7 result}
-      {[%#span43] len'0 (shallow_model'0 ( ^ self)) = len'0 (shallow_model'2 self)}
-      {[%#span42] resolve_elswhere'0 index (shallow_model'2 self) (shallow_model'0 ( ^ self))}
-      {[%#span41] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span40] has_value'0 index (shallow_model'2 self) ( * result)}
+    [ return' (result:borrowed int32)-> {[%#span40] inv'6 result}
+      {[%#span39] len'0 (shallow_model'0 ( ^ self)) = len'0 (shallow_model'2 self)}
+      {[%#span38] resolve_elswhere'0 index (shallow_model'2 self) (shallow_model'0 ( ^ self))}
+      {[%#span37] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span36] has_value'0 index (shallow_model'2 self) ( * result)}
       (! return' {result}) ]
     
   
@@ -562,7 +501,7 @@ module FilterPositive_M
   function num_of_pos'0 [#"../filter_positive.rs" 37 0 37 49] (i : int) (j : int) (t : Seq'0.t_seq int32) : int
   
   axiom num_of_pos'0_def : forall i : int, j : int, t : Seq'0.t_seq int32 . num_of_pos'0 i j t
-  = ([%#span46] if i >= j then
+  = ([%#span42] if i >= j then
     0
   else
     if Int32.to_int (index_logic'0 t (j - 1)) > 0 then num_of_pos'0 i (j - 1) t + 1 else num_of_pos'0 i (j - 1) t
@@ -572,43 +511,43 @@ module FilterPositive_M
     
   
   axiom lemma_num_of_pos_increasing'0_def : forall i : int, j : int, k : int, t : Seq'0.t_seq int32 . lemma_num_of_pos_increasing'0 i j k t
-  = ([%#span50] if j < k then lemma_num_of_pos_increasing'0 i (j + 1) k t else ())
+  = ([%#span46] if j < k then lemma_num_of_pos_increasing'0 i (j + 1) k t else ())
   
-  axiom lemma_num_of_pos_increasing'0_spec : forall i : int, j : int, k : int, t : Seq'0.t_seq int32 . ([%#span47] j
-  <= k)  -> ([%#span48] num_of_pos'0 i j t <= num_of_pos'0 i k t)
+  axiom lemma_num_of_pos_increasing'0_spec : forall i : int, j : int, k : int, t : Seq'0.t_seq int32 . ([%#span43] j
+  <= k)  -> ([%#span44] num_of_pos'0 i j t <= num_of_pos'0 i k t)
   
   function lemma_num_of_pos_strictly_increasing'0 [#"../filter_positive.rs" 79 0 79 60] (i : int) (t : Seq'0.t_seq int32) : ()
     
    =
-    [%#span54] ()
+    [%#span50] ()
   
-  axiom lemma_num_of_pos_strictly_increasing'0_spec : forall i : int, t : Seq'0.t_seq int32 . ([%#span51] 0 <= i
+  axiom lemma_num_of_pos_strictly_increasing'0_spec : forall i : int, t : Seq'0.t_seq int32 . ([%#span47] 0 <= i
   /\ i < len'0 t)
-   -> ([%#span52] Int32.to_int (index_logic'0 t i) > 0)  -> ([%#span53] num_of_pos'0 0 i t < num_of_pos'0 0 (i + 1) t)
+   -> ([%#span48] Int32.to_int (index_logic'0 t i) > 0)  -> ([%#span49] num_of_pos'0 0 i t < num_of_pos'0 0 (i + 1) t)
   
-  let rec from_elem'0 (elem:int32) (n:usize) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span55] inv'5 elem}
+  let rec from_elem'0 (elem:int32) (n:usize) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span51] inv'4 elem}
     any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span58] inv'0 result}
-      {[%#span57] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'1 result i = elem}
-      {[%#span56] len'0 (shallow_model'0 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span54] inv'0 result}
+      {[%#span53] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'1 result i = elem}
+      {[%#span52] len'0 (shallow_model'0 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
   function shallow_model'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span59] shallow_model'0 self
+    [%#span55] shallow_model'0 self
   
-  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span62] inv'3 index}
-    {[@expl:precondition] [%#span61] inv'2 self}
-    {[@expl:precondition] [%#span60] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span58] inv'2 index}
+    {[@expl:precondition] [%#span57] inv'1 self}
+    {[@expl:precondition] [%#span56] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:int32)-> {[%#span64] inv'4 result}
-      {[%#span63] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:int32)-> {[%#span60] inv'3 result}
+      {[%#span59] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
-  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span65] inv'2 self}
+  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span61] inv'1 self}
     any
-    [ return' (result:usize)-> {[%#span66] UIntSize.to_int result = len'0 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span62] UIntSize.to_int result = len'0 (shallow_model'1 self)} (! return' {result}) ]
     
   
   let rec m (t:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= (! bb0
diff --git a/creusot/tests/should_succeed/hashmap.coma b/creusot/tests/should_succeed/hashmap.coma
index 2c5d4dbeb0..c4e6f846a4 100644
--- a/creusot/tests/should_succeed/hashmap.coma
+++ b/creusot/tests/should_succeed/hashmap.coma
@@ -204,22 +204,7 @@ module Hashmap_MyHashMap_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Hashmap_Impl5_New
   type k
@@ -236,63 +221,55 @@ module Hashmap_Impl5_New
   
   let%span span4 = "" 0 0 0 0
   
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span6 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span7 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span7 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span10 = "../hashmap.rs" 30 12 33 13
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span11 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span12 = "../hashmap.rs" 90 20 90 66
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span13 = "../hashmap.rs" 85 8 85 53
   
-  let%span span14 = "../hashmap.rs" 30 12 33 13
-  
-  let%span span15 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span14 = "../hashmap.rs" 79 20 79 45
   
-  let%span span16 = "../hashmap.rs" 90 20 90 66
+  let%span span15 = "../hashmap.rs" 40 12 43 13
   
-  let%span span17 = "../hashmap.rs" 85 8 85 53
-  
-  let%span span18 = "../hashmap.rs" 79 20 79 45
+  let%span span16 = "../hashmap.rs" 200 8 202 9
   
-  let%span span19 = "../hashmap.rs" 40 12 43 13
+  let%span span17 = "../hashmap.rs" 209 8 212 9
   
-  let%span span20 = "../hashmap.rs" 200 8 202 9
+  let%span span18 = "" 0 0 0 0
   
-  let%span span21 = "../hashmap.rs" 209 8 212 9
+  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span22 = "" 0 0 0 0
+  let%span span20 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
-  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
+  let%span span21 = "" 0 0 0 0
   
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
-  
-  let%span span25 = "" 0 0 0 0
-  
-  predicate invariant'5 (self : v)
+  use Hashmap_List_Type as List'0
   
-  predicate inv'5 (_x : v)
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  axiom inv'5 : forall x : v . inv'5 x = true
+  predicate invariant'5 (self : Seq'0.t_seq (List'0.t_list (k, v)))
   
-  use Hashmap_List_Type as List'0
+  predicate inv'5 (_x : Seq'0.t_seq (List'0.t_list (k, v)))
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'5 : forall x : Seq'0.t_seq (List'0.t_list (k, v)) . inv'5 x = true
   
-  predicate invariant'4 (self : Seq'0.t_seq (List'0.t_list (k, v)))
+  predicate invariant'4 (self : v)
   
-  predicate inv'4 (_x : Seq'0.t_seq (List'0.t_list (k, v)))
+  predicate inv'4 (_x : v)
   
-  axiom inv'4 : forall x : Seq'0.t_seq (List'0.t_list (k, v)) . inv'4 x = true
+  axiom inv'4 : forall x : v . inv'4 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -306,35 +283,28 @@ module Hashmap_Impl5_New
   
   constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq (List'0.t_list (k, v))) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . ([%#span5] inv'4 self)
-   -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . [%#span5] len'0 self >= 0
   
   predicate inv'3 (_x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (k, v))
     
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span7] inv'3 self)
-   -> ([%#span9] inv'4 (shallow_model'1 self))
-  && ([%#span8] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span6] inv'3 self)
+   -> ([%#span7] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'3 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) =
-    [%#span10] inv'4 (shallow_model'1 self)
+    [%#span8] inv'5 (shallow_model'1 self)
   
   axiom inv'3 : forall x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . inv'3 x = true
   
-  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v)) = [%#span11] ()
+  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span13] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span12] len'0 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
   
   predicate invariant'2 (self : List'0.t_list (k, v))
   
@@ -369,19 +339,17 @@ module Hashmap_Impl5_New
   function get'0 [#"../hashmap.rs" 28 4 28 56] (self : List'0.t_list (k, v)) (index : deep_model_ty'0) : Option'0.t_option v
     
    =
-    [%#span14] match self with
+    [%#span10] match self with
       | List'0.C_Nil -> Option'0.C_None
       | List'0.C_Cons (k, v) tl -> if deep_model'0 k = index then Option'0.C_Some v else get'0 tl index
       end
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (x : int) : List'0.t_list (k, v)
+  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (_2 : int) : List'0.t_list (k, v)
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (ix : int) : List'0.t_list (k, v)
     
    =
-    [%#span15] index_logic'1 (shallow_model'1 self) ix
+    [%#span11] index_logic'1 (shallow_model'1 self) ix
   
   use int.EuclideanDivision
   
@@ -390,22 +358,22 @@ module Hashmap_Impl5_New
   function hash_log'0 [#"../hashmap.rs" 54 4 54 45] (_1 : deep_model_ty'0) : int
   
   function bucket_ix'0 [#"../hashmap.rs" 89 4 89 48] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : int =
-    [%#span16] EuclideanDivision.mod (hash_log'0 k) (len'0 (shallow_model'1 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
+    [%#span12] EuclideanDivision.mod (hash_log'0 k) (len'0 (shallow_model'1 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
   
   function bucket'0 [#"../hashmap.rs" 84 4 84 54] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : List'0.t_list (k, v)
     
    =
-    [%#span17] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
+    [%#span13] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
   
   use map.Map
   
   function shallow_model'0 [#"../hashmap.rs" 78 4 78 50] (self : MyHashMap'0.t_myhashmap k v) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span18] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
+    [%#span14] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
   
   predicate no_double_binding'0 [#"../hashmap.rs" 38 4 38 38] (self : List'0.t_list (k, v)) =
-    [%#span19] match self with
+    [%#span15] match self with
       | List'0.C_Nil -> true
       | List'0.C_Cons (k, _) tl -> get'0 tl (deep_model'0 k) = Option'0.C_None /\ no_double_binding'0 tl
       end
@@ -413,24 +381,24 @@ module Hashmap_Impl5_New
   predicate good_bucket'0 [#"../hashmap.rs" 199 4 199 57] (self : MyHashMap'0.t_myhashmap k v) (l : List'0.t_list (k, v)) (h : int)
     
    =
-    [%#span20] forall v : v . forall k : deep_model_ty'0 . inv'5 v
+    [%#span16] forall v : v . forall k : deep_model_ty'0 . inv'4 v
      -> inv'0 k  -> get'0 l k = Option'0.C_Some v  -> bucket_ix'0 self k = h
   
   use prelude.prelude.Borrow
   
   predicate hashmap_inv'0 [#"../hashmap.rs" 208 4 208 33] (self : MyHashMap'0.t_myhashmap k v) =
-    [%#span21] 0 < len'0 (shallow_model'1 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
+    [%#span17] 0 < len'0 (shallow_model'1 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
     /\ (forall i : int . 0 <= i /\ i < len'0 (shallow_model'1 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
      -> good_bucket'0 self (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i) i
     /\ no_double_binding'0 (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i))
   
   use prelude.prelude.Intrinsic
   
-  let rec from_elem'0 (elem:List'0.t_list (k, v)) (n:usize) (return'  (ret:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)))= {[@expl:precondition] [%#span22] inv'2 elem}
+  let rec from_elem'0 (elem:List'0.t_list (k, v)) (n:usize) (return'  (ret:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)))= {[@expl:precondition] [%#span18] inv'2 elem}
     any
-    [ return' (result:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))-> {[%#span25] inv'3 result}
-      {[%#span24] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
-      {[%#span23] len'0 (shallow_model'1 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))-> {[%#span21] inv'3 result}
+      {[%#span20] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
+      {[%#span19] len'0 (shallow_model'1 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
@@ -511,89 +479,81 @@ module Hashmap_Impl5_Add
   
   let%span span14 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span17 = "" 0 0 0 0
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span18 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span20 = "" 0 0 0 0
+  let%span span20 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span21 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span21 = "../hashmap.rs" 30 12 33 13
   
-  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span22 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span23 = "../hashmap.rs" 90 20 90 66
   
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span24 = "../hashmap.rs" 85 8 85 53
   
-  let%span span25 = "../hashmap.rs" 30 12 33 13
+  let%span span25 = "../hashmap.rs" 79 20 79 45
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span26 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span27 = "../hashmap.rs" 90 20 90 66
+  let%span span27 = "../hashmap.rs" 40 12 43 13
   
-  let%span span28 = "../hashmap.rs" 85 8 85 53
+  let%span span28 = "../hashmap.rs" 200 8 202 9
   
-  let%span span29 = "../hashmap.rs" 79 20 79 45
+  let%span span29 = "../hashmap.rs" 209 8 212 9
   
-  let%span span30 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span30 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span31 = "../hashmap.rs" 40 12 43 13
+  let%span span31 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
-  let%span span32 = "../hashmap.rs" 200 8 202 9
+  let%span span32 = "" 0 0 0 0
   
-  let%span span33 = "../hashmap.rs" 209 8 212 9
+  let%span span33 = "" 0 0 0 0
   
-  let%span span34 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span34 = "../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
   
-  let%span span35 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
+  let%span span35 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span36 = "" 0 0 0 0
+  let%span span36 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span37 = "" 0 0 0 0
+  let%span span37 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span38 = "../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
+  let%span span38 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span39 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span39 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span40 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span40 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span41 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span41 = "" 0 0 0 0
   
-  let%span span42 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span42 = "" 0 0 0 0
   
-  let%span span43 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span43 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span44 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span44 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span45 = "" 0 0 0 0
+  let%span span45 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span46 = "" 0 0 0 0
+  let%span span46 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span47 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span47 = "" 0 0 0 0
   
-  let%span span48 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span48 = "../hashmap.rs" 51 13 51 17
   
-  let%span span49 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span49 = "../hashmap.rs" 50 14 50 58
   
-  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span50 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
   let%span span51 = "" 0 0 0 0
   
-  let%span span52 = "../hashmap.rs" 51 13 51 17
-  
-  let%span span53 = "../hashmap.rs" 50 14 50 58
-  
-  let%span span54 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span55 = "" 0 0 0 0
-  
-  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
   use Hashmap_List_Type as List'0
   
@@ -634,21 +594,15 @@ module Hashmap_Impl5_Add
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . ([%#span15] inv'15 self)
-   -> ([%#span16] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . [%#span15] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v)) = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span18] len'1 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'1 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
   
   predicate invariant'11 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
   
@@ -722,19 +676,18 @@ module Hashmap_Impl5_Add
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span20] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span17] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
   
   function shallow_model'4 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (k, v))
     
   
-  axiom shallow_model'4_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span21] inv'0 self)
-   -> ([%#span23] inv'15 (shallow_model'4 self))
-  && ([%#span22] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'4_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span18] inv'0 self)
+   -> ([%#span19] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) =
-    [%#span24] inv'15 (shallow_model'4 self)
+    [%#span20] inv'15 (shallow_model'4 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . inv'0 x = true
   
@@ -747,19 +700,17 @@ module Hashmap_Impl5_Add
   function get'0 [#"../hashmap.rs" 28 4 28 56] (self : List'0.t_list (k, v)) (index : deep_model_ty'0) : Option'0.t_option v
     
    =
-    [%#span25] match self with
+    [%#span21] match self with
       | List'0.C_Nil -> Option'0.C_None
       | List'0.C_Cons (k, v) tl -> if deep_model'0 k = index then Option'0.C_Some v else get'0 tl index
       end
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (x : int) : List'0.t_list (k, v)
+  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (_2 : int) : List'0.t_list (k, v)
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (ix : int) : List'0.t_list (k, v)
     
    =
-    [%#span26] index_logic'1 (shallow_model'4 self) ix
+    [%#span22] index_logic'1 (shallow_model'4 self) ix
   
   use int.EuclideanDivision
   
@@ -768,24 +719,24 @@ module Hashmap_Impl5_Add
   function hash_log'0 [#"../hashmap.rs" 54 4 54 45] (_1 : deep_model_ty'0) : int
   
   function bucket_ix'0 [#"../hashmap.rs" 89 4 89 48] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : int =
-    [%#span27] EuclideanDivision.mod (hash_log'0 k) (len'1 (shallow_model'4 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
+    [%#span23] EuclideanDivision.mod (hash_log'0 k) (len'1 (shallow_model'4 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
   
   function bucket'0 [#"../hashmap.rs" 84 4 84 54] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : List'0.t_list (k, v)
     
    =
-    [%#span28] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
+    [%#span24] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
   
   use map.Map
   
   function shallow_model'0 [#"../hashmap.rs" 78 4 78 50] (self : MyHashMap'0.t_myhashmap k v) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span29] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
+    [%#span25] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
   
   function shallow_model'1 (self : borrowed (MyHashMap'0.t_myhashmap k v)) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span30] shallow_model'0 ( * self)
+    [%#span26] shallow_model'0 ( * self)
   
   use map.Map
   
@@ -794,7 +745,7 @@ module Hashmap_Impl5_Add
   use prelude.prelude.Intrinsic
   
   predicate no_double_binding'0 [#"../hashmap.rs" 38 4 38 38] (self : List'0.t_list (k, v)) =
-    [%#span31] match self with
+    [%#span27] match self with
       | List'0.C_Nil -> true
       | List'0.C_Cons (k, _) tl -> get'0 tl (deep_model'0 k) = Option'0.C_None /\ no_double_binding'0 tl
       end
@@ -802,17 +753,17 @@ module Hashmap_Impl5_Add
   predicate good_bucket'0 [#"../hashmap.rs" 199 4 199 57] (self : MyHashMap'0.t_myhashmap k v) (l : List'0.t_list (k, v)) (h : int)
     
    =
-    [%#span32] forall v : v . forall k : deep_model_ty'0 . inv'5 v
+    [%#span28] forall v : v . forall k : deep_model_ty'0 . inv'5 v
      -> inv'3 k  -> get'0 l k = Option'0.C_Some v  -> bucket_ix'0 self k = h
   
   predicate hashmap_inv'0 [#"../hashmap.rs" 208 4 208 33] (self : MyHashMap'0.t_myhashmap k v) =
-    [%#span33] 0 < len'1 (shallow_model'4 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
+    [%#span29] 0 < len'1 (shallow_model'4 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
     /\ (forall i : int . 0 <= i /\ i < len'1 (shallow_model'4 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
      -> good_bucket'0 self (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i) i
     /\ no_double_binding'0 (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i))
   
   predicate resolve'9 (self : borrowed (MyHashMap'0.t_myhashmap k v)) =
-    [%#span34]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate resolve'8 (self : List'0.t_list (k, v))
   
@@ -821,20 +772,20 @@ module Hashmap_Impl5_Add
   predicate resolve'6 (self : k)
   
   predicate resolve'5 (self : borrowed (List'0.t_list (k, v))) =
-    [%#span34]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate resolve'4 (self : borrowed k) =
-    [%#span34]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate resolve'3 (self : borrowed v) =
-    [%#span34]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   function deep_model'1 (self : k) : deep_model_ty'0 =
-    [%#span35] deep_model'0 self
+    [%#span31] deep_model'0 self
   
-  let rec eq'0 (self:k) (other:k) (return'  (ret:bool))= {[@expl:precondition] [%#span37] inv'12 other}
-    {[@expl:precondition] [%#span36] inv'12 self}
-    any [ return' (result:bool)-> {[%#span38] result = (deep_model'1 self = deep_model'1 other)} (! return' {result}) ] 
+  let rec eq'0 (self:k) (other:k) (return'  (ret:bool))= {[@expl:precondition] [%#span33] inv'12 other}
+    {[@expl:precondition] [%#span32] inv'12 self}
+    any [ return' (result:bool)-> {[%#span34] result = (deep_model'1 self = deep_model'1 other)} (! return' {result}) ] 
   
   function deref'1 (self : Snapshot'0.t_snapshot (borrowed (List'0.t_list (k, v)))) : borrowed (List'0.t_list (k, v))
   
@@ -847,42 +798,42 @@ module Hashmap_Impl5_Add
   
   function new'1 (x : borrowed (List'0.t_list (k, v))) : Snapshot'0.t_snapshot (borrowed (List'0.t_list (k, v)))
   
-  axiom new'1_spec : forall x : borrowed (List'0.t_list (k, v)) . ([%#span39] inv'2 x)
-   -> ([%#span40] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : borrowed (List'0.t_list (k, v)) . ([%#span35] inv'2 x)
+   -> ([%#span36] deref'1 (new'1 x) = x)
   
   predicate resolve'1 (self : borrowed (List'0.t_list (k, v))) =
-    [%#span34]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   use prelude.prelude.Slice
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq (List'0.t_list (k, v))) (fin : Seq'0.t_seq (List'0.t_list (k, v)))
     
    =
-    [%#span41] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
+    [%#span37] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
      -> index_logic'1 old' i = index_logic'1 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (List'0.t_list (k, v))) (out : List'0.t_list (k, v))
     
    =
-    [%#span42] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span38] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (List'0.t_list (k, v))) =
-    [%#span43] UIntSize.to_int self < len'1 seq
+    [%#span39] UIntSize.to_int self < len'1 seq
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))) : Seq'0.t_seq (List'0.t_list (k, v))
     
    =
-    [%#span30] shallow_model'4 ( * self)
+    [%#span26] shallow_model'4 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (List'0.t_list (k, v))))= {[@expl:precondition] [%#span46] inv'14 index}
-    {[@expl:precondition] [%#span45] inv'13 self}
-    {[@expl:precondition] [%#span44] in_bounds'0 index (shallow_model'3 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (List'0.t_list (k, v))))= {[@expl:precondition] [%#span42] inv'14 index}
+    {[@expl:precondition] [%#span41] inv'13 self}
+    {[@expl:precondition] [%#span40] in_bounds'0 index (shallow_model'3 self)}
     any
-    [ return' (result:borrowed (List'0.t_list (k, v)))-> {[%#span51] inv'2 result}
-      {[%#span50] len'1 (shallow_model'4 ( ^ self)) = len'1 (shallow_model'3 self)}
-      {[%#span49] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'4 ( ^ self))}
-      {[%#span48] has_value'0 index (shallow_model'4 ( ^ self)) ( ^ result)}
-      {[%#span47] has_value'0 index (shallow_model'3 self) ( * result)}
+    [ return' (result:borrowed (List'0.t_list (k, v)))-> {[%#span47] inv'2 result}
+      {[%#span46] len'1 (shallow_model'4 ( ^ self)) = len'1 (shallow_model'3 self)}
+      {[%#span45] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'4 ( ^ self))}
+      {[%#span44] has_value'0 index (shallow_model'4 ( ^ self)) ( ^ result)}
+      {[%#span43] has_value'0 index (shallow_model'3 self) ( * result)}
       (! return' {result}) ]
     
   
@@ -890,20 +841,20 @@ module Hashmap_Impl5_Add
   
   use prelude.prelude.UInt64
   
-  let rec hash'0 (self:k) (return'  (ret:uint64))= {[@expl:precondition] [%#span52] inv'12 self}
+  let rec hash'0 (self:k) (return'  (ret:uint64))= {[@expl:precondition] [%#span48] inv'12 self}
     any
-    [ return' (result:uint64)-> {[%#span53] UInt64.to_int result = hash_log'0 (deep_model'1 self)}
+    [ return' (result:uint64)-> {[%#span49] UInt64.to_int result = hash_log'0 (deep_model'1 self)}
       (! return' {result}) ]
     
   
   function shallow_model'2 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (k, v))
     
    =
-    [%#span54] shallow_model'4 self
+    [%#span50] shallow_model'4 self
   
-  let rec len'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span55] inv'11 self}
+  let rec len'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span51] inv'11 self}
     any
-    [ return' (result:usize)-> {[%#span56] UIntSize.to_int result = len'1 (shallow_model'2 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span52] UIntSize.to_int result = len'1 (shallow_model'2 self)} (! return' {result}) ]
     
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot (borrowed (MyHashMap'0.t_myhashmap k v)))
@@ -911,8 +862,8 @@ module Hashmap_Impl5_Add
   function new'0 (x : borrowed (MyHashMap'0.t_myhashmap k v)) : Snapshot'0.t_snapshot (borrowed (MyHashMap'0.t_myhashmap k v))
     
   
-  axiom new'0_spec : forall x : borrowed (MyHashMap'0.t_myhashmap k v) . ([%#span39] inv'10 x)
-   -> ([%#span40] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (MyHashMap'0.t_myhashmap k v) . ([%#span35] inv'10 x)
+   -> ([%#span36] deref'0 (new'0 x) = x)
   
   let rec add (self:borrowed (MyHashMap'0.t_myhashmap k v)) (key:k) (val':v) (return'  (ret:()))= {[%#shashmap11] inv'5 val'}
     {[%#shashmap10] inv'4 key}
@@ -1181,93 +1132,89 @@ module Hashmap_Impl5_Get
   
   let%span span7 = "" 0 0 0 0
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span12 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span14 = "../hashmap.rs" 30 12 33 13
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span15 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span16 = "../hashmap.rs" 90 20 90 66
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span17 = "../hashmap.rs" 85 8 85 53
   
-  let%span span18 = "../hashmap.rs" 30 12 33 13
+  let%span span18 = "../hashmap.rs" 79 20 79 45
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span19 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span20 = "../hashmap.rs" 90 20 90 66
+  let%span span20 = "../hashmap.rs" 40 12 43 13
   
-  let%span span21 = "../hashmap.rs" 85 8 85 53
+  let%span span21 = "../hashmap.rs" 200 8 202 9
   
-  let%span span22 = "../hashmap.rs" 79 20 79 45
+  let%span span22 = "../hashmap.rs" 209 8 212 9
   
-  let%span span23 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span23 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
-  let%span span24 = "../hashmap.rs" 40 12 43 13
+  let%span span24 = "" 0 0 0 0
   
-  let%span span25 = "../hashmap.rs" 200 8 202 9
+  let%span span25 = "" 0 0 0 0
   
-  let%span span26 = "../hashmap.rs" 209 8 212 9
+  let%span span26 = "../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
   
-  let%span span27 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
+  let%span span27 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span28 = "" 0 0 0 0
+  let%span span28 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span29 = "" 0 0 0 0
+  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span30 = "../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
+  let%span span30 = "" 0 0 0 0
   
-  let%span span31 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span31 = "" 0 0 0 0
   
-  let%span span32 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span32 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span33 = "" 0 0 0 0
   
   let%span span34 = "" 0 0 0 0
   
-  let%span span35 = "" 0 0 0 0
+  let%span span35 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span36 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span36 = "../hashmap.rs" 51 13 51 17
   
-  let%span span37 = "" 0 0 0 0
+  let%span span37 = "../hashmap.rs" 50 14 50 58
+  
+  use Hashmap_List_Type as List'0
   
-  let%span span38 = "" 0 0 0 0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span39 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  predicate invariant'12 (self : Seq'0.t_seq (List'0.t_list (k, v)))
   
-  let%span span40 = "../hashmap.rs" 51 13 51 17
+  predicate inv'12 (_x : Seq'0.t_seq (List'0.t_list (k, v)))
   
-  let%span span41 = "../hashmap.rs" 50 14 50 58
+  axiom inv'12 : forall x : Seq'0.t_seq (List'0.t_list (k, v)) . inv'12 x = true
   
   type deep_model_ty'0
   
-  predicate invariant'12 (self : deep_model_ty'0)
-  
-  predicate inv'12 (_x : deep_model_ty'0)
+  predicate invariant'11 (self : deep_model_ty'0)
   
-  axiom inv'12 : forall x : deep_model_ty'0 . inv'12 x = true
+  predicate inv'11 (_x : deep_model_ty'0)
   
-  predicate invariant'11 (self : v)
+  axiom inv'11 : forall x : deep_model_ty'0 . inv'11 x = true
   
-  predicate inv'11 (_x : v)
+  predicate invariant'10 (self : v)
   
-  axiom inv'11 : forall x : v . inv'11 x = true
+  predicate inv'10 (_x : v)
   
-  use Hashmap_List_Type as List'0
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate inv'9 (_x : Seq'0.t_seq (List'0.t_list (k, v)))
+  axiom inv'10 : forall x : v . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1281,46 +1228,35 @@ module Hashmap_Impl5_Get
   
   constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . ([%#span8] inv'9 self)
-   -> ([%#span9] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . [%#span8] len'1 self >= 0
   
-  predicate inv'10 (_x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
+  predicate inv'9 (_x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (k, v))
     
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span10] inv'10 self)
-   -> ([%#span12] inv'9 (shallow_model'2 self))
-  && ([%#span11] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'10 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) =
-    [%#span13] inv'9 (shallow_model'2 self)
-  
-  axiom inv'10 : forall x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . inv'10 x = true
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span9] inv'9 self)
+   -> ([%#span10] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'9 (self : Seq'0.t_seq (List'0.t_list (k, v)))
+  predicate invariant'9 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) =
+    [%#span11] inv'12 (shallow_model'2 self)
   
-  axiom inv'9 : forall x : Seq'0.t_seq (List'0.t_list (k, v)) . inv'9 x = true
+  axiom inv'9 : forall x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . inv'9 x = true
   
   predicate invariant'8 (self : usize) =
-    [%#span14] true
+    [%#span12] true
   
   predicate inv'8 (_x : usize)
   
   axiom inv'8 : forall x : usize . inv'8 x = true
   
-  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v)) = [%#span15] ()
+  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span17] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'1 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'1 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
   
   predicate invariant'7 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
   
@@ -1383,19 +1319,17 @@ module Hashmap_Impl5_Get
   function get'0 [#"../hashmap.rs" 28 4 28 56] (self : List'0.t_list (k, v)) (index : deep_model_ty'0) : Option'0.t_option v
     
    =
-    [%#span18] match self with
+    [%#span14] match self with
       | List'0.C_Nil -> Option'0.C_None
       | List'0.C_Cons (k, v) tl -> if deep_model'0 k = index then Option'0.C_Some v else get'0 tl index
       end
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (x : int) : List'0.t_list (k, v)
+  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (_2 : int) : List'0.t_list (k, v)
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (ix : int) : List'0.t_list (k, v)
     
    =
-    [%#span19] index_logic'1 (shallow_model'2 self) ix
+    [%#span15] index_logic'1 (shallow_model'2 self) ix
   
   use int.EuclideanDivision
   
@@ -1404,27 +1338,27 @@ module Hashmap_Impl5_Get
   function hash_log'0 [#"../hashmap.rs" 54 4 54 45] (_1 : deep_model_ty'0) : int
   
   function bucket_ix'0 [#"../hashmap.rs" 89 4 89 48] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : int =
-    [%#span20] EuclideanDivision.mod (hash_log'0 k) (len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
+    [%#span16] EuclideanDivision.mod (hash_log'0 k) (len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
   
   function bucket'0 [#"../hashmap.rs" 84 4 84 54] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : List'0.t_list (k, v)
     
    =
-    [%#span21] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
+    [%#span17] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
   
   use map.Map
   
   function shallow_model'3 [#"../hashmap.rs" 78 4 78 50] (self : MyHashMap'0.t_myhashmap k v) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span22] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
+    [%#span18] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
   
   use prelude.prelude.Borrow
   
   function shallow_model'0 (self : MyHashMap'0.t_myhashmap k v) : Map.map deep_model_ty'0 (Option'0.t_option v) =
-    [%#span23] shallow_model'3 self
+    [%#span19] shallow_model'3 self
   
   predicate no_double_binding'0 [#"../hashmap.rs" 38 4 38 38] (self : List'0.t_list (k, v)) =
-    [%#span24] match self with
+    [%#span20] match self with
       | List'0.C_Nil -> true
       | List'0.C_Cons (k, _) tl -> get'0 tl (deep_model'0 k) = Option'0.C_None /\ no_double_binding'0 tl
       end
@@ -1432,11 +1366,11 @@ module Hashmap_Impl5_Get
   predicate good_bucket'0 [#"../hashmap.rs" 199 4 199 57] (self : MyHashMap'0.t_myhashmap k v) (l : List'0.t_list (k, v)) (h : int)
     
    =
-    [%#span25] forall v : v . forall k : deep_model_ty'0 . inv'11 v
-     -> inv'12 k  -> get'0 l k = Option'0.C_Some v  -> bucket_ix'0 self k = h
+    [%#span21] forall v : v . forall k : deep_model_ty'0 . inv'10 v
+     -> inv'11 k  -> get'0 l k = Option'0.C_Some v  -> bucket_ix'0 self k = h
   
   predicate hashmap_inv'0 [#"../hashmap.rs" 208 4 208 33] (self : MyHashMap'0.t_myhashmap k v) =
-    [%#span26] 0 < len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
+    [%#span22] 0 < len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
     /\ (forall i : int . 0 <= i /\ i < len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
      -> good_bucket'0 self (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i) i
     /\ no_double_binding'0 (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i))
@@ -1450,11 +1384,11 @@ module Hashmap_Impl5_Get
   predicate resolve'3 (self : v)
   
   function deep_model'1 (self : k) : deep_model_ty'0 =
-    [%#span27] deep_model'0 self
+    [%#span23] deep_model'0 self
   
-  let rec eq'0 (self:k) (other:k) (return'  (ret:bool))= {[@expl:precondition] [%#span29] inv'2 other}
-    {[@expl:precondition] [%#span28] inv'2 self}
-    any [ return' (result:bool)-> {[%#span30] result = (deep_model'1 self = deep_model'1 other)} (! return' {result}) ] 
+  let rec eq'0 (self:k) (other:k) (return'  (ret:bool))= {[@expl:precondition] [%#span25] inv'2 other}
+    {[@expl:precondition] [%#span24] inv'2 self}
+    any [ return' (result:bool)-> {[%#span26] result = (deep_model'1 self = deep_model'1 other)} (! return' {result}) ] 
   
   predicate resolve'2 (self : k)
   
@@ -1465,39 +1399,39 @@ module Hashmap_Impl5_Get
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (List'0.t_list (k, v))) (out : List'0.t_list (k, v))
     
    =
-    [%#span31] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span27] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (List'0.t_list (k, v))) =
-    [%#span32] UIntSize.to_int self < len'1 seq
+    [%#span28] UIntSize.to_int self < len'1 seq
   
   function shallow_model'1 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (k, v))
     
    =
-    [%#span23] shallow_model'2 self
+    [%#span19] shallow_model'2 self
   
-  let rec index'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (index:usize) (return'  (ret:List'0.t_list (k, v)))= {[@expl:precondition] [%#span35] inv'8 index}
-    {[@expl:precondition] [%#span34] inv'7 self}
-    {[@expl:precondition] [%#span33] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (index:usize) (return'  (ret:List'0.t_list (k, v)))= {[@expl:precondition] [%#span31] inv'8 index}
+    {[@expl:precondition] [%#span30] inv'7 self}
+    {[@expl:precondition] [%#span29] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:List'0.t_list (k, v))-> {[%#span37] inv'1 result}
-      {[%#span36] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:List'0.t_list (k, v))-> {[%#span33] inv'1 result}
+      {[%#span32] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
   predicate resolve'0 (self : MyHashMap'0.t_myhashmap k v)
   
-  let rec len'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span38] inv'7 self}
+  let rec len'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span34] inv'7 self}
     any
-    [ return' (result:usize)-> {[%#span39] UIntSize.to_int result = len'1 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span35] UIntSize.to_int result = len'1 (shallow_model'1 self)} (! return' {result}) ]
     
   
   use prelude.prelude.UInt64
   
   use prelude.prelude.UInt64
   
-  let rec hash'0 (self:k) (return'  (ret:uint64))= {[@expl:precondition] [%#span40] inv'2 self}
+  let rec hash'0 (self:k) (return'  (ret:uint64))= {[@expl:precondition] [%#span36] inv'2 self}
     any
-    [ return' (result:uint64)-> {[%#span41] UInt64.to_int result = hash_log'0 (deep_model'1 self)}
+    [ return' (result:uint64)-> {[%#span37] UInt64.to_int result = hash_log'0 (deep_model'1 self)}
       (! return' {result}) ]
     
   
@@ -1659,140 +1593,132 @@ module Hashmap_Impl5_Resize
   
   let%span span19 = "" 0 0 0 0
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span21 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span25 = "../hashmap.rs" 30 12 33 13
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span26 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span27 = "../hashmap.rs" 90 20 90 66
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span28 = "../hashmap.rs" 85 8 85 53
   
-  let%span span29 = "../hashmap.rs" 30 12 33 13
+  let%span span29 = "../hashmap.rs" 79 20 79 45
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span30 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span31 = "../hashmap.rs" 90 20 90 66
+  let%span span31 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span32 = "../hashmap.rs" 85 8 85 53
+  let%span span32 = "../../../../creusot-contracts/src/resolve.rs" 35 8 35 31
   
-  let%span span33 = "../hashmap.rs" 79 20 79 45
+  let%span span33 = "../hashmap.rs" 40 12 43 13
   
-  let%span span34 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span34 = "../hashmap.rs" 200 8 202 9
   
-  let%span span35 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span35 = "../hashmap.rs" 209 8 212 9
   
-  let%span span36 = "../../../../creusot-contracts/src/resolve.rs" 35 8 35 31
+  let%span span36 = "../hashmap.rs" 103 15 103 36
   
-  let%span span37 = "../hashmap.rs" 40 12 43 13
+  let%span span37 = "../hashmap.rs" 106 20 106 24
   
-  let%span span38 = "../hashmap.rs" 200 8 202 9
+  let%span span38 = "../hashmap.rs" 106 26 106 29
   
-  let%span span39 = "../hashmap.rs" 209 8 212 9
+  let%span span39 = "../hashmap.rs" 106 34 106 37
   
-  let%span span40 = "../hashmap.rs" 103 15 103 36
+  let%span span40 = "../hashmap.rs" 104 14 104 35
   
-  let%span span41 = "../hashmap.rs" 106 20 106 24
+  let%span span41 = "../hashmap.rs" 105 4 105 124
   
-  let%span span42 = "../hashmap.rs" 106 26 106 29
+  let%span span42 = "" 0 0 0 0
   
-  let%span span43 = "../hashmap.rs" 106 34 106 37
+  let%span span43 = "" 0 0 0 0
   
-  let%span span44 = "../hashmap.rs" 104 14 104 35
+  let%span span44 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
   
-  let%span span45 = "../hashmap.rs" 105 4 105 124
+  let%span span45 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
   
   let%span span46 = "" 0 0 0 0
   
-  let%span span47 = "" 0 0 0 0
+  let%span span47 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span48 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
+  let%span span48 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span49 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
+  let%span span49 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span50 = "" 0 0 0 0
+  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span51 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span51 = "" 0 0 0 0
   
-  let%span span52 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span52 = "" 0 0 0 0
   
-  let%span span53 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span55 = "" 0 0 0 0
+  let%span span55 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span56 = "" 0 0 0 0
+  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span57 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span57 = "" 0 0 0 0
   
-  let%span span58 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span58 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span59 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span59 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span60 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span60 = "../hashmap.rs" 95 15 95 24
   
-  let%span span61 = "" 0 0 0 0
+  let%span span61 = "../hashmap.rs" 96 14 96 34
   
-  let%span span62 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span62 = "../hashmap.rs" 97 4 97 64
   
-  let%span span63 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
+  let%span span63 = "../hashmap.rs" 98 31 98 46
   
-  let%span span64 = "../hashmap.rs" 95 15 95 24
+  let%span span64 = "" 0 0 0 0
   
-  let%span span65 = "../hashmap.rs" 96 14 96 34
+  let%span span65 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span66 = "../hashmap.rs" 97 4 97 64
+  let%span span66 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span67 = "../hashmap.rs" 98 31 98 46
+  let%span span67 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span68 = "" 0 0 0 0
+  use Hashmap_List_Type as List'0
   
-  let%span span69 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  
+  predicate invariant'12 (self : Seq'0.t_seq (List'0.t_list (k, v)))
   
-  let%span span70 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  predicate inv'12 (_x : Seq'0.t_seq (List'0.t_list (k, v)))
   
-  let%span span71 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  axiom inv'12 : forall x : Seq'0.t_seq (List'0.t_list (k, v)) . inv'12 x = true
   
   use prelude.prelude.UIntSize
   
-  predicate invariant'12 (self : usize) =
+  predicate invariant'11 (self : usize) =
     [%#span18] true
   
-  predicate inv'12 (_x : usize)
+  predicate inv'11 (_x : usize)
   
-  axiom inv'12 : forall x : usize . inv'12 x = true
+  axiom inv'11 : forall x : usize . inv'11 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
-  use Hashmap_List_Type as List'0
-  
   use Alloc_Vec_Vec_Type as Vec'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'11 (self : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)))
-  
-  predicate inv'11 (_x : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)))
+  predicate invariant'10 (self : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)))
   
-  axiom inv'11 : forall x : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) . inv'11 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'10 (_x : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)))
   
-  predicate invariant'10 (self : Seq'0.t_seq (List'0.t_list (k, v)))
-  
-  predicate inv'10 (_x : Seq'0.t_seq (List'0.t_list (k, v)))
-  
-  axiom inv'10 : forall x : Seq'0.t_seq (List'0.t_list (k, v)) . inv'10 x = true
+  axiom inv'10 : forall x : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) . inv'10 x = true
   
   predicate invariant'9 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
   
@@ -1850,35 +1776,28 @@ module Hashmap_Impl5_Resize
   
   constant max'0 : usize = [%#span19] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . ([%#span20] inv'10 self)
-   -> ([%#span21] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (List'0.t_list (k, v)) . [%#span20] len'1 self >= 0
   
   predicate inv'1 (_x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (k, v))
     
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span22] inv'1 self)
-   -> ([%#span24] inv'10 (shallow_model'2 self))
-  && ([%#span23] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . ([%#span21] inv'1 self)
+   -> ([%#span22] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) =
-    [%#span25] inv'10 (shallow_model'2 self)
+    [%#span23] inv'12 (shallow_model'2 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global) . inv'1 x = true
   
-  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v)) = [%#span26] ()
+  constant empty'0 : Seq'0.t_seq (List'0.t_list (k, v))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span28] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span27] len'1 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span24] len'1 (empty'0 : Seq'0.t_seq (List'0.t_list (k, v))) = 0
   
   type deep_model_ty'0
   
@@ -1897,19 +1816,17 @@ module Hashmap_Impl5_Resize
   function get'0 [#"../hashmap.rs" 28 4 28 56] (self : List'0.t_list (k, v)) (index : deep_model_ty'0) : Option'0.t_option v
     
    =
-    [%#span29] match self with
+    [%#span25] match self with
       | List'0.C_Nil -> Option'0.C_None
       | List'0.C_Cons (k, v) tl -> if deep_model'0 k = index then Option'0.C_Some v else get'0 tl index
       end
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (x : int) : List'0.t_list (k, v)
+  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (k, v))) (_2 : int) : List'0.t_list (k, v)
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (ix : int) : List'0.t_list (k, v)
     
    =
-    [%#span30] index_logic'1 (shallow_model'2 self) ix
+    [%#span26] index_logic'1 (shallow_model'2 self) ix
   
   use int.EuclideanDivision
   
@@ -1918,43 +1835,43 @@ module Hashmap_Impl5_Resize
   function hash_log'0 [#"../hashmap.rs" 54 4 54 45] (_1 : deep_model_ty'0) : int
   
   function bucket_ix'0 [#"../hashmap.rs" 89 4 89 48] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : int =
-    [%#span31] EuclideanDivision.mod (hash_log'0 k) (len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
+    [%#span27] EuclideanDivision.mod (hash_log'0 k) (len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
   
   function bucket'0 [#"../hashmap.rs" 84 4 84 54] (self : MyHashMap'0.t_myhashmap k v) (k : deep_model_ty'0) : List'0.t_list (k, v)
     
    =
-    [%#span32] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
+    [%#span28] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
   
   use map.Map
   
   function shallow_model'1 [#"../hashmap.rs" 78 4 78 50] (self : MyHashMap'0.t_myhashmap k v) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span33] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
+    [%#span29] Mapping.from_fn (fun (k : deep_model_ty'0) -> get'0 (bucket'0 self k) k)
   
   function shallow_model'3 (self : borrowed (MyHashMap'0.t_myhashmap k v)) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span34] shallow_model'1 ( * self)
+    [%#span30] shallow_model'1 ( * self)
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'7 (self : borrowed (MyHashMap'0.t_myhashmap k v)) =
-    [%#span35]  ^ self =  * self
+    [%#span31]  ^ self =  * self
   
   predicate resolve'6 (self : MyHashMap'0.t_myhashmap k v)
   
   predicate resolve'2 (self : List'0.t_list (k, v))
   
   predicate resolve'5 (self : List'0.t_list (k, v)) =
-    [%#span36] resolve'2 self
+    [%#span32] resolve'2 self
   
   use map.Map
   
   predicate no_double_binding'0 [#"../hashmap.rs" 38 4 38 38] (self : List'0.t_list (k, v)) =
-    [%#span37] match self with
+    [%#span33] match self with
       | List'0.C_Nil -> true
       | List'0.C_Cons (k, _) tl -> get'0 tl (deep_model'0 k) = Option'0.C_None /\ no_double_binding'0 tl
       end
@@ -1962,24 +1879,24 @@ module Hashmap_Impl5_Resize
   predicate good_bucket'0 [#"../hashmap.rs" 199 4 199 57] (self : MyHashMap'0.t_myhashmap k v) (l : List'0.t_list (k, v)) (h : int)
     
    =
-    [%#span38] forall v : v . forall k : deep_model_ty'0 . inv'6 v
+    [%#span34] forall v : v . forall k : deep_model_ty'0 . inv'6 v
      -> inv'0 k  -> get'0 l k = Option'0.C_Some v  -> bucket_ix'0 self k = h
   
   predicate hashmap_inv'0 [#"../hashmap.rs" 208 4 208 33] (self : MyHashMap'0.t_myhashmap k v) =
-    [%#span39] 0 < len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
+    [%#span35] 0 < len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
     /\ (forall i : int . 0 <= i /\ i < len'1 (shallow_model'2 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
      -> good_bucket'0 self (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i) i
     /\ no_double_binding'0 (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i))
   
-  let rec add'0 (self:borrowed (MyHashMap'0.t_myhashmap k v)) (key:k) (val':v) (return'  (ret:()))= {[@expl:precondition] [%#span43] inv'6 val'}
-    {[@expl:precondition] [%#span42] inv'5 key}
-    {[@expl:precondition] [%#span41] inv'8 self}
-    {[@expl:precondition] [%#span40] hashmap_inv'0 ( * self)}
+  let rec add'0 (self:borrowed (MyHashMap'0.t_myhashmap k v)) (key:k) (val':v) (return'  (ret:()))= {[@expl:precondition] [%#span39] inv'6 val'}
+    {[@expl:precondition] [%#span38] inv'5 key}
+    {[@expl:precondition] [%#span37] inv'8 self}
+    {[@expl:precondition] [%#span36] hashmap_inv'0 ( * self)}
     any
-    [ return' (result:())-> {[%#span45] forall i : deep_model_ty'0 . inv'0 i
+    [ return' (result:())-> {[%#span41] forall i : deep_model_ty'0 . inv'0 i
        -> Map.get (shallow_model'1 ( ^ self)) i
       = (if i = deep_model'0 key then Option'0.C_Some val' else Map.get (shallow_model'3 self) i)}
-      {[%#span44] hashmap_inv'0 ( ^ self)}
+      {[%#span40] hashmap_inv'0 ( ^ self)}
       (! return' {result}) ]
     
   
@@ -1988,14 +1905,14 @@ module Hashmap_Impl5_Resize
   predicate resolve'3 (self : k)
   
   predicate resolve'1 (self : borrowed (List'0.t_list (k, v))) =
-    [%#span35]  ^ self =  * self
+    [%#span31]  ^ self =  * self
   
-  let rec replace'0 (dest:borrowed (List'0.t_list (k, v))) (src:List'0.t_list (k, v)) (return'  (ret:List'0.t_list (k, v)))= {[@expl:precondition] [%#span47] inv'2 src}
-    {[@expl:precondition] [%#span46] inv'3 dest}
+  let rec replace'0 (dest:borrowed (List'0.t_list (k, v))) (src:List'0.t_list (k, v)) (return'  (ret:List'0.t_list (k, v)))= {[@expl:precondition] [%#span43] inv'2 src}
+    {[@expl:precondition] [%#span42] inv'3 dest}
     any
-    [ return' (result:List'0.t_list (k, v))-> {[%#span50] inv'2 result}
-      {[%#span49] result =  * dest}
-      {[%#span48]  ^ dest = src}
+    [ return' (result:List'0.t_list (k, v))-> {[%#span46] inv'2 result}
+      {[%#span45] result =  * dest}
+      {[%#span44]  ^ dest = src}
       (! return' {result}) ]
     
   
@@ -2004,38 +1921,38 @@ module Hashmap_Impl5_Resize
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq (List'0.t_list (k, v))) (fin : Seq'0.t_seq (List'0.t_list (k, v)))
     
    =
-    [%#span51] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
+    [%#span47] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
      -> index_logic'1 old' i = index_logic'1 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (List'0.t_list (k, v))) (out : List'0.t_list (k, v))
     
    =
-    [%#span52] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span48] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (List'0.t_list (k, v))) =
-    [%#span53] UIntSize.to_int self < len'1 seq
+    [%#span49] UIntSize.to_int self < len'1 seq
   
   function shallow_model'6 (self : borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))) : Seq'0.t_seq (List'0.t_list (k, v))
     
    =
-    [%#span34] shallow_model'2 ( * self)
+    [%#span30] shallow_model'2 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (List'0.t_list (k, v))))= {[@expl:precondition] [%#span56] inv'12 index}
-    {[@expl:precondition] [%#span55] inv'11 self}
-    {[@expl:precondition] [%#span54] in_bounds'0 index (shallow_model'6 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (List'0.t_list (k, v))))= {[@expl:precondition] [%#span52] inv'11 index}
+    {[@expl:precondition] [%#span51] inv'10 self}
+    {[@expl:precondition] [%#span50] in_bounds'0 index (shallow_model'6 self)}
     any
-    [ return' (result:borrowed (List'0.t_list (k, v)))-> {[%#span61] inv'3 result}
-      {[%#span60] len'1 (shallow_model'2 ( ^ self)) = len'1 (shallow_model'6 self)}
-      {[%#span59] resolve_elswhere'0 index (shallow_model'6 self) (shallow_model'2 ( ^ self))}
-      {[%#span58] has_value'0 index (shallow_model'2 ( ^ self)) ( ^ result)}
-      {[%#span57] has_value'0 index (shallow_model'6 self) ( * result)}
+    [ return' (result:borrowed (List'0.t_list (k, v)))-> {[%#span57] inv'3 result}
+      {[%#span56] len'1 (shallow_model'2 ( ^ self)) = len'1 (shallow_model'6 self)}
+      {[%#span55] resolve_elswhere'0 index (shallow_model'6 self) (shallow_model'2 ( ^ self))}
+      {[%#span54] has_value'0 index (shallow_model'2 ( ^ self)) ( ^ result)}
+      {[%#span53] has_value'0 index (shallow_model'6 self) ( * result)}
       (! return' {result}) ]
     
   
   function shallow_model'5 (self : borrowed (MyHashMap'0.t_myhashmap k v)) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span62] shallow_model'3 self
+    [%#span58] shallow_model'3 self
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (MyHashMap'0.t_myhashmap k v))) : borrowed (MyHashMap'0.t_myhashmap k v)
     
@@ -2043,25 +1960,25 @@ module Hashmap_Impl5_Resize
   function shallow_model'0 (self : Snapshot'0.t_snapshot (borrowed (MyHashMap'0.t_myhashmap k v))) : Map.map deep_model_ty'0 (Option'0.t_option v)
     
    =
-    [%#span63] shallow_model'5 (deref'0 self)
+    [%#span59] shallow_model'5 (deref'0 self)
   
-  let rec new'1 (size:usize) (return'  (ret:MyHashMap'0.t_myhashmap k v))= {[@expl:precondition] [%#span64] 0
+  let rec new'1 (size:usize) (return'  (ret:MyHashMap'0.t_myhashmap k v))= {[@expl:precondition] [%#span60] 0
     < UIntSize.to_int size}
     any
-    [ return' (result:MyHashMap'0.t_myhashmap k v)-> {[%#span67] inv'4 result}
-      {[%#span66] forall i : deep_model_ty'0 . inv'0 i  -> Map.get (shallow_model'1 result) i = Option'0.C_None}
-      {[%#span65] hashmap_inv'0 result}
+    [ return' (result:MyHashMap'0.t_myhashmap k v)-> {[%#span63] inv'4 result}
+      {[%#span62] forall i : deep_model_ty'0 . inv'0 i  -> Map.get (shallow_model'1 result) i = Option'0.C_None}
+      {[%#span61] hashmap_inv'0 result}
       (! return' {result}) ]
     
   
   function shallow_model'4 (self : Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (k, v))
     
    =
-    [%#span62] shallow_model'2 self
+    [%#span58] shallow_model'2 self
   
-  let rec len'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span68] inv'9 self}
+  let rec len'0 (self:Vec'0.t_vec (List'0.t_list (k, v)) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span64] inv'9 self}
     any
-    [ return' (result:usize)-> {[%#span69] UIntSize.to_int result = len'1 (shallow_model'4 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span65] UIntSize.to_int result = len'1 (shallow_model'4 self)} (! return' {result}) ]
     
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot (borrowed (MyHashMap'0.t_myhashmap k v)))
@@ -2069,8 +1986,8 @@ module Hashmap_Impl5_Resize
   function new'0 (x : borrowed (MyHashMap'0.t_myhashmap k v)) : Snapshot'0.t_snapshot (borrowed (MyHashMap'0.t_myhashmap k v))
     
   
-  axiom new'0_spec : forall x : borrowed (MyHashMap'0.t_myhashmap k v) . ([%#span70] inv'8 x)
-   -> ([%#span71] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (MyHashMap'0.t_myhashmap k v) . ([%#span66] inv'8 x)
+   -> ([%#span67] deref'0 (new'0 x) = x)
   
   let rec resize (self:borrowed (MyHashMap'0.t_myhashmap k v)) (return'  (ret:()))= {[%#shashmap15] inv'8 self}
     {[%#shashmap14] hashmap_inv'0 ( * self)}
@@ -2321,77 +2238,69 @@ module Hashmap_Main
   
   let%span span19 = "" 0 0 0 0
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span21 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span29 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span25 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span30 = "../hashmap.rs" 30 12 33 13
+  let%span span26 = "../hashmap.rs" 30 12 33 13
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span27 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span32 = "../hashmap.rs" 65 20 65 21
+  let%span span28 = "../hashmap.rs" 65 20 65 21
   
-  let%span span33 = "../hashmap.rs" 90 20 90 66
+  let%span span29 = "../hashmap.rs" 90 20 90 66
   
-  let%span span34 = "../hashmap.rs" 85 8 85 53
+  let%span span30 = "../hashmap.rs" 85 8 85 53
   
-  let%span span35 = "../hashmap.rs" 79 20 79 45
+  let%span span31 = "../hashmap.rs" 79 20 79 45
   
-  let%span span36 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span32 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span37 = "../hashmap.rs" 40 12 43 13
+  let%span span33 = "../hashmap.rs" 40 12 43 13
   
-  let%span span38 = "../hashmap.rs" 200 8 202 9
+  let%span span34 = "../hashmap.rs" 200 8 202 9
   
-  let%span span39 = "../hashmap.rs" 209 8 212 9
+  let%span span35 = "../hashmap.rs" 209 8 212 9
   
-  let%span span40 = "../hashmap.rs" 103 15 103 36
+  let%span span36 = "../hashmap.rs" 103 15 103 36
   
-  let%span span41 = "../hashmap.rs" 106 20 106 24
+  let%span span37 = "../hashmap.rs" 106 20 106 24
   
-  let%span span42 = "../hashmap.rs" 106 26 106 29
+  let%span span38 = "../hashmap.rs" 106 26 106 29
   
-  let%span span43 = "../hashmap.rs" 106 34 106 37
+  let%span span39 = "../hashmap.rs" 106 34 106 37
   
-  let%span span44 = "../hashmap.rs" 104 14 104 35
+  let%span span40 = "../hashmap.rs" 104 14 104 35
   
-  let%span span45 = "../hashmap.rs" 105 4 105 124
+  let%span span41 = "../hashmap.rs" 105 4 105 124
   
-  let%span span46 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span42 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span47 = "../hashmap.rs" 136 15 136 33
+  let%span span43 = "../hashmap.rs" 136 15 136 33
   
-  let%span span48 = "../hashmap.rs" 141 16 141 20
+  let%span span44 = "../hashmap.rs" 141 16 141 20
   
-  let%span span49 = "../hashmap.rs" 141 22 141 25
+  let%span span45 = "../hashmap.rs" 141 22 141 25
   
-  let%span span50 = "../hashmap.rs" 137 14 140 5
+  let%span span46 = "../hashmap.rs" 137 14 140 5
   
-  let%span span51 = "../hashmap.rs" 141 33 141 43
+  let%span span47 = "../hashmap.rs" 141 33 141 43
   
-  let%span span52 = "../hashmap.rs" 95 15 95 24
+  let%span span48 = "../hashmap.rs" 95 15 95 24
   
-  let%span span53 = "../hashmap.rs" 96 14 96 34
+  let%span span49 = "../hashmap.rs" 96 14 96 34
   
-  let%span span54 = "../hashmap.rs" 97 4 97 64
+  let%span span50 = "../hashmap.rs" 97 4 97 64
   
-  let%span span55 = "../hashmap.rs" 98 31 98 46
+  let%span span51 = "../hashmap.rs" 98 31 98 46
   
   use prelude.prelude.IntSize
   
@@ -2418,35 +2327,28 @@ module Hashmap_Main
   
   constant max'0 : usize = [%#span19] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq (List'0.t_list (usize, isize))) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (List'0.t_list (usize, isize)) . ([%#span20] inv'8 self)
-   -> ([%#span21] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (List'0.t_list (usize, isize)) . [%#span20] len'0 self >= 0
   
   predicate inv'7 (_x : Vec'0.t_vec (List'0.t_list (usize, isize)) (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec (List'0.t_list (usize, isize)) (Global'0.t_global)) : Seq'0.t_seq (List'0.t_list (usize, isize))
     
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec (List'0.t_list (usize, isize)) (Global'0.t_global) . ([%#span22] inv'7 self)
-   -> ([%#span24] inv'8 (shallow_model'3 self))
-  && ([%#span23] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec (List'0.t_list (usize, isize)) (Global'0.t_global) . ([%#span21] inv'7 self)
+   -> ([%#span22] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'7 (self : Vec'0.t_vec (List'0.t_list (usize, isize)) (Global'0.t_global)) =
-    [%#span25] inv'8 (shallow_model'3 self)
+    [%#span23] inv'8 (shallow_model'3 self)
   
   axiom inv'7 : forall x : Vec'0.t_vec (List'0.t_list (usize, isize)) (Global'0.t_global) . inv'7 x = true
   
-  constant empty'0 : Seq'0.t_seq (List'0.t_list (usize, isize)) = [%#span26] ()
+  constant empty'0 : Seq'0.t_seq (List'0.t_list (usize, isize))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span28] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span27] len'0 (empty'0 : Seq'0.t_seq (List'0.t_list (usize, isize))) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span24] len'0 (empty'0 : Seq'0.t_seq (List'0.t_list (usize, isize))) = 0
   
   predicate invariant'6 (self : isize) =
     [%#span18] true
@@ -2512,54 +2414,52 @@ module Hashmap_Main
   use prelude.prelude.Mapping
   
   function deep_model'0 (self : usize) : int =
-    [%#span29] UIntSize.to_int self
+    [%#span25] UIntSize.to_int self
   
   function get'1 [#"../hashmap.rs" 28 4 28 56] (self : List'0.t_list (usize, isize)) (index : int) : Option'0.t_option isize
     
    =
-    [%#span30] match self with
+    [%#span26] match self with
       | List'0.C_Nil -> Option'0.C_None
       | List'0.C_Cons (k, v) tl -> if deep_model'0 k = index then Option'0.C_Some v else get'1 tl index
       end
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (usize, isize))) (x : int) : List'0.t_list (usize, isize)
+  function index_logic'1 (self : Seq'0.t_seq (List'0.t_list (usize, isize))) (_2 : int) : List'0.t_list (usize, isize)
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (List'0.t_list (usize, isize)) (Global'0.t_global)) (ix : int) : List'0.t_list (usize, isize)
     
    =
-    [%#span31] index_logic'1 (shallow_model'3 self) ix
+    [%#span27] index_logic'1 (shallow_model'3 self) ix
   
   use int.EuclideanDivision
   
   use Hashmap_MyHashMap_Type as Hashmap_MyHashMap_Type
   
   function hash_log'0 [#"../hashmap.rs" 64 4 64 30] (x : int) : int =
-    [%#span32] x
+    [%#span28] x
   
   function bucket_ix'0 [#"../hashmap.rs" 89 4 89 48] (self : MyHashMap'0.t_myhashmap usize isize) (k : int) : int =
-    [%#span33] EuclideanDivision.mod (hash_log'0 k) (len'0 (shallow_model'3 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
+    [%#span29] EuclideanDivision.mod (hash_log'0 k) (len'0 (shallow_model'3 (Hashmap_MyHashMap_Type.myhashmap_buckets self)))
   
   function bucket'0 [#"../hashmap.rs" 84 4 84 54] (self : MyHashMap'0.t_myhashmap usize isize) (k : int) : List'0.t_list (usize, isize)
     
    =
-    [%#span34] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
+    [%#span30] index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) (bucket_ix'0 self k)
   
   function shallow_model'0 [#"../hashmap.rs" 78 4 78 50] (self : MyHashMap'0.t_myhashmap usize isize) : Map.map int (Option'0.t_option isize)
     
    =
-    [%#span35] Mapping.from_fn (fun (k : int) -> get'1 (bucket'0 self k) k)
+    [%#span31] Mapping.from_fn (fun (k : int) -> get'1 (bucket'0 self k) k)
   
   function shallow_model'2 (self : borrowed (MyHashMap'0.t_myhashmap usize isize)) : Map.map int (Option'0.t_option isize)
     
    =
-    [%#span36] shallow_model'0 ( * self)
+    [%#span32] shallow_model'0 ( * self)
   
   use map.Map
   
   predicate no_double_binding'0 [#"../hashmap.rs" 38 4 38 38] (self : List'0.t_list (usize, isize)) =
-    [%#span37] match self with
+    [%#span33] match self with
       | List'0.C_Nil -> true
       | List'0.C_Cons (k, _) tl -> get'1 tl (deep_model'0 k) = Option'0.C_None /\ no_double_binding'0 tl
       end
@@ -2567,48 +2467,48 @@ module Hashmap_Main
   predicate good_bucket'0 [#"../hashmap.rs" 199 4 199 57] (self : MyHashMap'0.t_myhashmap usize isize) (l : List'0.t_list (usize, isize)) (h : int)
     
    =
-    [%#span38] forall v : isize . forall k : int . inv'6 v
+    [%#span34] forall v : isize . forall k : int . inv'6 v
      -> inv'0 k  -> get'1 l k = Option'0.C_Some v  -> bucket_ix'0 self k = h
   
   predicate hashmap_inv'0 [#"../hashmap.rs" 208 4 208 33] (self : MyHashMap'0.t_myhashmap usize isize) =
-    [%#span39] 0 < len'0 (shallow_model'3 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
+    [%#span35] 0 < len'0 (shallow_model'3 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
     /\ (forall i : int . 0 <= i /\ i < len'0 (shallow_model'3 (Hashmap_MyHashMap_Type.myhashmap_buckets self))
      -> good_bucket'0 self (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i) i
     /\ no_double_binding'0 (index_logic'0 (Hashmap_MyHashMap_Type.myhashmap_buckets self) i))
   
-  let rec add'0 (self:borrowed (MyHashMap'0.t_myhashmap usize isize)) (key:usize) (val':isize) (return'  (ret:()))= {[@expl:precondition] [%#span43] inv'6 val'}
-    {[@expl:precondition] [%#span42] inv'3 key}
-    {[@expl:precondition] [%#span41] inv'5 self}
-    {[@expl:precondition] [%#span40] hashmap_inv'0 ( * self)}
+  let rec add'0 (self:borrowed (MyHashMap'0.t_myhashmap usize isize)) (key:usize) (val':isize) (return'  (ret:()))= {[@expl:precondition] [%#span39] inv'6 val'}
+    {[@expl:precondition] [%#span38] inv'3 key}
+    {[@expl:precondition] [%#span37] inv'5 self}
+    {[@expl:precondition] [%#span36] hashmap_inv'0 ( * self)}
     any
-    [ return' (result:())-> {[%#span45] forall i : int . inv'0 i
+    [ return' (result:())-> {[%#span41] forall i : int . inv'0 i
        -> Map.get (shallow_model'0 ( ^ self)) i
       = (if i = deep_model'0 key then Option'0.C_Some val' else Map.get (shallow_model'2 self) i)}
-      {[%#span44] hashmap_inv'0 ( ^ self)}
+      {[%#span40] hashmap_inv'0 ( ^ self)}
       (! return' {result}) ]
     
   
   function shallow_model'1 (self : MyHashMap'0.t_myhashmap usize isize) : Map.map int (Option'0.t_option isize) =
-    [%#span46] shallow_model'0 self
+    [%#span42] shallow_model'0 self
   
-  let rec get'0 (self:MyHashMap'0.t_myhashmap usize isize) (key:usize) (return'  (ret:Option'0.t_option isize))= {[@expl:precondition] [%#span49] inv'3 key}
-    {[@expl:precondition] [%#span48] inv'2 self}
-    {[@expl:precondition] [%#span47] hashmap_inv'0 self}
+  let rec get'0 (self:MyHashMap'0.t_myhashmap usize isize) (key:usize) (return'  (ret:Option'0.t_option isize))= {[@expl:precondition] [%#span45] inv'3 key}
+    {[@expl:precondition] [%#span44] inv'2 self}
+    {[@expl:precondition] [%#span43] hashmap_inv'0 self}
     any
-    [ return' (result:Option'0.t_option isize)-> {[%#span51] inv'4 result}
-      {[%#span50] match result with
+    [ return' (result:Option'0.t_option isize)-> {[%#span47] inv'4 result}
+      {[%#span46] match result with
         | Option'0.C_Some v -> Map.get (shallow_model'1 self) (deep_model'0 key) = Option'0.C_Some v
         | Option'0.C_None -> Map.get (shallow_model'1 self) (deep_model'0 key) = Option'0.C_None
         end}
       (! return' {result}) ]
     
   
-  let rec new'0 (size:usize) (return'  (ret:MyHashMap'0.t_myhashmap usize isize))= {[@expl:precondition] [%#span52] 0
+  let rec new'0 (size:usize) (return'  (ret:MyHashMap'0.t_myhashmap usize isize))= {[@expl:precondition] [%#span48] 0
     < UIntSize.to_int size}
     any
-    [ return' (result:MyHashMap'0.t_myhashmap usize isize)-> {[%#span55] inv'1 result}
-      {[%#span54] forall i : int . inv'0 i  -> Map.get (shallow_model'0 result) i = Option'0.C_None}
-      {[%#span53] hashmap_inv'0 result}
+    [ return' (result:MyHashMap'0.t_myhashmap usize isize)-> {[%#span51] inv'1 result}
+      {[%#span50] forall i : int . inv'0 i  -> Map.get (shallow_model'0 result) i = Option'0.C_None}
+      {[%#span49] hashmap_inv'0 result}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/hillel.coma b/creusot/tests/should_succeed/hillel.coma
index 14f8e1552d..99752ab4b6 100644
--- a/creusot/tests/should_succeed/hillel.coma
+++ b/creusot/tests/should_succeed/hillel.coma
@@ -3,22 +3,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Ptr_NonNull_NonNull_Type
   use prelude.prelude.Opaque
@@ -150,85 +135,69 @@ module Hillel_RightPad
   
   let%span span12 = "" 0 0 0 0
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span16 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span17 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span16 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span18 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span18 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span22 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span25 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span26 = "" 0 0 0 0
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span27 = "" 0 0 0 0
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span29 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span30 = "" 0 0 0 0
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span31 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span33 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span32 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span34 = "" 0 0 0 0
+  let%span span33 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span35 = "" 0 0 0 0
+  let%span span34 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span36 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span35 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span37 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span38 = "" 0 0 0 0
-  
-  let%span span39 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
-  
-  let%span span40 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span41 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
+  predicate invariant'4 (self : Seq'0.t_seq t)
   
-  let%span span42 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  predicate inv'4 (_x : Seq'0.t_seq t)
   
-  let%span span43 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  axiom inv'4 : forall x : Seq'0.t_seq t . inv'4 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
   use Alloc_Vec_Vec_Type as Vec'0
   
-  predicate invariant'4 (self : Vec'0.t_vec t (Global'0.t_global))
+  predicate invariant'3 (self : Vec'0.t_vec t (Global'0.t_global))
   
-  predicate inv'4 (_x : Vec'0.t_vec t (Global'0.t_global))
+  predicate inv'3 (_x : Vec'0.t_vec t (Global'0.t_global))
   
-  axiom inv'4 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'4 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'3 (self : Seq'0.t_seq t)
-  
-  predicate inv'3 (_x : Seq'0.t_seq t)
-  
-  axiom inv'3 : forall x : Seq'0.t_seq t . inv'3 x = true
+  axiom inv'3 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'3 x = true
   
   use prelude.prelude.Borrow
   
@@ -252,108 +221,93 @@ module Hillel_RightPad
   
   constant max'0 : usize = [%#span12] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span13] inv'3 self)  -> ([%#span14] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span13] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span15] inv'0 self)
-   -> ([%#span17] inv'3 (shallow_model'2 self))
-  && ([%#span16] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span14] inv'0 self)
+   -> ([%#span15] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span18] inv'3 (shallow_model'2 self)
+    [%#span16] inv'4 (shallow_model'2 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq t = [%#span19] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span21] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span22]  ^ self =  * self
+    [%#span18]  ^ self =  * self
   
   predicate resolve'1 (self : t)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span23] inv'3 self)
-   -> ([%#span24] inv'3 other)
-   -> ([%#span27] inv'3 (concat'0 self other))
-  && ([%#span26] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span20] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span25] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span19] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span28] inv'1 v)
-   -> ([%#span31] inv'3 (singleton'0 v))
-  && ([%#span30] index_logic'1 (singleton'0 v) 0 = v) && ([%#span29] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span21] inv'1 v)
+   -> ([%#span23] index_logic'1 (singleton'0 v) 0 = v) && ([%#span22] len'0 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq t) (v : t) : Seq'0.t_seq t =
-    [%#span32] concat'0 self (singleton'0 v)
+    [%#span24] concat'0 self (singleton'0 v)
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span33] shallow_model'2 ( * self)
+    [%#span25] shallow_model'2 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (value:t) (return'  (ret:()))= {[@expl:precondition] [%#span35] inv'1 value}
-    {[@expl:precondition] [%#span34] inv'2 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (value:t) (return'  (ret:()))= {[@expl:precondition] [%#span27] inv'1 value}
+    {[@expl:precondition] [%#span26] inv'2 self}
     any
-    [ return' (result:())-> {[%#span36] shallow_model'2 ( ^ self) = push'1 (shallow_model'1 self) value}
+    [ return' (result:())-> {[%#span28] shallow_model'2 ( ^ self) = push'1 (shallow_model'1 self) value}
       (! return' {result}) ]
     
   
   function shallow_model'4 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t =
-    [%#span37] shallow_model'2 self
+    [%#span29] shallow_model'2 self
   
-  let rec len'1 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span38] inv'4 self}
+  let rec len'1 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span30] inv'3 self}
     any
-    [ return' (result:usize)-> {[%#span39] UIntSize.to_int result = len'0 (shallow_model'4 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span31] UIntSize.to_int result = len'0 (shallow_model'4 self)} (! return' {result}) ]
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span40] index_logic'1 (shallow_model'2 self) ix
+    [%#span32] index_logic'1 (shallow_model'2 self) ix
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span37] shallow_model'1 self
+    [%#span29] shallow_model'1 self
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))) : borrowed (Vec'0.t_vec t (Global'0.t_global))
     
   
   function shallow_model'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))) : Seq'0.t_seq t
    =
-    [%#span41] shallow_model'3 (deref'0 self)
+    [%#span33] shallow_model'3 (deref'0 self)
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global))))
   
   function new'0 (x : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))
     
   
-  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span42] inv'2 x)
-   -> ([%#span43] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span34] inv'2 x)
+   -> ([%#span35] deref'0 (new'0 x) = x)
   
   let rec right_pad (str:borrowed (Vec'0.t_vec t (Global'0.t_global))) (len:usize) (pad:t) (return'  (ret:()))= {[%#shillel5] inv'1 pad}
     {[%#shillel4] inv'2 str}
@@ -461,71 +415,63 @@ module Hillel_LeftPad
   
   let%span span15 = "" 0 0 0 0
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span17 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span18 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span18 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span20 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span21 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span21 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span22 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span23 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span24 = "" 0 0 0 0
   
-  let%span span25 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span25 = "" 0 0 0 0
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 102 26 102 59
   
-  let%span span27 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 103 16 103 89
   
-  let%span span28 = "" 0 0 0 0
+  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 104 26 104 52
   
-  let%span span29 = "" 0 0 0 0
+  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 105 16 105 105
   
-  let%span span30 = "../../../../creusot-contracts/src/std/vec.rs" 102 26 102 59
+  let%span span30 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span31 = "../../../../creusot-contracts/src/std/vec.rs" 103 16 103 89
+  let%span span31 = "" 0 0 0 0
   
-  let%span span32 = "../../../../creusot-contracts/src/std/vec.rs" 104 26 104 52
+  let%span span32 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 105 16 105 105
+  let%span span33 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span34 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span34 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span35 = "" 0 0 0 0
+  let%span span35 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span36 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span37 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
+  predicate invariant'5 (self : Seq'0.t_seq t)
   
-  let%span span38 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  predicate inv'5 (_x : Seq'0.t_seq t)
   
-  let%span span39 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  axiom inv'5 : forall x : Seq'0.t_seq t . inv'5 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
   use Alloc_Vec_Vec_Type as Vec'0
   
-  predicate invariant'5 (self : Vec'0.t_vec t (Global'0.t_global))
-  
-  predicate inv'5 (_x : Vec'0.t_vec t (Global'0.t_global))
-  
-  axiom inv'5 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'5 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'4 (self : Seq'0.t_seq t)
+  predicate invariant'4 (self : Vec'0.t_vec t (Global'0.t_global))
   
-  predicate inv'4 (_x : Seq'0.t_seq t)
+  predicate inv'4 (_x : Vec'0.t_vec t (Global'0.t_global))
   
-  axiom inv'4 : forall x : Seq'0.t_seq t . inv'4 x = true
+  axiom inv'4 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'4 x = true
   
   use prelude.prelude.Int
   
@@ -558,96 +504,88 @@ module Hillel_LeftPad
   
   constant max'0 : usize = [%#span15] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span16] inv'4 self)  -> ([%#span17] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span16] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span18] inv'0 self)
-   -> ([%#span20] inv'4 (shallow_model'2 self))
-  && ([%#span19] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span17] inv'0 self)
+   -> ([%#span18] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span21] inv'4 (shallow_model'2 self)
+    [%#span19] inv'5 (shallow_model'2 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq t = [%#span22] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span24] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span25]  ^ self =  * self
+    [%#span21]  ^ self =  * self
   
   predicate resolve'1 (self : t)
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span26] index_logic'1 (shallow_model'2 self) ix
+    [%#span22] index_logic'1 (shallow_model'2 self) ix
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span27] shallow_model'2 ( * self)
+    [%#span23] shallow_model'2 ( * self)
   
-  let rec insert'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:usize) (element:t) (return'  (ret:()))= {[@expl:precondition] [%#span29] inv'1 element}
-    {[@expl:precondition] [%#span28] inv'2 self}
+  let rec insert'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:usize) (element:t) (return'  (ret:()))= {[@expl:precondition] [%#span25] inv'1 element}
+    {[@expl:precondition] [%#span24] inv'2 self}
     any
-    [ return' (result:())-> {[%#span33] forall i : int . UIntSize.to_int index < i
+    [ return' (result:())-> {[%#span29] forall i : int . UIntSize.to_int index < i
       /\ i < len'0 (shallow_model'2 ( ^ self))  -> index_logic'0 ( ^ self) i = index_logic'0 ( * self) (i - 1)}
-      {[%#span32] index_logic'0 ( ^ self) (UIntSize.to_int index) = element}
-      {[%#span31] forall i : int . 0 <= i /\ i < UIntSize.to_int index
+      {[%#span28] index_logic'0 ( ^ self) (UIntSize.to_int index) = element}
+      {[%#span27] forall i : int . 0 <= i /\ i < UIntSize.to_int index
        -> index_logic'0 ( ^ self) i = index_logic'0 ( * self) i}
-      {[%#span30] len'0 (shallow_model'2 ( ^ self)) = len'0 (shallow_model'1 self) + 1}
+      {[%#span26] len'0 (shallow_model'2 ( ^ self)) = len'0 (shallow_model'1 self) + 1}
       (! return' {result}) ]
     
   
   function shallow_model'4 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t =
-    [%#span34] shallow_model'2 self
+    [%#span30] shallow_model'2 self
   
-  let rec len'1 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span35] inv'5 self}
+  let rec len'1 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span31] inv'4 self}
     any
-    [ return' (result:usize)-> {[%#span36] UIntSize.to_int result = len'0 (shallow_model'4 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span32] UIntSize.to_int result = len'0 (shallow_model'4 self)} (! return' {result}) ]
     
   
   function deref'1 (self : Snapshot'0.t_snapshot int) : int
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span34] shallow_model'1 self
+    [%#span30] shallow_model'1 self
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))) : borrowed (Vec'0.t_vec t (Global'0.t_global))
     
   
   function shallow_model'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))) : Seq'0.t_seq t
    =
-    [%#span37] shallow_model'3 (deref'0 self)
+    [%#span33] shallow_model'3 (deref'0 self)
   
   function new'1 (x : int) : Snapshot'0.t_snapshot int
   
-  axiom new'1_spec : forall x : int . ([%#span38] inv'3 x)  -> ([%#span39] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : int . ([%#span34] inv'3 x)  -> ([%#span35] deref'1 (new'1 x) = x)
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global))))
   
   function new'0 (x : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))
     
   
-  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span38] inv'2 x)
-   -> ([%#span39] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span34] inv'2 x)
+   -> ([%#span35] deref'0 (new'0 x) = x)
   
   let rec left_pad (str:borrowed (Vec'0.t_vec t (Global'0.t_global))) (len:usize) (pad:t) (return'  (ret:()))= {[%#shillel9] inv'1 pad}
     {[%#shillel8] inv'2 str}
@@ -728,109 +666,73 @@ end
 module Hillel_SubsetPush_Impl
   type t
   
-  let%span shillel0 = "../hillel.rs" 74 18 74 19
-  
-  let%span shillel1 = "../hillel.rs" 74 29 74 33
+  let%span shillel0 = "../hillel.rs" 74 29 74 33
   
-  let%span shillel2 = "../hillel.rs" 73 10 73 36
+  let%span shillel1 = "../hillel.rs" 73 10 73 36
   
-  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span2 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../hillel.rs" 60 4 62 5
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "../hillel.rs" 67 4 69 5
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span8 = "../hillel.rs" 60 4 62 5
+  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span9 = "../hillel.rs" 67 4 69 5
+  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'0 (_x : Seq'0.t_seq t)
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'0 self)  -> ([%#span4] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq t = [%#span5] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  constant empty'0 : Seq'0.t_seq t
   
-  predicate invariant'1 (self : t)
-  
-  predicate inv'1 (_x : t)
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom inv'1 : forall x : t . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
-  predicate invariant'0 (self : Seq'0.t_seq t)
+  predicate invariant'0 (self : t)
   
-  axiom inv'0 : forall x : Seq'0.t_seq t . inv'0 x = true
+  predicate inv'0 (_x : t)
   
-  use seq.Seq
+  axiom inv'0 : forall x : t . inv'0 x = true
   
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   predicate contains'0 [#"../hillel.rs" 59 0 59 44] (seq : Seq'0.t_seq t) (elem : t) =
-    [%#span8] exists i : int . 0 <= i /\ i < len'0 seq /\ index_logic'0 seq i = elem
+    [%#span4] exists i : int . 0 <= i /\ i < len'0 seq /\ index_logic'0 seq i = elem
   
   predicate is_subset'0 [#"../hillel.rs" 66 0 66 49] (sub : Seq'0.t_seq t) (sup : Seq'0.t_seq t) =
-    [%#span9] forall i : int . 0 <= i /\ i < len'0 sub  -> contains'0 sup (index_logic'0 sub i)
-  
-  use seq.Seq
+    [%#span5] forall i : int . 0 <= i /\ i < len'0 sub  -> contains'0 sup (index_logic'0 sub i)
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span10] inv'0 self)
-   -> ([%#span11] inv'0 other)
-   -> ([%#span14] inv'0 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span7] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span6] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span15] inv'1 v)
-   -> ([%#span18] inv'0 (singleton'0 v))
-  && ([%#span17] index_logic'0 (singleton'0 v) 0 = v) && ([%#span16] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span8] inv'0 v)
+   -> ([%#span10] index_logic'0 (singleton'0 v) 0 = v) && ([%#span9] len'0 (singleton'0 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq t) (v : t) : Seq'0.t_seq t =
-    [%#span19] concat'0 self (singleton'0 v)
+    [%#span11] concat'0 self (singleton'0 v)
   
   constant s  : Seq'0.t_seq t
   
@@ -838,8 +740,7 @@ module Hillel_SubsetPush_Impl
   
   function subset_push [#"../hillel.rs" 74 0 74 37] (s : Seq'0.t_seq t) (elem : t) : ()
   
-  goal vc_subset_push : ([%#shillel1] inv'1 elem)
-   -> ([%#shillel0] inv'0 s)  -> ([%#shillel2] is_subset'0 s (push'0 s elem))
+  goal vc_subset_push : ([%#shillel0] inv'0 elem)  -> ([%#shillel1] is_subset'0 s (push'0 s elem))
 end
 module Core_Slice_Iter_Iter_Type
   use prelude.prelude.Borrow
@@ -920,165 +821,129 @@ module Hillel_InsertUnique
   
   let%span shillel17 = "../hillel.rs" 80 10 80 58
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span20 = "" 0 0 0 0
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span21 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span23 = "" 0 0 0 0
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span26 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span27 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span28 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span29 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span30 = "../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span31 = "../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span32 = "../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
   
-  let%span span33 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span33 = "../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
   
-  let%span span34 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span34 = "../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
   
-  let%span span35 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span35 = "../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span36 = "../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
   
-  let%span span37 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span37 = "../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
   
-  let%span span38 = "../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
+  let%span span38 = "../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
   
-  let%span span39 = "../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
+  let%span span39 = "../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
   
-  let%span span40 = "../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
+  let%span span40 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span41 = "../../../../creusot-contracts/src/std/slice.rs" 76 4 76 35
+  let%span span41 = "../../../../creusot-contracts/src/std/vec.rs" 33 18 33 22
   
-  let%span span42 = "../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
+  let%span span42 = "../../../../creusot-contracts/src/std/vec.rs" 30 14 30 56
   
-  let%span span43 = "../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
+  let%span span43 = "../../../../creusot-contracts/src/std/vec.rs" 31 4 32 53
   
-  let%span span44 = "../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
+  let%span span44 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span45 = "../../../../creusot-contracts/src/std/slice.rs" 398 31 398 33
+  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span46 = "../../../../creusot-contracts/src/std/slice.rs" 398 61 398 63
+  let%span span46 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span47 = "../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
+  let%span span47 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span48 = "../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
+  let%span span48 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span49 = "../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
+  let%span span49 = "" 0 0 0 0
   
-  let%span span50 = "../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
+  let%span span50 = "" 0 0 0 0
   
-  let%span span51 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span51 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 33 18 33 22
+  let%span span52 = "../hillel.rs" 53 4 55 5
   
-  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 30 14 30 56
+  let%span span53 = "../hillel.rs" 60 4 62 5
   
-  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 31 4 32 53
+  let%span span54 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span55 = "../../../../creusot-contracts/src/std/vec.rs" 33 4 33 44
+  let%span span55 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
-  let%span span56 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span56 = "" 0 0 0 0
   
-  let%span span57 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span57 = "" 0 0 0 0
   
-  let%span span58 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span58 = "../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
   
-  let%span span59 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span59 = "../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
   
-  let%span span60 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span60 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span61 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span61 = "" 0 0 0 0
   
-  let%span span62 = "" 0 0 0 0
+  let%span span62 = "../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
   
-  let%span span63 = "" 0 0 0 0
+  let%span span63 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span64 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span64 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span65 = "../hillel.rs" 53 4 55 5
+  let%span span65 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span66 = "../hillel.rs" 60 4 62 5
+  let%span span66 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span67 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span67 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span68 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
+  let%span span68 = "" 0 0 0 0
   
   let%span span69 = "" 0 0 0 0
   
   let%span span70 = "" 0 0 0 0
   
-  let%span span71 = "../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
+  let%span span71 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span72 = "../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
+  let%span span72 = "" 0 0 0 0
   
-  let%span span73 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span73 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
   
   let%span span74 = "" 0 0 0 0
   
-  let%span span75 = "../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
-  
-  let%span span76 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span77 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span78 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span79 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span80 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span81 = "" 0 0 0 0
-  
-  let%span span82 = "" 0 0 0 0
-  
-  let%span span83 = "" 0 0 0 0
-  
-  let%span span84 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
-  
-  let%span span85 = "" 0 0 0 0
-  
-  let%span span86 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
-  
-  let%span span87 = "" 0 0 0 0
-  
-  let%span span88 = "../hillel.rs" 67 4 69 5
-  
-  let%span span89 = "../../../../creusot-contracts/src/model.rs" 99 8 99 28
-  
-  let%span span90 = "../hillel.rs" 74 18 74 19
+  let%span span75 = "../hillel.rs" 67 4 69 5
   
-  let%span span91 = "../hillel.rs" 74 29 74 33
+  let%span span76 = "../../../../creusot-contracts/src/model.rs" 99 8 99 28
   
-  let%span span92 = "../hillel.rs" 73 10 73 36
+  let%span span77 = "../hillel.rs" 74 29 74 33
   
-  let%span span93 = "../hillel.rs" 72 0 72 8
+  let%span span78 = "../hillel.rs" 73 10 73 36
   
-  use prelude.prelude.Slice
-  
-  predicate invariant'14 (self : slice t)
-  
-  predicate inv'14 (_x : slice t)
-  
-  axiom inv'14 : forall x : slice t . inv'14 x = true
+  let%span span79 = "../hillel.rs" 72 0 72 8
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
@@ -1088,81 +953,77 @@ module Hillel_InsertUnique
   
   axiom inv'13 : forall x : Seq'0.t_seq t . inv'13 x = true
   
-  use prelude.prelude.Int
+  use prelude.prelude.Slice
+  
+  predicate invariant'12 (self : slice t)
   
-  use seq.Seq
+  predicate inv'12 (_x : slice t)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  axiom inv'12 : forall x : slice t . inv'12 x = true
+  
+  use prelude.prelude.Int
   
   function len'2 (self : Seq'0.t_seq t) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq t . ([%#span18] inv'13 self)  -> ([%#span19] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq t . [%#span18] len'2 self >= 0
   
-  constant empty'2 : Seq'0.t_seq t = [%#span20] ()
+  constant empty'2 : Seq'0.t_seq t
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span22] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span21] len'2 (empty'2 : Seq'0.t_seq t) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span19] len'2 (empty'2 : Seq'0.t_seq t) = 0
   
-  predicate invariant'12 (self : t)
+  predicate invariant'11 (self : t)
   
-  predicate inv'12 (_x : t)
+  predicate inv'11 (_x : t)
   
-  axiom inv'12 : forall x : t . inv'12 x = true
+  axiom inv'11 : forall x : t . inv'11 x = true
   
-  predicate invariant'11 (self : Seq'0.t_seq t)
+  predicate invariant'10 (self : Seq'0.t_seq t)
   
-  predicate inv'11 (_x : Seq'0.t_seq t)
+  predicate inv'10 (_x : Seq'0.t_seq t)
   
-  axiom inv'11 : forall x : Seq'0.t_seq t . inv'11 x = true
+  axiom inv'10 : forall x : Seq'0.t_seq t . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
   use Alloc_Vec_Vec_Type as Vec'0
   
-  predicate invariant'10 (self : Vec'0.t_vec t (Global'0.t_global))
+  predicate invariant'9 (self : Vec'0.t_vec t (Global'0.t_global))
   
-  predicate inv'10 (_x : Vec'0.t_vec t (Global'0.t_global))
+  predicate inv'9 (_x : Vec'0.t_vec t (Global'0.t_global))
   
-  axiom inv'10 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'10 x = true
+  axiom inv'9 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'9 x = true
   
   type deep_model_ty'0
   
-  predicate invariant'9 (self : ())
+  predicate invariant'8 (self : ())
   
-  predicate inv'9 (_x : ())
+  predicate inv'8 (_x : ())
   
-  axiom inv'9 : forall x : () . inv'9 x = true
+  axiom inv'8 : forall x : () . inv'8 x = true
   
-  predicate invariant'8 (self : deep_model_ty'0)
+  predicate invariant'7 (self : deep_model_ty'0)
   
-  predicate inv'8 (_x : deep_model_ty'0)
+  predicate inv'7 (_x : deep_model_ty'0)
   
-  axiom inv'8 : forall x : deep_model_ty'0 . inv'8 x = true
-  
-  predicate invariant'7 (self : Seq'0.t_seq deep_model_ty'0)
-  
-  predicate inv'7 (_x : Seq'0.t_seq deep_model_ty'0)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq deep_model_ty'0 . inv'7 x = true
+  axiom inv'7 : forall x : deep_model_ty'0 . inv'7 x = true
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span23] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span20] (18446744073709551615 : usize)
   
   predicate inv'6 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span24] inv'6 self)
-   -> ([%#span26] inv'13 (shallow_model'3 self))
-  && ([%#span25] len'2 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span21] inv'6 self)
+   -> ([%#span22] len'2 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'6 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span27] inv'13 (shallow_model'3 self)
+    [%#span23] inv'13 (shallow_model'3 self)
   
   axiom inv'6 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'6 x = true
   
@@ -1196,74 +1057,61 @@ module Hillel_InsertUnique
   
   use Core_Slice_Iter_Iter_Type as Iter'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq t) (x : int) : t
-  
-  use seq.Seq
+  function index_logic'3 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span18] inv'11 self)  -> ([%#span19] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span18] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span28] inv'11 self)
-   -> ([%#span29] inv'11 other)
-   -> ([%#span32] inv'11 (concat'0 self other))
-  && ([%#span31] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span25] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'3 (concat'0 self other) i
   = (if i < len'0 self then index_logic'3 self i else index_logic'3 other (i - len'0 self)))
-  && ([%#span30] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span24] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  function index_logic'4 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'4 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function shallow_model'5 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'5_spec : forall self : slice t . ([%#span33] inv'14 self)
-   -> ([%#span35] inv'13 (shallow_model'5 self))
-  && ([%#span34] len'2 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'5_spec : forall self : slice t . ([%#span26] inv'12 self)
+   -> ([%#span27] len'2 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'5 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span36] index_logic'4 (shallow_model'5 self) ix
+    [%#span28] index_logic'4 (shallow_model'5 self) ix
   
   function shallow_model'0 (self : slice t) : Seq'0.t_seq t =
-    [%#span37] shallow_model'5 self
+    [%#span29] shallow_model'5 self
   
   predicate inv'0 (_x : slice t)
   
   function to_ref_seq'0 (self : slice t) : Seq'0.t_seq t
   
-  axiom to_ref_seq'0_spec : forall self : slice t . ([%#span38] inv'0 self)
-   -> ([%#span41] inv'11 (to_ref_seq'0 self))
-  && ([%#span40] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
+  axiom to_ref_seq'0_spec : forall self : slice t . ([%#span30] inv'0 self)
+   -> ([%#span32] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
    -> index_logic'3 (to_ref_seq'0 self) i = index_logic'5 self i)
-  && ([%#span39] len'0 (to_ref_seq'0 self) = len'2 (shallow_model'0 self))
+  && ([%#span31] len'0 (to_ref_seq'0 self) = len'2 (shallow_model'0 self))
   
   function shallow_model'2 (self : Iter'0.t_iter t) : slice t
   
   predicate produces'0 (self : Iter'0.t_iter t) (visited : Seq'0.t_seq t) (tl : Iter'0.t_iter t) =
-    [%#span42] to_ref_seq'0 (shallow_model'2 self) = concat'0 visited (to_ref_seq'0 (shallow_model'2 tl))
+    [%#span33] to_ref_seq'0 (shallow_model'2 self) = concat'0 visited (to_ref_seq'0 (shallow_model'2 tl))
   
   function produces_trans'0 (a : Iter'0.t_iter t) (ab : Seq'0.t_seq t) (b : Iter'0.t_iter t) (bc : Seq'0.t_seq t) (c : Iter'0.t_iter t) : ()
     
    =
-    [%#span48] ()
+    [%#span37] ()
   
-  axiom produces_trans'0_spec : forall a : Iter'0.t_iter t, ab : Seq'0.t_seq t, b : Iter'0.t_iter t, bc : Seq'0.t_seq t, c : Iter'0.t_iter t . ([%#span43] produces'0 a ab b)
-   -> ([%#span44] produces'0 b bc c)
-   -> ([%#span45] inv'11 ab)  -> ([%#span46] inv'11 bc)  -> ([%#span47] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Iter'0.t_iter t, ab : Seq'0.t_seq t, b : Iter'0.t_iter t, bc : Seq'0.t_seq t, c : Iter'0.t_iter t . ([%#span34] produces'0 a ab b)
+   -> ([%#span35] produces'0 b bc c)  -> ([%#span36] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq t = [%#span20] ()
+  constant empty'0 : Seq'0.t_seq t
   
   function produces_refl'0 (self : Iter'0.t_iter t) : () =
-    [%#span50] ()
+    [%#span39] ()
   
-  axiom produces_refl'0_spec : forall self : Iter'0.t_iter t . [%#span49] produces'0 self (empty'0 : Seq'0.t_seq t) self
+  axiom produces_refl'0_spec : forall self : Iter'0.t_iter t . [%#span38] produces'0 self (empty'0 : Seq'0.t_seq t) self
   
   predicate invariant'1 (self : Iter'0.t_iter t)
   
@@ -1271,134 +1119,116 @@ module Hillel_InsertUnique
   
   axiom inv'1 : forall x : Iter'0.t_iter t . inv'1 x = true
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span22] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span21] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span19] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'0 (self : slice t)
   
   axiom inv'0 : forall x : slice t . inv'0 x = true
   
-  use seq.Seq
-  
   function len'1 (self : Seq'0.t_seq deep_model_ty'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq deep_model_ty'0 . ([%#span18] inv'7 self)
-   -> ([%#span19] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq deep_model_ty'0 . [%#span18] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq deep_model_ty'0 = [%#span20] ()
+  constant empty'1 : Seq'0.t_seq deep_model_ty'0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span22] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span21] len'1 (empty'1 : Seq'0.t_seq deep_model_ty'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span19] len'1 (empty'1 : Seq'0.t_seq deep_model_ty'0) = 0
   
   function deep_model'1 (self : t) : deep_model_ty'0
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span51] index_logic'4 (shallow_model'3 self) ix
-  
-  use seq.Seq
+    [%#span40] index_logic'4 (shallow_model'3 self) ix
   
-  function index_logic'2 (self : Seq'0.t_seq deep_model_ty'0) (x : int) : deep_model_ty'0
+  function index_logic'2 (self : Seq'0.t_seq deep_model_ty'0) (_2 : int) : deep_model_ty'0
   
   function deep_model'3 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq deep_model_ty'0
   
-  axiom deep_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span52] inv'6 self)
-   -> ([%#span55] inv'7 (deep_model'3 self))
-  && ([%#span54] forall i : int . 0 <= i /\ i < len'2 (shallow_model'3 self)
+  axiom deep_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span41] inv'6 self)
+   -> ([%#span43] forall i : int . 0 <= i /\ i < len'2 (shallow_model'3 self)
    -> index_logic'2 (deep_model'3 self) i = deep_model'1 (index_logic'1 self i))
-  && ([%#span53] len'2 (shallow_model'3 self) = len'1 (deep_model'3 self))
+  && ([%#span42] len'2 (shallow_model'3 self) = len'1 (deep_model'3 self))
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   function concat'2 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'2_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span28] inv'13 self)
-   -> ([%#span29] inv'13 other)
-   -> ([%#span32] inv'13 (concat'2 self other))
-  && ([%#span31] forall i : int . 0 <= i /\ i < len'2 (concat'2 self other)
+  axiom concat'2_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span25] forall i : int . 0 <= i
+  /\ i < len'2 (concat'2 self other)
    -> index_logic'4 (concat'2 self other) i
   = (if i < len'2 self then index_logic'4 self i else index_logic'4 other (i - len'2 self)))
-  && ([%#span30] len'2 (concat'2 self other) = len'2 self + len'2 other)
-  
-  use seq.Seq
+  && ([%#span24] len'2 (concat'2 self other) = len'2 self + len'2 other)
   
   function singleton'2 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'2_spec : forall v : t . ([%#span56] inv'4 v)
-   -> ([%#span59] inv'13 (singleton'2 v))
-  && ([%#span58] index_logic'4 (singleton'2 v) 0 = v) && ([%#span57] len'2 (singleton'2 v) = 1)
+  axiom singleton'2_spec : forall v : t . ([%#span44] inv'4 v)
+   -> ([%#span46] index_logic'4 (singleton'2 v) 0 = v) && ([%#span45] len'2 (singleton'2 v) = 1)
   
   function push'2 [@inline:trivial] (self : Seq'0.t_seq t) (v : t) : Seq'0.t_seq t =
-    [%#span60] concat'2 self (singleton'2 v)
+    [%#span47] concat'2 self (singleton'2 v)
   
   function shallow_model'4 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span61] shallow_model'3 ( * self)
+    [%#span48] shallow_model'3 ( * self)
   
-  let rec push'1 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (value:t) (return'  (ret:()))= {[@expl:precondition] [%#span63] inv'4 value}
-    {[@expl:precondition] [%#span62] inv'5 self}
+  let rec push'1 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (value:t) (return'  (ret:()))= {[@expl:precondition] [%#span50] inv'4 value}
+    {[@expl:precondition] [%#span49] inv'5 self}
     any
-    [ return' (result:())-> {[%#span64] shallow_model'3 ( ^ self) = push'2 (shallow_model'4 self) value}
+    [ return' (result:())-> {[%#span51] shallow_model'3 ( ^ self) = push'2 (shallow_model'4 self) value}
       (! return' {result}) ]
     
   
   predicate is_unique'0 [#"../hillel.rs" 52 0 52 34] (s : Seq'0.t_seq deep_model_ty'0) =
-    [%#span65] forall j : int . forall i : int . 0 <= i /\ i < len'1 s /\ 0 <= j /\ j < len'1 s
+    [%#span52] forall j : int . forall i : int . 0 <= i /\ i < len'1 s /\ 0 <= j /\ j < len'1 s
      -> index_logic'2 s i = index_logic'2 s j  -> i = j
   
   predicate contains'0 [#"../hillel.rs" 59 0 59 44] (seq : Seq'0.t_seq deep_model_ty'0) (elem : deep_model_ty'0) =
-    [%#span66] exists i : int . 0 <= i /\ i < len'1 seq /\ index_logic'2 seq i = elem
+    [%#span53] exists i : int . 0 <= i /\ i < len'1 seq /\ index_logic'2 seq i = elem
   
   predicate resolve'10 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span67]  ^ self =  * self
+    [%#span54]  ^ self =  * self
   
   predicate resolve'9 (self : t)
   
   predicate resolve'8 (self : Iter'0.t_iter t)
   
   function deep_model'2 (self : t) : deep_model_ty'0 =
-    [%#span68] deep_model'1 self
+    [%#span55] deep_model'1 self
   
   function deep_model'4 (self : t) : deep_model_ty'0 =
-    [%#span68] deep_model'2 self
+    [%#span55] deep_model'2 self
   
-  let rec eq'0 (self:t) (other:t) (return'  (ret:bool))= {[@expl:precondition] [%#span70] inv'12 other}
-    {[@expl:precondition] [%#span69] inv'12 self}
-    any [ return' (result:bool)-> {[%#span71] result = (deep_model'4 self = deep_model'4 other)} (! return' {result}) ] 
+  let rec eq'0 (self:t) (other:t) (return'  (ret:bool))= {[@expl:precondition] [%#span57] inv'11 other}
+    {[@expl:precondition] [%#span56] inv'11 self}
+    any [ return' (result:bool)-> {[%#span58] result = (deep_model'4 self = deep_model'4 other)} (! return' {result}) ] 
   
   function deref'2 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))) : borrowed (Vec'0.t_vec t (Global'0.t_global))
     
   
   predicate resolve'7 (self : t)
   
-  use seq.Seq
-  
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span56] inv'3 v)
-   -> ([%#span59] inv'11 (singleton'0 v))
-  && ([%#span58] index_logic'3 (singleton'0 v) 0 = v) && ([%#span57] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span44] inv'3 v)
+   -> ([%#span46] index_logic'3 (singleton'0 v) 0 = v) && ([%#span45] len'0 (singleton'0 v) = 1)
   
   predicate resolve'6 (self : Option'0.t_option t)
   
   predicate resolve'5 (self : borrowed (Iter'0.t_iter t)) =
-    [%#span67]  ^ self =  * self
+    [%#span54]  ^ self =  * self
   
   function shallow_model'6 (self : borrowed (Iter'0.t_iter t)) : slice t =
-    [%#span61] shallow_model'2 ( * self)
+    [%#span48] shallow_model'2 ( * self)
   
   predicate completed'0 (self : borrowed (Iter'0.t_iter t)) =
-    [%#span72] resolve'5 self /\ shallow_model'5 (shallow_model'6 self) = (empty'2 : Seq'0.t_seq t)
+    [%#span59] resolve'5 self /\ shallow_model'5 (shallow_model'6 self) = (empty'2 : Seq'0.t_seq t)
   
   let rec next'0 (self:borrowed (Iter'0.t_iter t)) (return'  (ret:Option'0.t_option t))= any
-    [ return' (result:Option'0.t_option t)-> {[%#span74] inv'2 result}
-      {[%#span73] match result with
+    [ return' (result:Option'0.t_option t)-> {[%#span61] inv'2 result}
+      {[%#span60] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -1408,7 +1238,7 @@ module Hillel_InsertUnique
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq t)) : Seq'0.t_seq t
   
   function index_logic'0 [@inline:trivial] (self : Snapshot'0.t_snapshot (Seq'0.t_seq t)) (ix : int) : t =
-    [%#span75] index_logic'3 (deref'1 self) ix
+    [%#span62] index_logic'3 (deref'1 self) ix
   
   function inner'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq t)) : Seq'0.t_seq t
   
@@ -1420,40 +1250,40 @@ module Hillel_InsertUnique
   
   function new'3 (x : Seq'0.t_seq t) : Snapshot'0.t_snapshot (Seq'0.t_seq t)
   
-  axiom new'3_spec : forall x : Seq'0.t_seq t . ([%#span76] inv'11 x)  -> ([%#span77] deref'1 (new'3 x) = x)
+  axiom new'3_spec : forall x : Seq'0.t_seq t . ([%#span63] inv'10 x)  -> ([%#span64] deref'1 (new'3 x) = x)
   
   predicate resolve'3 (self : Snapshot'0.t_snapshot (Iter'0.t_iter t))
   
   function new'2 (x : Iter'0.t_iter t) : Snapshot'0.t_snapshot (Iter'0.t_iter t)
   
-  axiom new'2_spec : forall x : Iter'0.t_iter t . ([%#span76] inv'1 x)  -> ([%#span77] deref'4 (new'2 x) = x)
+  axiom new'2_spec : forall x : Iter'0.t_iter t . ([%#span63] inv'1 x)  -> ([%#span64] deref'4 (new'2 x) = x)
   
   predicate into_iter_post'0 (self : Iter'0.t_iter t) (res : Iter'0.t_iter t) =
-    [%#span78] self = res
+    [%#span65] self = res
   
   predicate into_iter_pre'0 (self : Iter'0.t_iter t) =
-    [%#span79] true
+    [%#span66] true
   
-  let rec into_iter'0 (self:Iter'0.t_iter t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span81] inv'1 self}
-    {[@expl:precondition] [%#span80] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Iter'0.t_iter t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span68] inv'1 self}
+    {[@expl:precondition] [%#span67] into_iter_pre'0 self}
     any
-    [ return' (result:Iter'0.t_iter t)-> {[%#span82] inv'1 result}
-      {[%#span80] into_iter_post'0 self result}
+    [ return' (result:Iter'0.t_iter t)-> {[%#span69] inv'1 result}
+      {[%#span67] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec iter'0 (self:slice t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span83] inv'0 self}
-    any [ return' (result:Iter'0.t_iter t)-> {[%#span84] shallow_model'2 result = self} (! return' {result}) ] 
+  let rec iter'0 (self:slice t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span70] inv'0 self}
+    any [ return' (result:Iter'0.t_iter t)-> {[%#span71] shallow_model'2 result = self} (! return' {result}) ] 
   
   predicate resolve'2 (self : slice t)
   
   function shallow_model'1 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t =
-    [%#span37] shallow_model'3 self
+    [%#span29] shallow_model'3 self
   
-  let rec deref'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:slice t))= {[@expl:precondition] [%#span85] inv'10 self}
+  let rec deref'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:slice t))= {[@expl:precondition] [%#span72] inv'9 self}
     any
-    [ return' (result:slice t)-> {[%#span87] inv'0 result}
-      {[%#span86] shallow_model'0 result = shallow_model'1 self}
+    [ return' (result:slice t)-> {[%#span74] inv'0 result}
+      {[%#span73] shallow_model'0 result = shallow_model'1 self}
       (! return' {result}) ]
     
   
@@ -1462,42 +1292,36 @@ module Hillel_InsertUnique
   function new'1 (x : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))
     
   
-  axiom new'1_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span76] inv'5 x)
-   -> ([%#span77] deref'2 (new'1 x) = x)
+  axiom new'1_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span63] inv'5 x)
+   -> ([%#span64] deref'2 (new'1 x) = x)
   
   predicate is_subset'0 [#"../hillel.rs" 66 0 66 49] (sub : Seq'0.t_seq deep_model_ty'0) (sup : Seq'0.t_seq deep_model_ty'0)
     
    =
-    [%#span88] forall i : int . 0 <= i /\ i < len'1 sub  -> contains'0 sup (index_logic'2 sub i)
-  
-  use seq.Seq
+    [%#span75] forall i : int . 0 <= i /\ i < len'1 sub  -> contains'0 sup (index_logic'2 sub i)
   
   function concat'1 (self : Seq'0.t_seq deep_model_ty'0) (other : Seq'0.t_seq deep_model_ty'0) : Seq'0.t_seq deep_model_ty'0
     
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq deep_model_ty'0, other : Seq'0.t_seq deep_model_ty'0 . ([%#span28] inv'7 self)
-   -> ([%#span29] inv'7 other)
-   -> ([%#span32] inv'7 (concat'1 self other))
-  && ([%#span31] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq deep_model_ty'0, other : Seq'0.t_seq deep_model_ty'0 . ([%#span25] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'2 (concat'1 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span30] len'1 (concat'1 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span24] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   function singleton'1 (v : deep_model_ty'0) : Seq'0.t_seq deep_model_ty'0
   
-  axiom singleton'1_spec : forall v : deep_model_ty'0 . ([%#span56] inv'8 v)
-   -> ([%#span59] inv'7 (singleton'1 v))
-  && ([%#span58] index_logic'2 (singleton'1 v) 0 = v) && ([%#span57] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : deep_model_ty'0 . ([%#span44] inv'7 v)
+   -> ([%#span46] index_logic'2 (singleton'1 v) 0 = v) && ([%#span45] len'1 (singleton'1 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq deep_model_ty'0) (v : deep_model_ty'0) : Seq'0.t_seq deep_model_ty'0
     
    =
-    [%#span60] concat'1 self (singleton'1 v)
+    [%#span47] concat'1 self (singleton'1 v)
   
   function deep_model'0 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq deep_model_ty'0 =
-    [%#span89] deep_model'3 ( * self)
+    [%#span76] deep_model'3 ( * self)
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot ())
   
@@ -1505,13 +1329,13 @@ module Hillel_InsertUnique
   
   function new'0 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'0_spec : forall x : () . ([%#span76] inv'9 x)  -> ([%#span77] deref'3 (new'0 x) = x)
+  axiom new'0_spec : forall x : () . ([%#span63] inv'8 x)  -> ([%#span64] deref'3 (new'0 x) = x)
   
   function subset_push'0 [#"../hillel.rs" 74 0 74 37] (s : Seq'0.t_seq deep_model_ty'0) (elem : deep_model_ty'0) : () =
-    [%#span93] ()
+    [%#span79] ()
   
-  axiom subset_push'0_spec : forall s : Seq'0.t_seq deep_model_ty'0, elem : deep_model_ty'0 . ([%#span90] inv'7 s)
-   -> ([%#span91] inv'8 elem)  -> ([%#span92] is_subset'0 s (push'0 s elem))
+  axiom subset_push'0_spec : forall s : Seq'0.t_seq deep_model_ty'0, elem : deep_model_ty'0 . ([%#span77] inv'7 elem)
+   -> ([%#span78] is_subset'0 s (push'0 s elem))
   
   let rec insert_unique (vec:borrowed (Vec'0.t_vec t (Global'0.t_global))) (elem:t) (return'  (ret:()))= {[%#shillel13] inv'4 elem}
     {[%#shillel12] inv'5 vec}
@@ -1739,225 +1563,185 @@ module Hillel_Unique
   
   let%span span20 = "" 0 0 0 0
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span28 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span29 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span30 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span31 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span32 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span33 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span34 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span35 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span35 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span36 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span36 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span37 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span37 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span38 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span39 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span40 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span40 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span41 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span41 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span42 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span42 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span43 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span43 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span44 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span44 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span45 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span46 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span46 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span47 = "../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span47 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span48 = "../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span48 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span49 = "../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span49 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span50 = "../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span50 = "../hillel.rs" 60 4 62 5
   
-  let%span span51 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span51 = "../hillel.rs" 67 4 69 5
   
-  let%span span52 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 33 18 33 22
   
-  let%span span53 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 30 14 30 56
   
-  let%span span54 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 31 4 32 53
   
-  let%span span55 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span55 = "../hillel.rs" 53 4 55 5
   
-  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span56 = "../../../../creusot-contracts/src/model.rs" 99 8 99 28
   
-  let%span span57 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span57 = "../hillel.rs" 76 11 76 38
   
-  let%span span58 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span58 = "../hillel.rs" 81 36 81 39
   
-  let%span span59 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span59 = "../hillel.rs" 81 54 81 58
   
-  let%span span60 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span60 = "../hillel.rs" 77 10 77 40
   
-  let%span span61 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span61 = "../hillel.rs" 78 10 78 58
   
-  let%span span62 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span62 = "../hillel.rs" 79 10 79 82
   
-  let%span span63 = "../hillel.rs" 60 4 62 5
+  let%span span63 = "../hillel.rs" 80 10 80 58
   
-  let%span span64 = "../hillel.rs" 67 4 69 5
+  let%span span64 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span65 = "../../../../creusot-contracts/src/std/vec.rs" 33 18 33 22
+  let%span span65 = "" 0 0 0 0
   
-  let%span span66 = "../../../../creusot-contracts/src/std/vec.rs" 30 14 30 56
+  let%span span66 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span67 = "../../../../creusot-contracts/src/std/vec.rs" 31 4 32 53
+  let%span span67 = "" 0 0 0 0
   
-  let%span span68 = "../../../../creusot-contracts/src/std/vec.rs" 33 4 33 44
+  let%span span68 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span69 = "../hillel.rs" 53 4 55 5
+  let%span span69 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span70 = "../../../../creusot-contracts/src/model.rs" 99 8 99 28
+  let%span span70 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span71 = "../hillel.rs" 76 11 76 38
+  let%span span71 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span72 = "../hillel.rs" 81 36 81 39
+  let%span span72 = "../../../../creusot-contracts/src/std/slice.rs" 31 18 31 22
   
-  let%span span73 = "../hillel.rs" 81 54 81 58
+  let%span span73 = "../../../../creusot-contracts/src/std/slice.rs" 29 14 29 44
   
-  let%span span74 = "../hillel.rs" 77 10 77 40
+  let%span span74 = "../../../../creusot-contracts/src/std/slice.rs" 30 4 30 98
   
-  let%span span75 = "../hillel.rs" 78 10 78 58
+  let%span span75 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
-  let%span span76 = "../hillel.rs" 79 10 79 82
+  let%span span76 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span77 = "../hillel.rs" 80 10 80 58
+  let%span span77 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span78 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span78 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span79 = "" 0 0 0 0
+  let%span span79 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span80 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span80 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
   let%span span81 = "" 0 0 0 0
   
-  let%span span82 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
-  
-  let%span span83 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
-  
-  let%span span84 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
-  
-  let%span span85 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
-  
-  let%span span86 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
-  
-  let%span span87 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
-  
-  let%span span88 = "../../../../creusot-contracts/src/std/slice.rs" 31 18 31 22
-  
-  let%span span89 = "../../../../creusot-contracts/src/std/slice.rs" 29 14 29 44
-  
-  let%span span90 = "../../../../creusot-contracts/src/std/slice.rs" 30 4 30 98
-  
-  let%span span91 = "../../../../creusot-contracts/src/std/slice.rs" 31 4 31 44
-  
-  let%span span92 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
-  
-  let%span span93 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span94 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span95 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span96 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span97 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span98 = "" 0 0 0 0
-  
-  let%span span99 = "" 0 0 0 0
+  let%span span82 = "" 0 0 0 0
   
-  let%span span100 = "" 0 0 0 0
+  let%span span83 = "" 0 0 0 0
   
-  let%span span101 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span84 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span102 = "../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
+  let%span span85 = "../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
-  let%span span103 = "" 0 0 0 0
+  let%span span86 = "" 0 0 0 0
   
   type deep_model_ty'0
   
-  predicate invariant'12 (self : deep_model_ty'0)
+  predicate invariant'11 (self : deep_model_ty'0)
   
-  predicate inv'12 (_x : deep_model_ty'0)
+  predicate inv'11 (_x : deep_model_ty'0)
   
-  axiom inv'12 : forall x : deep_model_ty'0 . inv'12 x = true
+  axiom inv'11 : forall x : deep_model_ty'0 . inv'11 x = true
   
   use prelude.prelude.Slice
   
-  predicate invariant'11 (self : slice t)
+  predicate invariant'10 (self : slice t)
   
-  predicate inv'11 (_x : slice t)
+  predicate inv'10 (_x : slice t)
   
-  axiom inv'11 : forall x : slice t . inv'11 x = true
+  axiom inv'10 : forall x : slice t . inv'10 x = true
   
   use prelude.prelude.UIntSize
   
-  predicate invariant'10 (self : usize) =
+  predicate invariant'9 (self : usize) =
     [%#span19] true
   
-  predicate inv'10 (_x : usize)
+  predicate inv'9 (_x : usize)
   
-  axiom inv'10 : forall x : usize . inv'10 x = true
+  axiom inv'9 : forall x : usize . inv'9 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'9 (self : Option'0.t_option usize) =
+  predicate invariant'8 (self : Option'0.t_option usize) =
     [%#span19] true
   
-  predicate inv'9 (_x : Option'0.t_option usize)
+  predicate inv'8 (_x : Option'0.t_option usize)
   
-  axiom inv'9 : forall x : Option'0.t_option usize . inv'9 x = true
+  axiom inv'8 : forall x : Option'0.t_option usize . inv'8 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'8 (self : borrowed (Range'0.t_range usize)) =
+  predicate invariant'7 (self : borrowed (Range'0.t_range usize)) =
     [%#span19] true
   
-  predicate inv'8 (_x : borrowed (Range'0.t_range usize))
+  predicate inv'7 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'8 : forall x : borrowed (Range'0.t_range usize) . inv'8 x = true
+  axiom inv'7 : forall x : borrowed (Range'0.t_range usize) . inv'7 x = true
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'7 (self : Seq'0.t_seq deep_model_ty'0)
-  
-  predicate inv'7 (_x : Seq'0.t_seq deep_model_ty'0)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq deep_model_ty'0 . inv'7 x = true
-  
   predicate invariant'6 (self : Seq'0.t_seq usize) =
     [%#span19] true
   
@@ -1999,74 +1783,57 @@ module Hillel_Unique
   
   constant max'0 : usize = [%#span20] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq t) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq t . ([%#span21] inv'5 self)  -> ([%#span22] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq t . [%#span21] len'2 self >= 0
   
   predicate inv'1 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span23] inv'1 self)
-   -> ([%#span25] inv'5 (shallow_model'1 self))
-  && ([%#span24] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span22] inv'1 self)
+   -> ([%#span23] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span26] inv'5 (shallow_model'1 self)
+    [%#span24] inv'5 (shallow_model'1 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'1 x = true
   
-  use seq.Seq
-  
   function len'3 (self : Seq'0.t_seq deep_model_ty'0) : int
   
-  axiom len'3_spec : forall self : Seq'0.t_seq deep_model_ty'0 . ([%#span21] inv'7 self)
-   -> ([%#span22] len'3 self >= 0)
+  axiom len'3_spec : forall self : Seq'0.t_seq deep_model_ty'0 . [%#span21] len'3 self >= 0
   
-  constant empty'2 : Seq'0.t_seq deep_model_ty'0 = [%#span27] ()
+  constant empty'2 : Seq'0.t_seq deep_model_ty'0
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span29] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span28] len'3 (empty'2 : Seq'0.t_seq deep_model_ty'0) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span25] len'3 (empty'2 : Seq'0.t_seq deep_model_ty'0) = 0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq usize) (x : int) : usize
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span21] inv'6 self)  -> ([%#span22] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span21] len'1 self >= 0
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span30] inv'6 self)
-   -> ([%#span31] inv'6 other)
-   -> ([%#span34] inv'6 (concat'0 self other))
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span27] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'1 self then index_logic'0 self i else index_logic'0 other (i - len'1 self)))
-  && ([%#span32] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span26] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : Range'0.t_range usize)
   
   use prelude.prelude.Int
   
   function deep_model'2 (self : usize) : int =
-    [%#span35] UIntSize.to_int self
+    [%#span28] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span36] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span29] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'2 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'2 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'1 visited > 0
@@ -2079,221 +1846,187 @@ module Hillel_Unique
   function produces_trans'0 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span37] produces'0 a ab b)
-   -> ([%#span38] produces'0 b bc c)
-   -> ([%#span39] inv'0 a)
-   -> ([%#span40] inv'6 ab)
-   -> ([%#span41] inv'0 b)
-   -> ([%#span42] inv'6 bc)  -> ([%#span43] inv'0 c)  -> ([%#span44] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span30] produces'0 a ab b)
+   -> ([%#span31] produces'0 b bc c)
+   -> ([%#span32] inv'0 a)
+   -> ([%#span33] inv'0 b)  -> ([%#span34] inv'0 c)  -> ([%#span35] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span27] ()
+  constant empty'1 : Seq'0.t_seq usize
   
   function produces_refl'0 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span45] inv'0 self)
-   -> ([%#span46] produces'0 self (empty'1 : Seq'0.t_seq usize) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span36] inv'0 self)
+   -> ([%#span37] produces'0 self (empty'1 : Seq'0.t_seq usize) self)
   
   predicate invariant'0 (self : Range'0.t_range usize) =
     [%#span19] true
   
   axiom inv'0 : forall x : Range'0.t_range usize . inv'0 x = true
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span29] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span28] len'1 (empty'1 : Seq'0.t_seq usize) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span25] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span27] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span29] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span28] len'2 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span25] len'2 (empty'0 : Seq'0.t_seq t) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq deep_model_ty'0) (x : int) : deep_model_ty'0
+  function index_logic'1 (self : Seq'0.t_seq deep_model_ty'0) (_2 : int) : deep_model_ty'0
   
   predicate ext_eq'0 (self : Seq'0.t_seq deep_model_ty'0) (oth : Seq'0.t_seq deep_model_ty'0)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq deep_model_ty'0, oth : Seq'0.t_seq deep_model_ty'0 . ([%#span47] inv'7 self)
-   -> ([%#span48] inv'7 oth)
-   -> ([%#span50] len'3 self = len'3 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq deep_model_ty'0, oth : Seq'0.t_seq deep_model_ty'0 . ([%#span39] len'3 self
+  = len'3 oth
   /\ (forall i : int . 0 <= i /\ i < len'3 self  -> index_logic'1 self i = index_logic'1 oth i)  -> ext_eq'0 self oth)
-  && ([%#span49] ext_eq'0 self oth  -> self = oth)
+  && ([%#span38] ext_eq'0 self oth  -> self = oth)
   
   function shallow_model'2 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : slice t . ([%#span51] inv'11 self)
-   -> ([%#span53] inv'5 (shallow_model'2 self))
-  && ([%#span52] len'2 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : slice t . ([%#span40] inv'10 self)
+   -> ([%#span41] len'2 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   function shallow_model'0 (self : slice t) : Seq'0.t_seq t =
-    [%#span54] shallow_model'2 self
+    [%#span42] shallow_model'2 self
   
   predicate resolve'5 (self : slice t)
   
   predicate resolve'2 (self : t)
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'3 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span55] index_logic'3 (shallow_model'1 self) ix
+    [%#span43] index_logic'3 (shallow_model'1 self) ix
   
   predicate resolve'4 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span56] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)  -> resolve'2 (index_logic'2 self i)
-  
-  use seq.Seq
+    [%#span44] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)  -> resolve'2 (index_logic'2 self i)
   
   function concat'1 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span30] inv'5 self)
-   -> ([%#span31] inv'5 other)
-   -> ([%#span34] inv'5 (concat'1 self other))
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'2 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span27] forall i : int . 0 <= i
+  /\ i < len'2 (concat'1 self other)
    -> index_logic'3 (concat'1 self other) i
   = (if i < len'2 self then index_logic'3 self i else index_logic'3 other (i - len'2 self)))
-  && ([%#span32] len'2 (concat'1 self other) = len'2 self + len'2 other)
-  
-  use seq.Seq
+  && ([%#span26] len'2 (concat'1 self other) = len'2 self + len'2 other)
   
   function singleton'1 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'1_spec : forall v : t . ([%#span57] inv'2 v)
-   -> ([%#span60] inv'5 (singleton'1 v))
-  && ([%#span59] index_logic'3 (singleton'1 v) 0 = v) && ([%#span58] len'2 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : t . ([%#span45] inv'2 v)
+   -> ([%#span47] index_logic'3 (singleton'1 v) 0 = v) && ([%#span46] len'2 (singleton'1 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq t) (v : t) : Seq'0.t_seq t =
-    [%#span61] concat'1 self (singleton'1 v)
+    [%#span48] concat'1 self (singleton'1 v)
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq t)) : Seq'0.t_seq t
   
   predicate resolve'3 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span62]  ^ self =  * self
+    [%#span49]  ^ self =  * self
   
   predicate contains'0 [#"../hillel.rs" 59 0 59 44] (seq : Seq'0.t_seq deep_model_ty'0) (elem : deep_model_ty'0) =
-    [%#span63] exists i : int . 0 <= i /\ i < len'3 seq /\ index_logic'1 seq i = elem
-  
-  use seq.Seq
+    [%#span50] exists i : int . 0 <= i /\ i < len'3 seq /\ index_logic'1 seq i = elem
   
   function concat'2 (self : Seq'0.t_seq deep_model_ty'0) (other : Seq'0.t_seq deep_model_ty'0) : Seq'0.t_seq deep_model_ty'0
     
   
-  axiom concat'2_spec : forall self : Seq'0.t_seq deep_model_ty'0, other : Seq'0.t_seq deep_model_ty'0 . ([%#span30] inv'7 self)
-   -> ([%#span31] inv'7 other)
-   -> ([%#span34] inv'7 (concat'2 self other))
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'3 (concat'2 self other)
+  axiom concat'2_spec : forall self : Seq'0.t_seq deep_model_ty'0, other : Seq'0.t_seq deep_model_ty'0 . ([%#span27] forall i : int . 0
+  <= i
+  /\ i < len'3 (concat'2 self other)
    -> index_logic'1 (concat'2 self other) i
   = (if i < len'3 self then index_logic'1 self i else index_logic'1 other (i - len'3 self)))
-  && ([%#span32] len'3 (concat'2 self other) = len'3 self + len'3 other)
-  
-  use seq.Seq
+  && ([%#span26] len'3 (concat'2 self other) = len'3 self + len'3 other)
   
   function singleton'2 (v : deep_model_ty'0) : Seq'0.t_seq deep_model_ty'0
   
-  axiom singleton'2_spec : forall v : deep_model_ty'0 . ([%#span57] inv'12 v)
-   -> ([%#span60] inv'7 (singleton'2 v))
-  && ([%#span59] index_logic'1 (singleton'2 v) 0 = v) && ([%#span58] len'3 (singleton'2 v) = 1)
+  axiom singleton'2_spec : forall v : deep_model_ty'0 . ([%#span45] inv'11 v)
+   -> ([%#span47] index_logic'1 (singleton'2 v) 0 = v) && ([%#span46] len'3 (singleton'2 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq deep_model_ty'0) (v : deep_model_ty'0) : Seq'0.t_seq deep_model_ty'0
     
    =
-    [%#span61] concat'2 self (singleton'2 v)
+    [%#span48] concat'2 self (singleton'2 v)
   
   function deep_model'3 (self : t) : deep_model_ty'0
   
   predicate is_subset'0 [#"../hillel.rs" 66 0 66 49] (sub : Seq'0.t_seq deep_model_ty'0) (sup : Seq'0.t_seq deep_model_ty'0)
     
    =
-    [%#span64] forall i : int . 0 <= i /\ i < len'3 sub  -> contains'0 sup (index_logic'1 sub i)
+    [%#span51] forall i : int . 0 <= i /\ i < len'3 sub  -> contains'0 sup (index_logic'1 sub i)
   
   function deep_model'0 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq deep_model_ty'0
   
-  axiom deep_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span65] inv'1 self)
-   -> ([%#span68] inv'7 (deep_model'0 self))
-  && ([%#span67] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)
+  axiom deep_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span52] inv'1 self)
+   -> ([%#span54] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)
    -> index_logic'1 (deep_model'0 self) i = deep_model'3 (index_logic'2 self i))
-  && ([%#span66] len'2 (shallow_model'1 self) = len'3 (deep_model'0 self))
+  && ([%#span53] len'2 (shallow_model'1 self) = len'3 (deep_model'0 self))
   
   predicate is_unique'0 [#"../hillel.rs" 52 0 52 34] (s : Seq'0.t_seq deep_model_ty'0) =
-    [%#span69] forall j : int . forall i : int . 0 <= i /\ i < len'3 s /\ 0 <= j /\ j < len'3 s
+    [%#span55] forall j : int . forall i : int . 0 <= i /\ i < len'3 s /\ 0 <= j /\ j < len'3 s
      -> index_logic'1 s i = index_logic'1 s j  -> i = j
   
   function deep_model'5 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq deep_model_ty'0 =
-    [%#span70] deep_model'0 ( * self)
+    [%#span56] deep_model'0 ( * self)
   
-  let rec insert_unique'0 (vec:borrowed (Vec'0.t_vec t (Global'0.t_global))) (elem:t) (return'  (ret:()))= {[@expl:precondition] [%#span73] inv'2 elem}
-    {[@expl:precondition] [%#span72] inv'3 vec}
-    {[@expl:precondition] [%#span71] is_unique'0 (deep_model'5 vec)}
+  let rec insert_unique'0 (vec:borrowed (Vec'0.t_vec t (Global'0.t_global))) (elem:t) (return'  (ret:()))= {[@expl:precondition] [%#span59] inv'2 elem}
+    {[@expl:precondition] [%#span58] inv'3 vec}
+    {[@expl:precondition] [%#span57] is_unique'0 (deep_model'5 vec)}
     any
-    [ return' (result:())-> {[%#span77] contains'0 (deep_model'0 ( ^ vec)) (deep_model'3 elem)}
-      {[%#span76] is_subset'0 (deep_model'0 ( ^ vec)) (push'1 (deep_model'5 vec) (deep_model'3 elem))}
-      {[%#span75] is_subset'0 (deep_model'5 vec) (deep_model'0 ( ^ vec))}
-      {[%#span74] is_unique'0 (deep_model'0 ( ^ vec))}
+    [ return' (result:())-> {[%#span63] contains'0 (deep_model'0 ( ^ vec)) (deep_model'3 elem)}
+      {[%#span62] is_subset'0 (deep_model'0 ( ^ vec)) (push'1 (deep_model'5 vec) (deep_model'3 elem))}
+      {[%#span61] is_subset'0 (deep_model'5 vec) (deep_model'0 ( ^ vec))}
+      {[%#span60] is_unique'0 (deep_model'0 ( ^ vec))}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span57] inv'10 v)
-   -> ([%#span60] inv'6 (singleton'0 v))
-  && ([%#span59] index_logic'0 (singleton'0 v) 0 = v) && ([%#span58] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span45] inv'9 v)
+   -> ([%#span47] index_logic'0 (singleton'0 v) 0 = v) && ([%#span46] len'1 (singleton'0 v) = 1)
   
   predicate resolve'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span62]  ^ self =  * self
+    [%#span49]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span78] resolve'1 self
+    [%#span64] resolve'1 self
     /\ deep_model'2 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'2 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span79] inv'8 self}
+  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span65] inv'7 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span81] inv'9 result}
-      {[%#span80] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span67] inv'8 result}
+      {[%#span66] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
       (! return' {result}) ]
     
   
-  use prelude.seq_ext.SeqExt
-  
   function subsequence'0 (self : Seq'0.t_seq deep_model_ty'0) (n : int) (m : int) : Seq'0.t_seq deep_model_ty'0
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq deep_model_ty'0, n : int, m : int . ([%#span82] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq deep_model_ty'0, n : int, m : int . ([%#span68] 0 <= n
   /\ n <= m /\ m <= len'3 self)
-   -> ([%#span83] inv'7 self)
-   -> ([%#span86] inv'7 (subsequence'0 self n m))
-  && ([%#span85] forall i : int . 0 <= i /\ i < len'3 (subsequence'0 self n m)
+   -> ([%#span70] forall i : int . 0 <= i /\ i < len'3 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span84] len'3 (subsequence'0 self n m) = m - n)
+  && ([%#span69] len'3 (subsequence'0 self n m) = m - n)
   
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
   function index_logic'4 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span87] index_logic'3 (shallow_model'2 self) ix
+    [%#span71] index_logic'3 (shallow_model'2 self) ix
   
   function deep_model'4 (self : slice t) : Seq'0.t_seq deep_model_ty'0
   
-  axiom deep_model'4_spec : forall self : slice t . ([%#span88] inv'11 self)
-   -> ([%#span91] inv'7 (deep_model'4 self))
-  && ([%#span90] forall i : int . 0 <= i /\ i < len'3 (deep_model'4 self)
+  axiom deep_model'4_spec : forall self : slice t . ([%#span72] inv'10 self)
+   -> ([%#span74] forall i : int . 0 <= i /\ i < len'3 (deep_model'4 self)
    -> index_logic'1 (deep_model'4 self) i = deep_model'3 (index_logic'4 self i))
-  && ([%#span89] len'2 (shallow_model'0 self) = len'3 (deep_model'4 self))
+  && ([%#span73] len'2 (shallow_model'0 self) = len'3 (deep_model'4 self))
   
   function deep_model'1 (self : slice t) : Seq'0.t_seq deep_model_ty'0 =
-    [%#span92] deep_model'4 self
+    [%#span75] deep_model'4 self
   
   function inner'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
@@ -2303,41 +2036,40 @@ module Hillel_Unique
   
   function new'3 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'3_spec : forall x : Seq'0.t_seq usize . ([%#span93] inv'6 x)  -> ([%#span94] deref'0 (new'3 x) = x)
+  axiom new'3_spec : forall x : Seq'0.t_seq usize . ([%#span76] inv'6 x)  -> ([%#span77] deref'0 (new'3 x) = x)
   
   function new'2 (x : Range'0.t_range usize) : Snapshot'0.t_snapshot (Range'0.t_range usize)
   
-  axiom new'2_spec : forall x : Range'0.t_range usize . ([%#span93] inv'0 x)  -> ([%#span94] deref'2 (new'2 x) = x)
+  axiom new'2_spec : forall x : Range'0.t_range usize . ([%#span76] inv'0 x)  -> ([%#span77] deref'2 (new'2 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span95] self = res
+    [%#span78] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range usize) =
-    [%#span96] true
+    [%#span79] true
   
-  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span98] inv'0 self}
-    {[@expl:precondition] [%#span97] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span81] inv'0 self}
+    {[@expl:precondition] [%#span80] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range usize)-> {[%#span99] inv'0 result}
-      {[%#span97] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range usize)-> {[%#span82] inv'0 result}
+      {[%#span80] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:slice t) (return'  (ret:usize))= {[@expl:precondition] [%#span100] inv'4 self}
+  let rec len'0 (self:slice t) (return'  (ret:usize))= {[@expl:precondition] [%#span83] inv'4 self}
     any
-    [ return' (result:usize)-> {[%#span101] len'2 (shallow_model'0 self) = UIntSize.to_int result}
-      (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span84] len'2 (shallow_model'0 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq t))
   
   function new'1 (x : Seq'0.t_seq t) : Snapshot'0.t_snapshot (Seq'0.t_seq t)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq t . ([%#span93] inv'5 x)  -> ([%#span94] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq t . ([%#span76] inv'5 x)  -> ([%#span77] deref'1 (new'1 x) = x)
   
   let rec new'0 (_1:()) (return'  (ret:Vec'0.t_vec t (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec t (Global'0.t_global))-> {[%#span103] inv'1 result}
-      {[%#span102] len'2 (shallow_model'1 result) = 0}
+    [ return' (result:Vec'0.t_vec t (Global'0.t_global))-> {[%#span86] inv'1 result}
+      {[%#span85] len'2 (shallow_model'1 result) = 0}
       (! return' {result}) ]
     
   
@@ -2493,51 +2225,29 @@ module Hillel_SumRange_Impl
   
   let%span shillel2 = "../hillel.rs" 122 10 122 19
   
-  let%span span3 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  use prelude.prelude.Int
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq uint32) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq uint32 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.UInt32
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   constant seq  : Seq'0.t_seq uint32
   
@@ -2563,67 +2273,45 @@ module Hillel_SumRangeSplit_Impl
   
   let%span shillel2 = "../hillel.rs" 134 10 134 18
   
-  let%span span3 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span5 = "../hillel.rs" 123 11 123 53
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span6 = "../hillel.rs" 124 10 124 21
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span7 = "../hillel.rs" 122 10 122 19
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span8 = "../hillel.rs" 121 0 121 8
   
-  let%span span9 = "../hillel.rs" 123 11 123 53
-  
-  let%span span10 = "../hillel.rs" 124 10 124 21
-  
-  let%span span11 = "../hillel.rs" 122 10 122 19
-  
-  let%span span12 = "../hillel.rs" 121 0 121 8
+  use prelude.prelude.Int
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq uint32) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq uint32 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.UInt32
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function sum_range'0 [#"../hillel.rs" 125 0 125 54] (seq : Seq'0.t_seq uint32) (from : int) (to' : int) : int
   
   axiom sum_range'0_def : forall seq : Seq'0.t_seq uint32, from : int, to' : int . sum_range'0 seq from to'
-  = ([%#span12] if to' - from > 0 then UInt32.to_int (index_logic'0 seq from) + sum_range'0 seq (from + 1) to' else 0)
+  = ([%#span8] if to' - from > 0 then UInt32.to_int (index_logic'0 seq from) + sum_range'0 seq (from + 1) to' else 0)
   
-  axiom sum_range'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int . ([%#span9] 0 <= from
-  /\ from <= to' /\ to' <= len'0 seq)  -> ([%#span10] sum_range'0 seq from to' >= 0)
+  axiom sum_range'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int . ([%#span5] 0 <= from
+  /\ from <= to' /\ to' <= len'0 seq)  -> ([%#span6] sum_range'0 seq from to' >= 0)
   
   constant seq  : Seq'0.t_seq uint32
   
@@ -2653,91 +2341,69 @@ module Hillel_Score_Impl
   
   let%span shillel2 = "../hillel.rs" 146 0 146 79
   
-  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span sseq24 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span shillel5 = "../hillel.rs" 135 11 135 63
-  
-  let%span shillel6 = "../hillel.rs" 136 10 136 85
+  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span shillel7 = "../hillel.rs" 134 10 134 18
+  let%span shillel4 = "../hillel.rs" 135 11 135 63
   
-  let%span shillel8 = "../hillel.rs" 123 11 123 53
+  let%span shillel5 = "../hillel.rs" 136 10 136 85
   
-  let%span shillel9 = "../hillel.rs" 124 10 124 21
+  let%span shillel6 = "../hillel.rs" 134 10 134 18
   
-  let%span shillel10 = "../hillel.rs" 122 10 122 19
+  let%span shillel7 = "../hillel.rs" 123 11 123 53
   
-  let%span span11 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span shillel8 = "../hillel.rs" 124 10 124 21
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span shillel9 = "../hillel.rs" 122 10 122 19
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span11 = "../../../../creusot-contracts/src/logic/int.rs" 55 4 55 12
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/int.rs" 55 4 55 12
+  let%span span12 = "../hillel.rs" 121 0 121 8
   
-  let%span span16 = "../hillel.rs" 121 0 121 8
+  let%span span13 = "../hillel.rs" 138 4 140 5
   
-  let%span span17 = "../hillel.rs" 138 4 140 5
+  use prelude.prelude.Int
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq uint32) =
-    [%#span11] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq uint32 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#sseq23] inv'0 self)  -> ([%#sseq24] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#sseq23] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span12] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span14] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   function abs_diff'0 (self : int) (other : int) : int =
-    [%#span15] if self < other then other - self else self - other
+    [%#span11] if self < other then other - self else self - other
   
   use prelude.prelude.UInt32
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function sum_range'0 [#"../hillel.rs" 125 0 125 54] (seq : Seq'0.t_seq uint32) (from : int) (to' : int) : int
   
   axiom sum_range'0_def : forall seq : Seq'0.t_seq uint32, from : int, to' : int . sum_range'0 seq from to'
-  = ([%#span16] if to' - from > 0 then UInt32.to_int (index_logic'0 seq from) + sum_range'0 seq (from + 1) to' else 0)
+  = ([%#span12] if to' - from > 0 then UInt32.to_int (index_logic'0 seq from) + sum_range'0 seq (from + 1) to' else 0)
   
-  axiom sum_range'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int . ([%#shillel8] 0 <= from
-  /\ from <= to' /\ to' <= len'0 seq)  -> ([%#shillel9] sum_range'0 seq from to' >= 0)
+  axiom sum_range'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int . ([%#shillel7] 0 <= from
+  /\ from <= to' /\ to' <= len'0 seq)  -> ([%#shillel8] sum_range'0 seq from to' >= 0)
   
   function sum_range_split'0 [#"../hillel.rs" 137 0 137 61] (seq : Seq'0.t_seq uint32) (from : int) (to' : int) (i : int) : ()
     
   
   axiom sum_range_split'0_def : forall seq : Seq'0.t_seq uint32, from : int, to' : int, i : int . sum_range_split'0 seq from to' i
-  = ([%#span17] if i > from then let _ = sum_range_split'0 seq (from + 1) to' i in () else ())
+  = ([%#span13] if i > from then let _ = sum_range_split'0 seq (from + 1) to' i in () else ())
   
-  axiom sum_range_split'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int, i : int . ([%#shillel5] 0
+  axiom sum_range_split'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int, i : int . ([%#shillel4] 0
   <= from
   /\ from <= i /\ i <= to' /\ to' <= len'0 seq)
-   -> ([%#shillel6] sum_range'0 seq from to' = sum_range'0 seq from i + sum_range'0 seq i to')
+   -> ([%#shillel5] sum_range'0 seq from to' = sum_range'0 seq from i + sum_range'0 seq i to')
   
   constant seq  : Seq'0.t_seq uint32
   
@@ -2746,19 +2412,17 @@ module Hillel_Score_Impl
   function score [#"../hillel.rs" 147 0 147 38] (seq : Seq'0.t_seq uint32) (i : int) : int
   
   goal vc_score : ([%#shillel0] 0 <= i /\ i <= len'0 seq)
-   -> ([%#sseq23] inv'0 seq)
-  /\ (([%#sseq24] len'0 seq >= 0)
-   -> ([%#shillel5] 0 <= 0 /\ 0 <= i /\ i <= len'0 seq /\ len'0 seq <= len'0 seq)
-  /\ (([%#shillel6] sum_range'0 seq 0 (len'0 seq) = sum_range'0 seq 0 i + sum_range'0 seq i (len'0 seq))
-   -> (let _ = sum_range_split'0 seq 0 (len'0 seq) i in ([%#shillel8] 0 <= 0 /\ 0 <= i /\ i <= len'0 seq)
-  /\ (([%#shillel9] sum_range'0 seq 0 i >= 0)
-   -> ([%#sseq23] inv'0 seq)
-  /\ (([%#sseq24] len'0 seq >= 0)
-   -> ([%#shillel8] 0 <= i /\ i <= len'0 seq /\ len'0 seq <= len'0 seq)
-  /\ (([%#shillel9] sum_range'0 seq i (len'0 seq) >= 0)
+   -> ([%#sseq23] len'0 seq >= 0)
+   -> ([%#shillel4] 0 <= 0 /\ 0 <= i /\ i <= len'0 seq /\ len'0 seq <= len'0 seq)
+  /\ (([%#shillel5] sum_range'0 seq 0 (len'0 seq) = sum_range'0 seq 0 i + sum_range'0 seq i (len'0 seq))
+   -> (let _ = sum_range_split'0 seq 0 (len'0 seq) i in ([%#shillel7] 0 <= 0 /\ 0 <= i /\ i <= len'0 seq)
+  /\ (([%#shillel8] sum_range'0 seq 0 i >= 0)
+   -> ([%#sseq23] len'0 seq >= 0)
+   -> ([%#shillel7] 0 <= i /\ i <= len'0 seq /\ len'0 seq <= len'0 seq)
+  /\ (([%#shillel8] sum_range'0 seq i (len'0 seq) >= 0)
    -> (let result = abs_diff'0 (sum_range'0 seq 0 i) (sum_range'0 seq i (len'0 seq)) in ([%#shillel2] 0 = i
   \/ i = len'0 seq  -> result = sum_range'0 seq 0 (len'0 seq))
-  && ([%#shillel1] 0 <= result /\ result <= sum_range'0 seq 0 (len'0 seq)))))))))
+  && ([%#shillel1] 0 <= result /\ result <= sum_range'0 seq 0 (len'0 seq)))))))
 end
 module Hillel_Fulcrum
   let%span shillel0 = "../hillel.rs" 160 25 160 26
@@ -2811,233 +2475,200 @@ module Hillel_Fulcrum
   
   let%span span24 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span32 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
-  
-  let%span span33 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
-  
-  let%span span34 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
-  
-  let%span span35 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
-  
-  let%span span36 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
-  
-  let%span span37 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
-  
-  let%span span38 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span39 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span40 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span41 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span28 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span42 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span29 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span43 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span30 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span44 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span31 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span32 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span46 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span33 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span47 = "" 0 0 0 0
+  let%span span34 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span48 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span35 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span49 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span36 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span50 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span37 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span51 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span52 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span39 = "" 0 0 0 0
   
-  let%span span53 = "../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
+  let%span span40 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span54 = "../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
+  let%span span41 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span55 = "../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
+  let%span span42 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span56 = "../../../../creusot-contracts/src/std/slice.rs" 76 4 76 35
+  let%span span43 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span57 = "../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
+  let%span span44 = "../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
   
-  let%span span58 = "../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
+  let%span span45 = "../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
   
-  let%span span59 = "../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
+  let%span span46 = "../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
   
-  let%span span60 = "../../../../creusot-contracts/src/std/slice.rs" 398 31 398 33
+  let%span span47 = "../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
   
-  let%span span61 = "../../../../creusot-contracts/src/std/slice.rs" 398 61 398 63
+  let%span span48 = "../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
   
-  let%span span62 = "../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
+  let%span span49 = "../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
   
-  let%span span63 = "../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
+  let%span span50 = "../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
   
-  let%span span64 = "../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
+  let%span span51 = "../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
   
-  let%span span65 = "../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
+  let%span span52 = "../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
   
-  let%span span66 = "../../../../creusot-contracts/src/logic/int.rs" 55 4 55 12
+  let%span span53 = "../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
   
-  let%span span67 = "../../../../creusot-contracts/src/std/num.rs" 221 26 221 59
+  let%span span54 = "../../../../creusot-contracts/src/logic/int.rs" 55 4 55 12
   
-  let%span span68 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span55 = "../../../../creusot-contracts/src/std/num.rs" 221 26 221 59
   
-  let%span span69 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span56 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span70 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span57 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span71 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span58 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span72 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span59 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span73 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span60 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span74 = "" 0 0 0 0
+  let%span span61 = "" 0 0 0 0
   
-  let%span span75 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span62 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span76 = "" 0 0 0 0
+  let%span span63 = "" 0 0 0 0
   
-  let%span span77 = "../hillel.rs" 123 11 123 53
+  let%span span64 = "../hillel.rs" 123 11 123 53
   
-  let%span span78 = "../hillel.rs" 124 10 124 21
+  let%span span65 = "../hillel.rs" 124 10 124 21
   
-  let%span span79 = "../hillel.rs" 122 10 122 19
+  let%span span66 = "../hillel.rs" 122 10 122 19
   
-  let%span span80 = "../hillel.rs" 121 0 121 8
+  let%span span67 = "../hillel.rs" 121 0 121 8
   
-  let%span span81 = "../hillel.rs" 135 11 135 63
+  let%span span68 = "../hillel.rs" 135 11 135 63
   
-  let%span span82 = "../hillel.rs" 136 10 136 85
+  let%span span69 = "../hillel.rs" 136 10 136 85
   
-  let%span span83 = "../hillel.rs" 134 10 134 18
+  let%span span70 = "../hillel.rs" 134 10 134 18
   
-  let%span span84 = "../hillel.rs" 138 4 140 5
+  let%span span71 = "../hillel.rs" 138 4 140 5
   
-  let%span span85 = "../hillel.rs" 144 11 144 35
+  let%span span72 = "../hillel.rs" 144 11 144 35
   
-  let%span span86 = "../hillel.rs" 145 10 145 64
+  let%span span73 = "../hillel.rs" 145 10 145 64
   
-  let%span span87 = "../hillel.rs" 146 0 146 79
+  let%span span74 = "../hillel.rs" 146 0 146 79
   
-  let%span span88 = "../hillel.rs" 148 4 148 41
+  let%span span75 = "../hillel.rs" 148 4 148 41
   
-  let%span span89 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span76 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span90 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span77 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span91 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
+  let%span span78 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span92 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
+  let%span span79 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span93 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span80 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span94 = "" 0 0 0 0
+  let%span span81 = "" 0 0 0 0
   
-  let%span span95 = "" 0 0 0 0
+  let%span span82 = "" 0 0 0 0
   
-  let%span span96 = "" 0 0 0 0
+  let%span span83 = "" 0 0 0 0
   
-  let%span span97 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span84 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span98 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span85 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span99 = "../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
+  let%span span86 = "../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
   
-  let%span span100 = "" 0 0 0 0
+  let%span span87 = "" 0 0 0 0
   
-  let%span span101 = "../../../../creusot-contracts/src/std/slice.rs" 344 20 344 32
+  let%span span88 = "../../../../creusot-contracts/src/std/slice.rs" 344 20 344 32
   
-  let%span span102 = "../../../../creusot-contracts/src/std/slice.rs" 338 20 338 24
+  let%span span89 = "../../../../creusot-contracts/src/std/slice.rs" 338 20 338 24
   
-  let%span span103 = "" 0 0 0 0
+  let%span span90 = "" 0 0 0 0
   
   use prelude.prelude.UInt32
   
   use prelude.prelude.Slice
   
-  predicate invariant'11 (self : slice uint32) =
+  predicate invariant'10 (self : slice uint32) =
     [%#span24] true
   
-  predicate inv'11 (_x : slice uint32)
+  predicate inv'10 (_x : slice uint32)
   
-  axiom inv'11 : forall x : slice uint32 . inv'11 x = true
+  axiom inv'10 : forall x : slice uint32 . inv'10 x = true
   
   use prelude.prelude.UIntSize
   
-  predicate invariant'10 (self : usize) =
+  predicate invariant'9 (self : usize) =
     [%#span24] true
   
-  predicate inv'10 (_x : usize)
+  predicate inv'9 (_x : usize)
   
-  axiom inv'10 : forall x : usize . inv'10 x = true
+  axiom inv'9 : forall x : usize . inv'9 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'9 (self : Option'0.t_option usize) =
+  predicate invariant'8 (self : Option'0.t_option usize) =
     [%#span24] true
   
-  predicate inv'9 (_x : Option'0.t_option usize)
+  predicate inv'8 (_x : Option'0.t_option usize)
   
-  axiom inv'9 : forall x : Option'0.t_option usize . inv'9 x = true
+  axiom inv'8 : forall x : Option'0.t_option usize . inv'8 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'8 (self : borrowed (Range'0.t_range usize)) =
+  predicate invariant'7 (self : borrowed (Range'0.t_range usize)) =
     [%#span24] true
   
-  predicate inv'8 (_x : borrowed (Range'0.t_range usize))
+  predicate inv'7 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'8 : forall x : borrowed (Range'0.t_range usize) . inv'8 x = true
+  axiom inv'7 : forall x : borrowed (Range'0.t_range usize) . inv'7 x = true
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'7 (self : Seq'0.t_seq usize) =
-    [%#span24] true
-  
-  predicate inv'7 (_x : Seq'0.t_seq usize)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq usize . inv'7 x = true
-  
-  predicate invariant'6 (self : uint32) =
+  predicate invariant'6 (self : Seq'0.t_seq usize) =
     [%#span24] true
   
-  predicate inv'6 (_x : uint32)
+  predicate inv'6 (_x : Seq'0.t_seq usize)
   
-  axiom inv'6 : forall x : uint32 . inv'6 x = true
+  axiom inv'6 : forall x : Seq'0.t_seq usize . inv'6 x = true
   
-  predicate invariant'5 (self : Option'0.t_option uint32) =
+  predicate invariant'5 (self : uint32) =
     [%#span24] true
   
-  predicate inv'5 (_x : Option'0.t_option uint32)
+  predicate inv'5 (_x : uint32)
   
-  axiom inv'5 : forall x : Option'0.t_option uint32 . inv'5 x = true
+  axiom inv'5 : forall x : uint32 . inv'5 x = true
   
-  predicate invariant'4 (self : Seq'0.t_seq uint32) =
+  predicate invariant'4 (self : Option'0.t_option uint32) =
     [%#span24] true
   
-  predicate inv'4 (_x : Seq'0.t_seq uint32)
+  predicate inv'4 (_x : Option'0.t_option uint32)
   
-  axiom inv'4 : forall x : Seq'0.t_seq uint32 . inv'4 x = true
+  axiom inv'4 : forall x : Option'0.t_option uint32 . inv'4 x = true
   
   predicate invariant'3 (self : Seq'0.t_seq uint32) =
     [%#span24] true
@@ -3053,31 +2684,21 @@ module Hillel_Fulcrum
   
   axiom inv'2 : forall x : slice uint32 . inv'2 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
-  
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function len'3 (self : Seq'0.t_seq usize) : int
   
-  axiom len'3_spec : forall self : Seq'0.t_seq usize . ([%#span25] inv'7 self)  -> ([%#span26] len'3 self >= 0)
+  axiom len'3_spec : forall self : Seq'0.t_seq usize . [%#span25] len'3 self >= 0
   
   function concat'1 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span27] inv'7 self)
-   -> ([%#span28] inv'7 other)
-   -> ([%#span31] inv'7 (concat'1 self other))
-  && ([%#span30] forall i : int . 0 <= i /\ i < len'3 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span27] forall i : int . 0 <= i
+  /\ i < len'3 (concat'1 self other)
    -> index_logic'2 (concat'1 self other) i
   = (if i < len'3 self then index_logic'2 self i else index_logic'2 other (i - len'3 self)))
-  && ([%#span29] len'3 (concat'1 self other) = len'3 self + len'3 other)
+  && ([%#span26] len'3 (concat'1 self other) = len'3 self + len'3 other)
   
   predicate inv'1 (_x : Range'0.t_range usize)
   
@@ -3086,12 +2707,12 @@ module Hillel_Fulcrum
   use prelude.prelude.UIntSize
   
   function deep_model'0 (self : usize) : int =
-    [%#span32] UIntSize.to_int self
+    [%#span28] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'1 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span33] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span29] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'3 visited > 0
@@ -3104,113 +2725,95 @@ module Hillel_Fulcrum
   function produces_trans'1 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span34] produces'1 a ab b)
-   -> ([%#span35] produces'1 b bc c)
-   -> ([%#span36] inv'1 a)
-   -> ([%#span37] inv'7 ab)
-   -> ([%#span38] inv'1 b)
-   -> ([%#span39] inv'7 bc)  -> ([%#span40] inv'1 c)  -> ([%#span41] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span30] produces'1 a ab b)
+   -> ([%#span31] produces'1 b bc c)
+   -> ([%#span32] inv'1 a)
+   -> ([%#span33] inv'1 b)  -> ([%#span34] inv'1 c)  -> ([%#span35] produces'1 a (concat'1 ab bc) c)
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span42] ()
+  constant empty'1 : Seq'0.t_seq usize
   
   function produces_refl'1 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span43] inv'1 self)
-   -> ([%#span44] produces'1 self (empty'1 : Seq'0.t_seq usize) self)
+  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span36] inv'1 self)
+   -> ([%#span37] produces'1 self (empty'1 : Seq'0.t_seq usize) self)
   
   predicate invariant'1 (self : Range'0.t_range usize) =
     [%#span24] true
   
   axiom inv'1 : forall x : Range'0.t_range usize . inv'1 x = true
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span46] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span45] len'3 (empty'1 : Seq'0.t_seq usize) = 0
-  
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span38] len'3 (empty'1 : Seq'0.t_seq usize) = 0
   
   function len'1 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . ([%#span25] inv'4 self)  -> ([%#span26] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . [%#span25] len'1 self >= 0
   
-  constant empty'2 : Seq'0.t_seq uint32 = [%#span42] ()
+  constant empty'2 : Seq'0.t_seq uint32
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span46] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span45] len'1 (empty'2 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span38] len'1 (empty'2 : Seq'0.t_seq uint32) = 0
   
   use Core_Slice_Iter_Iter_Type as Iter'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span25] inv'3 self)  -> ([%#span26] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span25] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span27] inv'3 self)
-   -> ([%#span28] inv'3 other)
-   -> ([%#span31] inv'3 (concat'0 self other))
-  && ([%#span30] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span27] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span29] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span26] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
-  
-  constant max'0 : usize = [%#span47] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span39] (18446744073709551615 : usize)
   
   function shallow_model'2 (self : slice uint32) : Seq'0.t_seq uint32
   
-  axiom shallow_model'2_spec : forall self : slice uint32 . ([%#span48] inv'11 self)
-   -> ([%#span50] inv'4 (shallow_model'2 self))
-  && ([%#span49] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : slice uint32 . ([%#span40] inv'10 self)
+   -> ([%#span41] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'3 [@inline:trivial] (self : slice uint32) (ix : int) : uint32 =
-    [%#span51] index_logic'0 (shallow_model'2 self) ix
+    [%#span42] index_logic'0 (shallow_model'2 self) ix
   
   function shallow_model'0 (self : slice uint32) : Seq'0.t_seq uint32 =
-    [%#span52] shallow_model'2 self
+    [%#span43] shallow_model'2 self
   
   function to_ref_seq'0 (self : slice uint32) : Seq'0.t_seq uint32
   
-  axiom to_ref_seq'0_spec : forall self : slice uint32 . ([%#span53] inv'2 self)
-   -> ([%#span56] inv'3 (to_ref_seq'0 self))
-  && ([%#span55] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
+  axiom to_ref_seq'0_spec : forall self : slice uint32 . ([%#span44] inv'2 self)
+   -> ([%#span46] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
    -> index_logic'1 (to_ref_seq'0 self) i = index_logic'3 self i)
-  && ([%#span54] len'0 (to_ref_seq'0 self) = len'1 (shallow_model'0 self))
+  && ([%#span45] len'0 (to_ref_seq'0 self) = len'1 (shallow_model'0 self))
   
   function shallow_model'1 (self : Iter'0.t_iter uint32) : slice uint32
   
   predicate produces'0 (self : Iter'0.t_iter uint32) (visited : Seq'0.t_seq uint32) (tl : Iter'0.t_iter uint32) =
-    [%#span57] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
+    [%#span47] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
   
   function produces_trans'0 (a : Iter'0.t_iter uint32) (ab : Seq'0.t_seq uint32) (b : Iter'0.t_iter uint32) (bc : Seq'0.t_seq uint32) (c : Iter'0.t_iter uint32) : ()
     
    =
-    [%#span63] ()
+    [%#span51] ()
   
-  axiom produces_trans'0_spec : forall a : Iter'0.t_iter uint32, ab : Seq'0.t_seq uint32, b : Iter'0.t_iter uint32, bc : Seq'0.t_seq uint32, c : Iter'0.t_iter uint32 . ([%#span58] produces'0 a ab b)
-   -> ([%#span59] produces'0 b bc c)
-   -> ([%#span60] inv'3 ab)  -> ([%#span61] inv'3 bc)  -> ([%#span62] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Iter'0.t_iter uint32, ab : Seq'0.t_seq uint32, b : Iter'0.t_iter uint32, bc : Seq'0.t_seq uint32, c : Iter'0.t_iter uint32 . ([%#span48] produces'0 a ab b)
+   -> ([%#span49] produces'0 b bc c)  -> ([%#span50] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span42] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   function produces_refl'0 (self : Iter'0.t_iter uint32) : () =
-    [%#span65] ()
+    [%#span53] ()
   
-  axiom produces_refl'0_spec : forall self : Iter'0.t_iter uint32 . [%#span64] produces'0 self (empty'0 : Seq'0.t_seq uint32) self
+  axiom produces_refl'0_spec : forall self : Iter'0.t_iter uint32 . [%#span52] produces'0 self (empty'0 : Seq'0.t_seq uint32) self
   
   predicate invariant'0 (self : Iter'0.t_iter uint32) =
     [%#span24] true
@@ -3219,46 +2822,42 @@ module Hillel_Fulcrum
   
   axiom inv'0 : forall x : Iter'0.t_iter uint32 . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span46] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span45] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span38] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   function abs_diff'1 (self : int) (other : int) : int =
-    [%#span66] if self < other then other - self else self - other
+    [%#span54] if self < other then other - self else self - other
   
   use prelude.prelude.UInt32
   
   let rec abs_diff'0 (self:uint32) (other:uint32) (return'  (ret:uint32))= any
-    [ return' (result:uint32)-> {[%#span67] UInt32.to_int result
+    [ return' (result:uint32)-> {[%#span55] UInt32.to_int result
       = abs_diff'1 (UInt32.to_int self) (UInt32.to_int other)}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'1 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'1_spec : forall v : usize . ([%#span68] inv'10 v)
-   -> ([%#span71] inv'7 (singleton'1 v))
-  && ([%#span70] index_logic'2 (singleton'1 v) 0 = v) && ([%#span69] len'3 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : usize . ([%#span56] inv'9 v)
+   -> ([%#span58] index_logic'2 (singleton'1 v) 0 = v) && ([%#span57] len'3 (singleton'1 v) = 1)
   
   predicate resolve'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span72]  ^ self =  * self
+    [%#span59]  ^ self =  * self
   
   predicate completed'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span73] resolve'1 self
+    [%#span60] resolve'1 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'1 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span74] inv'8 self}
+  let rec next'1 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span61] inv'7 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span76] inv'9 result}
-      {[%#span75] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span63] inv'8 result}
+      {[%#span62] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'1 v) ( ^ self)
         end}
@@ -3268,27 +2867,27 @@ module Hillel_Fulcrum
   function sum_range'0 [#"../hillel.rs" 125 0 125 54] (seq : Seq'0.t_seq uint32) (from : int) (to' : int) : int
   
   axiom sum_range'0_def : forall seq : Seq'0.t_seq uint32, from : int, to' : int . sum_range'0 seq from to'
-  = ([%#span80] if to' - from > 0 then UInt32.to_int (index_logic'0 seq from) + sum_range'0 seq (from + 1) to' else 0)
+  = ([%#span67] if to' - from > 0 then UInt32.to_int (index_logic'0 seq from) + sum_range'0 seq (from + 1) to' else 0)
   
-  axiom sum_range'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int . ([%#span77] 0 <= from
-  /\ from <= to' /\ to' <= len'1 seq)  -> ([%#span78] sum_range'0 seq from to' >= 0)
+  axiom sum_range'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int . ([%#span64] 0 <= from
+  /\ from <= to' /\ to' <= len'1 seq)  -> ([%#span65] sum_range'0 seq from to' >= 0)
   
   function sum_range_split'0 [#"../hillel.rs" 137 0 137 61] (seq : Seq'0.t_seq uint32) (from : int) (to' : int) (i : int) : ()
     
   
   axiom sum_range_split'0_def : forall seq : Seq'0.t_seq uint32, from : int, to' : int, i : int . sum_range_split'0 seq from to' i
-  = ([%#span84] if i > from then let _ = sum_range_split'0 seq (from + 1) to' i in () else ())
+  = ([%#span71] if i > from then let _ = sum_range_split'0 seq (from + 1) to' i in () else ())
   
-  axiom sum_range_split'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int, i : int . ([%#span81] 0 <= from
+  axiom sum_range_split'0_spec : forall seq : Seq'0.t_seq uint32, from : int, to' : int, i : int . ([%#span68] 0 <= from
   /\ from <= i /\ i <= to' /\ to' <= len'1 seq)
-   -> ([%#span82] sum_range'0 seq from to' = sum_range'0 seq from i + sum_range'0 seq i to')
+   -> ([%#span69] sum_range'0 seq from to' = sum_range'0 seq from i + sum_range'0 seq i to')
   
   function score'0 [#"../hillel.rs" 147 0 147 38] (seq : Seq'0.t_seq uint32) (i : int) : int =
-    [%#span88] let _ = sum_range_split'0 seq 0 (len'1 seq) i in abs_diff'1 (sum_range'0 seq 0 i) (sum_range'0 seq i (len'1 seq))
+    [%#span75] let _ = sum_range_split'0 seq 0 (len'1 seq) i in abs_diff'1 (sum_range'0 seq 0 i) (sum_range'0 seq i (len'1 seq))
   
-  axiom score'0_spec : forall seq : Seq'0.t_seq uint32, i : int . ([%#span85] 0 <= i /\ i <= len'1 seq)
-   -> ([%#span87] 0 = i \/ i = len'1 seq  -> score'0 seq i = sum_range'0 seq 0 (len'1 seq))
-  && ([%#span86] 0 <= score'0 seq i /\ score'0 seq i <= sum_range'0 seq 0 (len'1 seq))
+  axiom score'0_spec : forall seq : Seq'0.t_seq uint32, i : int . ([%#span72] 0 <= i /\ i <= len'1 seq)
+   -> ([%#span74] 0 = i \/ i = len'1 seq  -> score'0 seq i = sum_range'0 seq 0 (len'1 seq))
+  && ([%#span73] 0 <= score'0 seq i /\ score'0 seq i <= sum_range'0 seq 0 (len'1 seq))
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
@@ -3300,51 +2899,48 @@ module Hillel_Fulcrum
   
   function new'3 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'3_spec : forall x : Seq'0.t_seq usize . ([%#span89] inv'7 x)  -> ([%#span90] deref'1 (new'3 x) = x)
+  axiom new'3_spec : forall x : Seq'0.t_seq usize . ([%#span76] inv'6 x)  -> ([%#span77] deref'1 (new'3 x) = x)
   
   function new'2 (x : Range'0.t_range usize) : Snapshot'0.t_snapshot (Range'0.t_range usize)
   
-  axiom new'2_spec : forall x : Range'0.t_range usize . ([%#span89] inv'1 x)  -> ([%#span90] deref'3 (new'2 x) = x)
+  axiom new'2_spec : forall x : Range'0.t_range usize . ([%#span76] inv'1 x)  -> ([%#span77] deref'3 (new'2 x) = x)
   
   predicate into_iter_post'1 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span91] self = res
+    [%#span78] self = res
   
   predicate into_iter_pre'1 (self : Range'0.t_range usize) =
-    [%#span92] true
+    [%#span79] true
   
-  let rec into_iter'1 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span94] inv'1 self}
-    {[@expl:precondition] [%#span93] into_iter_pre'1 self}
+  let rec into_iter'1 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span81] inv'1 self}
+    {[@expl:precondition] [%#span80] into_iter_pre'1 self}
     any
-    [ return' (result:Range'0.t_range usize)-> {[%#span95] inv'1 result}
-      {[%#span93] into_iter_post'1 self result}
+    [ return' (result:Range'0.t_range usize)-> {[%#span82] inv'1 result}
+      {[%#span80] into_iter_post'1 self result}
       (! return' {result}) ]
     
   
-  let rec len'2 (self:slice uint32) (return'  (ret:usize))= {[@expl:precondition] [%#span96] inv'2 self}
+  let rec len'2 (self:slice uint32) (return'  (ret:usize))= {[@expl:precondition] [%#span83] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span97] len'1 (shallow_model'0 self) = UIntSize.to_int result} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span84] len'1 (shallow_model'0 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span68] inv'6 v)
-   -> ([%#span71] inv'3 (singleton'0 v))
-  && ([%#span70] index_logic'1 (singleton'0 v) 0 = v) && ([%#span69] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span56] inv'5 v)
+   -> ([%#span58] index_logic'1 (singleton'0 v) 0 = v) && ([%#span57] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Iter'0.t_iter uint32)) =
-    [%#span72]  ^ self =  * self
+    [%#span59]  ^ self =  * self
   
   function shallow_model'3 (self : borrowed (Iter'0.t_iter uint32)) : slice uint32 =
-    [%#span98] shallow_model'1 ( * self)
+    [%#span85] shallow_model'1 ( * self)
   
   predicate completed'0 (self : borrowed (Iter'0.t_iter uint32)) =
-    [%#span99] resolve'0 self /\ shallow_model'2 (shallow_model'3 self) = (empty'2 : Seq'0.t_seq uint32)
+    [%#span86] resolve'0 self /\ shallow_model'2 (shallow_model'3 self) = (empty'2 : Seq'0.t_seq uint32)
   
   let rec next'0 (self:borrowed (Iter'0.t_iter uint32)) (return'  (ret:Option'0.t_option uint32))= any
-    [ return' (result:Option'0.t_option uint32)-> {[%#span100] inv'5 result}
-      {[%#span75] match result with
+    [ return' (result:Option'0.t_option uint32)-> {[%#span87] inv'4 result}
+      {[%#span62] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -3361,21 +2957,21 @@ module Hillel_Fulcrum
   
   function new'1 (x : Seq'0.t_seq uint32) : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq uint32 . ([%#span89] inv'3 x)  -> ([%#span90] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq uint32 . ([%#span76] inv'3 x)  -> ([%#span77] deref'0 (new'1 x) = x)
   
   function new'0 (x : Iter'0.t_iter uint32) : Snapshot'0.t_snapshot (Iter'0.t_iter uint32)
   
-  axiom new'0_spec : forall x : Iter'0.t_iter uint32 . ([%#span89] inv'0 x)  -> ([%#span90] deref'2 (new'0 x) = x)
+  axiom new'0_spec : forall x : Iter'0.t_iter uint32 . ([%#span76] inv'0 x)  -> ([%#span77] deref'2 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : slice uint32) (res : Iter'0.t_iter uint32) =
-    [%#span101] self = shallow_model'1 res
+    [%#span88] self = shallow_model'1 res
   
   predicate into_iter_pre'0 (self : slice uint32) =
-    [%#span102] true
+    [%#span89] true
   
-  let rec into_iter'0 (self:slice uint32) (return'  (ret:Iter'0.t_iter uint32))= {[@expl:precondition] [%#span103] inv'2 self}
-    {[@expl:precondition] [%#span93] into_iter_pre'0 self}
-    any [ return' (result:Iter'0.t_iter uint32)-> {[%#span93] into_iter_post'0 self result} (! return' {result}) ] 
+  let rec into_iter'0 (self:slice uint32) (return'  (ret:Iter'0.t_iter uint32))= {[@expl:precondition] [%#span90] inv'2 self}
+    {[@expl:precondition] [%#span80] into_iter_pre'0 self}
+    any [ return' (result:Iter'0.t_iter uint32)-> {[%#span80] into_iter_post'0 self result} (! return' {result}) ] 
   
   let rec fulcrum (s:slice uint32) (return'  (ret:usize))= {[%#shillel21] len'1 (shallow_model'0 s) > 0}
     {[%#shillel20] sum_range'0 (shallow_model'0 s) 0 (len'1 (shallow_model'0 s)) <= 1000}
diff --git a/creusot/tests/should_succeed/index_range.coma b/creusot/tests/should_succeed/index_range.coma
index fe917841d5..8586689195 100644
--- a/creusot/tests/should_succeed/index_range.coma
+++ b/creusot/tests/should_succeed/index_range.coma
@@ -101,22 +101,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module IndexRange_CreateArr
   let%span sindex_range0 = "../index_range.rs" 15 18 15 28
@@ -137,57 +122,41 @@ module IndexRange_CreateArr
   
   let%span span8 = "" 0 0 0 0
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span14 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span21 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span29 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span22 = "" 0 0 0 0
   
-  let%span span30 = "" 0 0 0 0
+  let%span span23 = "" 0 0 0 0
   
-  let%span span31 = "" 0 0 0 0
+  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span32 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
-  let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
-  
-  let%span span34 = "" 0 0 0 0
+  let%span span26 = "" 0 0 0 0
   
   use prelude.prelude.Int32
   
@@ -228,81 +197,66 @@ module IndexRange_CreateArr
   
   constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq int32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int32 . ([%#span9] inv'3 self)  -> ([%#span10] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int32 . [%#span9] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span11] inv'0 self)
-   -> ([%#span13] inv'3 (shallow_model'0 self))
-  && ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span10] inv'0 self)
+   -> ([%#span11] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span14] inv'3 (shallow_model'0 self)
+    [%#span12] inv'3 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span15] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span17] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'0 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Int32
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span18] index_logic'1 (shallow_model'0 self) ix
+    [%#span14] index_logic'1 (shallow_model'0 self) ix
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq int32) (other : Seq'0.t_seq int32) : Seq'0.t_seq int32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span19] inv'3 self)
-   -> ([%#span20] inv'3 other)
-   -> ([%#span23] inv'3 (concat'0 self other))
-  && ([%#span22] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span16] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span21] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : int32) : Seq'0.t_seq int32
   
-  axiom singleton'0_spec : forall v : int32 . ([%#span24] inv'2 v)
-   -> ([%#span27] inv'3 (singleton'0 v))
-  && ([%#span26] index_logic'1 (singleton'0 v) 0 = v) && ([%#span25] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : int32 . ([%#span17] inv'2 v)
+   -> ([%#span19] index_logic'1 (singleton'0 v) 0 = v) && ([%#span18] len'0 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq int32) (v : int32) : Seq'0.t_seq int32 =
-    [%#span28] concat'0 self (singleton'0 v)
+    [%#span20] concat'0 self (singleton'0 v)
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span29] shallow_model'0 ( * self)
+    [%#span21] shallow_model'0 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (value:int32) (return'  (ret:()))= {[@expl:precondition] [%#span31] inv'2 value}
-    {[@expl:precondition] [%#span30] inv'1 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (value:int32) (return'  (ret:()))= {[@expl:precondition] [%#span23] inv'2 value}
+    {[@expl:precondition] [%#span22] inv'1 self}
     any
-    [ return' (result:())-> {[%#span32] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
+    [ return' (result:())-> {[%#span24] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
       (! return' {result}) ]
     
   
   let rec new'0 (_1:()) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span34] inv'0 result}
-      {[%#span33] len'0 (shallow_model'0 result) = 0}
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span26] inv'0 result}
+      {[%#span25] len'0 (shallow_model'0 result) = 0}
       (! return' {result}) ]
     
   
@@ -555,137 +509,123 @@ module IndexRange_TestRange
   
   let%span span73 = "" 0 0 0 0
   
-  let%span span74 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span74 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span75 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span75 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span76 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span76 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span77 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span77 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span78 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span78 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span79 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span79 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span80 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span80 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span81 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span81 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span82 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span82 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span83 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span83 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span84 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span84 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span85 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span85 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span86 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span86 = "" 0 0 0 0
   
-  let%span span87 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span87 = "" 0 0 0 0
   
-  let%span span88 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span88 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span89 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span89 = "" 0 0 0 0
   
   let%span span90 = "" 0 0 0 0
   
-  let%span span91 = "" 0 0 0 0
+  let%span span91 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span92 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span92 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span93 = "" 0 0 0 0
+  let%span span93 = "../../../../creusot-contracts/src/std/slice.rs" 134 8 137 9
   
-  let%span span94 = "" 0 0 0 0
+  let%span span94 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span95 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span95 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span96 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span96 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span97 = "../../../../creusot-contracts/src/std/slice.rs" 134 8 137 9
+  let%span span97 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span98 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span98 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span99 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span99 = "../../../../creusot-contracts/src/std/slice.rs" 128 20 128 67
   
-  let%span span100 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span100 = "../../../../creusot-contracts/src/std/slice.rs" 122 20 122 70
   
-  let%span span101 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span101 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span102 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span102 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span103 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span103 = "" 0 0 0 0
   
-  let%span span104 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span104 = "" 0 0 0 0
   
-  let%span span105 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span105 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span106 = "../../../../creusot-contracts/src/std/slice.rs" 128 20 128 67
+  let%span span106 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span107 = "../../../../creusot-contracts/src/std/slice.rs" 122 20 122 70
+  let%span span107 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span108 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span108 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span109 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span109 = "" 0 0 0 0
   
   let%span span110 = "" 0 0 0 0
   
-  let%span span111 = "" 0 0 0 0
+  let%span span111 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
   
-  let%span span112 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span112 = "" 0 0 0 0
   
-  let%span span113 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span113 = "" 0 0 0 0
   
-  let%span span114 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span114 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
   
-  let%span span115 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span115 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
   
   let%span span116 = "" 0 0 0 0
   
   let%span span117 = "" 0 0 0 0
   
-  let%span span118 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
+  let%span span118 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
   
   let%span span119 = "" 0 0 0 0
   
   let%span span120 = "" 0 0 0 0
   
-  let%span span121 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
-  
-  let%span span122 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
-  
-  let%span span123 = "" 0 0 0 0
+  let%span span121 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span124 = "" 0 0 0 0
-  
-  let%span span125 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
-  
-  let%span span126 = "" 0 0 0 0
-  
-  let%span span127 = "" 0 0 0 0
-  
-  let%span span128 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
-  
-  let%span span129 = "../index_range.rs" 7 4 12 22
+  let%span span122 = "../index_range.rs" 7 4 12 22
   
   use prelude.prelude.Int32
   
-  use prelude.prelude.Slice
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'11 (self : slice int32) =
+  predicate invariant'11 (self : Seq'0.t_seq int32) =
     [%#span72] true
   
-  predicate inv'11 (_x : slice int32)
+  predicate inv'11 (_x : Seq'0.t_seq int32)
   
-  axiom inv'11 : forall x : slice int32 . inv'11 x = true
+  axiom inv'11 : forall x : Seq'0.t_seq int32 . inv'11 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use prelude.prelude.Slice
   
-  predicate invariant'10 (self : Seq'0.t_seq int32) =
+  predicate invariant'10 (self : slice int32) =
     [%#span72] true
   
-  predicate inv'10 (_x : Seq'0.t_seq int32)
+  predicate inv'10 (_x : slice int32)
   
-  axiom inv'10 : forall x : Seq'0.t_seq int32 . inv'10 x = true
+  axiom inv'10 : forall x : slice int32 . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -699,24 +639,19 @@ module IndexRange_TestRange
   
   constant max'0 : usize = [%#span73] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq int32) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq int32 . ([%#span74] inv'10 self)  -> ([%#span75] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq int32 . [%#span74] len'2 self >= 0
   
   predicate inv'9 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span76] inv'9 self)
-   -> ([%#span78] inv'10 (shallow_model'0 self))
-  && ([%#span77] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span75] inv'9 self)
+   -> ([%#span76] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'9 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span79] inv'10 (shallow_model'0 self)
+    [%#span77] inv'11 (shallow_model'0 self)
   
   axiom inv'9 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'9 x = true
   
@@ -789,147 +724,139 @@ module IndexRange_TestRange
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span80] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span82] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span81] len'2 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span78] len'2 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : int32) =
-    [%#span83] true
+    [%#span79] true
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span84] index_logic'1 (shallow_model'0 self) ix
+    [%#span80] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span85] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span81] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) (out : int32) =
-    [%#span86] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span82] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) =
-    [%#span87] UIntSize.to_int self < len'2 seq
+    [%#span83] UIntSize.to_int self < len'2 seq
   
   function shallow_model'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span88] shallow_model'0 self
+    [%#span84] shallow_model'0 self
   
-  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span91] inv'7 index}
-    {[@expl:precondition] [%#span90] inv'0 self}
-    {[@expl:precondition] [%#span89] in_bounds'1 index (shallow_model'1 self)}
+  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span87] inv'7 index}
+    {[@expl:precondition] [%#span86] inv'0 self}
+    {[@expl:precondition] [%#span85] in_bounds'1 index (shallow_model'1 self)}
     any
-    [ return' (result:int32)-> {[%#span93] inv'8 result}
-      {[%#span92] has_value'1 index (shallow_model'1 self) result}
+    [ return' (result:int32)-> {[%#span89] inv'8 result}
+      {[%#span88] has_value'1 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
-  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span94] inv'0 self}
+  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span90] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span95] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span91] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (slice int32)) =
-    [%#span96]  ^ self =  * self
+    [%#span92]  ^ self =  * self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate resolve_elswhere'0 (self : Range'0.t_range usize) (old' : Seq'0.t_seq int32) (fin : Seq'0.t_seq int32) =
-    [%#span97] forall i : int . 0 <= i
+    [%#span93] forall i : int . 0 <= i
     /\ (i < UIntSize.to_int (Core_Ops_Range_Range_Type.range_start self)
     \/ UIntSize.to_int (Core_Ops_Range_Range_Type.range_end self) <= i)
     /\ i < len'2 old'  -> index_logic'1 old' i = index_logic'1 fin i
   
   function shallow_model'4 (self : slice int32) : Seq'0.t_seq int32
   
-  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span98] inv'11 self)
-   -> ([%#span100] inv'10 (shallow_model'4 self))
-  && ([%#span99] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
-  
-  use prelude.seq_ext.SeqExt
+  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span94] inv'10 self)
+   -> ([%#span95] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
   function subsequence'0 (self : Seq'0.t_seq int32) (n : int) (m : int) : Seq'0.t_seq int32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span101] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span96] 0 <= n
   /\ n <= m /\ m <= len'2 self)
-   -> ([%#span102] inv'10 self)
-   -> ([%#span105] inv'10 (subsequence'0 self n m))
-  && ([%#span104] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
+   -> ([%#span98] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span103] len'2 (subsequence'0 self n m) = m - n)
+  && ([%#span97] len'2 (subsequence'0 self n m) = m - n)
   
   predicate has_value'0 (self : Range'0.t_range usize) (seq : Seq'0.t_seq int32) (out : slice int32) =
-    [%#span106] subsequence'0 seq (UIntSize.to_int (Core_Ops_Range_Range_Type.range_start self)) (UIntSize.to_int (Core_Ops_Range_Range_Type.range_end self))
+    [%#span99] subsequence'0 seq (UIntSize.to_int (Core_Ops_Range_Range_Type.range_start self)) (UIntSize.to_int (Core_Ops_Range_Range_Type.range_end self))
     = shallow_model'4 out
   
   predicate in_bounds'0 (self : Range'0.t_range usize) (seq : Seq'0.t_seq int32) =
-    [%#span107] UIntSize.to_int (Core_Ops_Range_Range_Type.range_start self)
+    [%#span100] UIntSize.to_int (Core_Ops_Range_Range_Type.range_start self)
     <= UIntSize.to_int (Core_Ops_Range_Range_Type.range_end self)
     /\ UIntSize.to_int (Core_Ops_Range_Range_Type.range_end self) <= len'2 seq
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span108] shallow_model'0 ( * self)
+    [%#span101] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:Range'0.t_range usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span111] inv'1 index}
-    {[@expl:precondition] [%#span110] inv'5 self}
-    {[@expl:precondition] [%#span109] in_bounds'0 index (shallow_model'3 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:Range'0.t_range usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span104] inv'1 index}
+    {[@expl:precondition] [%#span103] inv'5 self}
+    {[@expl:precondition] [%#span102] in_bounds'0 index (shallow_model'3 self)}
     any
-    [ return' (result:borrowed (slice int32))-> {[%#span116] inv'6 result}
-      {[%#span115] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
-      {[%#span114] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
-      {[%#span113] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span112] has_value'0 index (shallow_model'3 self) ( * result)}
+    [ return' (result:borrowed (slice int32))-> {[%#span109] inv'6 result}
+      {[%#span108] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
+      {[%#span107] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
+      {[%#span106] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span105] has_value'0 index (shallow_model'3 self) ( * result)}
       (! return' {result}) ]
     
   
-  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span117] inv'4 self}
-    any [ return' (result:bool)-> {[%#span118] result = (self = Option'0.C_None)} (! return' {result}) ] 
+  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span110] inv'4 self}
+    any [ return' (result:bool)-> {[%#span111] result = (self = Option'0.C_None)} (! return' {result}) ] 
   
   function shallow_model'2 (self : slice int32) : Seq'0.t_seq int32 =
-    [%#span88] shallow_model'4 self
+    [%#span84] shallow_model'4 self
   
-  let rec get'0 (self:slice int32) (index:Range'0.t_range usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span120] inv'1 index}
-    {[@expl:precondition] [%#span119] inv'2 self}
+  let rec get'0 (self:slice int32) (index:Range'0.t_range usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span113] inv'1 index}
+    {[@expl:precondition] [%#span112] inv'2 self}
     any
-    [ return' (result:Option'0.t_option (slice int32))-> {[%#span123] inv'3 result}
-      {[%#span122] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
-      {[%#span121] in_bounds'0 index (shallow_model'2 self)
+    [ return' (result:Option'0.t_option (slice int32))-> {[%#span116] inv'3 result}
+      {[%#span115] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
+      {[%#span114] in_bounds'0 index (shallow_model'2 self)
        -> (exists r : slice int32 . inv'2 r
       /\ result = Option'0.C_Some r /\ has_value'0 index (shallow_model'2 self) r)}
       (! return' {result}) ]
     
   
-  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span124] inv'0 self}
+  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span117] inv'0 self}
     any
-    [ return' (result:slice int32)-> {[%#span126] inv'2 result}
-      {[%#span125] shallow_model'2 result = shallow_model'1 self}
+    [ return' (result:slice int32)-> {[%#span119] inv'2 result}
+      {[%#span118] shallow_model'2 result = shallow_model'1 self}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span127] inv'2 self}
+  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span120] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span128] len'2 (shallow_model'2 self) = UIntSize.to_int result}
+    [ return' (result:usize)-> {[%#span121] len'2 (shallow_model'2 self) = UIntSize.to_int result}
       (! return' {result}) ]
     
   
-  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:Range'0.t_range usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span91] inv'1 index}
-    {[@expl:precondition] [%#span90] inv'0 self}
-    {[@expl:precondition] [%#span89] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:Range'0.t_range usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span87] inv'1 index}
+    {[@expl:precondition] [%#span86] inv'0 self}
+    {[@expl:precondition] [%#span85] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:slice int32)-> {[%#span93] inv'2 result}
-      {[%#span92] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:slice int32)-> {[%#span89] inv'2 result}
+      {[%#span88] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
   use prelude.prelude.Int32
   
   let rec create_arr'0 (_1:()) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span129] len'2 (shallow_model'0 result) = 5
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span122] len'2 (shallow_model'0 result) = 5
       /\ Int32.to_int (index_logic'0 result 0) = 0
       /\ Int32.to_int (index_logic'0 result 1) = 1
       /\ Int32.to_int (index_logic'0 result 2) = 2
@@ -1391,137 +1318,123 @@ module IndexRange_TestRangeTo
   
   let%span span46 = "" 0 0 0 0
   
-  let%span span47 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span47 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span48 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span48 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span49 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span49 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span51 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span51 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span52 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span53 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span53 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span54 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span55 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span55 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span56 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span56 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span57 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span57 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span58 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span58 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span59 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span59 = "" 0 0 0 0
   
-  let%span span60 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span60 = "" 0 0 0 0
   
-  let%span span61 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span61 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span62 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span62 = "" 0 0 0 0
   
   let%span span63 = "" 0 0 0 0
   
-  let%span span64 = "" 0 0 0 0
+  let%span span64 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span65 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span65 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span66 = "" 0 0 0 0
+  let%span span66 = "../../../../creusot-contracts/src/std/slice.rs" 157 8 157 90
   
-  let%span span67 = "" 0 0 0 0
+  let%span span67 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span68 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span68 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span69 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span69 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span70 = "../../../../creusot-contracts/src/std/slice.rs" 157 8 157 90
+  let%span span70 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span71 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span71 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span72 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span72 = "../../../../creusot-contracts/src/std/slice.rs" 151 20 151 57
   
-  let%span span73 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span73 = "../../../../creusot-contracts/src/std/slice.rs" 145 20 145 42
   
-  let%span span74 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span74 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span75 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span75 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span76 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span76 = "" 0 0 0 0
   
-  let%span span77 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span77 = "" 0 0 0 0
   
-  let%span span78 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span78 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span79 = "../../../../creusot-contracts/src/std/slice.rs" 151 20 151 57
+  let%span span79 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span80 = "../../../../creusot-contracts/src/std/slice.rs" 145 20 145 42
+  let%span span80 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span81 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span81 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span82 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span82 = "" 0 0 0 0
   
   let%span span83 = "" 0 0 0 0
   
-  let%span span84 = "" 0 0 0 0
+  let%span span84 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
   
-  let%span span85 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span85 = "" 0 0 0 0
   
-  let%span span86 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span86 = "" 0 0 0 0
   
-  let%span span87 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span87 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
   
-  let%span span88 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span88 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
   
   let%span span89 = "" 0 0 0 0
   
   let%span span90 = "" 0 0 0 0
   
-  let%span span91 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
+  let%span span91 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
   
   let%span span92 = "" 0 0 0 0
   
   let%span span93 = "" 0 0 0 0
   
-  let%span span94 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
-  
-  let%span span95 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
-  
-  let%span span96 = "" 0 0 0 0
-  
-  let%span span97 = "" 0 0 0 0
-  
-  let%span span98 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
-  
-  let%span span99 = "" 0 0 0 0
-  
-  let%span span100 = "" 0 0 0 0
+  let%span span94 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span101 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
-  
-  let%span span102 = "../index_range.rs" 7 4 12 22
+  let%span span95 = "../index_range.rs" 7 4 12 22
   
   use prelude.prelude.Int32
   
-  use prelude.prelude.Slice
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'11 (self : slice int32) =
+  predicate invariant'11 (self : Seq'0.t_seq int32) =
     [%#span45] true
   
-  predicate inv'11 (_x : slice int32)
+  predicate inv'11 (_x : Seq'0.t_seq int32)
   
-  axiom inv'11 : forall x : slice int32 . inv'11 x = true
+  axiom inv'11 : forall x : Seq'0.t_seq int32 . inv'11 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use prelude.prelude.Slice
   
-  predicate invariant'10 (self : Seq'0.t_seq int32) =
+  predicate invariant'10 (self : slice int32) =
     [%#span45] true
   
-  predicate inv'10 (_x : Seq'0.t_seq int32)
+  predicate inv'10 (_x : slice int32)
   
-  axiom inv'10 : forall x : Seq'0.t_seq int32 . inv'10 x = true
+  axiom inv'10 : forall x : slice int32 . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1535,24 +1448,19 @@ module IndexRange_TestRangeTo
   
   constant max'0 : usize = [%#span46] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq int32) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq int32 . ([%#span47] inv'10 self)  -> ([%#span48] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq int32 . [%#span47] len'2 self >= 0
   
   predicate inv'9 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span49] inv'9 self)
-   -> ([%#span51] inv'10 (shallow_model'0 self))
-  && ([%#span50] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span48] inv'9 self)
+   -> ([%#span49] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'9 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span52] inv'10 (shallow_model'0 self)
+    [%#span50] inv'11 (shallow_model'0 self)
   
   axiom inv'9 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'9 x = true
   
@@ -1625,143 +1533,134 @@ module IndexRange_TestRangeTo
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span53] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span55] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span54] len'2 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span51] len'2 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : int32) =
-    [%#span56] true
-  
-  use seq.Seq
+    [%#span52] true
   
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span57] index_logic'1 (shallow_model'0 self) ix
+    [%#span53] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span58] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span54] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) (out : int32) =
-    [%#span59] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span55] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) =
-    [%#span60] UIntSize.to_int self < len'2 seq
+    [%#span56] UIntSize.to_int self < len'2 seq
   
   function shallow_model'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span61] shallow_model'0 self
+    [%#span57] shallow_model'0 self
   
-  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span64] inv'7 index}
-    {[@expl:precondition] [%#span63] inv'0 self}
-    {[@expl:precondition] [%#span62] in_bounds'1 index (shallow_model'1 self)}
+  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span60] inv'7 index}
+    {[@expl:precondition] [%#span59] inv'0 self}
+    {[@expl:precondition] [%#span58] in_bounds'1 index (shallow_model'1 self)}
     any
-    [ return' (result:int32)-> {[%#span66] inv'8 result}
-      {[%#span65] has_value'1 index (shallow_model'1 self) result}
+    [ return' (result:int32)-> {[%#span62] inv'8 result}
+      {[%#span61] has_value'1 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
-  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span67] inv'0 self}
+  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span63] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span68] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span64] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (slice int32)) =
-    [%#span69]  ^ self =  * self
+    [%#span65]  ^ self =  * self
   
   use Core_Ops_Range_RangeTo_Type as Core_Ops_Range_RangeTo_Type
   
   predicate resolve_elswhere'0 (self : RangeTo'0.t_rangeto usize) (old' : Seq'0.t_seq int32) (fin : Seq'0.t_seq int32) =
-    [%#span70] forall i : int . UIntSize.to_int (Core_Ops_Range_RangeTo_Type.rangeto_end self) <= i /\ i < len'2 old'
+    [%#span66] forall i : int . UIntSize.to_int (Core_Ops_Range_RangeTo_Type.rangeto_end self) <= i /\ i < len'2 old'
      -> index_logic'1 old' i = index_logic'1 fin i
   
   function shallow_model'4 (self : slice int32) : Seq'0.t_seq int32
   
-  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span71] inv'11 self)
-   -> ([%#span73] inv'10 (shallow_model'4 self))
-  && ([%#span72] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
-  
-  use prelude.seq_ext.SeqExt
+  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span67] inv'10 self)
+   -> ([%#span68] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
   function subsequence'0 (self : Seq'0.t_seq int32) (n : int) (m : int) : Seq'0.t_seq int32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span74] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span69] 0 <= n
   /\ n <= m /\ m <= len'2 self)
-   -> ([%#span75] inv'10 self)
-   -> ([%#span78] inv'10 (subsequence'0 self n m))
-  && ([%#span77] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
+   -> ([%#span71] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span76] len'2 (subsequence'0 self n m) = m - n)
+  && ([%#span70] len'2 (subsequence'0 self n m) = m - n)
   
   predicate has_value'0 (self : RangeTo'0.t_rangeto usize) (seq : Seq'0.t_seq int32) (out : slice int32) =
-    [%#span79] subsequence'0 seq 0 (UIntSize.to_int (Core_Ops_Range_RangeTo_Type.rangeto_end self))
+    [%#span72] subsequence'0 seq 0 (UIntSize.to_int (Core_Ops_Range_RangeTo_Type.rangeto_end self))
     = shallow_model'4 out
   
   predicate in_bounds'0 (self : RangeTo'0.t_rangeto usize) (seq : Seq'0.t_seq int32) =
-    [%#span80] UIntSize.to_int (Core_Ops_Range_RangeTo_Type.rangeto_end self) <= len'2 seq
+    [%#span73] UIntSize.to_int (Core_Ops_Range_RangeTo_Type.rangeto_end self) <= len'2 seq
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span81] shallow_model'0 ( * self)
+    [%#span74] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeTo'0.t_rangeto usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span84] inv'1 index}
-    {[@expl:precondition] [%#span83] inv'5 self}
-    {[@expl:precondition] [%#span82] in_bounds'0 index (shallow_model'3 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeTo'0.t_rangeto usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span77] inv'1 index}
+    {[@expl:precondition] [%#span76] inv'5 self}
+    {[@expl:precondition] [%#span75] in_bounds'0 index (shallow_model'3 self)}
     any
-    [ return' (result:borrowed (slice int32))-> {[%#span89] inv'6 result}
-      {[%#span88] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
-      {[%#span87] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
-      {[%#span86] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span85] has_value'0 index (shallow_model'3 self) ( * result)}
+    [ return' (result:borrowed (slice int32))-> {[%#span82] inv'6 result}
+      {[%#span81] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
+      {[%#span80] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
+      {[%#span79] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span78] has_value'0 index (shallow_model'3 self) ( * result)}
       (! return' {result}) ]
     
   
-  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span90] inv'4 self}
-    any [ return' (result:bool)-> {[%#span91] result = (self = Option'0.C_None)} (! return' {result}) ] 
+  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span83] inv'4 self}
+    any [ return' (result:bool)-> {[%#span84] result = (self = Option'0.C_None)} (! return' {result}) ] 
   
   function shallow_model'2 (self : slice int32) : Seq'0.t_seq int32 =
-    [%#span61] shallow_model'4 self
+    [%#span57] shallow_model'4 self
   
-  let rec get'0 (self:slice int32) (index:RangeTo'0.t_rangeto usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span93] inv'1 index}
-    {[@expl:precondition] [%#span92] inv'2 self}
+  let rec get'0 (self:slice int32) (index:RangeTo'0.t_rangeto usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span86] inv'1 index}
+    {[@expl:precondition] [%#span85] inv'2 self}
     any
-    [ return' (result:Option'0.t_option (slice int32))-> {[%#span96] inv'3 result}
-      {[%#span95] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
-      {[%#span94] in_bounds'0 index (shallow_model'2 self)
+    [ return' (result:Option'0.t_option (slice int32))-> {[%#span89] inv'3 result}
+      {[%#span88] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
+      {[%#span87] in_bounds'0 index (shallow_model'2 self)
        -> (exists r : slice int32 . inv'2 r
       /\ result = Option'0.C_Some r /\ has_value'0 index (shallow_model'2 self) r)}
       (! return' {result}) ]
     
   
-  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span97] inv'0 self}
+  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span90] inv'0 self}
     any
-    [ return' (result:slice int32)-> {[%#span99] inv'2 result}
-      {[%#span98] shallow_model'2 result = shallow_model'1 self}
+    [ return' (result:slice int32)-> {[%#span92] inv'2 result}
+      {[%#span91] shallow_model'2 result = shallow_model'1 self}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span100] inv'2 self}
+  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span93] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span101] len'2 (shallow_model'2 self) = UIntSize.to_int result}
-      (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span94] len'2 (shallow_model'2 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
-  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeTo'0.t_rangeto usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span64] inv'1 index}
-    {[@expl:precondition] [%#span63] inv'0 self}
-    {[@expl:precondition] [%#span62] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeTo'0.t_rangeto usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span60] inv'1 index}
+    {[@expl:precondition] [%#span59] inv'0 self}
+    {[@expl:precondition] [%#span58] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:slice int32)-> {[%#span66] inv'2 result}
-      {[%#span65] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:slice int32)-> {[%#span62] inv'2 result}
+      {[%#span61] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
   use prelude.prelude.Int32
   
   let rec create_arr'0 (_1:()) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span102] len'2 (shallow_model'0 result) = 5
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span95] len'2 (shallow_model'0 result) = 5
       /\ Int32.to_int (index_logic'0 result 0) = 0
       /\ Int32.to_int (index_logic'0 result 1) = 1
       /\ Int32.to_int (index_logic'0 result 2) = 2
@@ -2118,137 +2017,123 @@ module IndexRange_TestRangeFrom
   
   let%span span48 = "" 0 0 0 0
   
-  let%span span49 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span49 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span50 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span51 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span51 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span53 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span54 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span55 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span55 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span56 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span57 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span57 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span58 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span58 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span59 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span59 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span60 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span60 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span61 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span61 = "" 0 0 0 0
   
-  let%span span62 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span62 = "" 0 0 0 0
   
-  let%span span63 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span63 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span64 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span64 = "" 0 0 0 0
   
   let%span span65 = "" 0 0 0 0
   
-  let%span span66 = "" 0 0 0 0
+  let%span span66 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span67 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span67 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span68 = "" 0 0 0 0
+  let%span span68 = "../../../../creusot-contracts/src/std/slice.rs" 177 8 179 9
   
-  let%span span69 = "" 0 0 0 0
+  let%span span69 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span70 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span70 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span71 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span71 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span72 = "../../../../creusot-contracts/src/std/slice.rs" 177 8 179 9
+  let%span span72 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span73 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span73 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span74 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span74 = "../../../../creusot-contracts/src/std/slice.rs" 171 20 171 67
   
-  let%span span75 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span75 = "../../../../creusot-contracts/src/std/slice.rs" 165 20 165 44
   
-  let%span span76 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span76 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span77 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span77 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span78 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span78 = "" 0 0 0 0
   
-  let%span span79 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span79 = "" 0 0 0 0
   
-  let%span span80 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span80 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span81 = "../../../../creusot-contracts/src/std/slice.rs" 171 20 171 67
+  let%span span81 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span82 = "../../../../creusot-contracts/src/std/slice.rs" 165 20 165 44
+  let%span span82 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span83 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span83 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span84 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span84 = "" 0 0 0 0
   
   let%span span85 = "" 0 0 0 0
   
-  let%span span86 = "" 0 0 0 0
+  let%span span86 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
   
-  let%span span87 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span87 = "" 0 0 0 0
   
-  let%span span88 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span88 = "" 0 0 0 0
   
-  let%span span89 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span89 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
   
-  let%span span90 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span90 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
   
   let%span span91 = "" 0 0 0 0
   
   let%span span92 = "" 0 0 0 0
   
-  let%span span93 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
+  let%span span93 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
   
   let%span span94 = "" 0 0 0 0
   
   let%span span95 = "" 0 0 0 0
   
-  let%span span96 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
-  
-  let%span span97 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
-  
-  let%span span98 = "" 0 0 0 0
-  
-  let%span span99 = "" 0 0 0 0
-  
-  let%span span100 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
-  
-  let%span span101 = "" 0 0 0 0
-  
-  let%span span102 = "" 0 0 0 0
+  let%span span96 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span103 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
-  
-  let%span span104 = "../index_range.rs" 7 4 12 22
+  let%span span97 = "../index_range.rs" 7 4 12 22
   
   use prelude.prelude.Int32
   
-  use prelude.prelude.Slice
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'11 (self : slice int32) =
+  predicate invariant'11 (self : Seq'0.t_seq int32) =
     [%#span47] true
   
-  predicate inv'11 (_x : slice int32)
+  predicate inv'11 (_x : Seq'0.t_seq int32)
   
-  axiom inv'11 : forall x : slice int32 . inv'11 x = true
+  axiom inv'11 : forall x : Seq'0.t_seq int32 . inv'11 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use prelude.prelude.Slice
   
-  predicate invariant'10 (self : Seq'0.t_seq int32) =
+  predicate invariant'10 (self : slice int32) =
     [%#span47] true
   
-  predicate inv'10 (_x : Seq'0.t_seq int32)
+  predicate inv'10 (_x : slice int32)
   
-  axiom inv'10 : forall x : Seq'0.t_seq int32 . inv'10 x = true
+  axiom inv'10 : forall x : slice int32 . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -2262,24 +2147,19 @@ module IndexRange_TestRangeFrom
   
   constant max'0 : usize = [%#span48] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq int32) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq int32 . ([%#span49] inv'10 self)  -> ([%#span50] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq int32 . [%#span49] len'2 self >= 0
   
   predicate inv'9 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span51] inv'9 self)
-   -> ([%#span53] inv'10 (shallow_model'0 self))
-  && ([%#span52] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span50] inv'9 self)
+   -> ([%#span51] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'9 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span54] inv'10 (shallow_model'0 self)
+    [%#span52] inv'11 (shallow_model'0 self)
   
   axiom inv'9 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'9 x = true
   
@@ -2352,146 +2232,137 @@ module IndexRange_TestRangeFrom
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span55] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span57] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span56] len'2 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span53] len'2 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : int32) =
-    [%#span58] true
-  
-  use seq.Seq
+    [%#span54] true
   
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span59] index_logic'1 (shallow_model'0 self) ix
+    [%#span55] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span60] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span56] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) (out : int32) =
-    [%#span61] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span57] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) =
-    [%#span62] UIntSize.to_int self < len'2 seq
+    [%#span58] UIntSize.to_int self < len'2 seq
   
   function shallow_model'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span63] shallow_model'0 self
+    [%#span59] shallow_model'0 self
   
-  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span66] inv'7 index}
-    {[@expl:precondition] [%#span65] inv'0 self}
-    {[@expl:precondition] [%#span64] in_bounds'1 index (shallow_model'1 self)}
+  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span62] inv'7 index}
+    {[@expl:precondition] [%#span61] inv'0 self}
+    {[@expl:precondition] [%#span60] in_bounds'1 index (shallow_model'1 self)}
     any
-    [ return' (result:int32)-> {[%#span68] inv'8 result}
-      {[%#span67] has_value'1 index (shallow_model'1 self) result}
+    [ return' (result:int32)-> {[%#span64] inv'8 result}
+      {[%#span63] has_value'1 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
-  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span69] inv'0 self}
+  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span65] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span70] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span66] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (slice int32)) =
-    [%#span71]  ^ self =  * self
+    [%#span67]  ^ self =  * self
   
   use Core_Ops_Range_RangeFrom_Type as Core_Ops_Range_RangeFrom_Type
   
   predicate resolve_elswhere'0 (self : RangeFrom'0.t_rangefrom usize) (old' : Seq'0.t_seq int32) (fin : Seq'0.t_seq int32)
     
    =
-    [%#span72] forall i : int . 0 <= i
+    [%#span68] forall i : int . 0 <= i
     /\ i < UIntSize.to_int (Core_Ops_Range_RangeFrom_Type.rangefrom_start self) /\ i < len'2 old'
      -> index_logic'1 old' i = index_logic'1 fin i
   
   function shallow_model'4 (self : slice int32) : Seq'0.t_seq int32
   
-  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span73] inv'11 self)
-   -> ([%#span75] inv'10 (shallow_model'4 self))
-  && ([%#span74] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
-  
-  use prelude.seq_ext.SeqExt
+  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span69] inv'10 self)
+   -> ([%#span70] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
   function subsequence'0 (self : Seq'0.t_seq int32) (n : int) (m : int) : Seq'0.t_seq int32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span76] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span71] 0 <= n
   /\ n <= m /\ m <= len'2 self)
-   -> ([%#span77] inv'10 self)
-   -> ([%#span80] inv'10 (subsequence'0 self n m))
-  && ([%#span79] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
+   -> ([%#span73] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span78] len'2 (subsequence'0 self n m) = m - n)
+  && ([%#span72] len'2 (subsequence'0 self n m) = m - n)
   
   predicate has_value'0 (self : RangeFrom'0.t_rangefrom usize) (seq : Seq'0.t_seq int32) (out : slice int32) =
-    [%#span81] subsequence'0 seq (UIntSize.to_int (Core_Ops_Range_RangeFrom_Type.rangefrom_start self)) (len'2 seq)
+    [%#span74] subsequence'0 seq (UIntSize.to_int (Core_Ops_Range_RangeFrom_Type.rangefrom_start self)) (len'2 seq)
     = shallow_model'4 out
   
   predicate in_bounds'0 (self : RangeFrom'0.t_rangefrom usize) (seq : Seq'0.t_seq int32) =
-    [%#span82] UIntSize.to_int (Core_Ops_Range_RangeFrom_Type.rangefrom_start self) <= len'2 seq
+    [%#span75] UIntSize.to_int (Core_Ops_Range_RangeFrom_Type.rangefrom_start self) <= len'2 seq
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span83] shallow_model'0 ( * self)
+    [%#span76] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeFrom'0.t_rangefrom usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span86] inv'1 index}
-    {[@expl:precondition] [%#span85] inv'5 self}
-    {[@expl:precondition] [%#span84] in_bounds'0 index (shallow_model'3 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeFrom'0.t_rangefrom usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span79] inv'1 index}
+    {[@expl:precondition] [%#span78] inv'5 self}
+    {[@expl:precondition] [%#span77] in_bounds'0 index (shallow_model'3 self)}
     any
-    [ return' (result:borrowed (slice int32))-> {[%#span91] inv'6 result}
-      {[%#span90] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
-      {[%#span89] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
-      {[%#span88] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span87] has_value'0 index (shallow_model'3 self) ( * result)}
+    [ return' (result:borrowed (slice int32))-> {[%#span84] inv'6 result}
+      {[%#span83] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
+      {[%#span82] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
+      {[%#span81] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span80] has_value'0 index (shallow_model'3 self) ( * result)}
       (! return' {result}) ]
     
   
-  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span92] inv'4 self}
-    any [ return' (result:bool)-> {[%#span93] result = (self = Option'0.C_None)} (! return' {result}) ] 
+  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span85] inv'4 self}
+    any [ return' (result:bool)-> {[%#span86] result = (self = Option'0.C_None)} (! return' {result}) ] 
   
   function shallow_model'2 (self : slice int32) : Seq'0.t_seq int32 =
-    [%#span63] shallow_model'4 self
+    [%#span59] shallow_model'4 self
   
-  let rec get'0 (self:slice int32) (index:RangeFrom'0.t_rangefrom usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span95] inv'1 index}
-    {[@expl:precondition] [%#span94] inv'2 self}
+  let rec get'0 (self:slice int32) (index:RangeFrom'0.t_rangefrom usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span88] inv'1 index}
+    {[@expl:precondition] [%#span87] inv'2 self}
     any
-    [ return' (result:Option'0.t_option (slice int32))-> {[%#span98] inv'3 result}
-      {[%#span97] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
-      {[%#span96] in_bounds'0 index (shallow_model'2 self)
+    [ return' (result:Option'0.t_option (slice int32))-> {[%#span91] inv'3 result}
+      {[%#span90] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
+      {[%#span89] in_bounds'0 index (shallow_model'2 self)
        -> (exists r : slice int32 . inv'2 r
       /\ result = Option'0.C_Some r /\ has_value'0 index (shallow_model'2 self) r)}
       (! return' {result}) ]
     
   
-  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span99] inv'0 self}
+  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span92] inv'0 self}
     any
-    [ return' (result:slice int32)-> {[%#span101] inv'2 result}
-      {[%#span100] shallow_model'2 result = shallow_model'1 self}
+    [ return' (result:slice int32)-> {[%#span94] inv'2 result}
+      {[%#span93] shallow_model'2 result = shallow_model'1 self}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span102] inv'2 self}
+  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span95] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span103] len'2 (shallow_model'2 self) = UIntSize.to_int result}
-      (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span96] len'2 (shallow_model'2 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
-  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeFrom'0.t_rangefrom usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span66] inv'1 index}
-    {[@expl:precondition] [%#span65] inv'0 self}
-    {[@expl:precondition] [%#span64] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeFrom'0.t_rangefrom usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span62] inv'1 index}
+    {[@expl:precondition] [%#span61] inv'0 self}
+    {[@expl:precondition] [%#span60] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:slice int32)-> {[%#span68] inv'2 result}
-      {[%#span67] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:slice int32)-> {[%#span64] inv'2 result}
+      {[%#span63] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
   use prelude.prelude.Int32
   
   let rec create_arr'0 (_1:()) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span104] len'2 (shallow_model'0 result) = 5
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span97] len'2 (shallow_model'0 result) = 5
       /\ Int32.to_int (index_logic'0 result 0) = 0
       /\ Int32.to_int (index_logic'0 result 1) = 1
       /\ Int32.to_int (index_logic'0 result 2) = 2
@@ -2847,107 +2718,97 @@ module IndexRange_TestRangeFull
   
   let%span span44 = "" 0 0 0 0
   
-  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span46 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span46 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span47 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span47 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span48 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span48 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span49 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span49 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span50 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span51 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span51 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span52 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span53 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span53 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span54 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span54 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span55 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span55 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span57 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span57 = "" 0 0 0 0
   
-  let%span span58 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span58 = "" 0 0 0 0
   
-  let%span span59 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span59 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span60 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span60 = "" 0 0 0 0
   
   let%span span61 = "" 0 0 0 0
   
-  let%span span62 = "" 0 0 0 0
+  let%span span62 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span63 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span63 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span64 = "" 0 0 0 0
+  let%span span64 = "../../../../creusot-contracts/src/std/slice.rs" 199 20 199 24
   
-  let%span span65 = "" 0 0 0 0
+  let%span span65 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span66 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span66 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span67 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span67 = "../../../../creusot-contracts/src/std/slice.rs" 193 20 193 31
   
-  let%span span68 = "../../../../creusot-contracts/src/std/slice.rs" 199 20 199 24
+  let%span span68 = "../../../../creusot-contracts/src/std/slice.rs" 187 20 187 24
   
-  let%span span69 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span69 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span70 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span70 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span71 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span71 = "" 0 0 0 0
   
-  let%span span72 = "../../../../creusot-contracts/src/std/slice.rs" 193 20 193 31
+  let%span span72 = "" 0 0 0 0
   
-  let%span span73 = "../../../../creusot-contracts/src/std/slice.rs" 187 20 187 24
+  let%span span73 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span74 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span74 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span75 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span75 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span76 = "" 0 0 0 0
+  let%span span76 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
   let%span span77 = "" 0 0 0 0
   
-  let%span span78 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
-  
-  let%span span79 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
-  
-  let%span span80 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
-  
-  let%span span81 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span78 = "" 0 0 0 0
   
-  let%span span82 = "" 0 0 0 0
-  
-  let%span span83 = "" 0 0 0 0
-  
-  let%span span84 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span79 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span85 = "../index_range.rs" 7 4 12 22
+  let%span span80 = "../index_range.rs" 7 4 12 22
   
   use prelude.prelude.Int32
   
-  use prelude.prelude.Slice
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'9 (self : slice int32) =
+  predicate invariant'9 (self : Seq'0.t_seq int32) =
     [%#span43] true
   
-  predicate inv'9 (_x : slice int32)
+  predicate inv'9 (_x : Seq'0.t_seq int32)
   
-  axiom inv'9 : forall x : slice int32 . inv'9 x = true
+  axiom inv'9 : forall x : Seq'0.t_seq int32 . inv'9 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use prelude.prelude.Slice
   
-  predicate invariant'8 (self : Seq'0.t_seq int32) =
+  predicate invariant'8 (self : slice int32) =
     [%#span43] true
   
-  predicate inv'8 (_x : Seq'0.t_seq int32)
+  predicate inv'8 (_x : slice int32)
   
-  axiom inv'8 : forall x : Seq'0.t_seq int32 . inv'8 x = true
+  axiom inv'8 : forall x : slice int32 . inv'8 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -2961,24 +2822,19 @@ module IndexRange_TestRangeFull
   
   constant max'0 : usize = [%#span44] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq int32) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq int32 . ([%#span45] inv'8 self)  -> ([%#span46] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq int32 . [%#span45] len'2 self >= 0
   
   predicate inv'7 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span47] inv'7 self)
-   -> ([%#span49] inv'8 (shallow_model'0 self))
-  && ([%#span48] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span46] inv'7 self)
+   -> ([%#span47] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'7 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span50] inv'8 (shallow_model'0 self)
+    [%#span48] inv'9 (shallow_model'0 self)
   
   axiom inv'7 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'7 x = true
   
@@ -3035,105 +2891,101 @@ module IndexRange_TestRangeFull
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span51] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span53] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span52] len'2 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span49] len'2 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : int32) =
-    [%#span54] true
+    [%#span50] true
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span55] index_logic'1 (shallow_model'0 self) ix
+    [%#span51] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span56] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span52] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) (out : int32) =
-    [%#span57] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span53] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) =
-    [%#span58] UIntSize.to_int self < len'2 seq
+    [%#span54] UIntSize.to_int self < len'2 seq
   
   function shallow_model'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span59] shallow_model'0 self
+    [%#span55] shallow_model'0 self
   
-  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span62] inv'5 index}
-    {[@expl:precondition] [%#span61] inv'0 self}
-    {[@expl:precondition] [%#span60] in_bounds'1 index (shallow_model'1 self)}
+  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span58] inv'5 index}
+    {[@expl:precondition] [%#span57] inv'0 self}
+    {[@expl:precondition] [%#span56] in_bounds'1 index (shallow_model'1 self)}
     any
-    [ return' (result:int32)-> {[%#span64] inv'6 result}
-      {[%#span63] has_value'1 index (shallow_model'1 self) result}
+    [ return' (result:int32)-> {[%#span60] inv'6 result}
+      {[%#span59] has_value'1 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
-  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span65] inv'0 self}
+  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span61] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span66] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span62] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (slice int32)) =
-    [%#span67]  ^ self =  * self
+    [%#span63]  ^ self =  * self
   
   predicate resolve_elswhere'0 (self : RangeFull'0.t_rangefull) (_old : Seq'0.t_seq int32) (_fin : Seq'0.t_seq int32) =
-    [%#span68] true
+    [%#span64] true
   
   function shallow_model'4 (self : slice int32) : Seq'0.t_seq int32
   
-  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span69] inv'9 self)
-   -> ([%#span71] inv'8 (shallow_model'4 self))
-  && ([%#span70] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span65] inv'8 self)
+   -> ([%#span66] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate has_value'0 (self : RangeFull'0.t_rangefull) (seq : Seq'0.t_seq int32) (out : slice int32) =
-    [%#span72] seq = shallow_model'4 out
+    [%#span67] seq = shallow_model'4 out
   
   predicate in_bounds'0 (self : RangeFull'0.t_rangefull) (_seq : Seq'0.t_seq int32) =
-    [%#span73] true
+    [%#span68] true
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span74] shallow_model'0 ( * self)
+    [%#span69] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeFull'0.t_rangefull) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span77] inv'1 index}
-    {[@expl:precondition] [%#span76] inv'3 self}
-    {[@expl:precondition] [%#span75] in_bounds'0 index (shallow_model'3 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeFull'0.t_rangefull) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span72] inv'1 index}
+    {[@expl:precondition] [%#span71] inv'3 self}
+    {[@expl:precondition] [%#span70] in_bounds'0 index (shallow_model'3 self)}
     any
-    [ return' (result:borrowed (slice int32))-> {[%#span82] inv'4 result}
-      {[%#span81] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
-      {[%#span80] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
-      {[%#span79] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span78] has_value'0 index (shallow_model'3 self) ( * result)}
+    [ return' (result:borrowed (slice int32))-> {[%#span77] inv'4 result}
+      {[%#span76] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
+      {[%#span75] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
+      {[%#span74] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span73] has_value'0 index (shallow_model'3 self) ( * result)}
       (! return' {result}) ]
     
   
   function shallow_model'2 (self : slice int32) : Seq'0.t_seq int32 =
-    [%#span59] shallow_model'4 self
+    [%#span55] shallow_model'4 self
   
-  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span83] inv'2 self}
+  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span78] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span84] len'2 (shallow_model'2 self) = UIntSize.to_int result} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span79] len'2 (shallow_model'2 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
-  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeFull'0.t_rangefull) (return'  (ret:slice int32))= {[@expl:precondition] [%#span62] inv'1 index}
-    {[@expl:precondition] [%#span61] inv'0 self}
-    {[@expl:precondition] [%#span60] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeFull'0.t_rangefull) (return'  (ret:slice int32))= {[@expl:precondition] [%#span58] inv'1 index}
+    {[@expl:precondition] [%#span57] inv'0 self}
+    {[@expl:precondition] [%#span56] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:slice int32)-> {[%#span64] inv'2 result}
-      {[%#span63] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:slice int32)-> {[%#span60] inv'2 result}
+      {[%#span59] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
   use prelude.prelude.Int32
   
   let rec create_arr'0 (_1:()) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span85] len'2 (shallow_model'0 result) = 5
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span80] len'2 (shallow_model'0 result) = 5
       /\ Int32.to_int (index_logic'0 result 0) = 0
       /\ Int32.to_int (index_logic'0 result 1) = 1
       /\ Int32.to_int (index_logic'0 result 2) = 2
@@ -3490,137 +3342,123 @@ module IndexRange_TestRangeToInclusive
   
   let%span span43 = "" 0 0 0 0
   
-  let%span span44 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span44 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span45 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span46 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span46 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span47 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span47 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span48 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span48 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span49 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span49 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span50 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span50 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span51 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span51 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span52 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span52 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span53 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span53 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span54 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span54 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span55 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span55 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span56 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span56 = "" 0 0 0 0
   
-  let%span span57 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span57 = "" 0 0 0 0
   
-  let%span span58 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span58 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span59 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span59 = "" 0 0 0 0
   
   let%span span60 = "" 0 0 0 0
   
-  let%span span61 = "" 0 0 0 0
+  let%span span61 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span62 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span62 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span63 = "" 0 0 0 0
+  let%span span63 = "../../../../creusot-contracts/src/std/slice.rs" 219 8 219 89
   
-  let%span span64 = "" 0 0 0 0
+  let%span span64 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span65 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span65 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span66 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span66 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span67 = "../../../../creusot-contracts/src/std/slice.rs" 219 8 219 89
+  let%span span67 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span68 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span68 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span69 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span69 = "../../../../creusot-contracts/src/std/slice.rs" 213 20 213 61
   
-  let%span span70 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span70 = "../../../../creusot-contracts/src/std/slice.rs" 207 20 207 41
   
-  let%span span71 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span71 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span72 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span72 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span73 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span73 = "" 0 0 0 0
   
-  let%span span74 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span74 = "" 0 0 0 0
   
-  let%span span75 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span75 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span76 = "../../../../creusot-contracts/src/std/slice.rs" 213 20 213 61
+  let%span span76 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span77 = "../../../../creusot-contracts/src/std/slice.rs" 207 20 207 41
+  let%span span77 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span78 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span78 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span79 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span79 = "" 0 0 0 0
   
   let%span span80 = "" 0 0 0 0
   
-  let%span span81 = "" 0 0 0 0
+  let%span span81 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
   
-  let%span span82 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span82 = "" 0 0 0 0
   
-  let%span span83 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span83 = "" 0 0 0 0
   
-  let%span span84 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span84 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
   
-  let%span span85 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span85 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
   
   let%span span86 = "" 0 0 0 0
   
   let%span span87 = "" 0 0 0 0
   
-  let%span span88 = "../../../../creusot-contracts/src/std/option.rs" 38 26 38 51
+  let%span span88 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
   
   let%span span89 = "" 0 0 0 0
   
   let%span span90 = "" 0 0 0 0
   
-  let%span span91 = "../../../../creusot-contracts/src/std/slice.rs" 240 8 240 102
-  
-  let%span span92 = "../../../../creusot-contracts/src/std/slice.rs" 241 18 241 55
-  
-  let%span span93 = "" 0 0 0 0
-  
-  let%span span94 = "" 0 0 0 0
-  
-  let%span span95 = "../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
-  
-  let%span span96 = "" 0 0 0 0
-  
-  let%span span97 = "" 0 0 0 0
-  
-  let%span span98 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span91 = "../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span99 = "../index_range.rs" 7 4 12 22
+  let%span span92 = "../index_range.rs" 7 4 12 22
   
   use prelude.prelude.Int32
   
-  use prelude.prelude.Slice
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'11 (self : slice int32) =
+  predicate invariant'11 (self : Seq'0.t_seq int32) =
     [%#span42] true
   
-  predicate inv'11 (_x : slice int32)
+  predicate inv'11 (_x : Seq'0.t_seq int32)
   
-  axiom inv'11 : forall x : slice int32 . inv'11 x = true
+  axiom inv'11 : forall x : Seq'0.t_seq int32 . inv'11 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use prelude.prelude.Slice
   
-  predicate invariant'10 (self : Seq'0.t_seq int32) =
+  predicate invariant'10 (self : slice int32) =
     [%#span42] true
   
-  predicate inv'10 (_x : Seq'0.t_seq int32)
+  predicate inv'10 (_x : slice int32)
   
-  axiom inv'10 : forall x : Seq'0.t_seq int32 . inv'10 x = true
+  axiom inv'10 : forall x : slice int32 . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -3634,24 +3472,19 @@ module IndexRange_TestRangeToInclusive
   
   constant max'0 : usize = [%#span43] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq int32) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq int32 . ([%#span44] inv'10 self)  -> ([%#span45] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq int32 . [%#span44] len'2 self >= 0
   
   predicate inv'9 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span46] inv'9 self)
-   -> ([%#span48] inv'10 (shallow_model'0 self))
-  && ([%#span47] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span45] inv'9 self)
+   -> ([%#span46] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'9 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span49] inv'10 (shallow_model'0 self)
+    [%#span47] inv'11 (shallow_model'0 self)
   
   axiom inv'9 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'9 x = true
   
@@ -3724,147 +3557,139 @@ module IndexRange_TestRangeToInclusive
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span50] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span52] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span51] len'2 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span48] len'2 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : int32) =
-    [%#span53] true
+    [%#span49] true
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span54] index_logic'1 (shallow_model'0 self) ix
+    [%#span50] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span55] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span51] forall i : int . 0 <= i /\ i < len'2 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) (out : int32) =
-    [%#span56] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span52] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) =
-    [%#span57] UIntSize.to_int self < len'2 seq
+    [%#span53] UIntSize.to_int self < len'2 seq
   
   function shallow_model'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span58] shallow_model'0 self
+    [%#span54] shallow_model'0 self
   
-  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span61] inv'7 index}
-    {[@expl:precondition] [%#span60] inv'0 self}
-    {[@expl:precondition] [%#span59] in_bounds'1 index (shallow_model'1 self)}
+  let rec index'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:usize) (return'  (ret:int32))= {[@expl:precondition] [%#span57] inv'7 index}
+    {[@expl:precondition] [%#span56] inv'0 self}
+    {[@expl:precondition] [%#span55] in_bounds'1 index (shallow_model'1 self)}
     any
-    [ return' (result:int32)-> {[%#span63] inv'8 result}
-      {[%#span62] has_value'1 index (shallow_model'1 self) result}
+    [ return' (result:int32)-> {[%#span59] inv'8 result}
+      {[%#span58] has_value'1 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
-  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span64] inv'0 self}
+  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span60] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span65] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span61] UIntSize.to_int result = len'2 (shallow_model'1 self)} (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (slice int32)) =
-    [%#span66]  ^ self =  * self
+    [%#span62]  ^ self =  * self
   
   use Core_Ops_Range_RangeToInclusive_Type as Core_Ops_Range_RangeToInclusive_Type
   
   predicate resolve_elswhere'0 (self : RangeToInclusive'0.t_rangetoinclusive usize) (old' : Seq'0.t_seq int32) (fin : Seq'0.t_seq int32)
     
    =
-    [%#span67] forall i : int . UIntSize.to_int (Core_Ops_Range_RangeToInclusive_Type.rangetoinclusive_end self) < i
+    [%#span63] forall i : int . UIntSize.to_int (Core_Ops_Range_RangeToInclusive_Type.rangetoinclusive_end self) < i
     /\ i < len'2 old'  -> index_logic'1 old' i = index_logic'1 fin i
   
   function shallow_model'4 (self : slice int32) : Seq'0.t_seq int32
   
-  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span68] inv'11 self)
-   -> ([%#span70] inv'10 (shallow_model'4 self))
-  && ([%#span69] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
-  
-  use prelude.seq_ext.SeqExt
+  axiom shallow_model'4_spec : forall self : slice int32 . ([%#span64] inv'10 self)
+   -> ([%#span65] len'2 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
   function subsequence'0 (self : Seq'0.t_seq int32) (n : int) (m : int) : Seq'0.t_seq int32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span71] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq int32, n : int, m : int . ([%#span66] 0 <= n
   /\ n <= m /\ m <= len'2 self)
-   -> ([%#span72] inv'10 self)
-   -> ([%#span75] inv'10 (subsequence'0 self n m))
-  && ([%#span74] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
+   -> ([%#span68] forall i : int . 0 <= i /\ i < len'2 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span73] len'2 (subsequence'0 self n m) = m - n)
+  && ([%#span67] len'2 (subsequence'0 self n m) = m - n)
   
   predicate has_value'0 (self : RangeToInclusive'0.t_rangetoinclusive usize) (seq : Seq'0.t_seq int32) (out : slice int32)
     
    =
-    [%#span76] subsequence'0 seq 0 (UIntSize.to_int (Core_Ops_Range_RangeToInclusive_Type.rangetoinclusive_end self)
+    [%#span69] subsequence'0 seq 0 (UIntSize.to_int (Core_Ops_Range_RangeToInclusive_Type.rangetoinclusive_end self)
     + 1)
     = shallow_model'4 out
   
   predicate in_bounds'0 (self : RangeToInclusive'0.t_rangetoinclusive usize) (seq : Seq'0.t_seq int32) =
-    [%#span77] UIntSize.to_int (Core_Ops_Range_RangeToInclusive_Type.rangetoinclusive_end self) < len'2 seq
+    [%#span70] UIntSize.to_int (Core_Ops_Range_RangeToInclusive_Type.rangetoinclusive_end self) < len'2 seq
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span78] shallow_model'0 ( * self)
+    [%#span71] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeToInclusive'0.t_rangetoinclusive usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span81] inv'1 index}
-    {[@expl:precondition] [%#span80] inv'5 self}
-    {[@expl:precondition] [%#span79] in_bounds'0 index (shallow_model'3 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:RangeToInclusive'0.t_rangetoinclusive usize) (return'  (ret:borrowed (slice int32)))= {[@expl:precondition] [%#span74] inv'1 index}
+    {[@expl:precondition] [%#span73] inv'5 self}
+    {[@expl:precondition] [%#span72] in_bounds'0 index (shallow_model'3 self)}
     any
-    [ return' (result:borrowed (slice int32))-> {[%#span86] inv'6 result}
-      {[%#span85] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
-      {[%#span84] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
-      {[%#span83] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span82] has_value'0 index (shallow_model'3 self) ( * result)}
+    [ return' (result:borrowed (slice int32))-> {[%#span79] inv'6 result}
+      {[%#span78] len'2 (shallow_model'0 ( ^ self)) = len'2 (shallow_model'3 self)}
+      {[%#span77] resolve_elswhere'0 index (shallow_model'3 self) (shallow_model'0 ( ^ self))}
+      {[%#span76] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span75] has_value'0 index (shallow_model'3 self) ( * result)}
       (! return' {result}) ]
     
   
-  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span87] inv'4 self}
-    any [ return' (result:bool)-> {[%#span88] result = (self = Option'0.C_None)} (! return' {result}) ] 
+  let rec is_none'0 (self:Option'0.t_option (slice int32)) (return'  (ret:bool))= {[@expl:precondition] [%#span80] inv'4 self}
+    any [ return' (result:bool)-> {[%#span81] result = (self = Option'0.C_None)} (! return' {result}) ] 
   
   function shallow_model'2 (self : slice int32) : Seq'0.t_seq int32 =
-    [%#span58] shallow_model'4 self
+    [%#span54] shallow_model'4 self
   
-  let rec get'0 (self:slice int32) (index:RangeToInclusive'0.t_rangetoinclusive usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span90] inv'1 index}
-    {[@expl:precondition] [%#span89] inv'2 self}
+  let rec get'0 (self:slice int32) (index:RangeToInclusive'0.t_rangetoinclusive usize) (return'  (ret:Option'0.t_option (slice int32)))= {[@expl:precondition] [%#span83] inv'1 index}
+    {[@expl:precondition] [%#span82] inv'2 self}
     any
-    [ return' (result:Option'0.t_option (slice int32))-> {[%#span93] inv'3 result}
-      {[%#span92] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
-      {[%#span91] in_bounds'0 index (shallow_model'2 self)
+    [ return' (result:Option'0.t_option (slice int32))-> {[%#span86] inv'3 result}
+      {[%#span85] in_bounds'0 index (shallow_model'2 self) \/ result = Option'0.C_None}
+      {[%#span84] in_bounds'0 index (shallow_model'2 self)
        -> (exists r : slice int32 . inv'2 r
       /\ result = Option'0.C_Some r /\ has_value'0 index (shallow_model'2 self) r)}
       (! return' {result}) ]
     
   
-  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span94] inv'0 self}
+  let rec deref'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:slice int32))= {[@expl:precondition] [%#span87] inv'0 self}
     any
-    [ return' (result:slice int32)-> {[%#span96] inv'2 result}
-      {[%#span95] shallow_model'2 result = shallow_model'1 self}
+    [ return' (result:slice int32)-> {[%#span89] inv'2 result}
+      {[%#span88] shallow_model'2 result = shallow_model'1 self}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span97] inv'2 self}
+  let rec len'0 (self:slice int32) (return'  (ret:usize))= {[@expl:precondition] [%#span90] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span98] len'2 (shallow_model'2 self) = UIntSize.to_int result} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span91] len'2 (shallow_model'2 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
-  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeToInclusive'0.t_rangetoinclusive usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span61] inv'1 index}
-    {[@expl:precondition] [%#span60] inv'0 self}
-    {[@expl:precondition] [%#span59] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (index:RangeToInclusive'0.t_rangetoinclusive usize) (return'  (ret:slice int32))= {[@expl:precondition] [%#span57] inv'1 index}
+    {[@expl:precondition] [%#span56] inv'0 self}
+    {[@expl:precondition] [%#span55] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:slice int32)-> {[%#span63] inv'2 result}
-      {[%#span62] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:slice int32)-> {[%#span59] inv'2 result}
+      {[%#span58] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
   use prelude.prelude.Int32
   
   let rec create_arr'0 (_1:()) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span99] len'2 (shallow_model'0 result) = 5
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span92] len'2 (shallow_model'0 result) = 5
       /\ Int32.to_int (index_logic'0 result 0) = 0
       /\ Int32.to_int (index_logic'0 result 1) = 1
       /\ Int32.to_int (index_logic'0 result 2) = 2
diff --git a/creusot/tests/should_succeed/inferred_invarianrs.coma b/creusot/tests/should_succeed/inferred_invarianrs.coma
index 5013062252..da3a802c64 100644
--- a/creusot/tests/should_succeed/inferred_invarianrs.coma
+++ b/creusot/tests/should_succeed/inferred_invarianrs.coma
@@ -227,22 +227,7 @@ module InferredInvarianrs_TempMove
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Ptr_NonNull_NonNull_Type
   use prelude.prelude.Opaque
@@ -360,71 +345,68 @@ module InferredInvarianrs_Y
   
   let%span sinferred_invarianrs6 = "../inferred_invarianrs.rs" 46 15 46 17
   
-  let%span span7 = "" 0 0 0 0
+  let%span span7 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span8 = "" 0 0 0 0
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span14 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span14 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span18 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span15 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span19 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span16 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span20 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span17 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span21 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span18 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span22 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span20 = "" 0 0 0 0
   
-  let%span span24 = "" 0 0 0 0
+  let%span span21 = "" 0 0 0 0
   
-  let%span span25 = "" 0 0 0 0
+  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span26 = "" 0 0 0 0
   
-  let%span span30 = "" 0 0 0 0
+  let%span span27 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span31 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span28 = "" 0 0 0 0
   
-  let%span span32 = "" 0 0 0 0
+  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span30 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span34 = "../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
+  let%span span31 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span35 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span36 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span32 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
   use prelude.prelude.Int32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq int32)
+  predicate invariant'5 (self : Seq'0.t_seq int32) =
+    [%#span7] true
+  
+  predicate inv'5 (_x : Seq'0.t_seq int32)
+  
+  axiom inv'5 : forall x : Seq'0.t_seq int32 . inv'5 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -436,136 +418,123 @@ module InferredInvarianrs_Y
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq int32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int32 . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int32 . [%#span9] len'0 self >= 0
   
-  predicate inv'5 (_x : Vec'0.t_vec int32 (Global'0.t_global))
+  predicate inv'4 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span10] inv'5 self)
-   -> ([%#span12] inv'1 (shallow_model'3 self))
-  && ([%#span11] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span10] inv'4 self)
+   -> ([%#span11] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'5 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span13] inv'1 (shallow_model'3 self)
+  predicate invariant'4 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
+    [%#span12] inv'5 (shallow_model'3 self)
   
-  axiom inv'5 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'5 x = true
+  axiom inv'4 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'4 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'4 (self : borrowed int32) =
-    [%#span14] true
-  
-  predicate inv'4 (_x : borrowed int32)
+  predicate invariant'3 (self : borrowed int32) =
+    [%#span7] true
   
-  axiom inv'4 : forall x : borrowed int32 . inv'4 x = true
+  predicate inv'3 (_x : borrowed int32)
   
-  predicate invariant'3 (self : usize) =
-    [%#span14] true
+  axiom inv'3 : forall x : borrowed int32 . inv'3 x = true
   
-  predicate inv'3 (_x : usize)
+  predicate invariant'2 (self : usize) =
+    [%#span7] true
   
-  axiom inv'3 : forall x : usize . inv'3 x = true
+  predicate inv'2 (_x : usize)
   
-  predicate invariant'2 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span14] true
+  axiom inv'2 : forall x : usize . inv'2 x = true
   
-  predicate inv'2 (_x : Vec'0.t_vec int32 (Global'0.t_global))
+  predicate invariant'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
+    [%#span7] true
   
-  axiom inv'2 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'2 x = true
+  predicate inv'1 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
-  predicate invariant'1 (self : Seq'0.t_seq int32) =
-    [%#span14] true
-  
-  axiom inv'1 : forall x : Seq'0.t_seq int32 . inv'1 x = true
+  axiom inv'1 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'1 x = true
   
   predicate invariant'0 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) =
-    [%#span14] true
+    [%#span7] true
   
   predicate inv'0 (_x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)))
   
   axiom inv'0 : forall x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span15] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span17] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'0 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq int32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed int32) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   use prelude.prelude.Slice
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'0 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq int32) (fin : Seq'0.t_seq int32) =
-    [%#span19] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
+    [%#span15] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
      -> index_logic'0 old' i = index_logic'0 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) (out : int32) =
-    [%#span20] index_logic'0 seq (UIntSize.to_int self) = out
+    [%#span16] index_logic'0 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq int32) =
-    [%#span21] UIntSize.to_int self < len'0 seq
+    [%#span17] UIntSize.to_int self < len'0 seq
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span22] shallow_model'3 ( * self)
+    [%#span18] shallow_model'3 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:usize) (return'  (ret:borrowed int32))= {[@expl:precondition] [%#span25] inv'3 index}
-    {[@expl:precondition] [%#span24] inv'0 self}
-    {[@expl:precondition] [%#span23] in_bounds'0 index (shallow_model'1 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (index:usize) (return'  (ret:borrowed int32))= {[@expl:precondition] [%#span21] inv'2 index}
+    {[@expl:precondition] [%#span20] inv'0 self}
+    {[@expl:precondition] [%#span19] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:borrowed int32)-> {[%#span30] inv'4 result}
-      {[%#span29] len'0 (shallow_model'3 ( ^ self)) = len'0 (shallow_model'1 self)}
-      {[%#span28] resolve_elswhere'0 index (shallow_model'1 self) (shallow_model'3 ( ^ self))}
-      {[%#span27] has_value'0 index (shallow_model'3 ( ^ self)) ( ^ result)}
-      {[%#span26] has_value'0 index (shallow_model'1 self) ( * result)}
+    [ return' (result:borrowed int32)-> {[%#span26] inv'3 result}
+      {[%#span25] len'0 (shallow_model'3 ( ^ self)) = len'0 (shallow_model'1 self)}
+      {[%#span24] resolve_elswhere'0 index (shallow_model'1 self) (shallow_model'3 ( ^ self))}
+      {[%#span23] has_value'0 index (shallow_model'3 ( ^ self)) ( ^ result)}
+      {[%#span22] has_value'0 index (shallow_model'1 self) ( * result)}
       (! return' {result}) ]
     
   
   function shallow_model'4 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span31] shallow_model'3 self
+    [%#span27] shallow_model'3 self
   
-  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span32] inv'2 self}
+  let rec len'1 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span28] inv'1 self}
     any
-    [ return' (result:usize)-> {[%#span33] UIntSize.to_int result = len'0 (shallow_model'4 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span29] UIntSize.to_int result = len'0 (shallow_model'4 self)} (! return' {result}) ]
     
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec int32 (Global'0.t_global)))) : borrowed (Vec'0.t_vec int32 (Global'0.t_global))
     
   
   function shallow_model'2 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span31] shallow_model'1 self
+    [%#span27] shallow_model'1 self
   
   function shallow_model'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec int32 (Global'0.t_global)))) : Seq'0.t_seq int32
     
    =
-    [%#span34] shallow_model'2 (deref'0 self)
+    [%#span30] shallow_model'2 (deref'0 self)
   
   function new'0 (x : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec int32 (Global'0.t_global)))
     
   
-  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)) . ([%#span35] inv'0 x)
-   -> ([%#span36] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec int32 (Global'0.t_global)) . ([%#span31] inv'0 x)
+   -> ([%#span32] deref'0 (new'0 x) = x)
   
   let rec y (v:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (return'  (ret:()))= (! bb0
     [ bb0 = s0 [ s0 =  [ &old_v <- [%#sinferred_invarianrs0] new'0 v ] s1 | s1 = bb1 ] 
diff --git a/creusot/tests/should_succeed/invariant_moves.coma b/creusot/tests/should_succeed/invariant_moves.coma
index a4b71faeaa..b874181946 100644
--- a/creusot/tests/should_succeed/invariant_moves.coma
+++ b/creusot/tests/should_succeed/invariant_moves.coma
@@ -117,22 +117,7 @@ module Core_Option_Option_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module InvariantMoves_TestInvariantMove
   let%span sinvariant_moves0 = "../invariant_moves.rs" 6 16 6 22
@@ -141,87 +126,67 @@ module InvariantMoves_TestInvariantMove
   
   let%span span2 = "" 0 0 0 0
   
-  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span6 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span7 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span4 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span12 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span5 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span6 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span8 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span9 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span11 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span21 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span22 = "" 0 0 0 0
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 86 26 91 17
   
-  let%span span31 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
-  
-  let%span span32 = "" 0 0 0 0
-  
-  let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 86 26 91 17
-  
-  let%span span34 = "" 0 0 0 0
+  let%span span24 = "" 0 0 0 0
   
   use prelude.prelude.UInt32
   
-  predicate invariant'4 (self : uint32) =
-    [%#span1] true
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'4 (_x : uint32)
+  predicate invariant'4 (self : Seq'0.t_seq uint32) =
+    [%#span1] true
   
-  axiom inv'4 : forall x : uint32 . inv'4 x = true
+  predicate inv'4 (_x : Seq'0.t_seq uint32)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'4 : forall x : Seq'0.t_seq uint32 . inv'4 x = true
   
-  predicate invariant'3 (self : Seq'0.t_seq uint32) =
+  predicate invariant'3 (self : uint32) =
     [%#span1] true
   
-  predicate inv'3 (_x : Seq'0.t_seq uint32)
+  predicate inv'3 (_x : uint32)
   
-  axiom inv'3 : forall x : Seq'0.t_seq uint32 . inv'3 x = true
+  axiom inv'3 : forall x : uint32 . inv'3 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -235,24 +200,19 @@ module InvariantMoves_TestInvariantMove
   
   constant max'0 : usize = [%#span2] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span3] len'0 self >= 0
   
   predicate inv'2 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span5] inv'2 self)
-   -> ([%#span7] inv'3 (shallow_model'0 self))
-  && ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span4] inv'2 self)
+   -> ([%#span5] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'2 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span8] inv'3 (shallow_model'0 self)
+    [%#span6] inv'4 (shallow_model'0 self)
   
   axiom inv'2 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'2 x = true
   
@@ -265,12 +225,11 @@ module InvariantMoves_TestInvariantMove
   
   axiom inv'1 : forall x : Option'0.t_option uint32 . inv'1 x = true
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span9] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span11] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.Borrow
   
@@ -284,63 +243,51 @@ module InvariantMoves_TestInvariantMove
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : uint32) =
-    [%#span12] true
-  
-  use seq.Seq
+    [%#span8] true
   
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span13] index_logic'1 (shallow_model'0 self) ix
+    [%#span9] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span14] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span10] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate resolve'0 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) =
-    [%#span15]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span11]  ^ self =  * self
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span16] inv'3 self)
-   -> ([%#span17] inv'3 other)
-   -> ([%#span20] inv'3 (concat'0 self other))
-  && ([%#span19] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span13] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span18] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span21] inv'4 v)
-   -> ([%#span24] inv'3 (singleton'0 v))
-  && ([%#span23] index_logic'1 (singleton'0 v) 0 = v) && ([%#span22] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span14] inv'3 v)
+   -> ([%#span16] index_logic'1 (singleton'0 v) 0 = v) && ([%#span15] len'0 (singleton'0 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq uint32) (v : uint32) : Seq'0.t_seq uint32 =
-    [%#span25] concat'0 self (singleton'0 v)
-  
-  use prelude.seq_ext.SeqExt
+    [%#span17] concat'0 self (singleton'0 v)
   
   function subsequence'0 (self : Seq'0.t_seq uint32) (n : int) (m : int) : Seq'0.t_seq uint32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span26] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span18] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span27] inv'3 self)
-   -> ([%#span30] inv'3 (subsequence'0 self n m))
-  && ([%#span29] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span20] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span28] len'0 (subsequence'0 self n m) = m - n)
+  && ([%#span19] len'0 (subsequence'0 self n m) = m - n)
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) : Seq'0.t_seq uint32 =
-    [%#span31] shallow_model'0 ( * self)
+    [%#span21] shallow_model'0 ( * self)
   
-  let rec pop'0 (self:borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span32] inv'0 self}
+  let rec pop'0 (self:borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span22] inv'0 self}
     any
-    [ return' (result:Option'0.t_option uint32)-> {[%#span34] inv'1 result}
-      {[%#span33] match result with
+    [ return' (result:Option'0.t_option uint32)-> {[%#span24] inv'1 result}
+      {[%#span23] match result with
         | Option'0.C_Some t -> shallow_model'0 ( ^ self)
         = subsequence'0 (shallow_model'1 self) 0 (len'0 (shallow_model'1 self) - 1)
         /\ shallow_model'1 self = push'0 (shallow_model'0 ( ^ self)) t
diff --git a/creusot/tests/should_succeed/iterators/01_range.coma b/creusot/tests/should_succeed/iterators/01_range.coma
index 1ccf0d8ccd..9b60722a7f 100644
--- a/creusot/tests/should_succeed/iterators/01_range.coma
+++ b/creusot/tests/should_succeed/iterators/01_range.coma
@@ -25,73 +25,36 @@ module C01Range_Range_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C01Range_Impl0_ProducesRefl_Impl
   let%span s01_range0 = "../01_range.rs" 43 14 43 45
   
-  let%span span1 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span3 = "../01_range.rs" 32 8 38 9
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../01_range.rs" 32 8 38 9
+  use prelude.prelude.Int
   
   use prelude.prelude.IntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq isize) =
-    [%#span1] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq isize)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq isize . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq isize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq isize . ([%#span2] inv'0 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq isize . [%#span1] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq isize = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq isize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq isize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span2] len'0 (empty'0 : Seq'0.t_seq isize) = 0
   
   use C01Range_Range_Type as Range'0
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq isize) (x : int) : isize
+  function index_logic'0 (self : Seq'0.t_seq isize) (_2 : int) : isize
   
   use prelude.prelude.IntSize
   
@@ -100,7 +63,7 @@ module C01Range_Impl0_ProducesRefl_Impl
   predicate produces'0 [#"../01_range.rs" 31 4 31 64] (self : Range'0.t_range) (visited : Seq'0.t_seq isize) (o : Range'0.t_range)
     
    =
-    [%#span7] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
+    [%#span3] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
     /\ C01Range_Range_Type.range_start self <= C01Range_Range_Type.range_start o
     /\ (len'0 visited > 0  -> C01Range_Range_Type.range_start o <= C01Range_Range_Type.range_end o)
     /\ len'0 visited
@@ -121,75 +84,43 @@ module C01Range_Impl0_ProducesTrans_Impl
   
   let%span s01_range2 = "../01_range.rs" 50 14 50 42
   
-  let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span7 = "../01_range.rs" 32 8 38 9
   
-  let%span span14 = "../01_range.rs" 32 8 38 9
+  use prelude.prelude.Int
   
   use prelude.prelude.IntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq isize) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq isize)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq isize . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq isize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq isize . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq isize . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq isize = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq isize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq isize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq isize) = 0
   
   use C01Range_Range_Type as Range'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq isize) (x : int) : isize
+  function index_logic'0 (self : Seq'0.t_seq isize) (_2 : int) : isize
   
   function concat'0 (self : Seq'0.t_seq isize) (other : Seq'0.t_seq isize) : Seq'0.t_seq isize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span9] inv'0 self)
-   -> ([%#span10] inv'0 other)
-   -> ([%#span13] inv'0 (concat'0 self other))
-  && ([%#span12] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span6] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span11] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span5] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   use prelude.prelude.IntSize
   
@@ -198,7 +129,7 @@ module C01Range_Impl0_ProducesTrans_Impl
   predicate produces'0 [#"../01_range.rs" 31 4 31 64] (self : Range'0.t_range) (visited : Seq'0.t_seq isize) (o : Range'0.t_range)
     
    =
-    [%#span14] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
+    [%#span7] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
     /\ C01Range_Range_Type.range_start self <= C01Range_Range_Type.range_start o
     /\ (len'0 visited > 0  -> C01Range_Range_Type.range_start o <= C01Range_Range_Type.range_end o)
     /\ len'0 visited
@@ -245,41 +176,24 @@ module C01Range_Impl0_Next
   
   let%span span2 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "../01_range.rs" 32 8 38 9
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span8 = "../01_range.rs" 32 8 38 9
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span9 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span13 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span14 = "../01_range.rs" 25 12 25 52
+  let%span span10 = "../01_range.rs" 25 12 25 52
   
   use prelude.prelude.IntSize
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq isize) =
-    [%#span2] true
-  
-  predicate inv'1 (_x : Seq'0.t_seq isize)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq isize . inv'1 x = true
-  
   predicate invariant'0 (self : isize) =
     [%#span2] true
   
@@ -289,24 +203,19 @@ module C01Range_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq isize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq isize . ([%#span3] inv'1 self)  -> ([%#span4] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq isize = [%#span5] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq isize . [%#span3] len'0 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  constant empty'0 : Seq'0.t_seq isize
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq isize) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq isize) = 0
   
-  function index_logic'0 (self : Seq'0.t_seq isize) (x : int) : isize
+  function index_logic'0 (self : Seq'0.t_seq isize) (_2 : int) : isize
   
   use prelude.prelude.IntSize
   
@@ -317,7 +226,7 @@ module C01Range_Impl0_Next
   predicate produces'0 [#"../01_range.rs" 31 4 31 64] (self : Range'0.t_range) (visited : Seq'0.t_seq isize) (o : Range'0.t_range)
     
    =
-    [%#span8] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
+    [%#span5] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
     /\ C01Range_Range_Type.range_start self <= C01Range_Range_Type.range_start o
     /\ (len'0 visited > 0  -> C01Range_Range_Type.range_start o <= C01Range_Range_Type.range_end o)
     /\ len'0 visited
@@ -325,21 +234,18 @@ module C01Range_Impl0_Next
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> IntSize.to_int (index_logic'0 visited i) = IntSize.to_int (C01Range_Range_Type.range_start self) + i)
   
-  use seq.Seq
-  
   function singleton'0 (v : isize) : Seq'0.t_seq isize
   
-  axiom singleton'0_spec : forall v : isize . ([%#span9] inv'0 v)
-   -> ([%#span12] inv'1 (singleton'0 v))
-  && ([%#span11] index_logic'0 (singleton'0 v) 0 = v) && ([%#span10] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : isize . ([%#span6] inv'0 v)
+   -> ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
   
   use prelude.prelude.Borrow
   
   predicate resolve'0 (self : borrowed (Range'0.t_range)) =
-    [%#span13]  ^ self =  * self
+    [%#span9]  ^ self =  * self
   
   predicate completed'0 [#"../01_range.rs" 23 4 23 35] (self : borrowed (Range'0.t_range)) =
-    [%#span14] resolve'0 self /\ C01Range_Range_Type.range_start ( * self) >= C01Range_Range_Type.range_end ( * self)
+    [%#span10] resolve'0 self /\ C01Range_Range_Type.range_start ( * self) >= C01Range_Range_Type.range_end ( * self)
   
   use prelude.prelude.Intrinsic
   
@@ -428,59 +334,45 @@ module C01Range_SumRange
   
   let%span span12 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span20 = "../01_range.rs" 32 8 38 9
-  
-  let%span span21 = "../01_range.rs" 48 15 48 32
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span22 = "../01_range.rs" 49 15 49 32
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span23 = "../01_range.rs" 50 14 50 42
+  let%span span16 = "../01_range.rs" 32 8 38 9
   
-  let%span span24 = "../01_range.rs" 46 4 46 10
+  let%span span17 = "../01_range.rs" 48 15 48 32
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span18 = "../01_range.rs" 49 15 49 32
   
-  let%span span26 = "../01_range.rs" 43 14 43 45
+  let%span span19 = "../01_range.rs" 50 14 50 42
   
-  let%span span27 = "../01_range.rs" 41 4 41 10
+  let%span span20 = "../01_range.rs" 46 4 46 10
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span21 = "../01_range.rs" 43 14 43 45
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span22 = "../01_range.rs" 41 4 41 10
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span34 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span27 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span35 = "../01_range.rs" 25 12 25 52
+  let%span span28 = "../01_range.rs" 25 12 25 52
   
-  let%span span36 = "../01_range.rs" 53 14 56 5
+  let%span span29 = "../01_range.rs" 53 14 56 5
   
-  let%span span37 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span30 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span38 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span31 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span39 = "../01_range.rs" 69 14 69 28
+  let%span span32 = "../01_range.rs" 69 14 69 28
   
   use prelude.prelude.IntSize
   
@@ -504,29 +396,19 @@ module C01Range_SumRange
   
   use C01Range_Range_Type as Range'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq isize) (x : int) : isize
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq isize) (_2 : int) : isize
   
   function len'0 (self : Seq'0.t_seq isize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq isize . ([%#span13] inv'1 self)  -> ([%#span14] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq isize . [%#span13] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq isize) (other : Seq'0.t_seq isize) : Seq'0.t_seq isize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span15] inv'1 self)
-   -> ([%#span16] inv'1 other)
-   -> ([%#span19] inv'1 (concat'0 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span15] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span17] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   use prelude.prelude.IntSize
   
@@ -535,7 +417,7 @@ module C01Range_SumRange
   predicate produces'0 [#"../01_range.rs" 31 4 31 64] (self : Range'0.t_range) (visited : Seq'0.t_seq isize) (o : Range'0.t_range)
     
    =
-    [%#span20] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
+    [%#span16] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
     /\ C01Range_Range_Type.range_start self <= C01Range_Range_Type.range_start o
     /\ (len'0 visited > 0  -> C01Range_Range_Type.range_start o <= C01Range_Range_Type.range_end o)
     /\ len'0 visited
@@ -546,17 +428,17 @@ module C01Range_SumRange
   function produces_trans'0 [#"../01_range.rs" 51 4 51 90] (a : Range'0.t_range) (ab : Seq'0.t_seq isize) (b : Range'0.t_range) (bc : Seq'0.t_seq isize) (c : Range'0.t_range) : ()
     
    =
-    [%#span24] ()
+    [%#span20] ()
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range, ab : Seq'0.t_seq isize, b : Range'0.t_range, bc : Seq'0.t_seq isize, c : Range'0.t_range . ([%#span21] produces'0 a ab b)
-   -> ([%#span22] produces'0 b bc c)  -> ([%#span23] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range, ab : Seq'0.t_seq isize, b : Range'0.t_range, bc : Seq'0.t_seq isize, c : Range'0.t_range . ([%#span17] produces'0 a ab b)
+   -> ([%#span18] produces'0 b bc c)  -> ([%#span19] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq isize = [%#span25] ()
+  constant empty'0 : Seq'0.t_seq isize
   
   function produces_refl'0 [#"../01_range.rs" 44 4 44 26] (self : Range'0.t_range) : () =
-    [%#span27] ()
+    [%#span22] ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range . [%#span26] produces'0 self (empty'0 : Seq'0.t_seq isize) self
+  axiom produces_refl'0_spec : forall self : Range'0.t_range . [%#span21] produces'0 self (empty'0 : Seq'0.t_seq isize) self
   
   predicate invariant'0 (self : Range'0.t_range) =
     [%#span12] true
@@ -565,35 +447,31 @@ module C01Range_SumRange
   
   axiom inv'0 : forall x : Range'0.t_range . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span29] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span28] len'0 (empty'0 : Seq'0.t_seq isize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'0 (empty'0 : Seq'0.t_seq isize) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   function singleton'0 (v : isize) : Seq'0.t_seq isize
   
-  axiom singleton'0_spec : forall v : isize . ([%#span30] inv'2 v)
-   -> ([%#span33] inv'1 (singleton'0 v))
-  && ([%#span32] index_logic'0 (singleton'0 v) 0 = v) && ([%#span31] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : isize . ([%#span24] inv'2 v)
+   -> ([%#span26] index_logic'0 (singleton'0 v) 0 = v) && ([%#span25] len'0 (singleton'0 v) = 1)
   
   use Core_Option_Option_Type as Option'0
   
   use prelude.prelude.Borrow
   
   predicate resolve'0 (self : borrowed (Range'0.t_range)) =
-    [%#span34]  ^ self =  * self
+    [%#span27]  ^ self =  * self
   
   predicate completed'0 [#"../01_range.rs" 23 4 23 35] (self : borrowed (Range'0.t_range)) =
-    [%#span35] resolve'0 self /\ C01Range_Range_Type.range_start ( * self) >= C01Range_Range_Type.range_end ( * self)
+    [%#span28] resolve'0 self /\ C01Range_Range_Type.range_start ( * self) >= C01Range_Range_Type.range_end ( * self)
   
   let rec next'0 (self:borrowed (Range'0.t_range)) (return'  (ret:Option'0.t_option isize))= any
-    [ return' (result:Option'0.t_option isize)-> {[%#span36] match result with
+    [ return' (result:Option'0.t_option isize)-> {[%#span29] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -608,14 +486,14 @@ module C01Range_SumRange
   
   function new'1 (x : Seq'0.t_seq isize) : Snapshot'0.t_snapshot (Seq'0.t_seq isize)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq isize . ([%#span37] inv'1 x)  -> ([%#span38] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq isize . ([%#span30] inv'1 x)  -> ([%#span31] deref'1 (new'1 x) = x)
   
   function new'0 (x : Range'0.t_range) : Snapshot'0.t_snapshot (Range'0.t_range)
   
-  axiom new'0_spec : forall x : Range'0.t_range . ([%#span37] inv'0 x)  -> ([%#span38] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Range'0.t_range . ([%#span30] inv'0 x)  -> ([%#span31] deref'0 (new'0 x) = x)
   
   let rec into_iter'0 (self:Range'0.t_range) (return'  (ret:Range'0.t_range))= any
-    [ return' (result:Range'0.t_range)-> {[%#span39] result = self} (! return' {result}) ]
+    [ return' (result:Range'0.t_range)-> {[%#span32] result = self} (! return' {result}) ]
     
   
   let rec sum_range (n:isize) (return'  (ret:isize))= {[%#s01_range10] IntSize.to_int n >= 0}
@@ -680,73 +558,52 @@ module C01Range_Impl0
   
   let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span11 = "../01_range.rs" 25 12 25 52
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span8 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span9 = "../01_range.rs" 25 12 25 52
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span18 = "../01_range.rs" 32 8 38 9
+  let%span span12 = "../01_range.rs" 32 8 38 9
   
   use prelude.prelude.IntSize
   
-  predicate invariant'4 (self : isize) =
+  predicate invariant'3 (self : isize) =
     [%#span3] true
   
-  predicate inv'4 (_x : isize)
+  predicate inv'3 (_x : isize)
   
-  axiom inv'4 : forall x : isize . inv'4 x = true
+  axiom inv'3 : forall x : isize . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'3 (self : Option'0.t_option isize) =
+  predicate invariant'2 (self : Option'0.t_option isize) =
     [%#span3] true
   
-  predicate inv'3 (_x : Option'0.t_option isize)
+  predicate inv'2 (_x : Option'0.t_option isize)
   
-  axiom inv'3 : forall x : Option'0.t_option isize . inv'3 x = true
+  axiom inv'2 : forall x : Option'0.t_option isize . inv'2 x = true
   
   use C01Range_Range_Type as Range'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'2 (self : borrowed (Range'0.t_range)) =
-    [%#span3] true
-  
-  predicate inv'2 (_x : borrowed (Range'0.t_range))
-  
-  axiom inv'2 : forall x : borrowed (Range'0.t_range) . inv'2 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq isize) =
+  predicate invariant'1 (self : borrowed (Range'0.t_range)) =
     [%#span3] true
   
-  predicate inv'1 (_x : Seq'0.t_seq isize)
+  predicate inv'1 (_x : borrowed (Range'0.t_range))
   
-  axiom inv'1 : forall x : Seq'0.t_seq isize . inv'1 x = true
+  axiom inv'1 : forall x : borrowed (Range'0.t_range) . inv'1 x = true
   
   predicate invariant'0 (self : Range'0.t_range) =
     [%#span3] true
@@ -757,54 +614,43 @@ module C01Range_Impl0
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq isize) (x : int) : isize
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq isize) (_2 : int) : isize
   
   function len'0 (self : Seq'0.t_seq isize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq isize . ([%#span4] inv'1 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq isize . [%#span4] len'0 self >= 0
   
   function singleton'0 (v : isize) : Seq'0.t_seq isize
   
-  axiom singleton'0_spec : forall v : isize . ([%#span6] inv'4 v)
-   -> ([%#span9] inv'1 (singleton'0 v))
-  && ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : isize . ([%#span5] inv'3 v)
+   -> ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
   
   use C01Range_Range_Type as C01Range_Range_Type
   
   predicate resolve'0 (self : borrowed (Range'0.t_range)) =
-    [%#span10]  ^ self =  * self
+    [%#span8]  ^ self =  * self
   
   predicate completed'0 [#"../01_range.rs" 23 4 23 35] (self : borrowed (Range'0.t_range)) =
-    [%#span11] resolve'0 self /\ C01Range_Range_Type.range_start ( * self) >= C01Range_Range_Type.range_end ( * self)
-  
-  use seq.Seq
+    [%#span9] resolve'0 self /\ C01Range_Range_Type.range_start ( * self) >= C01Range_Range_Type.range_end ( * self)
   
   function concat'0 (self : Seq'0.t_seq isize) (other : Seq'0.t_seq isize) : Seq'0.t_seq isize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span12] inv'1 self)
-   -> ([%#span13] inv'1 other)
-   -> ([%#span16] inv'1 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span11] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span10] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  constant empty'0 : Seq'0.t_seq isize = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq isize
   
   use prelude.prelude.IntSize
   
   predicate produces'0 [#"../01_range.rs" 31 4 31 64] (self : Range'0.t_range) (visited : Seq'0.t_seq isize) (o : Range'0.t_range)
     
    =
-    [%#span18] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
+    [%#span12] C01Range_Range_Type.range_end self = C01Range_Range_Type.range_end o
     /\ C01Range_Range_Type.range_start self <= C01Range_Range_Type.range_start o
     /\ (len'0 visited > 0  -> C01Range_Range_Type.range_start o <= C01Range_Range_Type.range_end o)
     /\ len'0 visited
@@ -812,23 +658,23 @@ module C01Range_Impl0
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> IntSize.to_int (index_logic'0 visited i) = IntSize.to_int (C01Range_Range_Type.range_start self) + i)
   
-  constant empty'0 : Seq'0.t_seq isize = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq isize
   
   goal produces_refl_refn : [%#s01_range0] forall self : Range'0.t_range . inv'0 self
    -> (forall result : () . produces'0 self (empty'0 : Seq'0.t_seq isize) self
    -> produces'0 self (empty'1 : Seq'0.t_seq isize) self)
   
   goal produces_trans_refn : [%#s01_range1] forall a : Range'0.t_range . forall ab : Seq'0.t_seq isize . forall b : Range'0.t_range . forall bc : Seq'0.t_seq isize . forall c : Range'0.t_range . inv'0 c
-  /\ inv'1 bc /\ inv'0 b /\ inv'1 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
   
-  goal next_refn : [%#s01_range2] forall self : borrowed (Range'0.t_range) . inv'2 self
+  goal next_refn : [%#s01_range2] forall self : borrowed (Range'0.t_range) . inv'1 self
    -> (forall result : Option'0.t_option isize . match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
     end
-   -> inv'3 result
+   -> inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
diff --git a/creusot/tests/should_succeed/iterators/02_iter_mut.coma b/creusot/tests/should_succeed/iterators/02_iter_mut.coma
index 6aa49f4e9b..d55a37c654 100644
--- a/creusot/tests/should_succeed/iterators/02_iter_mut.coma
+++ b/creusot/tests/should_succeed/iterators/02_iter_mut.coma
@@ -20,22 +20,7 @@ module C02IterMut_IterMut_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C02IterMut_Impl1_ProducesRefl_Impl
   type t
@@ -44,130 +29,93 @@ module C02IterMut_Impl1_ProducesRefl_Impl
   
   let%span s02_iter_mut1 = "../02_iter_mut.rs" 49 14 49 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "" 0 0 0 0
-  
-  let%span span8 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
-  
-  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span11 = "../02_iter_mut.rs" 22 20 22 64
+  let%span span4 = "" 0 0 0 0
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span5 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "../02_iter_mut.rs" 22 20 22 64
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span10 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span18 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span11 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
+  let%span span12 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
+  let%span span13 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
+  let%span span14 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
+  let%span span15 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 67 4 67 43
-  
-  let%span span24 = "../02_iter_mut.rs" 39 12 43 13
+  let%span span16 = "../02_iter_mut.rs" 39 12 43 13
   
   use prelude.prelude.Slice
   
-  predicate invariant'4 (self : slice t)
-  
-  predicate inv'4 (_x : slice t)
-  
-  axiom inv'4 : forall x : slice t . inv'4 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'3 (self : Seq'0.t_seq t)
+  predicate invariant'2 (self : slice t)
   
-  predicate inv'3 (_x : Seq'0.t_seq t)
+  predicate inv'2 (_x : slice t)
   
-  axiom inv'3 : forall x : Seq'0.t_seq t . inv'3 x = true
+  axiom inv'2 : forall x : slice t . inv'2 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'2 (self : borrowed (slice t))
+  predicate invariant'1 (self : borrowed (slice t))
   
-  predicate inv'2 (_x : borrowed (slice t))
+  predicate inv'1 (_x : borrowed (slice t))
   
-  axiom inv'2 : forall x : borrowed (slice t) . inv'2 x = true
+  axiom inv'1 : forall x : borrowed (slice t) . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'3 self)  -> ([%#span3] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span4] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span6] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span5] len'0 (empty'1 : Seq'0.t_seq t) = 0
+  constant empty'1 : Seq'0.t_seq t
   
-  predicate invariant'1 (self : Seq'0.t_seq (borrowed t))
+  function empty_len'1 (_1 : ()) : ()
   
-  predicate inv'1 (_x : Seq'0.t_seq (borrowed t))
-  
-  axiom inv'1 : forall x : Seq'0.t_seq (borrowed t) . inv'1 x = true
-  
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span3] len'0 (empty'1 : Seq'0.t_seq t) = 0
   
   function len'1 (self : Seq'0.t_seq (borrowed t)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . ([%#span2] inv'1 self)  -> ([%#span3] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . [%#span2] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (borrowed t) = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq (borrowed t)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'1 (empty'0 : Seq'0.t_seq (borrowed t)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'1 (empty'0 : Seq'0.t_seq (borrowed t)) = 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : slice t . ([%#span8] inv'4 self)
-   -> ([%#span10] inv'3 (shallow_model'1 self))
-  && ([%#span9] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice t . ([%#span5] inv'2 self)
+   -> ([%#span6] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   use C02IterMut_IterMut_Type as C02IterMut_IterMut_Type
   
   use C02IterMut_IterMut_Type as IterMut'0
   
   predicate invariant'0 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut t) =
-    [%#span11] len'0 (shallow_model'1 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span7] len'0 (shallow_model'1 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
     = len'0 (shallow_model'1 ( * C02IterMut_IterMut_Type.itermut_inner self))
   
   predicate inv'0 (_x : IterMut'0.t_itermut t)
@@ -178,46 +126,38 @@ module C02IterMut_Impl1_ProducesRefl_Impl
     | IterMut'0.C_IterMut inner -> true
     end)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (x : int) : borrowed t
+  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (_2 : int) : borrowed t
   
   function concat'0 (self : Seq'0.t_seq (borrowed t)) (other : Seq'0.t_seq (borrowed t)) : Seq'0.t_seq (borrowed t)
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span12] inv'1 self)
-   -> ([%#span13] inv'1 other)
-   -> ([%#span16] inv'1 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'1 self then index_logic'0 self i else index_logic'0 other (i - len'1 self)))
-  && ([%#span14] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span8] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'1 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span17] index_logic'2 (shallow_model'1 self) ix
+    [%#span10] index_logic'2 (shallow_model'1 self) ix
   
   function shallow_model'0 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span18] shallow_model'1 ( * self)
+    [%#span11] shallow_model'1 ( * self)
   
   function to_mut_seq'0 (self : borrowed (slice t)) : Seq'0.t_seq (borrowed t)
   
-  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span19] inv'2 self)
-   -> ([%#span23] inv'1 (to_mut_seq'0 self))
-  && ([%#span22] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span12] inv'1 self)
+   -> ([%#span15] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  ^ index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( ^ self) i)
-  && ([%#span21] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  && ([%#span14] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  * index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( * self) i)
-  && ([%#span20] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
+  && ([%#span13] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
   
   predicate produces'0 [#"../02_iter_mut.rs" 37 4 37 65] (self : IterMut'0.t_itermut t) (visited : Seq'0.t_seq (borrowed t)) (tl : IterMut'0.t_itermut t)
     
    =
-    [%#span24] len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span16] len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
     = len'1 visited + len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner tl))
     /\ (forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
      ->  * index_logic'0 (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner self)) i
@@ -241,140 +181,99 @@ module C02IterMut_Impl1_ProducesTrans_Impl
   
   let%span s02_iter_mut2 = "../02_iter_mut.rs" 57 22 57 23
   
-  let%span s02_iter_mut3 = "../02_iter_mut.rs" 57 31 57 33
-  
-  let%span s02_iter_mut4 = "../02_iter_mut.rs" 57 52 57 53
-  
-  let%span s02_iter_mut5 = "../02_iter_mut.rs" 57 61 57 63
-  
-  let%span s02_iter_mut6 = "../02_iter_mut.rs" 57 82 57 83
-  
-  let%span s02_iter_mut7 = "../02_iter_mut.rs" 56 14 56 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span s02_iter_mut3 = "../02_iter_mut.rs" 57 52 57 53
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span s02_iter_mut4 = "../02_iter_mut.rs" 57 82 57 83
   
-  let%span span13 = "" 0 0 0 0
+  let%span s02_iter_mut5 = "../02_iter_mut.rs" 56 14 56 42
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
-  
-  let%span span17 = "../02_iter_mut.rs" 22 20 22 64
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span8 = "" 0 0 0 0
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span10 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span11 = "../02_iter_mut.rs" 22 20 22 64
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span24 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span14 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
+  let%span span15 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
+  let%span span17 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
+  let%span span18 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 67 4 67 43
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
   
-  let%span span30 = "../02_iter_mut.rs" 39 12 43 13
+  let%span span20 = "../02_iter_mut.rs" 39 12 43 13
   
   use prelude.prelude.Slice
   
-  predicate invariant'4 (self : slice t)
+  predicate invariant'2 (self : slice t)
   
-  predicate inv'4 (_x : slice t)
+  predicate inv'2 (_x : slice t)
   
-  axiom inv'4 : forall x : slice t . inv'4 x = true
+  axiom inv'2 : forall x : slice t . inv'2 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'3 (self : borrowed (slice t))
-  
-  predicate inv'3 (_x : borrowed (slice t))
-  
-  axiom inv'3 : forall x : borrowed (slice t) . inv'3 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'2 (self : Seq'0.t_seq t)
+  predicate invariant'1 (self : borrowed (slice t))
   
-  predicate inv'2 (_x : Seq'0.t_seq t)
+  predicate inv'1 (_x : borrowed (slice t))
   
-  axiom inv'2 : forall x : Seq'0.t_seq t . inv'2 x = true
+  axiom inv'1 : forall x : borrowed (slice t) . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span8] inv'2 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span10] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span6] len'0 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'0 (empty'1 : Seq'0.t_seq t) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq (borrowed t))
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'0 (empty'1 : Seq'0.t_seq t) = 0
   
   function len'1 (self : Seq'0.t_seq (borrowed t)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . ([%#span8] inv'1 self)  -> ([%#span9] len'1 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq (borrowed t) = [%#span10] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . [%#span6] len'1 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'0 : Seq'0.t_seq (borrowed t)
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'1 (empty'0 : Seq'0.t_seq (borrowed t)) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq (borrowed t))
-  
-  axiom inv'1 : forall x : Seq'0.t_seq (borrowed t) . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'1 (empty'0 : Seq'0.t_seq (borrowed t)) = 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span13] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : slice t . ([%#span14] inv'4 self)
-   -> ([%#span16] inv'2 (shallow_model'1 self))
-  && ([%#span15] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice t . ([%#span9] inv'2 self)
+   -> ([%#span10] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   use C02IterMut_IterMut_Type as C02IterMut_IterMut_Type
   
   use C02IterMut_IterMut_Type as IterMut'0
   
   predicate invariant'0 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut t) =
-    [%#span17] len'0 (shallow_model'1 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span11] len'0 (shallow_model'1 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
     = len'0 (shallow_model'1 ( * C02IterMut_IterMut_Type.itermut_inner self))
   
   predicate inv'0 (_x : IterMut'0.t_itermut t)
@@ -385,46 +284,38 @@ module C02IterMut_Impl1_ProducesTrans_Impl
     | IterMut'0.C_IterMut inner -> true
     end)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (x : int) : borrowed t
+  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (_2 : int) : borrowed t
   
   function concat'0 (self : Seq'0.t_seq (borrowed t)) (other : Seq'0.t_seq (borrowed t)) : Seq'0.t_seq (borrowed t)
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span18] inv'1 self)
-   -> ([%#span19] inv'1 other)
-   -> ([%#span22] inv'1 (concat'0 self other))
-  && ([%#span21] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span13] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'1 self then index_logic'0 self i else index_logic'0 other (i - len'1 self)))
-  && ([%#span20] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span12] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'1 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span23] index_logic'2 (shallow_model'1 self) ix
+    [%#span14] index_logic'2 (shallow_model'1 self) ix
   
   function shallow_model'0 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span24] shallow_model'1 ( * self)
+    [%#span15] shallow_model'1 ( * self)
   
   function to_mut_seq'0 (self : borrowed (slice t)) : Seq'0.t_seq (borrowed t)
   
-  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span25] inv'3 self)
-   -> ([%#span29] inv'1 (to_mut_seq'0 self))
-  && ([%#span28] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span16] inv'1 self)
+   -> ([%#span19] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  ^ index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( ^ self) i)
-  && ([%#span27] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  && ([%#span18] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  * index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( * self) i)
-  && ([%#span26] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
+  && ([%#span17] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
   
   predicate produces'0 [#"../02_iter_mut.rs" 37 4 37 65] (self : IterMut'0.t_itermut t) (visited : Seq'0.t_seq (borrowed t)) (tl : IterMut'0.t_itermut t)
     
    =
-    [%#span30] len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span20] len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
     = len'1 visited + len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner tl))
     /\ (forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
      ->  * index_logic'0 (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner self)) i
@@ -445,13 +336,11 @@ module C02IterMut_Impl1_ProducesTrans_Impl
   function produces_trans [#"../02_iter_mut.rs" 57 4 57 90] (a : IterMut'0.t_itermut t) (ab : Seq'0.t_seq (borrowed t)) (b : IterMut'0.t_itermut t) (bc : Seq'0.t_seq (borrowed t)) (c : IterMut'0.t_itermut t) : ()
     
   
-  goal vc_produces_trans : ([%#s02_iter_mut6] inv'0 c)
-   -> ([%#s02_iter_mut5] inv'1 bc)
-   -> ([%#s02_iter_mut4] inv'0 b)
-   -> ([%#s02_iter_mut3] inv'1 ab)
+  goal vc_produces_trans : ([%#s02_iter_mut4] inv'0 c)
+   -> ([%#s02_iter_mut3] inv'0 b)
    -> ([%#s02_iter_mut2] inv'0 a)
    -> ([%#s02_iter_mut1] produces'0 b bc c)
-   -> ([%#s02_iter_mut0] produces'0 a ab b)  -> ([%#s02_iter_mut7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s02_iter_mut0] produces'0 a ab b)  -> ([%#s02_iter_mut5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -478,89 +367,63 @@ module C02IterMut_Impl1_Next
   
   let%span s02_iter_mut2 = "../02_iter_mut.rs" 63 26 63 44
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "" 0 0 0 0
-  
-  let%span span6 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span4 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span5 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span9 = "../02_iter_mut.rs" 22 20 22 64
+  let%span span6 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span7 = "../02_iter_mut.rs" 22 20 22 64
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span19 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
+  let%span span11 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
+  let%span span12 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
+  let%span span13 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
+  let%span span14 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 67 4 67 43
+  let%span span15 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
   
-  let%span span25 = "../02_iter_mut.rs" 39 12 43 13
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span17 = "../02_iter_mut.rs" 39 12 43 13
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span23 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span24 = "../02_iter_mut.rs" 32 8 32 76
   
-  let%span span34 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span35 = "../02_iter_mut.rs" 32 8 32 76
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 62 8 62 39
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span29 = "" 0 0 0 0
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 269 18 276 9
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
-  
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 66 8 66 39
-  
-  let%span span42 = "" 0 0 0 0
-  
-  let%span span43 = "../../../../../creusot-contracts/src/std/slice.rs" 269 18 276 9
-  
-  let%span span44 = "" 0 0 0 0
+  let%span span31 = "" 0 0 0 0
   
   use prelude.prelude.Slice
   
@@ -572,59 +435,42 @@ module C02IterMut_Impl1_Next
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  predicate inv'7 (_x : Seq'0.t_seq t)
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'7 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
-  predicate inv'6 (_x : slice t)
+  predicate inv'5 (_x : slice t)
   
   function shallow_model'0 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'0_spec : forall self : slice t . ([%#span6] inv'6 self)
-   -> ([%#span8] inv'7 (shallow_model'0 self))
-  && ([%#span7] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : slice t . ([%#span5] inv'5 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   use C02IterMut_IterMut_Type as C02IterMut_IterMut_Type
   
   use C02IterMut_IterMut_Type as IterMut'0
   
-  predicate invariant'8 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut t) =
-    [%#span9] len'0 (shallow_model'0 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
+  predicate invariant'6 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut t) =
+    [%#span7] len'0 (shallow_model'0 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
     = len'0 (shallow_model'0 ( * C02IterMut_IterMut_Type.itermut_inner self))
   
-  predicate inv'8 (_x : IterMut'0.t_itermut t)
+  predicate inv'6 (_x : IterMut'0.t_itermut t)
   
-  axiom inv'8 : forall x : IterMut'0.t_itermut t . inv'8 x
-  = (invariant'8 x
+  axiom inv'6 : forall x : IterMut'0.t_itermut t . inv'6 x
+  = (invariant'6 x
   /\ match x with
     | IterMut'0.C_IterMut inner -> true
     end)
   
-  predicate invariant'7 (self : Seq'0.t_seq t)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq t . inv'7 x = true
-  
-  predicate invariant'6 (self : slice t)
-  
-  axiom inv'6 : forall x : slice t . inv'6 x = true
+  predicate invariant'5 (self : slice t)
   
-  predicate invariant'5 (self : Seq'0.t_seq (borrowed t))
-  
-  predicate inv'5 (_x : Seq'0.t_seq (borrowed t))
-  
-  axiom inv'5 : forall x : Seq'0.t_seq (borrowed t) . inv'5 x = true
+  axiom inv'5 : forall x : slice t . inv'5 x = true
   
   predicate invariant'4 (self : borrowed t)
   
@@ -632,12 +478,11 @@ module C02IterMut_Impl1_Next
   
   axiom inv'4 : forall x : borrowed t . inv'4 x = true
   
-  constant empty'0 : Seq'0.t_seq t = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'3 (self : borrowed (borrowed (slice t)))
   
@@ -653,69 +498,58 @@ module C02IterMut_Impl1_Next
   
   axiom inv'2 : forall x : Option'0.t_option (borrowed t) . inv'2 x = true
   
-  use seq.Seq
-  
   function len'1 (self : Seq'0.t_seq (borrowed t)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . ([%#span3] inv'5 self)  -> ([%#span4] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . [%#span3] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq (borrowed t) = [%#span10] ()
+  constant empty'1 : Seq'0.t_seq (borrowed t)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq (borrowed t)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'1 (empty'1 : Seq'0.t_seq (borrowed t)) = 0
   
   predicate invariant'1 (self : borrowed (IterMut'0.t_itermut t))
   
   predicate inv'1 (_x : borrowed (IterMut'0.t_itermut t))
   
-  axiom inv'1 : forall x : borrowed (IterMut'0.t_itermut t) . inv'1 x = (inv'8 ( * x) /\ inv'8 ( ^ x))
+  axiom inv'1 : forall x : borrowed (IterMut'0.t_itermut t) . inv'1 x = (inv'6 ( * x) /\ inv'6 ( ^ x))
   
   predicate invariant'0 (self : borrowed (slice t))
   
   axiom inv'0 : forall x : borrowed (slice t) . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (borrowed t)) (x : int) : borrowed t
+  function index_logic'1 (self : Seq'0.t_seq (borrowed t)) (_2 : int) : borrowed t
   
   function concat'0 (self : Seq'0.t_seq (borrowed t)) (other : Seq'0.t_seq (borrowed t)) : Seq'0.t_seq (borrowed t)
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span13] inv'5 self)
-   -> ([%#span14] inv'5 other)
-   -> ([%#span17] inv'5 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span10] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span15] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span9] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'0 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span18] index_logic'2 (shallow_model'0 self) ix
+    [%#span11] index_logic'2 (shallow_model'0 self) ix
   
   function shallow_model'1 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span19] shallow_model'0 ( * self)
+    [%#span12] shallow_model'0 ( * self)
   
   function to_mut_seq'0 (self : borrowed (slice t)) : Seq'0.t_seq (borrowed t)
   
-  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span20] inv'0 self)
-   -> ([%#span24] inv'5 (to_mut_seq'0 self))
-  && ([%#span23] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span13] inv'0 self)
+   -> ([%#span16] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  ^ index_logic'1 (to_mut_seq'0 self) i = index_logic'0 ( ^ self) i)
-  && ([%#span22] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  && ([%#span15] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  * index_logic'1 (to_mut_seq'0 self) i = index_logic'0 ( * self) i)
-  && ([%#span21] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'1 self))
+  && ([%#span14] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'1 self))
   
   predicate produces'0 [#"../02_iter_mut.rs" 37 4 37 65] (self : IterMut'0.t_itermut t) (visited : Seq'0.t_seq (borrowed t)) (tl : IterMut'0.t_itermut t)
     
    =
-    [%#span25] len'0 (shallow_model'1 (C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span17] len'0 (shallow_model'1 (C02IterMut_IterMut_Type.itermut_inner self))
     = len'1 visited + len'0 (shallow_model'1 (C02IterMut_IterMut_Type.itermut_inner tl))
     /\ (forall i : int . 0 <= i /\ i < len'0 (shallow_model'1 (C02IterMut_IterMut_Type.itermut_inner self))
      ->  * index_logic'1 (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner self)) i
@@ -723,55 +557,44 @@ module C02IterMut_Impl1_Next
     /\  ^ index_logic'1 (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner self)) i
     =  ^ index_logic'1 (concat'0 visited (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner tl))) i)
   
-  use seq.Seq
-  
   function singleton'0 (v : borrowed t) : Seq'0.t_seq (borrowed t)
   
-  axiom singleton'0_spec : forall v : borrowed t . ([%#span26] inv'4 v)
-   -> ([%#span29] inv'5 (singleton'0 v))
-  && ([%#span28] index_logic'1 (singleton'0 v) 0 = v) && ([%#span27] len'1 (singleton'0 v) = 1)
-  
-  use seq.Seq
+  axiom singleton'0_spec : forall v : borrowed t . ([%#span18] inv'4 v)
+   -> ([%#span20] index_logic'1 (singleton'0 v) 0 = v) && ([%#span19] len'1 (singleton'0 v) = 1)
   
   predicate ext_eq'0 (self : Seq'0.t_seq t) (oth : Seq'0.t_seq t)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span30] inv'7 self)
-   -> ([%#span31] inv'7 oth)
-   -> ([%#span33] len'0 self = len'0 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span22] len'0 self = len'0 oth
   /\ (forall i : int . 0 <= i /\ i < len'0 self  -> index_logic'2 self i = index_logic'2 oth i)  -> ext_eq'0 self oth)
-  && ([%#span32] ext_eq'0 self oth  -> self = oth)
+  && ([%#span21] ext_eq'0 self oth  -> self = oth)
   
   predicate resolve'1 (self : borrowed (slice t)) =
-    [%#span34]  ^ self =  * self
+    [%#span23]  ^ self =  * self
   
   predicate completed'0 [#"../02_iter_mut.rs" 31 4 31 35] (self : borrowed (IterMut'0.t_itermut t)) =
-    [%#span35] resolve'1 (C02IterMut_IterMut_Type.itermut_inner ( * self))
+    [%#span24] resolve'1 (C02IterMut_IterMut_Type.itermut_inner ( * self))
     /\ ext_eq'0 (shallow_model'1 (C02IterMut_IterMut_Type.itermut_inner ( * self))) (empty'0 : Seq'0.t_seq t)
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed (IterMut'0.t_itermut t)) =
-    [%#span34]  ^ self =  * self
-  
-  use prelude.seq_ext.SeqExt
+    [%#span23]  ^ self =  * self
   
   function subsequence'0 (self : Seq'0.t_seq t) (n : int) (m : int) : Seq'0.t_seq t
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq t, n : int, m : int . ([%#span36] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq t, n : int, m : int . ([%#span25] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span37] inv'7 self)
-   -> ([%#span40] inv'7 (subsequence'0 self n m))
-  && ([%#span39] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span27] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'2 (subsequence'0 self n m) i = index_logic'2 self (n + i))
-  && ([%#span38] len'0 (subsequence'0 self n m) = m - n)
+  && ([%#span26] len'0 (subsequence'0 self n m) = m - n)
   
   function tail'0 [@inline:trivial] (self : Seq'0.t_seq t) : Seq'0.t_seq t =
-    [%#span41] subsequence'0 self 1 (len'0 self)
+    [%#span28] subsequence'0 self 1 (len'0 self)
   
-  let rec take_first_mut'0 (self:borrowed (borrowed (slice t))) (return'  (ret:Option'0.t_option (borrowed t)))= {[@expl:precondition] [%#span42] inv'3 self}
+  let rec take_first_mut'0 (self:borrowed (borrowed (slice t))) (return'  (ret:Option'0.t_option (borrowed t)))= {[@expl:precondition] [%#span29] inv'3 self}
     any
-    [ return' (result:Option'0.t_option (borrowed t))-> {[%#span44] inv'2 result}
-      {[%#span43] match result with
+    [ return' (result:Option'0.t_option (borrowed t))-> {[%#span31] inv'2 result}
+      {[%#span30] match result with
         | Option'0.C_Some r ->  * r = index_logic'0 ( *  * self) 0
         /\  ^ r = index_logic'0 ( ^  * self) 0
         /\ len'0 (shallow_model'0 ( *  * self)) > 0
@@ -825,33 +648,17 @@ module C02IterMut_Impl2_IntoIter
   
   let%span s02_iter_mut2 = "../02_iter_mut.rs" 70 26 70 30
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span8 = "" 0 0 0 0
-  
-  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
-  
-  let%span span12 = "../02_iter_mut.rs" 22 20 22 64
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  let%span span5 = "" 0 0 0 0
   
-  predicate invariant'3 (self : Seq'0.t_seq t)
+  let%span span6 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  predicate inv'3 (_x : Seq'0.t_seq t)
+  let%span span7 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  axiom inv'3 : forall x : Seq'0.t_seq t . inv'3 x = true
+  let%span span8 = "../02_iter_mut.rs" 22 20 22 64
   
   use prelude.prelude.Slice
   
@@ -863,20 +670,17 @@ module C02IterMut_Impl2_IntoIter
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use prelude.prelude.Borrow
   
@@ -890,20 +694,19 @@ module C02IterMut_Impl2_IntoIter
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
   
   function shallow_model'0 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'0_spec : forall self : slice t . ([%#span9] inv'2 self)
-   -> ([%#span11] inv'3 (shallow_model'0 self))
-  && ([%#span10] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : slice t . ([%#span6] inv'2 self)
+   -> ([%#span7] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   use C02IterMut_IterMut_Type as C02IterMut_IterMut_Type
   
   use C02IterMut_IterMut_Type as IterMut'0
   
   predicate invariant'0 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut t) =
-    [%#span12] len'0 (shallow_model'0 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span8] len'0 (shallow_model'0 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
     = len'0 (shallow_model'0 ( * C02IterMut_IterMut_Type.itermut_inner self))
   
   predicate inv'0 (_x : IterMut'0.t_itermut t)
@@ -1054,60 +857,50 @@ module C02IterMut_IterMut
   
   let%span span5 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span7 = "" 0 0 0 0
   
-  let%span span8 = "" 0 0 0 0
+  let%span span8 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span10 = "../02_iter_mut.rs" 22 20 22 64
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span12 = "../02_iter_mut.rs" 22 20 22 64
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span15 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span16 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span17 = "../../../../../creusot-contracts/src/std/slice.rs" 199 20 199 24
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span18 = "../../../../../creusot-contracts/src/std/slice.rs" 193 20 193 31
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 187 20 187 24
   
-  let%span span20 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span21 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span21 = "" 0 0 0 0
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 199 20 199 24
+  let%span span22 = "" 0 0 0 0
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 193 20 193 31
+  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 187 20 187 24
+  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span26 = "" 0 0 0 0
+  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
   let%span span27 = "" 0 0 0 0
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
-  
-  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
-  
-  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
-  
-  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
-  
-  let%span span32 = "" 0 0 0 0
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   predicate invariant'6 (self : Seq'0.t_seq t)
@@ -1133,34 +926,29 @@ module C02IterMut_IterMut
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span6] inv'6 self)  -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span6] len'0 self >= 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
   predicate inv'1 (_x : slice t)
   
   function shallow_model'2 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : slice t . ([%#span9] inv'1 self)
-   -> ([%#span11] inv'6 (shallow_model'2 self))
-  && ([%#span10] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : slice t . ([%#span8] inv'1 self)
+   -> ([%#span9] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   use C02IterMut_IterMut_Type as C02IterMut_IterMut_Type
   
   use C02IterMut_IterMut_Type as IterMut'0
   
   predicate invariant'4 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut t) =
-    [%#span12] len'0 (shallow_model'2 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span10] len'0 (shallow_model'2 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
     = len'0 (shallow_model'2 ( * C02IterMut_IterMut_Type.itermut_inner self))
   
   predicate inv'4 (_x : IterMut'0.t_itermut t)
@@ -1171,12 +959,11 @@ module C02IterMut_IterMut
     | IterMut'0.C_IterMut inner -> true
     end)
   
-  constant empty'0 : Seq'0.t_seq t = [%#span13] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span15] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span14] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1200,47 +987,46 @@ module C02IterMut_IterMut
   
   function shallow_model'3 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span16] inv'0 self)
-   -> ([%#span18] inv'6 (shallow_model'3 self))
-  && ([%#span17] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span12] inv'0 self)
+   -> ([%#span13] len'0 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span19] inv'6 (shallow_model'3 self)
+    [%#span14] inv'6 (shallow_model'3 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span20] shallow_model'3 ( * self)
+    [%#span15] shallow_model'3 ( * self)
   
   function shallow_model'0 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span20] shallow_model'2 ( * self)
+    [%#span15] shallow_model'2 ( * self)
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span21]  ^ self =  * self
+    [%#span16]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed (slice t)) =
-    [%#span21]  ^ self =  * self
+    [%#span16]  ^ self =  * self
   
   predicate resolve_elswhere'0 (self : RangeFull'0.t_rangefull) (_old : Seq'0.t_seq t) (_fin : Seq'0.t_seq t) =
-    [%#span22] true
+    [%#span17] true
   
   predicate has_value'0 (self : RangeFull'0.t_rangefull) (seq : Seq'0.t_seq t) (out : slice t) =
-    [%#span23] seq = shallow_model'2 out
+    [%#span18] seq = shallow_model'2 out
   
   predicate in_bounds'0 (self : RangeFull'0.t_rangefull) (_seq : Seq'0.t_seq t) =
-    [%#span24] true
+    [%#span19] true
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:RangeFull'0.t_rangefull) (return'  (ret:borrowed (slice t)))= {[@expl:precondition] [%#span27] inv'5 index}
-    {[@expl:precondition] [%#span26] inv'3 self}
-    {[@expl:precondition] [%#span25] in_bounds'0 index (shallow_model'1 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:RangeFull'0.t_rangefull) (return'  (ret:borrowed (slice t)))= {[@expl:precondition] [%#span22] inv'5 index}
+    {[@expl:precondition] [%#span21] inv'3 self}
+    {[@expl:precondition] [%#span20] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:borrowed (slice t))-> {[%#span32] inv'2 result}
-      {[%#span31] len'0 (shallow_model'3 ( ^ self)) = len'0 (shallow_model'1 self)}
-      {[%#span30] resolve_elswhere'0 index (shallow_model'1 self) (shallow_model'3 ( ^ self))}
-      {[%#span29] has_value'0 index (shallow_model'3 ( ^ self)) ( ^ result)}
-      {[%#span28] has_value'0 index (shallow_model'1 self) ( * result)}
+    [ return' (result:borrowed (slice t))-> {[%#span27] inv'2 result}
+      {[%#span26] len'0 (shallow_model'3 ( ^ self)) = len'0 (shallow_model'1 self)}
+      {[%#span25] resolve_elswhere'0 index (shallow_model'1 self) (shallow_model'3 ( ^ self))}
+      {[%#span24] has_value'0 index (shallow_model'3 ( ^ self)) ( ^ result)}
+      {[%#span23] has_value'0 index (shallow_model'1 self) ( * result)}
       (! return' {result}) ]
     
   
@@ -1319,160 +1105,132 @@ module C02IterMut_AllZero
   
   let%span span11 = "" 0 0 0 0
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span21 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span22 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
   
-  let%span span30 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span27 = "../02_iter_mut.rs" 39 12 43 13
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
+  let%span span28 = "../02_iter_mut.rs" 54 15 54 32
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
+  let%span span29 = "../02_iter_mut.rs" 55 15 55 32
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
+  let%span span30 = "../02_iter_mut.rs" 57 22 57 23
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
+  let%span span31 = "../02_iter_mut.rs" 57 52 57 53
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/slice.rs" 67 4 67 43
+  let%span span32 = "../02_iter_mut.rs" 57 82 57 83
   
-  let%span span36 = "../02_iter_mut.rs" 39 12 43 13
+  let%span span33 = "../02_iter_mut.rs" 56 14 56 42
   
-  let%span span37 = "../02_iter_mut.rs" 54 15 54 32
+  let%span span34 = "../02_iter_mut.rs" 52 4 52 10
   
-  let%span span38 = "../02_iter_mut.rs" 55 15 55 32
+  let%span span35 = "../02_iter_mut.rs" 50 21 50 25
   
-  let%span span39 = "../02_iter_mut.rs" 57 22 57 23
+  let%span span36 = "../02_iter_mut.rs" 49 14 49 45
   
-  let%span span40 = "../02_iter_mut.rs" 57 31 57 33
+  let%span span37 = "../02_iter_mut.rs" 47 4 47 10
   
-  let%span span41 = "../02_iter_mut.rs" 57 52 57 53
+  let%span span38 = "../02_iter_mut.rs" 22 20 22 64
   
-  let%span span42 = "../02_iter_mut.rs" 57 61 57 63
+  let%span span39 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span43 = "../02_iter_mut.rs" 57 82 57 83
+  let%span span40 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span44 = "../02_iter_mut.rs" 56 14 56 42
+  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span45 = "../02_iter_mut.rs" 52 4 52 10
+  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span46 = "../02_iter_mut.rs" 50 21 50 25
+  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span47 = "../02_iter_mut.rs" 49 14 49 45
+  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span48 = "../02_iter_mut.rs" 47 4 47 10
+  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span49 = "../02_iter_mut.rs" 22 20 22 64
+  let%span span46 = "../02_iter_mut.rs" 32 8 32 76
   
-  let%span span50 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span47 = "../02_iter_mut.rs" 63 17 63 21
   
-  let%span span51 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span48 = "../02_iter_mut.rs" 59 14 62 5
   
-  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span49 = "../02_iter_mut.rs" 63 26 63 44
   
-  let%span span53 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span50 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
   
-  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span51 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span55 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span52 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span56 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span53 = "../02_iter_mut.rs" 70 17 70 21
   
-  let%span span57 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span54 = "../02_iter_mut.rs" 69 14 69 28
   
-  let%span span58 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span55 = "../02_iter_mut.rs" 70 26 70 30
   
-  let%span span59 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span56 = "../02_iter_mut.rs" 78 19 78 20
   
-  let%span span60 = "../02_iter_mut.rs" 32 8 32 76
+  let%span span57 = "../02_iter_mut.rs" 75 10 75 29
   
-  let%span span61 = "../02_iter_mut.rs" 63 17 63 21
+  let%span span58 = "../02_iter_mut.rs" 76 10 76 35
   
-  let%span span62 = "../02_iter_mut.rs" 59 14 62 5
+  let%span span59 = "../02_iter_mut.rs" 77 10 77 33
   
-  let%span span63 = "../02_iter_mut.rs" 63 26 63 44
+  let%span span60 = "../02_iter_mut.rs" 78 41 78 55
   
-  let%span span64 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
-  
-  let%span span65 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span66 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span67 = "../02_iter_mut.rs" 70 17 70 21
-  
-  let%span span68 = "../02_iter_mut.rs" 69 14 69 28
-  
-  let%span span69 = "../02_iter_mut.rs" 70 26 70 30
-  
-  let%span span70 = "../02_iter_mut.rs" 78 19 78 20
-  
-  let%span span71 = "../02_iter_mut.rs" 75 10 75 29
+  use prelude.prelude.UIntSize
   
-  let%span span72 = "../02_iter_mut.rs" 76 10 76 35
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span73 = "../02_iter_mut.rs" 77 10 77 33
+  predicate invariant'9 (self : Seq'0.t_seq usize) =
+    [%#span10] true
   
-  let%span span74 = "../02_iter_mut.rs" 78 41 78 55
+  predicate inv'9 (_x : Seq'0.t_seq usize)
   
-  use prelude.prelude.UIntSize
+  axiom inv'9 : forall x : Seq'0.t_seq usize . inv'9 x = true
   
   use prelude.prelude.Slice
   
   use prelude.prelude.Borrow
   
-  predicate invariant'9 (self : borrowed (slice usize)) =
-    [%#span10] true
-  
-  predicate inv'9 (_x : borrowed (slice usize))
-  
-  axiom inv'9 : forall x : borrowed (slice usize) . inv'9 x = true
-  
-  predicate invariant'8 (self : slice usize) =
+  predicate invariant'8 (self : borrowed (slice usize)) =
     [%#span10] true
   
-  predicate inv'8 (_x : slice usize)
-  
-  axiom inv'8 : forall x : slice usize . inv'8 x = true
+  predicate inv'8 (_x : borrowed (slice usize))
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'8 : forall x : borrowed (slice usize) . inv'8 x = true
   
-  predicate invariant'7 (self : Seq'0.t_seq usize) =
+  predicate invariant'7 (self : slice usize) =
     [%#span10] true
   
-  predicate inv'7 (_x : Seq'0.t_seq usize)
+  predicate inv'7 (_x : slice usize)
   
-  axiom inv'7 : forall x : Seq'0.t_seq usize . inv'7 x = true
+  axiom inv'7 : forall x : slice usize . inv'7 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1484,24 +1242,19 @@ module C02IterMut_AllZero
   
   constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span12] inv'7 self)  -> ([%#span13] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span12] len'1 self >= 0
   
   predicate inv'6 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span14] inv'6 self)
-   -> ([%#span16] inv'7 (shallow_model'0 self))
-  && ([%#span15] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span13] inv'6 self)
+   -> ([%#span14] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'6 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span17] inv'7 (shallow_model'0 self)
+    [%#span15] inv'9 (shallow_model'0 self)
   
   axiom inv'6 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'6 x = true
   
@@ -1546,69 +1299,56 @@ module C02IterMut_AllZero
   
   axiom inv'1 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'1 x = true
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span18] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span20] ()
-  
-  axiom empty_len'1_spec : forall _1 : () . [%#span19] len'1 (empty'1 : Seq'0.t_seq usize) = 0
-  
-  use seq.Seq
+  constant empty'1 : Seq'0.t_seq usize
   
-  use seq.Seq
+  function empty_len'1 (_1 : ()) : ()
   
-  function index_logic'2 (self : Seq'0.t_seq (borrowed usize)) (x : int) : borrowed usize
+  axiom empty_len'1_spec : forall _1 : () . [%#span16] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq (borrowed usize)) (_2 : int) : borrowed usize
   
   function len'0 (self : Seq'0.t_seq (borrowed usize)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (borrowed usize) . ([%#span12] inv'2 self)
-   -> ([%#span13] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (borrowed usize) . [%#span12] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq (borrowed usize)) (other : Seq'0.t_seq (borrowed usize)) : Seq'0.t_seq (borrowed usize)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed usize), other : Seq'0.t_seq (borrowed usize) . ([%#span21] inv'2 self)
-   -> ([%#span22] inv'2 other)
-   -> ([%#span25] inv'2 (concat'0 self other))
-  && ([%#span24] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed usize), other : Seq'0.t_seq (borrowed usize) . ([%#span18] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'0 self then index_logic'2 self i else index_logic'2 other (i - len'0 self)))
-  && ([%#span23] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span17] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'3 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function shallow_model'3 (self : slice usize) : Seq'0.t_seq usize
   
-  axiom shallow_model'3_spec : forall self : slice usize . ([%#span26] inv'8 self)
-   -> ([%#span28] inv'7 (shallow_model'3 self))
-  && ([%#span27] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : slice usize . ([%#span19] inv'7 self)
+   -> ([%#span20] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'4 [@inline:trivial] (self : slice usize) (ix : int) : usize =
-    [%#span29] index_logic'3 (shallow_model'3 self) ix
+    [%#span21] index_logic'3 (shallow_model'3 self) ix
   
   function shallow_model'2 (self : borrowed (slice usize)) : Seq'0.t_seq usize =
-    [%#span30] shallow_model'3 ( * self)
+    [%#span22] shallow_model'3 ( * self)
   
   function to_mut_seq'0 (self : borrowed (slice usize)) : Seq'0.t_seq (borrowed usize)
   
-  axiom to_mut_seq'0_spec : forall self : borrowed (slice usize) . ([%#span31] inv'9 self)
-   -> ([%#span35] inv'2 (to_mut_seq'0 self))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
+  axiom to_mut_seq'0_spec : forall self : borrowed (slice usize) . ([%#span23] inv'8 self)
+   -> ([%#span26] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
    ->  ^ index_logic'2 (to_mut_seq'0 self) i = index_logic'4 ( ^ self) i)
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
+  && ([%#span25] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
    ->  * index_logic'2 (to_mut_seq'0 self) i = index_logic'4 ( * self) i)
-  && ([%#span32] len'0 (to_mut_seq'0 self) = len'1 (shallow_model'2 self))
+  && ([%#span24] len'0 (to_mut_seq'0 self) = len'1 (shallow_model'2 self))
   
   use C02IterMut_IterMut_Type as C02IterMut_IterMut_Type
   
   predicate produces'0 [#"../02_iter_mut.rs" 37 4 37 65] (self : IterMut'0.t_itermut usize) (visited : Seq'0.t_seq (borrowed usize)) (tl : IterMut'0.t_itermut usize)
     
    =
-    [%#span36] len'1 (shallow_model'2 (C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span27] len'1 (shallow_model'2 (C02IterMut_IterMut_Type.itermut_inner self))
     = len'0 visited + len'1 (shallow_model'2 (C02IterMut_IterMut_Type.itermut_inner tl))
     /\ (forall i : int . 0 <= i /\ i < len'1 (shallow_model'2 (C02IterMut_IterMut_Type.itermut_inner self))
      ->  * index_logic'2 (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner self)) i
@@ -1619,25 +1359,23 @@ module C02IterMut_AllZero
   function produces_trans'0 [#"../02_iter_mut.rs" 57 4 57 90] (a : IterMut'0.t_itermut usize) (ab : Seq'0.t_seq (borrowed usize)) (b : IterMut'0.t_itermut usize) (bc : Seq'0.t_seq (borrowed usize)) (c : IterMut'0.t_itermut usize) : ()
     
    =
-    [%#span45] ()
+    [%#span34] ()
   
-  axiom produces_trans'0_spec : forall a : IterMut'0.t_itermut usize, ab : Seq'0.t_seq (borrowed usize), b : IterMut'0.t_itermut usize, bc : Seq'0.t_seq (borrowed usize), c : IterMut'0.t_itermut usize . ([%#span37] produces'0 a ab b)
-   -> ([%#span38] produces'0 b bc c)
-   -> ([%#span39] inv'0 a)
-   -> ([%#span40] inv'2 ab)
-   -> ([%#span41] inv'0 b)
-   -> ([%#span42] inv'2 bc)  -> ([%#span43] inv'0 c)  -> ([%#span44] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : IterMut'0.t_itermut usize, ab : Seq'0.t_seq (borrowed usize), b : IterMut'0.t_itermut usize, bc : Seq'0.t_seq (borrowed usize), c : IterMut'0.t_itermut usize . ([%#span28] produces'0 a ab b)
+   -> ([%#span29] produces'0 b bc c)
+   -> ([%#span30] inv'0 a)
+   -> ([%#span31] inv'0 b)  -> ([%#span32] inv'0 c)  -> ([%#span33] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq (borrowed usize) = [%#span18] ()
+  constant empty'0 : Seq'0.t_seq (borrowed usize)
   
   function produces_refl'0 [#"../02_iter_mut.rs" 50 4 50 26] (self : IterMut'0.t_itermut usize) : () =
-    [%#span48] ()
+    [%#span37] ()
   
-  axiom produces_refl'0_spec : forall self : IterMut'0.t_itermut usize . ([%#span46] inv'0 self)
-   -> ([%#span47] produces'0 self (empty'0 : Seq'0.t_seq (borrowed usize)) self)
+  axiom produces_refl'0_spec : forall self : IterMut'0.t_itermut usize . ([%#span35] inv'0 self)
+   -> ([%#span36] produces'0 self (empty'0 : Seq'0.t_seq (borrowed usize)) self)
   
   predicate invariant'0 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut usize) =
-    [%#span49] len'1 (shallow_model'3 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span38] len'1 (shallow_model'3 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
     = len'1 (shallow_model'3 ( * C02IterMut_IterMut_Type.itermut_inner self))
   
   axiom inv'0 : forall x : IterMut'0.t_itermut usize . inv'0 x
@@ -1646,56 +1384,48 @@ module C02IterMut_AllZero
     | IterMut'0.C_IterMut inner -> true
     end)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span20] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span19] len'0 (empty'0 : Seq'0.t_seq (borrowed usize)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'0 (empty'0 : Seq'0.t_seq (borrowed usize)) = 0
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span50] index_logic'3 (shallow_model'0 self) ix
+    [%#span39] index_logic'3 (shallow_model'0 self) ix
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span30] shallow_model'0 ( * self)
+    [%#span22] shallow_model'0 ( * self)
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span51]  ^ self =  * self
+    [%#span40]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed usize) =
-    [%#span51]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span40]  ^ self =  * self
   
   function singleton'0 (v : borrowed usize) : Seq'0.t_seq (borrowed usize)
   
-  axiom singleton'0_spec : forall v : borrowed usize . ([%#span52] inv'5 v)
-   -> ([%#span55] inv'2 (singleton'0 v))
-  && ([%#span54] index_logic'2 (singleton'0 v) 0 = v) && ([%#span53] len'0 (singleton'0 v) = 1)
-  
-  use seq.Seq
+  axiom singleton'0_spec : forall v : borrowed usize . ([%#span41] inv'5 v)
+   -> ([%#span43] index_logic'2 (singleton'0 v) 0 = v) && ([%#span42] len'0 (singleton'0 v) = 1)
   
   predicate ext_eq'0 (self : Seq'0.t_seq usize) (oth : Seq'0.t_seq usize)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq usize, oth : Seq'0.t_seq usize . ([%#span56] inv'7 self)
-   -> ([%#span57] inv'7 oth)
-   -> ([%#span59] len'1 self = len'1 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq usize, oth : Seq'0.t_seq usize . ([%#span45] len'1 self = len'1 oth
   /\ (forall i : int . 0 <= i /\ i < len'1 self  -> index_logic'3 self i = index_logic'3 oth i)  -> ext_eq'0 self oth)
-  && ([%#span58] ext_eq'0 self oth  -> self = oth)
+  && ([%#span44] ext_eq'0 self oth  -> self = oth)
   
   predicate resolve'2 (self : borrowed (slice usize)) =
-    [%#span51]  ^ self =  * self
+    [%#span40]  ^ self =  * self
   
   predicate completed'0 [#"../02_iter_mut.rs" 31 4 31 35] (self : borrowed (IterMut'0.t_itermut usize)) =
-    [%#span60] resolve'2 (C02IterMut_IterMut_Type.itermut_inner ( * self))
+    [%#span46] resolve'2 (C02IterMut_IterMut_Type.itermut_inner ( * self))
     /\ ext_eq'0 (shallow_model'2 (C02IterMut_IterMut_Type.itermut_inner ( * self))) (empty'1 : Seq'0.t_seq usize)
   
-  let rec next'0 (self:borrowed (IterMut'0.t_itermut usize)) (return'  (ret:Option'0.t_option (borrowed usize)))= {[@expl:precondition] [%#span61] inv'3 self}
+  let rec next'0 (self:borrowed (IterMut'0.t_itermut usize)) (return'  (ret:Option'0.t_option (borrowed usize)))= {[@expl:precondition] [%#span47] inv'3 self}
     any
-    [ return' (result:Option'0.t_option (borrowed usize))-> {[%#span63] inv'4 result}
-      {[%#span62] match result with
+    [ return' (result:Option'0.t_option (borrowed usize))-> {[%#span49] inv'4 result}
+      {[%#span48] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -1707,7 +1437,7 @@ module C02IterMut_AllZero
   function index_logic'0 [@inline:trivial] (self : Snapshot'0.t_snapshot (Seq'0.t_seq (borrowed usize))) (ix : int) : borrowed usize
     
    =
-    [%#span64] index_logic'2 (deref'1 self) ix
+    [%#span50] index_logic'2 (deref'1 self) ix
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq (borrowed usize))) : Seq'0.t_seq (borrowed usize)
   
@@ -1715,26 +1445,26 @@ module C02IterMut_AllZero
   
   function new'1 (x : Seq'0.t_seq (borrowed usize)) : Snapshot'0.t_snapshot (Seq'0.t_seq (borrowed usize))
   
-  axiom new'1_spec : forall x : Seq'0.t_seq (borrowed usize) . ([%#span65] inv'2 x)
-   -> ([%#span66] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq (borrowed usize) . ([%#span51] inv'2 x)
+   -> ([%#span52] deref'1 (new'1 x) = x)
   
   function new'0 (x : IterMut'0.t_itermut usize) : Snapshot'0.t_snapshot (IterMut'0.t_itermut usize)
   
-  axiom new'0_spec : forall x : IterMut'0.t_itermut usize . ([%#span65] inv'0 x)  -> ([%#span66] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : IterMut'0.t_itermut usize . ([%#span51] inv'0 x)  -> ([%#span52] deref'0 (new'0 x) = x)
   
-  let rec into_iter'0 (self:IterMut'0.t_itermut usize) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span67] inv'0 self}
+  let rec into_iter'0 (self:IterMut'0.t_itermut usize) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span53] inv'0 self}
     any
-    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span69] inv'0 result}
-      {[%#span68] result = self}
+    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span55] inv'0 result}
+      {[%#span54] result = self}
       (! return' {result}) ]
     
   
-  let rec iter_mut'0 (v:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span70] inv'1 v}
+  let rec iter_mut'0 (v:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span56] inv'1 v}
     any
-    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span74] inv'0 result}
-      {[%#span73] len'1 (shallow_model'0 ( ^ v)) = len'1 (shallow_model'1 v)}
-      {[%#span72] shallow_model'3 ( ^ C02IterMut_IterMut_Type.itermut_inner result) = shallow_model'0 ( ^ v)}
-      {[%#span71] shallow_model'2 (C02IterMut_IterMut_Type.itermut_inner result) = shallow_model'1 v}
+    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span60] inv'0 result}
+      {[%#span59] len'1 (shallow_model'0 ( ^ v)) = len'1 (shallow_model'1 v)}
+      {[%#span58] shallow_model'3 ( ^ C02IterMut_IterMut_Type.itermut_inner result) = shallow_model'0 ( ^ v)}
+      {[%#span57] shallow_model'2 (C02IterMut_IterMut_Type.itermut_inner result) = shallow_model'1 v}
       (! return' {result}) ]
     
   
@@ -1824,103 +1554,69 @@ module C02IterMut_Impl1
   
   let%span s02_iter_mut2 = "../02_iter_mut.rs" 57 4 57 90
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span4 = "" 0 0 0 0
   
-  let%span span5 = "" 0 0 0 0
+  let%span span5 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span6 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span7 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span7 = "../02_iter_mut.rs" 22 20 22 64
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span9 = "../02_iter_mut.rs" 22 20 22 64
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span15 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span16 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span17 = "../02_iter_mut.rs" 32 8 32 76
   
-  let%span span24 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
-  
-  let%span span25 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span26 = "../02_iter_mut.rs" 32 8 32 76
-  
-  let%span span27 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
-  
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
+  let%span span18 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
+  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 67 4 67 43
+  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
   
-  let%span span33 = "../02_iter_mut.rs" 39 12 43 13
+  let%span span23 = "../02_iter_mut.rs" 39 12 43 13
   
   use prelude.prelude.Slice
   
-  predicate invariant'7 (self : slice t)
-  
-  predicate inv'7 (_x : slice t)
-  
-  axiom inv'7 : forall x : slice t . inv'7 x = true
+  predicate invariant'5 (self : slice t)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'6 (self : Seq'0.t_seq t)
+  predicate inv'5 (_x : slice t)
   
-  predicate inv'6 (_x : Seq'0.t_seq t)
-  
-  axiom inv'6 : forall x : Seq'0.t_seq t . inv'6 x = true
+  axiom inv'5 : forall x : slice t . inv'5 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'5 (self : borrowed (slice t))
+  predicate invariant'4 (self : borrowed (slice t))
   
-  predicate inv'5 (_x : borrowed (slice t))
+  predicate inv'4 (_x : borrowed (slice t))
   
-  axiom inv'5 : forall x : borrowed (slice t) . inv'5 x = true
-  
-  predicate invariant'4 (self : borrowed t)
+  axiom inv'4 : forall x : borrowed (slice t) . inv'4 x = true
   
-  predicate inv'4 (_x : borrowed t)
-  
-  axiom inv'4 : forall x : borrowed t . inv'4 x = true
+  predicate invariant'3 (self : borrowed t)
   
-  predicate invariant'3 (self : Seq'0.t_seq (borrowed t))
+  predicate inv'3 (_x : borrowed t)
   
-  predicate inv'3 (_x : Seq'0.t_seq (borrowed t))
-  
-  axiom inv'3 : forall x : Seq'0.t_seq (borrowed t) . inv'3 x = true
+  axiom inv'3 : forall x : borrowed t . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
@@ -1942,30 +1638,27 @@ module C02IterMut_Impl1
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'6 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : slice t . ([%#span6] inv'7 self)
-   -> ([%#span8] inv'6 (shallow_model'1 self))
-  && ([%#span7] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice t . ([%#span5] inv'5 self)
+   -> ([%#span6] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   use C02IterMut_IterMut_Type as C02IterMut_IterMut_Type
   
   predicate invariant'0 [#"../02_iter_mut.rs" 20 4 20 30] (self : IterMut'0.t_itermut t) =
-    [%#span9] len'0 (shallow_model'1 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span7] len'0 (shallow_model'1 ( ^ C02IterMut_IterMut_Type.itermut_inner self))
     = len'0 (shallow_model'1 ( * C02IterMut_IterMut_Type.itermut_inner self))
   
   axiom inv'0 : forall x : IterMut'0.t_itermut t . inv'0 x
@@ -1974,81 +1667,64 @@ module C02IterMut_Impl1
     | IterMut'0.C_IterMut inner -> true
     end)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (x : int) : borrowed t
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq (borrowed t)) (_2 : int) : borrowed t
   
   function len'1 (self : Seq'0.t_seq (borrowed t)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . ([%#span3] inv'3 self)  -> ([%#span4] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed t) . [%#span3] len'1 self >= 0
   
   function concat'0 (self : Seq'0.t_seq (borrowed t)) (other : Seq'0.t_seq (borrowed t)) : Seq'0.t_seq (borrowed t)
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span10] inv'3 self)
-   -> ([%#span11] inv'3 other)
-   -> ([%#span14] inv'3 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed t), other : Seq'0.t_seq (borrowed t) . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'1 self then index_logic'0 self i else index_logic'0 other (i - len'1 self)))
-  && ([%#span12] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span8] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function singleton'0 (v : borrowed t) : Seq'0.t_seq (borrowed t)
   
-  axiom singleton'0_spec : forall v : borrowed t . ([%#span15] inv'4 v)
-   -> ([%#span18] inv'3 (singleton'0 v))
-  && ([%#span17] index_logic'0 (singleton'0 v) 0 = v) && ([%#span16] len'1 (singleton'0 v) = 1)
-  
-  use seq.Seq
-  
-  use seq.Seq
+  axiom singleton'0_spec : forall v : borrowed t . ([%#span10] inv'3 v)
+   -> ([%#span12] index_logic'0 (singleton'0 v) 0 = v) && ([%#span11] len'1 (singleton'0 v) = 1)
   
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   predicate ext_eq'0 (self : Seq'0.t_seq t) (oth : Seq'0.t_seq t)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span19] inv'6 self)
-   -> ([%#span20] inv'6 oth)
-   -> ([%#span22] len'0 self = len'0 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span14] len'0 self = len'0 oth
   /\ (forall i : int . 0 <= i /\ i < len'0 self  -> index_logic'2 self i = index_logic'2 oth i)  -> ext_eq'0 self oth)
-  && ([%#span21] ext_eq'0 self oth  -> self = oth)
+  && ([%#span13] ext_eq'0 self oth  -> self = oth)
   
-  constant empty'2 : Seq'0.t_seq t = [%#span23] ()
+  constant empty'2 : Seq'0.t_seq t
   
   function shallow_model'0 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span24] shallow_model'1 ( * self)
+    [%#span15] shallow_model'1 ( * self)
   
   predicate resolve'0 (self : borrowed (slice t)) =
-    [%#span25]  ^ self =  * self
+    [%#span16]  ^ self =  * self
   
   predicate completed'0 [#"../02_iter_mut.rs" 31 4 31 35] (self : borrowed (IterMut'0.t_itermut t)) =
-    [%#span26] resolve'0 (C02IterMut_IterMut_Type.itermut_inner ( * self))
+    [%#span17] resolve'0 (C02IterMut_IterMut_Type.itermut_inner ( * self))
     /\ ext_eq'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner ( * self))) (empty'2 : Seq'0.t_seq t)
   
-  constant empty'0 : Seq'0.t_seq (borrowed t) = [%#span23] ()
+  constant empty'0 : Seq'0.t_seq (borrowed t)
   
   function index_logic'1 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span27] index_logic'2 (shallow_model'1 self) ix
+    [%#span18] index_logic'2 (shallow_model'1 self) ix
   
   function to_mut_seq'0 (self : borrowed (slice t)) : Seq'0.t_seq (borrowed t)
   
-  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span28] inv'5 self)
-   -> ([%#span32] inv'3 (to_mut_seq'0 self))
-  && ([%#span31] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  axiom to_mut_seq'0_spec : forall self : borrowed (slice t) . ([%#span19] inv'4 self)
+   -> ([%#span22] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  ^ index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( ^ self) i)
-  && ([%#span30] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
+  && ([%#span21] forall i : int . 0 <= i /\ i < len'1 (to_mut_seq'0 self)
    ->  * index_logic'0 (to_mut_seq'0 self) i = index_logic'1 ( * self) i)
-  && ([%#span29] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
+  && ([%#span20] len'1 (to_mut_seq'0 self) = len'0 (shallow_model'0 self))
   
   predicate produces'0 [#"../02_iter_mut.rs" 37 4 37 65] (self : IterMut'0.t_itermut t) (visited : Seq'0.t_seq (borrowed t)) (tl : IterMut'0.t_itermut t)
     
    =
-    [%#span33] len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
+    [%#span23] len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
     = len'1 visited + len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner tl))
     /\ (forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 (C02IterMut_IterMut_Type.itermut_inner self))
      ->  * index_logic'0 (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner self)) i
@@ -2056,7 +1732,7 @@ module C02IterMut_Impl1
     /\  ^ index_logic'0 (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner self)) i
     =  ^ index_logic'0 (concat'0 visited (to_mut_seq'0 (C02IterMut_IterMut_Type.itermut_inner tl))) i)
   
-  constant empty'0 : Seq'0.t_seq (borrowed t) = [%#span23] ()
+  constant empty'0 : Seq'0.t_seq (borrowed t)
   
   goal produces_refl_refn : [%#s02_iter_mut0] forall self : IterMut'0.t_itermut t . inv'0 self
    -> inv'0 self
@@ -2077,11 +1753,9 @@ module C02IterMut_Impl1
     end)
   
   goal produces_trans_refn : [%#s02_iter_mut2] forall a : IterMut'0.t_itermut t . forall ab : Seq'0.t_seq (borrowed t) . forall b : IterMut'0.t_itermut t . forall bc : Seq'0.t_seq (borrowed t) . forall c : IterMut'0.t_itermut t . inv'0 c
-  /\ inv'3 bc /\ inv'0 b /\ inv'3 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'0 c
-  /\ inv'3 bc
   /\ inv'0 b
-  /\ inv'3 ab
   /\ inv'0 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
diff --git a/creusot/tests/should_succeed/iterators/03_std_iterators.coma b/creusot/tests/should_succeed/iterators/03_std_iterators.coma
index 6529879955..bf1a4ca083 100644
--- a/creusot/tests/should_succeed/iterators/03_std_iterators.coma
+++ b/creusot/tests/should_succeed/iterators/03_std_iterators.coma
@@ -50,22 +50,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -106,116 +91,88 @@ module C03StdIterators_SliceIter
   
   let%span s03_std_iterators9 = "../03_std_iterators.rs" 5 10 5 33
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span20 = "" 0 0 0 0
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span14 = "" 0 0 0 0
   
-  let%span span25 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span15 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
+  let%span span17 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
+  let%span span18 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 76 4 76 35
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
+  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 398 31 398 33
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 398 61 398 63
+  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
+  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
+  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
+  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
+  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span32 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span43 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span33 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span44 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span36 = "" 0 0 0 0
   
-  let%span span47 = "" 0 0 0 0
+  let%span span37 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span48 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span38 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span49 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span39 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
+  let%span span40 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span51 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
+  let%span span41 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span42 = "" 0 0 0 0
   
-  let%span span53 = "" 0 0 0 0
+  let%span span43 = "" 0 0 0 0
   
-  let%span span54 = "" 0 0 0 0
+  let%span span44 = "" 0 0 0 0
   
-  let%span span55 = "" 0 0 0 0
-  
-  let%span span56 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span45 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
   use prelude.prelude.Slice
   
-  predicate invariant'6 (self : slice t)
+  predicate invariant'5 (self : slice t)
   
-  predicate inv'6 (_x : slice t)
+  predicate inv'5 (_x : slice t)
   
-  axiom inv'6 : forall x : slice t . inv'6 x = true
+  axiom inv'5 : forall x : slice t . inv'5 x = true
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'5 (self : Seq'0.t_seq t)
-  
-  predicate inv'5 (_x : Seq'0.t_seq t)
-  
-  axiom inv'5 : forall x : Seq'0.t_seq t . inv'5 x = true
-  
   predicate invariant'4 (self : Seq'0.t_seq t)
   
   predicate inv'4 (_x : Seq'0.t_seq t)
@@ -224,20 +181,15 @@ module C03StdIterators_SliceIter
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span10] inv'5 self)  -> ([%#span11] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span10] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq t = [%#span12] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span14] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span13] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
   predicate invariant'3 (self : t)
   
@@ -257,80 +209,67 @@ module C03StdIterators_SliceIter
   
   use Core_Slice_Iter_Iter_Type as Iter'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span10] inv'4 self)  -> ([%#span11] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span10] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span15] inv'4 self)
-   -> ([%#span16] inv'4 other)
-   -> ([%#span19] inv'4 (concat'0 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span13] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span17] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span20] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span14] (18446744073709551615 : usize)
   
   function shallow_model'2 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : slice t . ([%#span21] inv'6 self)
-   -> ([%#span23] inv'5 (shallow_model'2 self))
-  && ([%#span22] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : slice t . ([%#span15] inv'5 self)
+   -> ([%#span16] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'1 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span24] index_logic'2 (shallow_model'2 self) ix
+    [%#span17] index_logic'2 (shallow_model'2 self) ix
   
   function shallow_model'0 (self : slice t) : Seq'0.t_seq t =
-    [%#span25] shallow_model'2 self
+    [%#span18] shallow_model'2 self
   
   predicate inv'0 (_x : slice t)
   
   function to_ref_seq'0 (self : slice t) : Seq'0.t_seq t
   
-  axiom to_ref_seq'0_spec : forall self : slice t . ([%#span26] inv'0 self)
-   -> ([%#span29] inv'4 (to_ref_seq'0 self))
-  && ([%#span28] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
+  axiom to_ref_seq'0_spec : forall self : slice t . ([%#span19] inv'0 self)
+   -> ([%#span21] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
    -> index_logic'0 (to_ref_seq'0 self) i = index_logic'1 self i)
-  && ([%#span27] len'0 (to_ref_seq'0 self) = len'1 (shallow_model'0 self))
+  && ([%#span20] len'0 (to_ref_seq'0 self) = len'1 (shallow_model'0 self))
   
   function shallow_model'1 (self : Iter'0.t_iter t) : slice t
   
   predicate produces'0 (self : Iter'0.t_iter t) (visited : Seq'0.t_seq t) (tl : Iter'0.t_iter t) =
-    [%#span30] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
+    [%#span22] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
   
   function produces_trans'0 (a : Iter'0.t_iter t) (ab : Seq'0.t_seq t) (b : Iter'0.t_iter t) (bc : Seq'0.t_seq t) (c : Iter'0.t_iter t) : ()
     
    =
-    [%#span36] ()
+    [%#span26] ()
   
-  axiom produces_trans'0_spec : forall a : Iter'0.t_iter t, ab : Seq'0.t_seq t, b : Iter'0.t_iter t, bc : Seq'0.t_seq t, c : Iter'0.t_iter t . ([%#span31] produces'0 a ab b)
-   -> ([%#span32] produces'0 b bc c)
-   -> ([%#span33] inv'4 ab)  -> ([%#span34] inv'4 bc)  -> ([%#span35] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Iter'0.t_iter t, ab : Seq'0.t_seq t, b : Iter'0.t_iter t, bc : Seq'0.t_seq t, c : Iter'0.t_iter t . ([%#span23] produces'0 a ab b)
+   -> ([%#span24] produces'0 b bc c)  -> ([%#span25] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq t = [%#span12] ()
+  constant empty'0 : Seq'0.t_seq t
   
   function produces_refl'0 (self : Iter'0.t_iter t) : () =
-    [%#span38] ()
+    [%#span28] ()
   
-  axiom produces_refl'0_spec : forall self : Iter'0.t_iter t . [%#span37] produces'0 self (empty'0 : Seq'0.t_seq t) self
+  axiom produces_refl'0_spec : forall self : Iter'0.t_iter t . [%#span27] produces'0 self (empty'0 : Seq'0.t_seq t) self
   
   predicate invariant'1 (self : Iter'0.t_iter t)
   
@@ -338,10 +277,9 @@ module C03StdIterators_SliceIter
   
   axiom inv'1 : forall x : Iter'0.t_iter t . inv'1 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span14] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'0 (self : slice t)
   
@@ -355,28 +293,25 @@ module C03StdIterators_SliceIter
   
   predicate resolve'5 (self : t)
   
-  use seq.Seq
-  
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span39] inv'3 v)
-   -> ([%#span42] inv'4 (singleton'0 v))
-  && ([%#span41] index_logic'0 (singleton'0 v) 0 = v) && ([%#span40] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span29] inv'3 v)
+   -> ([%#span31] index_logic'0 (singleton'0 v) 0 = v) && ([%#span30] len'0 (singleton'0 v) = 1)
   
   predicate resolve'4 (self : Option'0.t_option t)
   
   predicate resolve'3 (self : borrowed (Iter'0.t_iter t)) =
-    [%#span43]  ^ self =  * self
+    [%#span32]  ^ self =  * self
   
   function shallow_model'3 (self : borrowed (Iter'0.t_iter t)) : slice t =
-    [%#span44] shallow_model'1 ( * self)
+    [%#span33] shallow_model'1 ( * self)
   
   predicate completed'0 (self : borrowed (Iter'0.t_iter t)) =
-    [%#span45] resolve'3 self /\ shallow_model'2 (shallow_model'3 self) = (empty'1 : Seq'0.t_seq t)
+    [%#span34] resolve'3 self /\ shallow_model'2 (shallow_model'3 self) = (empty'1 : Seq'0.t_seq t)
   
   let rec next'0 (self:borrowed (Iter'0.t_iter t)) (return'  (ret:Option'0.t_option t))= any
-    [ return' (result:Option'0.t_option t)-> {[%#span47] inv'2 result}
-      {[%#span46] match result with
+    [ return' (result:Option'0.t_option t)-> {[%#span36] inv'2 result}
+      {[%#span35] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -395,30 +330,30 @@ module C03StdIterators_SliceIter
   
   function new'1 (x : Seq'0.t_seq t) : Snapshot'0.t_snapshot (Seq'0.t_seq t)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq t . ([%#span48] inv'4 x)  -> ([%#span49] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq t . ([%#span37] inv'4 x)  -> ([%#span38] deref'0 (new'1 x) = x)
   
   predicate resolve'1 (self : Snapshot'0.t_snapshot (Iter'0.t_iter t))
   
   function new'0 (x : Iter'0.t_iter t) : Snapshot'0.t_snapshot (Iter'0.t_iter t)
   
-  axiom new'0_spec : forall x : Iter'0.t_iter t . ([%#span48] inv'1 x)  -> ([%#span49] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Iter'0.t_iter t . ([%#span37] inv'1 x)  -> ([%#span38] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Iter'0.t_iter t) (res : Iter'0.t_iter t) =
-    [%#span50] self = res
+    [%#span39] self = res
   
   predicate into_iter_pre'0 (self : Iter'0.t_iter t) =
-    [%#span51] true
+    [%#span40] true
   
-  let rec into_iter'0 (self:Iter'0.t_iter t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span53] inv'1 self}
-    {[@expl:precondition] [%#span52] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Iter'0.t_iter t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span42] inv'1 self}
+    {[@expl:precondition] [%#span41] into_iter_pre'0 self}
     any
-    [ return' (result:Iter'0.t_iter t)-> {[%#span54] inv'1 result}
-      {[%#span52] into_iter_post'0 self result}
+    [ return' (result:Iter'0.t_iter t)-> {[%#span43] inv'1 result}
+      {[%#span41] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec iter'0 (self:slice t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span55] inv'0 self}
-    any [ return' (result:Iter'0.t_iter t)-> {[%#span56] shallow_model'1 result = self} (! return' {result}) ] 
+  let rec iter'0 (self:slice t) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span44] inv'0 self}
+    any [ return' (result:Iter'0.t_iter t)-> {[%#span45] shallow_model'1 result = self} (! return' {result}) ] 
   
   predicate resolve'0 (self : slice t)
   
@@ -617,111 +552,91 @@ module C03StdIterators_VecIter
   
   let%span span10 = "" 0 0 0 0
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span18 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span20 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span21 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
+  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
+  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 76 4 76 35
+  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
+  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
+  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
+  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/slice.rs" 398 31 398 33
+  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/slice.rs" 398 61 398 63
+  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
+  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
+  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
+  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
+  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span35 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span36 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span37 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
   
-  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span38 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span47 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span39 = "" 0 0 0 0
   
-  let%span span48 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span40 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
+  let%span span41 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span42 = "../../../../../creusot-contracts/src/std/vec.rs" 205 20 205 34
   
-  let%span span51 = "" 0 0 0 0
+  let%span span43 = "../../../../../creusot-contracts/src/std/vec.rs" 199 20 199 24
   
-  let%span span52 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span53 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span45 = "" 0 0 0 0
   
-  let%span span54 = "../../../../../creusot-contracts/src/std/vec.rs" 205 20 205 34
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span55 = "../../../../../creusot-contracts/src/std/vec.rs" 199 20 199 24
+  predicate invariant'8 (self : Seq'0.t_seq t)
   
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  predicate inv'8 (_x : Seq'0.t_seq t)
   
-  let%span span57 = "" 0 0 0 0
+  axiom inv'8 : forall x : Seq'0.t_seq t . inv'8 x = true
   
   use prelude.prelude.Slice
   
-  predicate invariant'8 (self : slice t)
+  predicate invariant'7 (self : slice t)
   
-  predicate inv'8 (_x : slice t)
+  predicate inv'7 (_x : slice t)
   
-  axiom inv'8 : forall x : slice t . inv'8 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate inv'5 (_x : Seq'0.t_seq t)
+  axiom inv'7 : forall x : slice t . inv'7 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -735,36 +650,27 @@ module C03StdIterators_VecIter
   
   constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span11] inv'5 self)  -> ([%#span12] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span11] len'1 self >= 0
   
-  predicate inv'7 (_x : Vec'0.t_vec t (Global'0.t_global))
+  predicate inv'6 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span13] inv'7 self)
-   -> ([%#span15] inv'5 (shallow_model'2 self))
-  && ([%#span14] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'7 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span16] inv'5 (shallow_model'2 self)
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span12] inv'6 self)
+   -> ([%#span13] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
-  axiom inv'7 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'7 x = true
+  predicate invariant'6 (self : Vec'0.t_vec t (Global'0.t_global)) =
+    [%#span14] inv'8 (shallow_model'2 self)
   
-  predicate invariant'6 (self : slice t)
+  axiom inv'6 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'6 x = true
   
-  predicate inv'6 (_x : slice t)
+  predicate invariant'5 (self : slice t)
   
-  axiom inv'6 : forall x : slice t . inv'6 x = true
+  predicate inv'5 (_x : slice t)
   
-  predicate invariant'5 (self : Seq'0.t_seq t)
-  
-  axiom inv'5 : forall x : Seq'0.t_seq t . inv'5 x = true
+  axiom inv'5 : forall x : slice t . inv'5 x = true
   
   predicate invariant'4 (self : Seq'0.t_seq t)
   
@@ -772,12 +678,11 @@ module C03StdIterators_VecIter
   
   axiom inv'4 : forall x : Seq'0.t_seq t . inv'4 x = true
   
-  constant empty'1 : Seq'0.t_seq t = [%#span17] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span18] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span15] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
   predicate invariant'3 (self : t)
   
@@ -797,72 +702,59 @@ module C03StdIterators_VecIter
   
   use Core_Slice_Iter_Iter_Type as Iter'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span11] inv'4 self)  -> ([%#span12] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span11] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span20] inv'4 self)
-   -> ([%#span21] inv'4 other)
-   -> ([%#span24] inv'4 (concat'0 self other))
-  && ([%#span23] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span17] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span22] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span16] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function shallow_model'5 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'5_spec : forall self : slice t . ([%#span25] inv'8 self)
-   -> ([%#span27] inv'5 (shallow_model'5 self))
-  && ([%#span26] len'1 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'5_spec : forall self : slice t . ([%#span18] inv'7 self)
+   -> ([%#span19] len'1 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'1 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span28] index_logic'2 (shallow_model'5 self) ix
+    [%#span20] index_logic'2 (shallow_model'5 self) ix
   
   function shallow_model'3 (self : slice t) : Seq'0.t_seq t =
-    [%#span29] shallow_model'5 self
+    [%#span21] shallow_model'5 self
   
   function to_ref_seq'0 (self : slice t) : Seq'0.t_seq t
   
-  axiom to_ref_seq'0_spec : forall self : slice t . ([%#span30] inv'6 self)
-   -> ([%#span33] inv'4 (to_ref_seq'0 self))
-  && ([%#span32] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
+  axiom to_ref_seq'0_spec : forall self : slice t . ([%#span22] inv'5 self)
+   -> ([%#span24] forall i : int . 0 <= i /\ i < len'0 (to_ref_seq'0 self)
    -> index_logic'0 (to_ref_seq'0 self) i = index_logic'1 self i)
-  && ([%#span31] len'0 (to_ref_seq'0 self) = len'1 (shallow_model'3 self))
+  && ([%#span23] len'0 (to_ref_seq'0 self) = len'1 (shallow_model'3 self))
   
   function shallow_model'1 (self : Iter'0.t_iter t) : slice t
   
   predicate produces'0 (self : Iter'0.t_iter t) (visited : Seq'0.t_seq t) (tl : Iter'0.t_iter t) =
-    [%#span34] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
+    [%#span25] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
   
   function produces_trans'0 (a : Iter'0.t_iter t) (ab : Seq'0.t_seq t) (b : Iter'0.t_iter t) (bc : Seq'0.t_seq t) (c : Iter'0.t_iter t) : ()
     
    =
-    [%#span40] ()
+    [%#span29] ()
   
-  axiom produces_trans'0_spec : forall a : Iter'0.t_iter t, ab : Seq'0.t_seq t, b : Iter'0.t_iter t, bc : Seq'0.t_seq t, c : Iter'0.t_iter t . ([%#span35] produces'0 a ab b)
-   -> ([%#span36] produces'0 b bc c)
-   -> ([%#span37] inv'4 ab)  -> ([%#span38] inv'4 bc)  -> ([%#span39] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Iter'0.t_iter t, ab : Seq'0.t_seq t, b : Iter'0.t_iter t, bc : Seq'0.t_seq t, c : Iter'0.t_iter t . ([%#span26] produces'0 a ab b)
+   -> ([%#span27] produces'0 b bc c)  -> ([%#span28] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq t = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq t
   
   function produces_refl'0 (self : Iter'0.t_iter t) : () =
-    [%#span42] ()
+    [%#span31] ()
   
-  axiom produces_refl'0_spec : forall self : Iter'0.t_iter t . [%#span41] produces'0 self (empty'0 : Seq'0.t_seq t) self
+  axiom produces_refl'0_spec : forall self : Iter'0.t_iter t . [%#span30] produces'0 self (empty'0 : Seq'0.t_seq t) self
   
   predicate invariant'1 (self : Iter'0.t_iter t)
   
@@ -870,10 +762,9 @@ module C03StdIterators_VecIter
   
   axiom inv'1 : forall x : Iter'0.t_iter t . inv'1 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span18] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global))
   
@@ -882,7 +773,7 @@ module C03StdIterators_VecIter
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
   function shallow_model'0 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t =
-    [%#span29] shallow_model'2 self
+    [%#span21] shallow_model'2 self
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
@@ -892,28 +783,25 @@ module C03StdIterators_VecIter
   
   predicate resolve'5 (self : t)
   
-  use seq.Seq
-  
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span43] inv'3 v)
-   -> ([%#span46] inv'4 (singleton'0 v))
-  && ([%#span45] index_logic'0 (singleton'0 v) 0 = v) && ([%#span44] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span32] inv'3 v)
+   -> ([%#span34] index_logic'0 (singleton'0 v) 0 = v) && ([%#span33] len'0 (singleton'0 v) = 1)
   
   predicate resolve'4 (self : Option'0.t_option t)
   
   predicate resolve'3 (self : borrowed (Iter'0.t_iter t)) =
-    [%#span47]  ^ self =  * self
+    [%#span35]  ^ self =  * self
   
   function shallow_model'4 (self : borrowed (Iter'0.t_iter t)) : slice t =
-    [%#span48] shallow_model'1 ( * self)
+    [%#span36] shallow_model'1 ( * self)
   
   predicate completed'0 (self : borrowed (Iter'0.t_iter t)) =
-    [%#span49] resolve'3 self /\ shallow_model'5 (shallow_model'4 self) = (empty'1 : Seq'0.t_seq t)
+    [%#span37] resolve'3 self /\ shallow_model'5 (shallow_model'4 self) = (empty'1 : Seq'0.t_seq t)
   
   let rec next'0 (self:borrowed (Iter'0.t_iter t)) (return'  (ret:Option'0.t_option t))= any
-    [ return' (result:Option'0.t_option t)-> {[%#span51] inv'2 result}
-      {[%#span50] match result with
+    [ return' (result:Option'0.t_option t)-> {[%#span39] inv'2 result}
+      {[%#span38] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -932,23 +820,23 @@ module C03StdIterators_VecIter
   
   function new'1 (x : Seq'0.t_seq t) : Snapshot'0.t_snapshot (Seq'0.t_seq t)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq t . ([%#span52] inv'4 x)  -> ([%#span53] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq t . ([%#span40] inv'4 x)  -> ([%#span41] deref'0 (new'1 x) = x)
   
   predicate resolve'1 (self : Snapshot'0.t_snapshot (Iter'0.t_iter t))
   
   function new'0 (x : Iter'0.t_iter t) : Snapshot'0.t_snapshot (Iter'0.t_iter t)
   
-  axiom new'0_spec : forall x : Iter'0.t_iter t . ([%#span52] inv'1 x)  -> ([%#span53] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Iter'0.t_iter t . ([%#span40] inv'1 x)  -> ([%#span41] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Vec'0.t_vec t (Global'0.t_global)) (res : Iter'0.t_iter t) =
-    [%#span54] shallow_model'0 self = shallow_model'3 (shallow_model'1 res)
+    [%#span42] shallow_model'0 self = shallow_model'3 (shallow_model'1 res)
   
   predicate into_iter_pre'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span55] true
+    [%#span43] true
   
-  let rec into_iter'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span57] inv'0 self}
-    {[@expl:precondition] [%#span56] into_iter_pre'0 self}
-    any [ return' (result:Iter'0.t_iter t)-> {[%#span56] into_iter_post'0 self result} (! return' {result}) ] 
+  let rec into_iter'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:Iter'0.t_iter t))= {[@expl:precondition] [%#span45] inv'0 self}
+    {[@expl:precondition] [%#span44] into_iter_pre'0 self}
+    any [ return' (result:Iter'0.t_iter t)-> {[%#span44] into_iter_post'0 self result} (! return' {result}) ] 
   
   predicate resolve'0 (self : Vec'0.t_vec t (Global'0.t_global))
   
@@ -1085,143 +973,119 @@ module C03StdIterators_AllZero
   
   let%span span8 = "" 0 0 0 0
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
-  
-  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
-  
-  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span27 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
+  let%span span17 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
+  let%span span18 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
+  let%span span19 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 67 23 67 27
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 67 4 67 43
+  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 64 14 64 41
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 407 14 407 50
+  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 65 4 65 82
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 408 4 408 50
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 66 4 66 85
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/slice.rs" 433 12 433 66
+  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 407 14 407 50
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/slice.rs" 444 15 444 32
+  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 408 4 408 50
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/slice.rs" 445 15 445 32
+  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 433 12 433 66
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/slice.rs" 447 31 447 33
+  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 444 15 444 32
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/slice.rs" 447 61 447 63
+  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 445 15 445 32
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/slice.rs" 446 14 446 42
+  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 446 14 446 42
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/slice.rs" 442 4 442 10
+  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 442 4 442 10
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/slice.rs" 439 14 439 45
+  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 439 14 439 45
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/slice.rs" 437 4 437 10
+  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 437 4 437 10
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span33 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span45 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span34 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/slice.rs" 418 20 418 36
+  let%span span35 = "../../../../../creusot-contracts/src/std/slice.rs" 418 20 418 36
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span39 = "../../../../../creusot-contracts/src/std/slice.rs" 426 20 426 61
   
-  let%span span51 = "../../../../../creusot-contracts/src/std/slice.rs" 426 20 426 61
-  
-  let%span span52 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span40 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span53 = "" 0 0 0 0
+  let%span span41 = "" 0 0 0 0
   
-  let%span span54 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
+  let%span span42 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
   
-  let%span span55 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span43 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span56 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span44 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
+  let%span span45 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span58 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
+  let%span span46 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span47 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span60 = "" 0 0 0 0
+  let%span span48 = "" 0 0 0 0
   
-  let%span span61 = "" 0 0 0 0
+  let%span span49 = "" 0 0 0 0
   
-  let%span span62 = "" 0 0 0 0
+  let%span span50 = "" 0 0 0 0
   
-  let%span span63 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span51 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span64 = "" 0 0 0 0
+  let%span span52 = "" 0 0 0 0
   
-  let%span span65 = "../../../../../creusot-contracts/src/std/vec.rs" 169 26 169 42
+  let%span span53 = "../../../../../creusot-contracts/src/std/vec.rs" 169 26 169 42
   
-  let%span span66 = "../../../../../creusot-contracts/src/std/vec.rs" 170 26 170 48
+  let%span span54 = "../../../../../creusot-contracts/src/std/vec.rs" 170 26 170 48
   
-  let%span span67 = "" 0 0 0 0
+  let%span span55 = "" 0 0 0 0
   
   use prelude.prelude.UIntSize
   
-  use prelude.prelude.Slice
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'8 (self : slice usize) =
+  predicate invariant'8 (self : Seq'0.t_seq usize) =
     [%#span7] true
   
-  predicate inv'8 (_x : slice usize)
+  predicate inv'8 (_x : Seq'0.t_seq usize)
   
-  axiom inv'8 : forall x : slice usize . inv'8 x = true
+  axiom inv'8 : forall x : Seq'0.t_seq usize . inv'8 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use prelude.prelude.Slice
   
-  predicate invariant'7 (self : Seq'0.t_seq usize) =
+  predicate invariant'7 (self : slice usize) =
     [%#span7] true
   
-  predicate inv'7 (_x : Seq'0.t_seq usize)
+  predicate inv'7 (_x : slice usize)
   
-  axiom inv'7 : forall x : Seq'0.t_seq usize . inv'7 x = true
+  axiom inv'7 : forall x : slice usize . inv'7 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1233,24 +1097,19 @@ module C03StdIterators_AllZero
   
   constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span9] inv'7 self)  -> ([%#span10] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span9] len'1 self >= 0
   
   predicate inv'6 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span11] inv'6 self)
-   -> ([%#span13] inv'7 (shallow_model'0 self))
-  && ([%#span12] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span10] inv'6 self)
+   -> ([%#span11] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'6 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span14] inv'7 (shallow_model'0 self)
+    [%#span12] inv'8 (shallow_model'0 self)
   
   axiom inv'6 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'6 x = true
   
@@ -1293,90 +1152,76 @@ module C03StdIterators_AllZero
   
   axiom inv'1 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'1 x = true
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span15] ()
+  constant empty'1 : Seq'0.t_seq usize
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span17] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span16] len'1 (empty'1 : Seq'0.t_seq usize) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span13] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
   use Core_Slice_Iter_IterMut_Type as IterMut'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq (borrowed usize)) (x : int) : borrowed usize
-  
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq (borrowed usize)) (_2 : int) : borrowed usize
   
   function len'0 (self : Seq'0.t_seq (borrowed usize)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (borrowed usize) . ([%#span9] inv'3 self)
-   -> ([%#span10] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (borrowed usize) . [%#span9] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq (borrowed usize)) (other : Seq'0.t_seq (borrowed usize)) : Seq'0.t_seq (borrowed usize)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed usize), other : Seq'0.t_seq (borrowed usize) . ([%#span18] inv'3 self)
-   -> ([%#span19] inv'3 other)
-   -> ([%#span22] inv'3 (concat'0 self other))
-  && ([%#span21] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (borrowed usize), other : Seq'0.t_seq (borrowed usize) . ([%#span15] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'0 self then index_logic'2 self i else index_logic'2 other (i - len'0 self)))
-  && ([%#span20] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  function index_logic'3 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'3 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function shallow_model'3 (self : slice usize) : Seq'0.t_seq usize
   
-  axiom shallow_model'3_spec : forall self : slice usize . ([%#span23] inv'8 self)
-   -> ([%#span25] inv'7 (shallow_model'3 self))
-  && ([%#span24] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : slice usize . ([%#span16] inv'7 self)
+   -> ([%#span17] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'4 [@inline:trivial] (self : slice usize) (ix : int) : usize =
-    [%#span26] index_logic'3 (shallow_model'3 self) ix
+    [%#span18] index_logic'3 (shallow_model'3 self) ix
   
   function shallow_model'2 (self : borrowed (slice usize)) : Seq'0.t_seq usize =
-    [%#span27] shallow_model'3 ( * self)
+    [%#span19] shallow_model'3 ( * self)
   
   function to_mut_seq'0 (self : borrowed (slice usize)) : Seq'0.t_seq (borrowed usize)
   
-  axiom to_mut_seq'0_spec : forall self : borrowed (slice usize) . ([%#span28] inv'2 self)
-   -> ([%#span32] inv'3 (to_mut_seq'0 self))
-  && ([%#span31] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
+  axiom to_mut_seq'0_spec : forall self : borrowed (slice usize) . ([%#span20] inv'2 self)
+   -> ([%#span23] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
    ->  ^ index_logic'2 (to_mut_seq'0 self) i = index_logic'4 ( ^ self) i)
-  && ([%#span30] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
+  && ([%#span22] forall i : int . 0 <= i /\ i < len'0 (to_mut_seq'0 self)
    ->  * index_logic'2 (to_mut_seq'0 self) i = index_logic'4 ( * self) i)
-  && ([%#span29] len'0 (to_mut_seq'0 self) = len'1 (shallow_model'2 self))
+  && ([%#span21] len'0 (to_mut_seq'0 self) = len'1 (shallow_model'2 self))
   
   function shallow_model'4 (self : IterMut'0.t_itermut usize) : borrowed (slice usize)
   
-  axiom shallow_model'4_spec : forall self : IterMut'0.t_itermut usize . ([%#span34] inv'2 (shallow_model'4 self))
-  && ([%#span33] len'1 (shallow_model'3 ( ^ shallow_model'4 self)) = len'1 (shallow_model'3 ( * shallow_model'4 self)))
+  axiom shallow_model'4_spec : forall self : IterMut'0.t_itermut usize . ([%#span25] inv'2 (shallow_model'4 self))
+  && ([%#span24] len'1 (shallow_model'3 ( ^ shallow_model'4 self)) = len'1 (shallow_model'3 ( * shallow_model'4 self)))
   
   predicate produces'0 (self : IterMut'0.t_itermut usize) (visited : Seq'0.t_seq (borrowed usize)) (tl : IterMut'0.t_itermut usize)
     
    =
-    [%#span35] to_mut_seq'0 (shallow_model'4 self) = concat'0 visited (to_mut_seq'0 (shallow_model'4 tl))
+    [%#span26] to_mut_seq'0 (shallow_model'4 self) = concat'0 visited (to_mut_seq'0 (shallow_model'4 tl))
   
   function produces_trans'0 (a : IterMut'0.t_itermut usize) (ab : Seq'0.t_seq (borrowed usize)) (b : IterMut'0.t_itermut usize) (bc : Seq'0.t_seq (borrowed usize)) (c : IterMut'0.t_itermut usize) : ()
     
    =
-    [%#span41] ()
+    [%#span30] ()
   
-  axiom produces_trans'0_spec : forall a : IterMut'0.t_itermut usize, ab : Seq'0.t_seq (borrowed usize), b : IterMut'0.t_itermut usize, bc : Seq'0.t_seq (borrowed usize), c : IterMut'0.t_itermut usize . ([%#span36] produces'0 a ab b)
-   -> ([%#span37] produces'0 b bc c)
-   -> ([%#span38] inv'3 ab)  -> ([%#span39] inv'3 bc)  -> ([%#span40] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : IterMut'0.t_itermut usize, ab : Seq'0.t_seq (borrowed usize), b : IterMut'0.t_itermut usize, bc : Seq'0.t_seq (borrowed usize), c : IterMut'0.t_itermut usize . ([%#span27] produces'0 a ab b)
+   -> ([%#span28] produces'0 b bc c)  -> ([%#span29] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq (borrowed usize) = [%#span15] ()
+  constant empty'0 : Seq'0.t_seq (borrowed usize)
   
   function produces_refl'0 (self : IterMut'0.t_itermut usize) : () =
-    [%#span43] ()
+    [%#span32] ()
   
-  axiom produces_refl'0_spec : forall self : IterMut'0.t_itermut usize . [%#span42] produces'0 self (empty'0 : Seq'0.t_seq (borrowed usize)) self
+  axiom produces_refl'0_spec : forall self : IterMut'0.t_itermut usize . [%#span31] produces'0 self (empty'0 : Seq'0.t_seq (borrowed usize)) self
   
   predicate invariant'0 (self : IterMut'0.t_itermut usize) =
     [%#span7] true
@@ -1385,50 +1230,46 @@ module C03StdIterators_AllZero
   
   axiom inv'0 : forall x : IterMut'0.t_itermut usize . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span17] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'0 (empty'0 : Seq'0.t_seq (borrowed usize)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq (borrowed usize)) = 0
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span44] index_logic'3 (shallow_model'0 self) ix
+    [%#span33] index_logic'3 (shallow_model'0 self) ix
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span27] shallow_model'0 ( * self)
+    [%#span19] shallow_model'0 ( * self)
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'4 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span45]  ^ self =  * self
+    [%#span34]  ^ self =  * self
   
   predicate resolve'3 (self : IterMut'0.t_itermut usize) =
-    [%#span46]  * shallow_model'4 self =  ^ shallow_model'4 self
+    [%#span35]  * shallow_model'4 self =  ^ shallow_model'4 self
   
   predicate resolve'2 (self : borrowed usize) =
-    [%#span45]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span34]  ^ self =  * self
   
   function singleton'0 (v : borrowed usize) : Seq'0.t_seq (borrowed usize)
   
-  axiom singleton'0_spec : forall v : borrowed usize . ([%#span47] inv'5 v)
-   -> ([%#span50] inv'3 (singleton'0 v))
-  && ([%#span49] index_logic'2 (singleton'0 v) 0 = v) && ([%#span48] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : borrowed usize . ([%#span36] inv'5 v)
+   -> ([%#span38] index_logic'2 (singleton'0 v) 0 = v) && ([%#span37] len'0 (singleton'0 v) = 1)
   
   predicate resolve'1 (self : borrowed (IterMut'0.t_itermut usize)) =
-    [%#span45]  ^ self =  * self
+    [%#span34]  ^ self =  * self
   
   function shallow_model'5 (self : borrowed (IterMut'0.t_itermut usize)) : borrowed (slice usize) =
-    [%#span27] shallow_model'4 ( * self)
+    [%#span19] shallow_model'4 ( * self)
   
   predicate completed'0 (self : borrowed (IterMut'0.t_itermut usize)) =
-    [%#span51] resolve'1 self /\ shallow_model'3 ( * shallow_model'5 self) = (empty'1 : Seq'0.t_seq usize)
+    [%#span39] resolve'1 self /\ shallow_model'3 ( * shallow_model'5 self) = (empty'1 : Seq'0.t_seq usize)
   
   let rec next'0 (self:borrowed (IterMut'0.t_itermut usize)) (return'  (ret:Option'0.t_option (borrowed usize)))= any
-    [ return' (result:Option'0.t_option (borrowed usize))-> {[%#span53] inv'4 result}
-      {[%#span52] match result with
+    [ return' (result:Option'0.t_option (borrowed usize))-> {[%#span41] inv'4 result}
+      {[%#span40] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -1440,7 +1281,7 @@ module C03StdIterators_AllZero
   function index_logic'0 [@inline:trivial] (self : Snapshot'0.t_snapshot (Seq'0.t_seq (borrowed usize))) (ix : int) : borrowed usize
     
    =
-    [%#span54] index_logic'2 (deref'0 self) ix
+    [%#span42] index_logic'2 (deref'0 self) ix
   
   function inner'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq (borrowed usize))) : Seq'0.t_seq (borrowed usize)
   
@@ -1450,40 +1291,40 @@ module C03StdIterators_AllZero
   
   function new'1 (x : Seq'0.t_seq (borrowed usize)) : Snapshot'0.t_snapshot (Seq'0.t_seq (borrowed usize))
   
-  axiom new'1_spec : forall x : Seq'0.t_seq (borrowed usize) . ([%#span55] inv'3 x)
-   -> ([%#span56] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq (borrowed usize) . ([%#span43] inv'3 x)
+   -> ([%#span44] deref'0 (new'1 x) = x)
   
   function new'0 (x : IterMut'0.t_itermut usize) : Snapshot'0.t_snapshot (IterMut'0.t_itermut usize)
   
-  axiom new'0_spec : forall x : IterMut'0.t_itermut usize . ([%#span55] inv'0 x)  -> ([%#span56] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : IterMut'0.t_itermut usize . ([%#span43] inv'0 x)  -> ([%#span44] deref'1 (new'0 x) = x)
   
   predicate resolve'0 (self : borrowed (slice usize)) =
-    [%#span45]  ^ self =  * self
+    [%#span34]  ^ self =  * self
   
   predicate into_iter_post'0 (self : IterMut'0.t_itermut usize) (res : IterMut'0.t_itermut usize) =
-    [%#span57] self = res
+    [%#span45] self = res
   
   predicate into_iter_pre'0 (self : IterMut'0.t_itermut usize) =
-    [%#span58] true
+    [%#span46] true
   
-  let rec into_iter'0 (self:IterMut'0.t_itermut usize) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span60] inv'0 self}
-    {[@expl:precondition] [%#span59] into_iter_pre'0 self}
+  let rec into_iter'0 (self:IterMut'0.t_itermut usize) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span48] inv'0 self}
+    {[@expl:precondition] [%#span47] into_iter_pre'0 self}
     any
-    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span61] inv'0 result}
-      {[%#span59] into_iter_post'0 self result}
+    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span49] inv'0 result}
+      {[%#span47] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec iter_mut'0 (self:borrowed (slice usize)) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span62] inv'2 self}
+  let rec iter_mut'0 (self:borrowed (slice usize)) (return'  (ret:IterMut'0.t_itermut usize))= {[@expl:precondition] [%#span50] inv'2 self}
     any
-    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span63] shallow_model'4 result = self} (! return' {result}) ]
+    [ return' (result:IterMut'0.t_itermut usize)-> {[%#span51] shallow_model'4 result = self} (! return' {result}) ]
     
   
-  let rec deref_mut'0 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (return'  (ret:borrowed (slice usize)))= {[@expl:precondition] [%#span64] inv'1 self}
+  let rec deref_mut'0 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (return'  (ret:borrowed (slice usize)))= {[@expl:precondition] [%#span52] inv'1 self}
     any
-    [ return' (result:borrowed (slice usize))-> {[%#span67] inv'2 result}
-      {[%#span66] shallow_model'3 ( ^ result) = shallow_model'0 ( ^ self)}
-      {[%#span65] shallow_model'2 result = shallow_model'1 self}
+    [ return' (result:borrowed (slice usize))-> {[%#span55] inv'2 result}
+      {[%#span54] shallow_model'3 ( ^ result) = shallow_model'0 ( ^ self)}
+      {[%#span53] shallow_model'2 result = shallow_model'1 self}
       (! return' {result}) ]
     
   
@@ -1620,179 +1461,142 @@ module C03StdIterators_SkipTake
   
   let%span s03_std_iterators1 = "../03_std_iterators.rs" 35 30 35 34
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
+  let%span span5 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
+  let%span span6 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/iter.rs" 41 31 41 33
+  let%span span7 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
+  let%span span8 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/iter.rs" 41 61 41 63
+  let%span span9 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
+  let%span span10 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
+  let%span span11 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span12 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
+  let%span span13 = "" 0 0 0 0
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
+  let%span span14 = "../../../../../creusot-contracts/src/std/iter/take.rs" 34 9 34 13
   
-  let%span span20 = "" 0 0 0 0
+  let%span span15 = "../../../../../creusot-contracts/src/std/iter/take.rs" 33 14 33 50
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/iter/take.rs" 34 9 34 13
+  let%span span16 = "../../../../../creusot-contracts/src/std/iter/take.rs" 64 12 64 88
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/iter/take.rs" 33 14 33 50
+  let%span span17 = "../../../../../creusot-contracts/src/std/iter/take.rs" 75 15 75 32
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/iter/take.rs" 64 12 64 88
+  let%span span18 = "../../../../../creusot-contracts/src/std/iter/take.rs" 76 15 76 32
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/iter/take.rs" 75 15 75 32
+  let%span span19 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 22 78 23
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/iter/take.rs" 76 15 76 32
+  let%span span20 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 52 78 53
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 22 78 23
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 82 78 83
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 31 78 33
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter/take.rs" 77 14 77 42
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 52 78 53
+  let%span span23 = "../../../../../creusot-contracts/src/std/iter/take.rs" 71 21 71 25
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 61 78 63
+  let%span span24 = "../../../../../creusot-contracts/src/std/iter/take.rs" 70 14 70 45
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/take.rs" 78 82 78 83
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/iter/take.rs" 77 14 77 42
+  let%span span26 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 23 9 23 13
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/iter/take.rs" 71 21 71 25
+  let%span span27 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 22 14 22 50
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/iter/take.rs" 70 14 70 45
+  let%span span28 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 57 8 64 9
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span29 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 74 15 74 32
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span30 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 75 15 75 32
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 23 9 23 13
+  let%span span31 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 22 77 23
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 22 14 22 50
+  let%span span32 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 52 77 53
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 57 8 64 9
+  let%span span33 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 82 77 83
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 74 15 74 32
+  let%span span34 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 76 14 76 42
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 75 15 75 32
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 70 21 70 25
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 22 77 23
+  let%span span36 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 69 14 69 45
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 31 77 33
+  let%span span37 = "../../../../../creusot-contracts/src/std/iter/take.rs" 45 12 45 33
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 52 77 53
+  let%span span38 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 34 12 34 33
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 61 77 63
+  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 77 82 77 83
+  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 76 14 76 42
+  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 70 21 70 25
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter/take.rs" 26 21 26 25
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 69 14 69 45
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter/take.rs" 25 14 25 68
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/iter/take.rs" 45 12 45 33
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter/take.rs" 26 4 26 36
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 34 12 34 33
-  
-  let%span span51 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span53 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span55 = "../../../../../creusot-contracts/src/std/iter/take.rs" 26 21 26 25
-  
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter/take.rs" 25 14 25 68
-  
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter/take.rs" 26 4 26 36
-  
-  let%span span58 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span45 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/iter/take.rs" 55 12 56 92
+  let%span span46 = "../../../../../creusot-contracts/src/std/iter/take.rs" 55 12 56 92
   
-  let%span span60 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 43 8 51 9
+  let%span span47 = "../../../../../creusot-contracts/src/std/iter/skip.rs" 43 8 51 9
   
-  let%span span61 = "" 0 0 0 0
+  let%span span48 = "" 0 0 0 0
   
-  let%span span62 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span49 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span63 = "" 0 0 0 0
+  let%span span50 = "" 0 0 0 0
   
-  let%span span64 = "" 0 0 0 0
+  let%span span51 = "" 0 0 0 0
   
-  let%span span65 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span52 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span66 = "" 0 0 0 0
+  let%span span53 = "" 0 0 0 0
   
-  let%span span67 = "" 0 0 0 0
+  let%span span54 = "" 0 0 0 0
   
-  let%span span68 = "" 0 0 0 0
+  let%span span55 = "" 0 0 0 0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'8 (self : borrowed i)
+  predicate invariant'7 (self : borrowed i)
   
-  predicate inv'8 (_x : borrowed i)
+  predicate inv'7 (_x : borrowed i)
   
-  axiom inv'8 : forall x : borrowed i . inv'8 x = true
+  axiom inv'7 : forall x : borrowed i . inv'7 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
-  
-  predicate inv'6 (_x : Seq'0.t_seq item'0)
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'6 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] inv'6 self)
-   -> ([%#span5] inv'6 other)
-   -> ([%#span8] inv'6 (concat'0 self other))
-  && ([%#span7] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span6] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span3] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'2 (_x : i)
   
@@ -1800,25 +1604,23 @@ module C03StdIterators_SkipTake
   
   function produces_trans'2 (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
   
-  axiom produces_trans'2_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'2 a ab b)
-   -> ([%#span10] produces'2 b bc c)
-   -> ([%#span11] inv'2 a)
-   -> ([%#span12] inv'6 ab)
-   -> ([%#span13] inv'2 b)
-   -> ([%#span14] inv'6 bc)  -> ([%#span15] inv'2 c)  -> ([%#span16] produces'2 a (concat'0 ab bc) c)
+  axiom produces_trans'2_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span5] produces'2 a ab b)
+   -> ([%#span6] produces'2 b bc c)
+   -> ([%#span7] inv'2 a)
+   -> ([%#span8] inv'2 b)  -> ([%#span9] inv'2 c)  -> ([%#span10] produces'2 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'2 (self : i) : ()
   
-  axiom produces_refl'2_spec : forall self : i . ([%#span18] inv'2 self)
-   -> ([%#span19] produces'2 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'2_spec : forall self : i . ([%#span11] inv'2 self)
+   -> ([%#span12] produces'2 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  predicate invariant'7 (self : item'0)
+  predicate invariant'6 (self : item'0)
   
-  predicate inv'7 (_x : item'0)
+  predicate inv'6 (_x : item'0)
   
-  axiom inv'7 : forall x : item'0 . inv'7 x = true
+  axiom inv'6 : forall x : item'0 . inv'6 x = true
   
   use Core_Iter_Adapters_Take_Take_Type as Take'0
   
@@ -1830,34 +1632,28 @@ module C03StdIterators_SkipTake
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span20] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span13] (18446744073709551615 : usize)
   
   function n'0 (self : Take'0.t_take i) : int
   
-  axiom n'0_spec : forall self : Take'0.t_take i . ([%#span21] inv'3 self)
-   -> ([%#span22] n'0 self >= 0 /\ n'0 self <= UIntSize.to_int (max'0 : usize))
+  axiom n'0_spec : forall self : Take'0.t_take i . ([%#span14] inv'3 self)
+   -> ([%#span15] n'0 self >= 0 /\ n'0 self <= UIntSize.to_int (max'0 : usize))
   
   predicate produces'1 (self : Take'0.t_take i) (visited : Seq'0.t_seq item'0) (o : Take'0.t_take i) =
-    [%#span23] n'0 self = n'0 o + len'0 visited /\ produces'2 (iter'0 self) visited (iter'0 o)
+    [%#span16] n'0 self = n'0 o + len'0 visited /\ produces'2 (iter'0 self) visited (iter'0 o)
   
   function produces_trans'1 (a : Take'0.t_take i) (ab : Seq'0.t_seq item'0) (b : Take'0.t_take i) (bc : Seq'0.t_seq item'0) (c : Take'0.t_take i) : ()
     
   
-  axiom produces_trans'1_spec : forall a : Take'0.t_take i, ab : Seq'0.t_seq item'0, b : Take'0.t_take i, bc : Seq'0.t_seq item'0, c : Take'0.t_take i . ([%#span24] produces'1 a ab b)
-   -> ([%#span25] produces'1 b bc c)
-   -> ([%#span26] inv'3 a)
-   -> ([%#span27] inv'6 ab)
-   -> ([%#span28] inv'3 b)
-   -> ([%#span29] inv'6 bc)  -> ([%#span30] inv'3 c)  -> ([%#span31] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : Take'0.t_take i, ab : Seq'0.t_seq item'0, b : Take'0.t_take i, bc : Seq'0.t_seq item'0, c : Take'0.t_take i . ([%#span17] produces'1 a ab b)
+   -> ([%#span18] produces'1 b bc c)
+   -> ([%#span19] inv'3 a)
+   -> ([%#span20] inv'3 b)  -> ([%#span21] inv'3 c)  -> ([%#span22] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'1 (self : Take'0.t_take i) : ()
   
-  axiom produces_refl'1_spec : forall self : Take'0.t_take i . ([%#span32] inv'3 self)
-   -> ([%#span33] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
-  
-  predicate invariant'6 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'6 : forall x : Seq'0.t_seq item'0 . inv'6 x = true
+  axiom produces_refl'1_spec : forall self : Take'0.t_take i . ([%#span23] inv'3 self)
+   -> ([%#span24] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'5 (self : borrowed (Take'0.t_take i))
   
@@ -1865,10 +1661,9 @@ module C03StdIterators_SkipTake
   
   axiom inv'5 : forall x : borrowed (Take'0.t_take i) . inv'5 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span35] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span34] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span25] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use Core_Iter_Adapters_Skip_Skip_Type as Skip'0
   
@@ -1880,34 +1675,31 @@ module C03StdIterators_SkipTake
   
   function n'1 (self : Skip'0.t_skip (Take'0.t_take i)) : int
   
-  axiom n'1_spec : forall self : Skip'0.t_skip (Take'0.t_take i) . ([%#span36] inv'0 self)
-   -> ([%#span37] n'1 self >= 0 /\ n'1 self <= UIntSize.to_int (max'0 : usize))
+  axiom n'1_spec : forall self : Skip'0.t_skip (Take'0.t_take i) . ([%#span26] inv'0 self)
+   -> ([%#span27] n'1 self >= 0 /\ n'1 self <= UIntSize.to_int (max'0 : usize))
   
   predicate produces'0 (self : Skip'0.t_skip (Take'0.t_take i)) (visited : Seq'0.t_seq item'0) (o : Skip'0.t_skip (Take'0.t_take i))
     
    =
-    [%#span38] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
+    [%#span28] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
     \/ n'1 o = 0
     /\ len'0 visited > 0
-    /\ (exists s : Seq'0.t_seq item'0 . inv'6 s
-    /\ len'0 s = n'1 self
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = n'1 self
     /\ produces'1 (iter'1 self) (concat'0 s visited) (iter'1 o)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'3 (index_logic'0 s i)))
   
   function produces_trans'0 (a : Skip'0.t_skip (Take'0.t_take i)) (ab : Seq'0.t_seq item'0) (b : Skip'0.t_skip (Take'0.t_take i)) (bc : Seq'0.t_seq item'0) (c : Skip'0.t_skip (Take'0.t_take i)) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Skip'0.t_skip (Take'0.t_take i), ab : Seq'0.t_seq item'0, b : Skip'0.t_skip (Take'0.t_take i), bc : Seq'0.t_seq item'0, c : Skip'0.t_skip (Take'0.t_take i) . ([%#span39] produces'0 a ab b)
-   -> ([%#span40] produces'0 b bc c)
-   -> ([%#span41] inv'0 a)
-   -> ([%#span42] inv'6 ab)
-   -> ([%#span43] inv'0 b)
-   -> ([%#span44] inv'6 bc)  -> ([%#span45] inv'0 c)  -> ([%#span46] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Skip'0.t_skip (Take'0.t_take i), ab : Seq'0.t_seq item'0, b : Skip'0.t_skip (Take'0.t_take i), bc : Seq'0.t_seq item'0, c : Skip'0.t_skip (Take'0.t_take i) . ([%#span29] produces'0 a ab b)
+   -> ([%#span30] produces'0 b bc c)
+   -> ([%#span31] inv'0 a)
+   -> ([%#span32] inv'0 b)  -> ([%#span33] inv'0 c)  -> ([%#span34] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 (self : Skip'0.t_skip (Take'0.t_take i)) : ()
   
-  axiom produces_refl'0_spec : forall self : Skip'0.t_skip (Take'0.t_take i) . ([%#span47] inv'0 self)
-   -> ([%#span48] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : Skip'0.t_skip (Take'0.t_take i) . ([%#span35] inv'0 self)
+   -> ([%#span36] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'4 (self : borrowed (Skip'0.t_skip (Take'0.t_take i)))
   
@@ -1942,64 +1734,60 @@ module C03StdIterators_SkipTake
   predicate resolve'4 (self : i)
   
   predicate resolve'2 (self : Take'0.t_take i) =
-    [%#span49] resolve'4 (iter'0 self)
+    [%#span37] resolve'4 (iter'0 self)
   
   predicate resolve'0 (self : Skip'0.t_skip (Take'0.t_take i)) =
-    [%#span50] resolve'2 (iter'1 self)
-  
-  use seq.Seq
+    [%#span38] resolve'2 (iter'1 self)
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span51] inv'7 v)
-   -> ([%#span54] inv'6 (singleton'0 v))
-  && ([%#span53] index_logic'0 (singleton'0 v) 0 = v) && ([%#span52] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span39] inv'6 v)
+   -> ([%#span41] index_logic'0 (singleton'0 v) 0 = v) && ([%#span40] len'0 (singleton'0 v) = 1)
   
   predicate completed'2 (self : borrowed i)
   
   function iter_mut'0 (self : borrowed (Take'0.t_take i)) : borrowed i
   
-  axiom iter_mut'0_spec : forall self : borrowed (Take'0.t_take i) . ([%#span55] inv'5 self)
-   -> ([%#span57] inv'8 (iter_mut'0 self))
-  && ([%#span56] iter'0 ( * self) =  * iter_mut'0 self /\ iter'0 ( ^ self) =  ^ iter_mut'0 self)
+  axiom iter_mut'0_spec : forall self : borrowed (Take'0.t_take i) . ([%#span42] inv'5 self)
+   -> ([%#span44] inv'7 (iter_mut'0 self))
+  && ([%#span43] iter'0 ( * self) =  * iter_mut'0 self /\ iter'0 ( ^ self) =  ^ iter_mut'0 self)
   
   predicate resolve'5 (self : borrowed (Take'0.t_take i)) =
-    [%#span58]  ^ self =  * self
+    [%#span45]  ^ self =  * self
   
   predicate completed'1 (self : borrowed (Take'0.t_take i)) =
-    [%#span59] n'0 ( * self) = 0 /\ resolve'5 self
+    [%#span46] n'0 ( * self) = 0 /\ resolve'5 self
     \/ n'0 ( * self) > 0 /\ n'0 ( * self) = n'0 ( ^ self) + 1 /\ completed'2 (iter_mut'0 self)
   
   predicate completed'0 (self : borrowed (Skip'0.t_skip (Take'0.t_take i))) =
-    [%#span60] n'1 ( ^ self) = 0
+    [%#span47] n'1 ( ^ self) = 0
     /\ (exists i : borrowed (Take'0.t_take i) . exists s : Seq'0.t_seq item'0 . inv'5 i
-    /\ inv'6 s
     /\ len'0 s <= n'1 ( * self)
     /\ produces'1 (iter'1 ( * self)) s ( * i)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'3 (index_logic'0 s i))
     /\ completed'1 i /\  ^ i = iter'1 ( ^ self))
   
-  let rec next'0 (self:borrowed (Skip'0.t_skip (Take'0.t_take i))) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span61] inv'4 self}
+  let rec next'0 (self:borrowed (Skip'0.t_skip (Take'0.t_take i))) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span48] inv'4 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span63] inv'1 result}
-      {[%#span62] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span50] inv'1 result}
+      {[%#span49] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
       (! return' {result}) ]
     
   
-  let rec skip'0 (self:Take'0.t_take i) (n:usize) (return'  (ret:Skip'0.t_skip (Take'0.t_take i)))= {[@expl:precondition] [%#span64] inv'3 self}
+  let rec skip'0 (self:Take'0.t_take i) (n:usize) (return'  (ret:Skip'0.t_skip (Take'0.t_take i)))= {[@expl:precondition] [%#span51] inv'3 self}
     any
-    [ return' (result:Skip'0.t_skip (Take'0.t_take i))-> {[%#span66] inv'0 result}
-      {[%#span65] iter'1 result = self /\ n'1 result = UIntSize.to_int n}
+    [ return' (result:Skip'0.t_skip (Take'0.t_take i))-> {[%#span53] inv'0 result}
+      {[%#span52] iter'1 result = self /\ n'1 result = UIntSize.to_int n}
       (! return' {result}) ]
     
   
-  let rec take'0 (self:i) (n:usize) (return'  (ret:Take'0.t_take i))= {[@expl:precondition] [%#span67] inv'2 self}
+  let rec take'0 (self:i) (n:usize) (return'  (ret:Take'0.t_take i))= {[@expl:precondition] [%#span54] inv'2 self}
     any
-    [ return' (result:Take'0.t_take i)-> {[%#span68] inv'3 result}
-      {[%#span65] iter'0 result = self /\ n'0 result = UIntSize.to_int n}
+    [ return' (result:Take'0.t_take i)-> {[%#span55] inv'3 result}
+      {[%#span52] iter'0 result = self /\ n'0 result = UIntSize.to_int n}
       (! return' {result}) ]
     
   
@@ -2100,49 +1888,29 @@ module C03StdIterators_Counter_Closure0
   
   let%span s03_std_iterators2 = "../03_std_iterators.rs" 48 22 48 89
   
-  let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span9 = "" 0 0 0 0
-  
-  let%span span10 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  use prelude.prelude.Int
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq uint32) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq uint32 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.Int16
   
@@ -2164,7 +1932,7 @@ module C03StdIterators_Counter_Closure0
    =
      ^ field_0'0 _2 =  ^ field_0'0 self
   
-  constant max'0 : usize = [%#span9] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
   
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) : Seq'0.t_seq uint32
   
@@ -2173,7 +1941,7 @@ module C03StdIterators_Counter_Closure0
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed Closure'0.c03stditerators_counter_closure0) =
-    [%#span10]  ^ self =  * self
+    [%#span6]  ^ self =  * self
   
   let rec c03stditerators_counter_closure0 (_1:borrowed Closure'0.c03stditerators_counter_closure0) (x:uint32) (_prod:Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) (return'  (ret:uint32))= {[%#s03_std_iterators1] UIntSize.to_int ( * field_0'0 ( * _1))
     = len'0 (deref'0 _prod)
@@ -2221,229 +1989,192 @@ module C03StdIterators_Counter
   
   let%span span4 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span10 = "" 0 0 0 0
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span20 = "../03_std_iterators.rs" 47 23 47 65
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span21 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span22 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span7 = "" 0 0 0 0
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span13 = "../03_std_iterators.rs" 47 23 47 65
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span14 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span15 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span32 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/slice.rs" 76 4 76 35
+  let%span span21 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
+  let%span span22 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 37 8 49 9
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 28 15 28 32
+  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 29 15 29 32
+  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 22 31 23
+  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 31 31 33
+  let%span span27 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 37 8 49 9
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 52 31 53
+  let%span span28 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 28 15 28 32
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 61 31 63
+  let%span span29 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 29 15 29 32
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 82 31 83
+  let%span span30 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 22 31 23
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 30 14 30 42
+  let%span span31 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 52 31 53
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 24 21 24 25
+  let%span span32 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 82 31 83
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 23 14 23 45
+  let%span span33 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 30 14 30 42
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span34 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 24 21 24 25
   
-  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 23 14 23 45
   
-  let%span span51 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span53 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 112 8 116 9
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span39 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 112 8 116 9
   
-  let%span span55 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 135 8 142 9
+  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 24 121 28
+  let%span span41 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 135 8 142 9
   
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 33 121 37
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 24 121 28
   
-  let%span span58 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 42 121 50
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 33 121 37
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 120 4 120 83
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 120 4 120 83
   
-  let%span span60 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span45 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span61 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span46 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span62 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
+  let%span span47 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
   
-  let%span span63 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 148 8 153 9
+  let%span span48 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 148 8 153 9
   
-  let%span span64 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
+  let%span span49 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
   
-  let%span span65 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
+  let%span span50 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
   
-  let%span span66 = "../../../../../creusot-contracts/src/std/slice.rs" 398 31 398 33
+  let%span span51 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
   
-  let%span span67 = "../../../../../creusot-contracts/src/std/slice.rs" 398 61 398 63
+  let%span span52 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
   
-  let%span span68 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
+  let%span span53 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
   
-  let%span span69 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
+  let%span span54 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
   
-  let%span span70 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
+  let%span span55 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
   
-  let%span span71 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
+  let%span span56 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
   
-  let%span span72 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
+  let%span span57 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
   
-  let%span span73 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
+  let%span span58 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
   
-  let%span span74 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
+  let%span span59 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
   
-  let%span span75 = "../../../../../creusot-contracts/src/std/iter.rs" 41 31 41 33
+  let%span span60 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
   
-  let%span span76 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
+  let%span span61 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
   
-  let%span span77 = "../../../../../creusot-contracts/src/std/iter.rs" 41 61 41 63
+  let%span span62 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
   
-  let%span span78 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
+  let%span span63 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span79 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
+  let%span span64 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span80 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
+  let%span span65 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span81 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
+  let%span span66 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span82 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span67 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span83 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span68 = "../../../../../creusot-contracts/src/std/vec.rs" 275 20 275 32
   
-  let%span span84 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span69 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 15 8 18 9
   
-  let%span span85 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span70 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 56 4 56 27
   
-  let%span span86 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span71 = "" 0 0 0 0
   
-  let%span span87 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span72 = "../../../../../creusot-contracts/src/std/iter.rs" 136 16 137 83
   
-  let%span span88 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
-  
-  let%span span89 = "../../../../../creusot-contracts/src/std/vec.rs" 275 20 275 32
-  
-  let%span span90 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 15 8 18 9
+  let%span span73 = "" 0 0 0 0
   
-  let%span span91 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 56 4 56 27
+  let%span span74 = "../../../../../creusot-contracts/src/std/iter.rs" 43 4 43 141
   
-  let%span span92 = "" 0 0 0 0
+  let%span span75 = "../../../../../creusot-contracts/src/std/iter.rs" 44 15 44 51
   
-  let%span span93 = "../../../../../creusot-contracts/src/std/iter.rs" 136 16 137 83
+  let%span span76 = "../../../../../creusot-contracts/src/std/iter.rs" 45 15 45 70
   
-  let%span span94 = "" 0 0 0 0
+  let%span span77 = "../../../../../creusot-contracts/src/std/iter.rs" 47 21 47 25
   
-  let%span span95 = "../../../../../creusot-contracts/src/std/iter.rs" 43 4 43 141
+  let%span span78 = "../../../../../creusot-contracts/src/std/iter.rs" 47 27 47 31
   
-  let%span span96 = "../../../../../creusot-contracts/src/std/iter.rs" 44 15 44 51
+  let%span span79 = "../../../../../creusot-contracts/src/std/iter.rs" 46 14 46 88
   
-  let%span span97 = "../../../../../creusot-contracts/src/std/iter.rs" 45 15 45 70
+  let%span span80 = "../../../../../creusot-contracts/src/std/iter.rs" 47 4 50 61
   
-  let%span span98 = "../../../../../creusot-contracts/src/std/iter.rs" 47 21 47 25
+  let%span span81 = "" 0 0 0 0
   
-  let%span span99 = "../../../../../creusot-contracts/src/std/iter.rs" 47 27 47 31
+  let%span span82 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span100 = "../../../../../creusot-contracts/src/std/iter.rs" 46 14 46 88
+  let%span span83 = "" 0 0 0 0
   
-  let%span span101 = "../../../../../creusot-contracts/src/std/iter.rs" 47 4 50 61
+  let%span span84 = "../../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
   
-  let%span span102 = "" 0 0 0 0
+  let%span span85 = "" 0 0 0 0
   
-  let%span span103 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  use prelude.prelude.UInt32
   
-  let%span span104 = "" 0 0 0 0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span105 = "../../../../../creusot-contracts/src/std/vec.rs" 163 26 163 42
+  predicate invariant'13 (self : Seq'0.t_seq uint32) =
+    [%#span4] true
   
-  let%span span106 = "" 0 0 0 0
+  predicate inv'13 (_x : Seq'0.t_seq uint32)
   
-  use prelude.prelude.UInt32
+  axiom inv'13 : forall x : Seq'0.t_seq uint32 . inv'13 x = true
   
   use prelude.prelude.Slice
   
-  predicate invariant'14 (self : slice uint32) =
+  predicate invariant'12 (self : slice uint32) =
     [%#span4] true
   
-  predicate inv'14 (_x : slice uint32)
+  predicate inv'12 (_x : slice uint32)
   
-  axiom inv'14 : forall x : slice uint32 . inv'14 x = true
+  axiom inv'12 : forall x : slice uint32 . inv'12 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   use prelude.prelude.UIntSize
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Int16
@@ -2452,59 +2183,47 @@ module C03StdIterators_Counter
   
   use C03StdIterators_Counter_Closure0_Type as Closure'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  predicate inv'13 (_x : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0))
-  
   function len'2 (self : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0) . ([%#span5] inv'13 self)
-   -> ([%#span6] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0) . [%#span5] len'2 self
+  >= 0
   
-  constant empty'2 : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0) = [%#span7] ()
+  constant empty'2 : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0)
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span8] len'2 (empty'2 : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0))
+  axiom empty_len'2_spec : forall _1 : () . [%#span6] len'2 (empty'2 : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0))
   = 0
   
-  predicate invariant'13 (self : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0)) =
+  predicate invariant'11 (self : borrowed Closure'0.c03stditerators_counter_closure0) =
     [%#span4] true
   
-  axiom inv'13 : forall x : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0) . inv'13 x = true
+  predicate inv'11 (_x : borrowed Closure'0.c03stditerators_counter_closure0)
   
-  predicate invariant'12 (self : borrowed Closure'0.c03stditerators_counter_closure0) =
-    [%#span4] true
-  
-  predicate inv'12 (_x : borrowed Closure'0.c03stditerators_counter_closure0)
+  axiom inv'11 : forall x : borrowed Closure'0.c03stditerators_counter_closure0 . inv'11 x = true
   
-  axiom inv'12 : forall x : borrowed Closure'0.c03stditerators_counter_closure0 . inv'12 x = true
-  
-  predicate invariant'11 (self : uint32) =
+  predicate invariant'10 (self : uint32) =
     [%#span4] true
   
-  predicate inv'11 (_x : uint32)
+  predicate inv'10 (_x : uint32)
   
-  axiom inv'11 : forall x : uint32 . inv'11 x = true
+  axiom inv'10 : forall x : uint32 . inv'10 x = true
   
   use Core_Slice_Iter_Iter_Type as Iter'0
   
-  predicate invariant'10 (self : borrowed (Iter'0.t_iter uint32)) =
+  predicate invariant'9 (self : borrowed (Iter'0.t_iter uint32)) =
     [%#span4] true
   
-  predicate inv'10 (_x : borrowed (Iter'0.t_iter uint32))
+  predicate inv'9 (_x : borrowed (Iter'0.t_iter uint32))
   
-  axiom inv'10 : forall x : borrowed (Iter'0.t_iter uint32) . inv'10 x = true
+  axiom inv'9 : forall x : borrowed (Iter'0.t_iter uint32) . inv'9 x = true
   
-  predicate invariant'9 (self : Seq'0.t_seq uint32) =
+  predicate invariant'8 (self : Seq'0.t_seq uint32) =
     [%#span4] true
   
-  predicate inv'9 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'9 : forall x : Seq'0.t_seq uint32 . inv'9 x = true
+  predicate inv'8 (_x : Seq'0.t_seq uint32)
   
-  predicate inv'6 (_x : Seq'0.t_seq uint32)
+  axiom inv'8 : forall x : Seq'0.t_seq uint32 . inv'8 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -2512,44 +2231,36 @@ module C03StdIterators_Counter
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
-  
-  use seq.Seq
+  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span5] inv'6 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span5] len'0 self >= 0
   
-  predicate inv'8 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
+  predicate inv'7 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span11] inv'8 self)
-   -> ([%#span13] inv'6 (shallow_model'0 self))
-  && ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span8] inv'7 self)
+   -> ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'8 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span14] inv'6 (shallow_model'0 self)
+  predicate invariant'7 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
+    [%#span10] inv'13 (shallow_model'0 self)
   
-  axiom inv'8 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'8 x = true
+  axiom inv'7 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'7 x = true
   
   use CreusotContracts_Std1_Iter_MapInv_MapInv_Type as MapInv'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function concat'1 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span15] inv'6 self)
-   -> ([%#span16] inv'6 other)
-   -> ([%#span19] inv'6 (concat'1 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'0 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span12] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span17] len'0 (concat'1 self other) = len'0 self + len'0 other)
+  && ([%#span11] len'0 (concat'1 self other) = len'0 self + len'0 other)
   
   predicate inv'5 (_x : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0)
   
@@ -2563,11 +2274,9 @@ module C03StdIterators_Counter
    =
      ^ field_0'0 _2 =  ^ field_0'0 self
   
-  use seq.Seq
-  
   function len'1 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . ([%#span5] inv'9 self)  -> ([%#span6] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . [%#span5] len'1 self >= 0
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) : Seq'0.t_seq uint32
   
@@ -2581,45 +2290,34 @@ module C03StdIterators_Counter
   predicate precondition'0 [#"../03_std_iterators.rs" 48 12 48 91] (self : Closure'0.c03stditerators_counter_closure0) (args : (uint32, Snapshot'0.t_snapshot (Seq'0.t_seq uint32)))
     
    =
-    [%#span20] let (x, _prod) = args in UIntSize.to_int ( * field_0'0 self) = len'1 (deref'1 _prod)
+    [%#span13] let (x, _prod) = args in UIntSize.to_int ( * field_0'0 self) = len'1 (deref'1 _prod)
     /\  * field_0'0 self < (max'0 : usize)
   
   function new'0 (x : Seq'0.t_seq uint32) : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq uint32 . ([%#span21] inv'9 x)  -> ([%#span22] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Seq'0.t_seq uint32 . ([%#span14] inv'8 x)  -> ([%#span15] deref'1 (new'0 x) = x)
   
-  use prelude.seq_ext.SeqExt
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'2 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function subsequence'0 (self : Seq'0.t_seq uint32) (n : int) (m : int) : Seq'0.t_seq uint32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span23] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span16] 0 <= n
   /\ n <= m /\ m <= len'1 self)
-   -> ([%#span24] inv'9 self)
-   -> ([%#span27] inv'9 (subsequence'0 self n m))
-  && ([%#span26] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
+   -> ([%#span18] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
    -> index_logic'2 (subsequence'0 self n m) i = index_logic'2 self (n + i))
-  && ([%#span25] len'1 (subsequence'0 self n m) = m - n)
+  && ([%#span17] len'1 (subsequence'0 self n m) = m - n)
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0)) (x : int) : borrowed Closure'0.c03stditerators_counter_closure0
+  function index_logic'3 (self : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0)) (_2 : int) : borrowed Closure'0.c03stditerators_counter_closure0
     
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span15] inv'9 self)
-   -> ([%#span16] inv'9 other)
-   -> ([%#span19] inv'9 (concat'0 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span12] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span17] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span11] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) : Seq'0.t_seq uint32
   
@@ -2627,42 +2325,38 @@ module C03StdIterators_Counter
   
   function shallow_model'4 (self : slice uint32) : Seq'0.t_seq uint32
   
-  axiom shallow_model'4_spec : forall self : slice uint32 . ([%#span28] inv'14 self)
-   -> ([%#span30] inv'6 (shallow_model'4 self))
-  && ([%#span29] len'0 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'4_spec : forall self : slice uint32 . ([%#span19] inv'12 self)
+   -> ([%#span20] len'0 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'4 [@inline:trivial] (self : slice uint32) (ix : int) : uint32 =
-    [%#span31] index_logic'1 (shallow_model'4 self) ix
+    [%#span21] index_logic'1 (shallow_model'4 self) ix
   
   function shallow_model'1 (self : slice uint32) : Seq'0.t_seq uint32 =
-    [%#span32] shallow_model'4 self
+    [%#span22] shallow_model'4 self
   
   predicate inv'1 (_x : slice uint32)
   
   function to_ref_seq'0 (self : slice uint32) : Seq'0.t_seq uint32
   
-  axiom to_ref_seq'0_spec : forall self : slice uint32 . ([%#span33] inv'1 self)
-   -> ([%#span36] inv'9 (to_ref_seq'0 self))
-  && ([%#span35] forall i : int . 0 <= i /\ i < len'1 (to_ref_seq'0 self)
+  axiom to_ref_seq'0_spec : forall self : slice uint32 . ([%#span23] inv'1 self)
+   -> ([%#span25] forall i : int . 0 <= i /\ i < len'1 (to_ref_seq'0 self)
    -> index_logic'2 (to_ref_seq'0 self) i = index_logic'4 self i)
-  && ([%#span34] len'1 (to_ref_seq'0 self) = len'0 (shallow_model'1 self))
+  && ([%#span24] len'1 (to_ref_seq'0 self) = len'0 (shallow_model'1 self))
   
   function shallow_model'3 (self : Iter'0.t_iter uint32) : slice uint32
   
   predicate produces'0 (self : Iter'0.t_iter uint32) (visited : Seq'0.t_seq uint32) (tl : Iter'0.t_iter uint32) =
-    [%#span37] to_ref_seq'0 (shallow_model'3 self) = concat'0 visited (to_ref_seq'0 (shallow_model'3 tl))
+    [%#span26] to_ref_seq'0 (shallow_model'3 self) = concat'0 visited (to_ref_seq'0 (shallow_model'3 tl))
   
   predicate produces'1 [@inline:trivial] (self : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) (visited : Seq'0.t_seq uint32) (succ : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0)
     
    =
-    [%#span38] unnest'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self) (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func succ)
-    /\ (exists s : Seq'0.t_seq uint32 . inv'9 s
-    /\ len'1 s = len'0 visited
+    [%#span27] unnest'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self) (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func succ)
+    /\ (exists s : Seq'0.t_seq uint32 . len'1 s = len'0 visited
     /\ produces'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter self) s (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter succ)
     /\ inner'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced succ)
     = concat'0 (deref'1 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0) . inv'13 fs
-    /\ len'2 fs = len'0 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed Closure'0.c03stditerators_counter_closure0) . len'2 fs = len'0 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'3 fs (i - 1) =  * index_logic'3 fs i)
     /\ (if len'0 visited = 0 then
       CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self
@@ -2679,95 +2373,83 @@ module C03StdIterators_Counter
   function produces_trans'2 (a : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) (ab : Seq'0.t_seq uint32) (b : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) (bc : Seq'0.t_seq uint32) (c : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) : ()
     
   
-  axiom produces_trans'2_spec : forall a : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0, ab : Seq'0.t_seq uint32, b : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0, bc : Seq'0.t_seq uint32, c : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0 . ([%#span39] produces'1 a ab b)
-   -> ([%#span40] produces'1 b bc c)
-   -> ([%#span41] inv'5 a)
-   -> ([%#span42] inv'6 ab)
-   -> ([%#span43] inv'5 b)
-   -> ([%#span44] inv'6 bc)  -> ([%#span45] inv'5 c)  -> ([%#span46] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'2_spec : forall a : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0, ab : Seq'0.t_seq uint32, b : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0, bc : Seq'0.t_seq uint32, c : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0 . ([%#span28] produces'1 a ab b)
+   -> ([%#span29] produces'1 b bc c)
+   -> ([%#span30] inv'5 a)
+   -> ([%#span31] inv'5 b)  -> ([%#span32] inv'5 c)  -> ([%#span33] produces'1 a (concat'1 ab bc) c)
   
-  constant empty'1 : Seq'0.t_seq uint32 = [%#span7] ()
+  constant empty'1 : Seq'0.t_seq uint32
   
   function produces_refl'2 (self : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) : ()
     
   
-  axiom produces_refl'2_spec : forall self : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0 . ([%#span47] inv'5 self)
-   -> ([%#span48] produces'1 self (empty'1 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'2_spec : forall self : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0 . ([%#span34] inv'5 self)
+   -> ([%#span35] produces'1 self (empty'1 : Seq'0.t_seq uint32) self)
   
-  predicate invariant'7 (self : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0))
+  predicate invariant'6 (self : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0))
     
    =
     [%#span4] true
   
-  predicate inv'7 (_x : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0))
+  predicate inv'6 (_x : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0))
     
   
-  axiom inv'7 : forall x : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) . inv'7 x
+  axiom inv'6 : forall x : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) . inv'6 x
   = (inv'5 ( * x) /\ inv'5 ( ^ x))
   
-  predicate invariant'6 (self : Seq'0.t_seq uint32) =
-    [%#span4] true
-  
-  axiom inv'6 : forall x : Seq'0.t_seq uint32 . inv'6 x = true
-  
-  use seq.Seq
-  
   predicate inv'3 (_x : uint32)
   
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span49] inv'3 v)
-   -> ([%#span52] inv'9 (singleton'0 v))
-  && ([%#span51] index_logic'2 (singleton'0 v) 0 = v) && ([%#span50] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span36] inv'3 v)
+   -> ([%#span38] index_logic'2 (singleton'0 v) 0 = v) && ([%#span37] len'1 (singleton'0 v) = 1)
   
   predicate inv'2 (_x : Iter'0.t_iter uint32)
   
   predicate next_precondition'0 (iter : Iter'0.t_iter uint32) (func : Closure'0.c03stditerators_counter_closure0) (produced : Seq'0.t_seq uint32)
     
    =
-    [%#span53] forall i : Iter'0.t_iter uint32 . forall e : uint32 . inv'2 i
+    [%#span39] forall i : Iter'0.t_iter uint32 . forall e : uint32 . inv'2 i
      -> inv'3 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq uint32) (v : uint32) : Seq'0.t_seq uint32 =
-    [%#span54] concat'0 self (singleton'0 v)
+    [%#span40] concat'0 self (singleton'0 v)
   
   predicate preservation'0 (iter : Iter'0.t_iter uint32) (func : Closure'0.c03stditerators_counter_closure0) =
-    [%#span55] forall i : Iter'0.t_iter uint32 . forall b : uint32 . forall f : borrowed Closure'0.c03stditerators_counter_closure0 . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
-     -> inv'11 b
-     -> inv'12 f
+    [%#span41] forall i : Iter'0.t_iter uint32 . forall b : uint32 . forall f : borrowed Closure'0.c03stditerators_counter_closure0 . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
+     -> inv'10 b
+     -> inv'11 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'9 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
      -> postcondition_mut'0 f (e1, new'0 s) b  -> precondition'0 ( ^ f) (e2, new'0 (push'0 s e1))
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   predicate inv'4 (_x : Closure'0.c03stditerators_counter_closure0)
   
   predicate preservation_inv'0 (iter : Iter'0.t_iter uint32) (func : Closure'0.c03stditerators_counter_closure0) (produced : Seq'0.t_seq uint32)
     
   
-  axiom preservation_inv'0_spec : forall iter : Iter'0.t_iter uint32, func : Closure'0.c03stditerators_counter_closure0, produced : Seq'0.t_seq uint32 . ([%#span56] inv'2 iter)
-   -> ([%#span57] inv'4 func)
-   -> ([%#span58] inv'9 produced)
-   -> ([%#span59] produced = (empty'0 : Seq'0.t_seq uint32)
+  axiom preservation_inv'0_spec : forall iter : Iter'0.t_iter uint32, func : Closure'0.c03stditerators_counter_closure0, produced : Seq'0.t_seq uint32 . ([%#span42] inv'2 iter)
+   -> ([%#span43] inv'4 func)
+   -> ([%#span44] produced = (empty'0 : Seq'0.t_seq uint32)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   function shallow_model'5 (self : borrowed (Iter'0.t_iter uint32)) : slice uint32 =
-    [%#span60] shallow_model'3 ( * self)
+    [%#span45] shallow_model'3 ( * self)
   
   predicate resolve'5 (self : borrowed (Iter'0.t_iter uint32)) =
-    [%#span61]  ^ self =  * self
+    [%#span46]  ^ self =  * self
   
   predicate completed'1 (self : borrowed (Iter'0.t_iter uint32)) =
-    [%#span62] resolve'5 self /\ shallow_model'4 (shallow_model'5 self) = (empty'1 : Seq'0.t_seq uint32)
+    [%#span47] resolve'5 self /\ shallow_model'4 (shallow_model'5 self) = (empty'1 : Seq'0.t_seq uint32)
   
   predicate reinitialize'0 (_1 : ()) =
-    [%#span63] forall func : Closure'0.c03stditerators_counter_closure0 . forall iter : borrowed (Iter'0.t_iter uint32) . inv'4 func
-     -> inv'10 iter
+    [%#span48] forall func : Closure'0.c03stditerators_counter_closure0 . forall iter : borrowed (Iter'0.t_iter uint32) . inv'4 func
+     -> inv'9 iter
      -> completed'1 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq uint32) /\ preservation'0 ( ^ iter) func
   
@@ -2788,21 +2470,19 @@ module C03StdIterators_Counter
   function produces_trans'1 (a : Iter'0.t_iter uint32) (ab : Seq'0.t_seq uint32) (b : Iter'0.t_iter uint32) (bc : Seq'0.t_seq uint32) (c : Iter'0.t_iter uint32) : ()
     
    =
-    [%#span69] ()
+    [%#span52] ()
   
-  axiom produces_trans'1_spec : forall a : Iter'0.t_iter uint32, ab : Seq'0.t_seq uint32, b : Iter'0.t_iter uint32, bc : Seq'0.t_seq uint32, c : Iter'0.t_iter uint32 . ([%#span64] produces'0 a ab b)
-   -> ([%#span65] produces'0 b bc c)
-   -> ([%#span66] inv'9 ab)  -> ([%#span67] inv'9 bc)  -> ([%#span68] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : Iter'0.t_iter uint32, ab : Seq'0.t_seq uint32, b : Iter'0.t_iter uint32, bc : Seq'0.t_seq uint32, c : Iter'0.t_iter uint32 . ([%#span49] produces'0 a ab b)
+   -> ([%#span50] produces'0 b bc c)  -> ([%#span51] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'1 (self : Iter'0.t_iter uint32) : () =
-    [%#span71] ()
+    [%#span54] ()
   
-  axiom produces_refl'1_spec : forall self : Iter'0.t_iter uint32 . [%#span70] produces'0 self (empty'0 : Seq'0.t_seq uint32) self
+  axiom produces_refl'1_spec : forall self : Iter'0.t_iter uint32 . [%#span53] produces'0 self (empty'0 : Seq'0.t_seq uint32) self
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span8] len'1 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'0 : Seq'0.t_seq uint32) = 0
   
   predicate invariant'3 (self : uint32) =
     [%#span4] true
@@ -2826,106 +2506,98 @@ module C03StdIterators_Counter
   
   axiom inv'0 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'1 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'1 : Seq'0.t_seq uint32) = 0
   
   function produces_trans'0 (a : Iter'0.t_iter uint32) (ab : Seq'0.t_seq uint32) (b : Iter'0.t_iter uint32) (bc : Seq'0.t_seq uint32) (c : Iter'0.t_iter uint32) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Iter'0.t_iter uint32, ab : Seq'0.t_seq uint32, b : Iter'0.t_iter uint32, bc : Seq'0.t_seq uint32, c : Iter'0.t_iter uint32 . ([%#span72] produces'0 a ab b)
-   -> ([%#span73] produces'0 b bc c)
-   -> ([%#span74] inv'2 a)
-   -> ([%#span75] inv'9 ab)
-   -> ([%#span76] inv'2 b)
-   -> ([%#span77] inv'9 bc)  -> ([%#span78] inv'2 c)  -> ([%#span79] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Iter'0.t_iter uint32, ab : Seq'0.t_seq uint32, b : Iter'0.t_iter uint32, bc : Seq'0.t_seq uint32, c : Iter'0.t_iter uint32 . ([%#span55] produces'0 a ab b)
+   -> ([%#span56] produces'0 b bc c)
+   -> ([%#span57] inv'2 a)
+   -> ([%#span58] inv'2 b)  -> ([%#span59] inv'2 c)  -> ([%#span60] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 (self : Iter'0.t_iter uint32) : ()
   
-  axiom produces_refl'0_spec : forall self : Iter'0.t_iter uint32 . ([%#span80] inv'2 self)
-   -> ([%#span81] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'0_spec : forall self : Iter'0.t_iter uint32 . ([%#span61] inv'2 self)
+   -> ([%#span62] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   predicate ext_eq'0 (self : Seq'0.t_seq uint32) (oth : Seq'0.t_seq uint32)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq uint32, oth : Seq'0.t_seq uint32 . ([%#span82] inv'6 self)
-   -> ([%#span83] inv'6 oth)
-   -> ([%#span85] len'0 self = len'0 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq uint32, oth : Seq'0.t_seq uint32 . ([%#span64] len'0 self = len'0 oth
   /\ (forall i : int . 0 <= i /\ i < len'0 self  -> index_logic'1 self i = index_logic'1 oth i)  -> ext_eq'0 self oth)
-  && ([%#span84] ext_eq'0 self oth  -> self = oth)
+  && ([%#span63] ext_eq'0 self oth  -> self = oth)
   
   predicate resolve'2 (self : uint32) =
-    [%#span86] true
+    [%#span65] true
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span87] index_logic'1 (shallow_model'0 self) ix
+    [%#span66] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span88] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span67] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate from_iter_post'0 (prod : Seq'0.t_seq uint32) (res : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span89] prod = shallow_model'0 res
+    [%#span68] prod = shallow_model'0 res
   
   predicate completed'0 (self : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0))
     
    =
-    [%#span90] deref'1 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced ( ^ self))
+    [%#span69] deref'1 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced ( ^ self))
     = (empty'0 : Seq'0.t_seq uint32)
     /\ completed'1 (Borrow.borrow_logic (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter ( * self)) (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func ( * self)
     = CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func ( ^ self)
   
   predicate resolve'6 (self : borrowed usize) =
-    [%#span61]  ^ self =  * self
+    [%#span46]  ^ self =  * self
   
   predicate resolve'4 [#"../03_std_iterators.rs" 48 12 48 91] (_1 : Closure'0.c03stditerators_counter_closure0) =
     resolve'6 (field_0'0 _1)
   
   predicate resolve'3 (self : Iter'0.t_iter uint32) =
-    [%#span86] true
+    [%#span65] true
   
   predicate resolve'1 (self : MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0)
     
    =
-    [%#span91] resolve'3 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter self)
+    [%#span70] resolve'3 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter self)
     /\ resolve'4 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self)
   
-  let rec collect'0 (self:MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) (return'  (ret:Vec'0.t_vec uint32 (Global'0.t_global)))= {[@expl:precondition] [%#span92] inv'5 self}
+  let rec collect'0 (self:MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) (return'  (ret:Vec'0.t_vec uint32 (Global'0.t_global)))= {[@expl:precondition] [%#span71] inv'5 self}
     any
-    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span94] inv'8 result}
-      {[%#span93] exists prod : Seq'0.t_seq uint32 . exists done' : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) . inv'6 prod
-      /\ inv'7 done'
+    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span73] inv'7 result}
+      {[%#span72] exists prod : Seq'0.t_seq uint32 . exists done' : borrowed (MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0) . inv'6 done'
       /\ resolve'1 ( ^ done') /\ completed'0 done' /\ produces'1 self prod ( * done') /\ from_iter_post'0 prod result}
       (! return' {result}) ]
     
   
-  let rec map_inv'0 (self:Iter'0.t_iter uint32) (func:Closure'0.c03stditerators_counter_closure0) (return'  (ret:MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0))= {[@expl:precondition] [%#span99] inv'4 func}
-    {[@expl:precondition] [%#span98] inv'2 self}
-    {[@expl:precondition] [%#span97] preservation'0 self func}
-    {[@expl:precondition] [%#span96] reinitialize'0 ()}
-    {[@expl:precondition] [%#span95] forall i2 : Iter'0.t_iter uint32 . forall e : uint32 . inv'2 i2
+  let rec map_inv'0 (self:Iter'0.t_iter uint32) (func:Closure'0.c03stditerators_counter_closure0) (return'  (ret:MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0))= {[@expl:precondition] [%#span78] inv'4 func}
+    {[@expl:precondition] [%#span77] inv'2 self}
+    {[@expl:precondition] [%#span76] preservation'0 self func}
+    {[@expl:precondition] [%#span75] reinitialize'0 ()}
+    {[@expl:precondition] [%#span74] forall i2 : Iter'0.t_iter uint32 . forall e : uint32 . inv'2 i2
      -> inv'3 e
      -> produces'0 self (singleton'0 e) i2  -> precondition'0 func (e, new'0 (empty'0 : Seq'0.t_seq uint32))}
     any
-    [ return' (result:MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0)-> {[%#span101] inv'5 result}
-      {[%#span100] result = MapInv'0.C_MapInv self func (new'0 (empty'0 : Seq'0.t_seq uint32))}
+    [ return' (result:MapInv'0.t_mapinv (Iter'0.t_iter uint32) uint32 Closure'0.c03stditerators_counter_closure0)-> {[%#span80] inv'5 result}
+      {[%#span79] result = MapInv'0.C_MapInv self func (new'0 (empty'0 : Seq'0.t_seq uint32))}
       (! return' {result}) ]
     
   
-  let rec iter'0 (self:slice uint32) (return'  (ret:Iter'0.t_iter uint32))= {[@expl:precondition] [%#span102] inv'1 self}
-    any [ return' (result:Iter'0.t_iter uint32)-> {[%#span103] shallow_model'3 result = self} (! return' {result}) ] 
+  let rec iter'0 (self:slice uint32) (return'  (ret:Iter'0.t_iter uint32))= {[@expl:precondition] [%#span81] inv'1 self}
+    any [ return' (result:Iter'0.t_iter uint32)-> {[%#span82] shallow_model'3 result = self} (! return' {result}) ] 
   
   function shallow_model'2 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32 =
-    [%#span32] shallow_model'0 self
+    [%#span22] shallow_model'0 self
   
-  let rec deref'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:slice uint32))= {[@expl:precondition] [%#span104] inv'0 self}
+  let rec deref'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:slice uint32))= {[@expl:precondition] [%#span83] inv'0 self}
     any
-    [ return' (result:slice uint32)-> {[%#span106] inv'1 result}
-      {[%#span105] shallow_model'1 result = shallow_model'2 self}
+    [ return' (result:slice uint32)-> {[%#span85] inv'1 result}
+      {[%#span84] shallow_model'1 result = shallow_model'2 self}
       (! return' {result}) ]
     
   
@@ -3020,82 +2692,64 @@ module C03StdIterators_SumRange
   
   let%span span10 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span14 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span15 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span16 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span17 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span18 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span19 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span20 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span23 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span28 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span30 = "" 0 0 0 0
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span31 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span32 = "" 0 0 0 0
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span33 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span34 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span36 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span37 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span37 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span38 = "" 0 0 0 0
   
   let%span span39 = "" 0 0 0 0
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
-  
-  let%span span41 = "" 0 0 0 0
-  
-  let%span span42 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span43 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span44 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span45 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span47 = "" 0 0 0 0
-  
-  let%span span48 = "" 0 0 0 0
-  
   use prelude.prelude.IntSize
   
   predicate invariant'4 (self : isize) =
@@ -3134,31 +2788,21 @@ module C03StdIterators_SumRange
   
   axiom inv'1 : forall x : Seq'0.t_seq isize . inv'1 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq isize) (x : int) : isize
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq isize) (_2 : int) : isize
   
   function len'0 (self : Seq'0.t_seq isize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq isize . ([%#span11] inv'1 self)  -> ([%#span12] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq isize . [%#span11] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq isize) (other : Seq'0.t_seq isize) : Seq'0.t_seq isize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq isize, other : Seq'0.t_seq isize . ([%#span13] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : Range'0.t_range isize)
   
@@ -3167,12 +2811,12 @@ module C03StdIterators_SumRange
   use prelude.prelude.IntSize
   
   function deep_model'0 (self : isize) : int =
-    [%#span18] IntSize.to_int self
+    [%#span14] IntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range isize) (visited : Seq'0.t_seq isize) (o : Range'0.t_range isize) =
-    [%#span19] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span15] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'0 visited > 0
@@ -3185,54 +2829,48 @@ module C03StdIterators_SumRange
   function produces_trans'0 (a : Range'0.t_range isize) (ab : Seq'0.t_seq isize) (b : Range'0.t_range isize) (bc : Seq'0.t_seq isize) (c : Range'0.t_range isize) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range isize, ab : Seq'0.t_seq isize, b : Range'0.t_range isize, bc : Seq'0.t_seq isize, c : Range'0.t_range isize . ([%#span20] produces'0 a ab b)
-   -> ([%#span21] produces'0 b bc c)
-   -> ([%#span22] inv'0 a)
-   -> ([%#span23] inv'1 ab)
-   -> ([%#span24] inv'0 b)
-   -> ([%#span25] inv'1 bc)  -> ([%#span26] inv'0 c)  -> ([%#span27] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range isize, ab : Seq'0.t_seq isize, b : Range'0.t_range isize, bc : Seq'0.t_seq isize, c : Range'0.t_range isize . ([%#span16] produces'0 a ab b)
+   -> ([%#span17] produces'0 b bc c)
+   -> ([%#span18] inv'0 a)
+   -> ([%#span19] inv'0 b)  -> ([%#span20] inv'0 c)  -> ([%#span21] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq isize = [%#span28] ()
+  constant empty'0 : Seq'0.t_seq isize
   
   function produces_refl'0 (self : Range'0.t_range isize) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range isize . ([%#span29] inv'0 self)
-   -> ([%#span30] produces'0 self (empty'0 : Seq'0.t_seq isize) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range isize . ([%#span22] inv'0 self)
+   -> ([%#span23] produces'0 self (empty'0 : Seq'0.t_seq isize) self)
   
   predicate invariant'0 (self : Range'0.t_range isize) =
     [%#span10] true
   
   axiom inv'0 : forall x : Range'0.t_range isize . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span32] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span31] len'0 (empty'0 : Seq'0.t_seq isize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span24] len'0 (empty'0 : Seq'0.t_seq isize) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   function singleton'0 (v : isize) : Seq'0.t_seq isize
   
-  axiom singleton'0_spec : forall v : isize . ([%#span33] inv'4 v)
-   -> ([%#span36] inv'1 (singleton'0 v))
-  && ([%#span35] index_logic'0 (singleton'0 v) 0 = v) && ([%#span34] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : isize . ([%#span25] inv'4 v)
+   -> ([%#span27] index_logic'0 (singleton'0 v) 0 = v) && ([%#span26] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Range'0.t_range isize)) =
-    [%#span37]  ^ self =  * self
+    [%#span28]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range isize)) =
-    [%#span38] resolve'0 self
+    [%#span29] resolve'0 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range isize)) (return'  (ret:Option'0.t_option isize))= {[@expl:precondition] [%#span39] inv'2 self}
+  let rec next'0 (self:borrowed (Range'0.t_range isize)) (return'  (ret:Option'0.t_option isize))= {[@expl:precondition] [%#span30] inv'2 self}
     any
-    [ return' (result:Option'0.t_option isize)-> {[%#span41] inv'3 result}
-      {[%#span40] match result with
+    [ return' (result:Option'0.t_option isize)-> {[%#span32] inv'3 result}
+      {[%#span31] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -3249,23 +2887,23 @@ module C03StdIterators_SumRange
   
   function new'1 (x : Seq'0.t_seq isize) : Snapshot'0.t_snapshot (Seq'0.t_seq isize)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq isize . ([%#span42] inv'1 x)  -> ([%#span43] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq isize . ([%#span33] inv'1 x)  -> ([%#span34] deref'0 (new'1 x) = x)
   
   function new'0 (x : Range'0.t_range isize) : Snapshot'0.t_snapshot (Range'0.t_range isize)
   
-  axiom new'0_spec : forall x : Range'0.t_range isize . ([%#span42] inv'0 x)  -> ([%#span43] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Range'0.t_range isize . ([%#span33] inv'0 x)  -> ([%#span34] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range isize) (res : Range'0.t_range isize) =
-    [%#span44] self = res
+    [%#span35] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range isize) =
-    [%#span45] true
+    [%#span36] true
   
-  let rec into_iter'0 (self:Range'0.t_range isize) (return'  (ret:Range'0.t_range isize))= {[@expl:precondition] [%#span47] inv'0 self}
-    {[@expl:precondition] [%#span46] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range isize) (return'  (ret:Range'0.t_range isize))= {[@expl:precondition] [%#span38] inv'0 self}
+    {[@expl:precondition] [%#span37] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range isize)-> {[%#span48] inv'0 result}
-      {[%#span46] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range isize)-> {[%#span39] inv'0 result}
+      {[%#span37] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
@@ -3364,119 +3002,97 @@ module C03StdIterators_EnumerateRange
   
   let%span span6 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span11 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span12 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span13 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span14 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span15 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span16 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span17 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span18 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span19 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span20 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 62 8 67 9
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 77 15 77 32
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span23 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 78 15 78 32
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span24 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 22 80 23
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span25 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 52 80 53
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span26 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 82 80 83
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span27 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 79 14 79 42
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span28 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 73 21 73 25
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 62 8 67 9
+  let%span span29 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 72 14 72 45
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 77 15 77 32
+  let%span span30 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 78 15 78 32
+  let%span span31 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 22 80 23
+  let%span span32 = "" 0 0 0 0
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 31 80 33
+  let%span span33 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 52 80 53
+  let%span span34 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 33 12 33 33
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 61 80 63
+  let%span span35 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 80 82 80 83
+  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 79 14 79 42
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 73 21 73 25
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 72 14 72 45
+  let%span span39 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 56 8 56 115
   
-  let%span span40 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span40 = "" 0 0 0 0
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span41 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
   let%span span42 = "" 0 0 0 0
   
-  let%span span43 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span43 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 33 12 33 33
+  let%span span44 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span45 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
+  let%span span45 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span46 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span47 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span48 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span49 = "" 0 0 0 0
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter/enumerate.rs" 56 8 56 115
+  let%span span50 = "" 0 0 0 0
   
   let%span span51 = "" 0 0 0 0
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
-  
-  let%span span53 = "" 0 0 0 0
-  
-  let%span span54 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
-  
-  let%span span55 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span56 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span58 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span59 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span60 = "" 0 0 0 0
-  
-  let%span span61 = "" 0 0 0 0
-  
-  let%span span62 = "" 0 0 0 0
-  
-  let%span span63 = "" 0 0 0 0
+  let%span span52 = "" 0 0 0 0
   
   use prelude.prelude.UIntSize
   
@@ -3484,65 +3100,52 @@ module C03StdIterators_EnumerateRange
   
   use prelude.prelude.Borrow
   
-  predicate invariant'7 (self : borrowed (Range'0.t_range usize)) =
+  predicate invariant'6 (self : borrowed (Range'0.t_range usize)) =
     [%#span6] true
   
-  predicate inv'7 (_x : borrowed (Range'0.t_range usize))
+  predicate inv'6 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'7 : forall x : borrowed (Range'0.t_range usize) . inv'7 x = true
+  axiom inv'6 : forall x : borrowed (Range'0.t_range usize) . inv'6 x = true
   
-  predicate invariant'6 (self : (usize, usize)) =
+  predicate invariant'5 (self : (usize, usize)) =
     [%#span6] true
   
-  predicate inv'6 (_x : (usize, usize))
+  predicate inv'5 (_x : (usize, usize))
   
-  axiom inv'6 : forall x : (usize, usize) . inv'6 x = true
+  axiom inv'5 : forall x : (usize, usize) . inv'5 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'5 (self : Option'0.t_option (usize, usize)) =
+  predicate invariant'4 (self : Option'0.t_option (usize, usize)) =
     [%#span6] true
   
-  predicate inv'5 (_x : Option'0.t_option (usize, usize))
+  predicate inv'4 (_x : Option'0.t_option (usize, usize))
   
-  axiom inv'5 : forall x : Option'0.t_option (usize, usize) . inv'5 x = true
+  axiom inv'4 : forall x : Option'0.t_option (usize, usize) . inv'4 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'4 (_x : Seq'0.t_seq usize)
-  
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span7] inv'4 self)  -> ([%#span8] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq usize = [%#span9] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span7] len'1 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span11] ()
+  constant empty'1 : Seq'0.t_seq usize
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span10] len'1 (empty'1 : Seq'0.t_seq usize) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span8] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function concat'1 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span12] inv'4 self)
-   -> ([%#span13] inv'4 other)
-   -> ([%#span16] inv'4 (concat'1 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span10] forall i : int . 0 <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'2 (concat'1 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span14] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span9] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   predicate inv'2 (_x : Range'0.t_range usize)
   
@@ -3551,12 +3154,12 @@ module C03StdIterators_EnumerateRange
   use prelude.prelude.UIntSize
   
   function deep_model'0 (self : usize) : int =
-    [%#span17] UIntSize.to_int self
+    [%#span11] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'1 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span18] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span12] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'1 visited > 0
@@ -3569,22 +3172,15 @@ module C03StdIterators_EnumerateRange
   function produces_trans'1 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span19] produces'1 a ab b)
-   -> ([%#span20] produces'1 b bc c)
-   -> ([%#span21] inv'2 a)
-   -> ([%#span22] inv'4 ab)
-   -> ([%#span23] inv'2 b)
-   -> ([%#span24] inv'4 bc)  -> ([%#span25] inv'2 c)  -> ([%#span26] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span13] produces'1 a ab b)
+   -> ([%#span14] produces'1 b bc c)
+   -> ([%#span15] inv'2 a)
+   -> ([%#span16] inv'2 b)  -> ([%#span17] inv'2 c)  -> ([%#span18] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'1 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span27] inv'2 self)
-   -> ([%#span28] produces'1 self (empty'1 : Seq'0.t_seq usize) self)
-  
-  predicate invariant'4 (self : Seq'0.t_seq usize) =
-    [%#span6] true
-  
-  axiom inv'4 : forall x : Seq'0.t_seq usize . inv'4 x = true
+  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span19] inv'2 self)
+   -> ([%#span20] produces'1 self (empty'1 : Seq'0.t_seq usize) self)
   
   predicate invariant'3 (self : Seq'0.t_seq (usize, usize)) =
     [%#span6] true
@@ -3610,28 +3206,21 @@ module C03StdIterators_EnumerateRange
   axiom inv'1 : forall x : borrowed (Enumerate'0.t_enumerate (Range'0.t_range usize)) . inv'1 x
   = (inv'0 ( * x) /\ inv'0 ( ^ x))
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (usize, usize)) (x : int) : (usize, usize)
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq (usize, usize)) (_2 : int) : (usize, usize)
   
   function len'0 (self : Seq'0.t_seq (usize, usize)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (usize, usize) . ([%#span7] inv'3 self)  -> ([%#span8] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (usize, usize) . [%#span7] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq (usize, usize)) (other : Seq'0.t_seq (usize, usize)) : Seq'0.t_seq (usize, usize)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, usize), other : Seq'0.t_seq (usize, usize) . ([%#span12] inv'3 self)
-   -> ([%#span13] inv'3 other)
-   -> ([%#span16] inv'3 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, usize), other : Seq'0.t_seq (usize, usize) . ([%#span10] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function iter'0 (self : Enumerate'0.t_enumerate (Range'0.t_range usize)) : Range'0.t_range usize
   
@@ -3640,9 +3229,8 @@ module C03StdIterators_EnumerateRange
   predicate produces'0 (self : Enumerate'0.t_enumerate (Range'0.t_range usize)) (visited : Seq'0.t_seq (usize, usize)) (o : Enumerate'0.t_enumerate (Range'0.t_range usize))
     
    =
-    [%#span29] len'0 visited = n'0 o - n'0 self
-    /\ (exists s : Seq'0.t_seq usize . inv'4 s
-    /\ produces'1 (iter'0 self) s (iter'0 o)
+    [%#span21] len'0 visited = n'0 o - n'0 self
+    /\ (exists s : Seq'0.t_seq usize . produces'1 (iter'0 self) s (iter'0 o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s
      -> UIntSize.to_int (let (a, _) = index_logic'1 visited i in a) = n'0 self + i
@@ -3651,29 +3239,27 @@ module C03StdIterators_EnumerateRange
   function produces_trans'0 (a : Enumerate'0.t_enumerate (Range'0.t_range usize)) (ab : Seq'0.t_seq (usize, usize)) (b : Enumerate'0.t_enumerate (Range'0.t_range usize)) (bc : Seq'0.t_seq (usize, usize)) (c : Enumerate'0.t_enumerate (Range'0.t_range usize)) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Enumerate'0.t_enumerate (Range'0.t_range usize), ab : Seq'0.t_seq (usize, usize), b : Enumerate'0.t_enumerate (Range'0.t_range usize), bc : Seq'0.t_seq (usize, usize), c : Enumerate'0.t_enumerate (Range'0.t_range usize) . ([%#span30] produces'0 a ab b)
-   -> ([%#span31] produces'0 b bc c)
-   -> ([%#span32] inv'0 a)
-   -> ([%#span33] inv'3 ab)
-   -> ([%#span34] inv'0 b)
-   -> ([%#span35] inv'3 bc)  -> ([%#span36] inv'0 c)  -> ([%#span37] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Enumerate'0.t_enumerate (Range'0.t_range usize), ab : Seq'0.t_seq (usize, usize), b : Enumerate'0.t_enumerate (Range'0.t_range usize), bc : Seq'0.t_seq (usize, usize), c : Enumerate'0.t_enumerate (Range'0.t_range usize) . ([%#span22] produces'0 a ab b)
+   -> ([%#span23] produces'0 b bc c)
+   -> ([%#span24] inv'0 a)
+   -> ([%#span25] inv'0 b)  -> ([%#span26] inv'0 c)  -> ([%#span27] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq (usize, usize) = [%#span9] ()
+  constant empty'0 : Seq'0.t_seq (usize, usize)
   
   function produces_refl'0 (self : Enumerate'0.t_enumerate (Range'0.t_range usize)) : ()
   
-  axiom produces_refl'0_spec : forall self : Enumerate'0.t_enumerate (Range'0.t_range usize) . ([%#span38] inv'0 self)
-   -> ([%#span39] produces'0 self (empty'0 : Seq'0.t_seq (usize, usize)) self)
+  axiom produces_refl'0_spec : forall self : Enumerate'0.t_enumerate (Range'0.t_range usize) . ([%#span28] inv'0 self)
+   -> ([%#span29] produces'0 self (empty'0 : Seq'0.t_seq (usize, usize)) self)
   
   predicate resolve'5 (self : borrowed (Range'0.t_range usize)) =
-    [%#span40]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate completed'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span41] resolve'5 self
+    [%#span31] resolve'5 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  constant max'0 : usize = [%#span42] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span32] (18446744073709551615 : usize)
   
   predicate invariant'0 (self : Enumerate'0.t_enumerate (Range'0.t_range usize))
   
@@ -3683,46 +3269,42 @@ module C03StdIterators_EnumerateRange
     | Enumerate'0.C_Enumerate iter count -> true
     end)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span11] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq (usize, usize)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq (usize, usize)) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'4 (self : Range'0.t_range usize) =
-    [%#span43] true
+    [%#span33] true
   
   predicate resolve'2 (self : Enumerate'0.t_enumerate (Range'0.t_range usize)) =
-    [%#span44] resolve'4 (iter'0 self)
+    [%#span34] resolve'4 (iter'0 self)
   
   predicate resolve'3 (self : usize) =
-    [%#span43] true
+    [%#span33] true
   
   predicate resolve'1 (self : (usize, usize)) =
-    [%#span45] resolve'3 (let (a, _) = self in a) /\ resolve'3 (let (_, a) = self in a)
-  
-  use seq.Seq
+    [%#span35] resolve'3 (let (a, _) = self in a) /\ resolve'3 (let (_, a) = self in a)
   
   function singleton'0 (v : (usize, usize)) : Seq'0.t_seq (usize, usize)
   
-  axiom singleton'0_spec : forall v : (usize, usize) . ([%#span46] inv'6 v)
-   -> ([%#span49] inv'3 (singleton'0 v))
-  && ([%#span48] index_logic'1 (singleton'0 v) 0 = v) && ([%#span47] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (usize, usize) . ([%#span36] inv'5 v)
+   -> ([%#span38] index_logic'1 (singleton'0 v) 0 = v) && ([%#span37] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Enumerate'0.t_enumerate (Range'0.t_range usize))) =
-    [%#span40]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Enumerate'0.t_enumerate (Range'0.t_range usize))) =
-    [%#span50] exists inner : borrowed (Range'0.t_range usize) . inv'7 inner
+    [%#span39] exists inner : borrowed (Range'0.t_range usize) . inv'6 inner
     /\  * inner = iter'0 ( * self) /\  ^ inner = iter'0 ( ^ self) /\ completed'1 inner
   
-  let rec next'0 (self:borrowed (Enumerate'0.t_enumerate (Range'0.t_range usize))) (return'  (ret:Option'0.t_option (usize, usize)))= {[@expl:precondition] [%#span51] inv'1 self}
+  let rec next'0 (self:borrowed (Enumerate'0.t_enumerate (Range'0.t_range usize))) (return'  (ret:Option'0.t_option (usize, usize)))= {[@expl:precondition] [%#span40] inv'1 self}
     any
-    [ return' (result:Option'0.t_option (usize, usize))-> {[%#span53] inv'5 result}
-      {[%#span52] match result with
+    [ return' (result:Option'0.t_option (usize, usize))-> {[%#span42] inv'4 result}
+      {[%#span41] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -3734,7 +3316,7 @@ module C03StdIterators_EnumerateRange
   function index_logic'0 [@inline:trivial] (self : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, usize))) (ix : int) : (usize, usize)
     
    =
-    [%#span54] index_logic'1 (deref'0 self) ix
+    [%#span43] index_logic'1 (deref'0 self) ix
   
   function inner'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, usize))) : Seq'0.t_seq (usize, usize)
   
@@ -3746,34 +3328,34 @@ module C03StdIterators_EnumerateRange
   
   function new'1 (x : Seq'0.t_seq (usize, usize)) : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, usize))
   
-  axiom new'1_spec : forall x : Seq'0.t_seq (usize, usize) . ([%#span55] inv'3 x)  -> ([%#span56] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq (usize, usize) . ([%#span44] inv'3 x)  -> ([%#span45] deref'0 (new'1 x) = x)
   
   function new'0 (x : Enumerate'0.t_enumerate (Range'0.t_range usize)) : Snapshot'0.t_snapshot (Enumerate'0.t_enumerate (Range'0.t_range usize))
     
   
-  axiom new'0_spec : forall x : Enumerate'0.t_enumerate (Range'0.t_range usize) . ([%#span55] inv'0 x)
-   -> ([%#span56] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Enumerate'0.t_enumerate (Range'0.t_range usize) . ([%#span44] inv'0 x)
+   -> ([%#span45] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Enumerate'0.t_enumerate (Range'0.t_range usize)) (res : Enumerate'0.t_enumerate (Range'0.t_range usize))
     
    =
-    [%#span57] self = res
+    [%#span46] self = res
   
   predicate into_iter_pre'0 (self : Enumerate'0.t_enumerate (Range'0.t_range usize)) =
-    [%#span58] true
+    [%#span47] true
   
-  let rec into_iter'0 (self:Enumerate'0.t_enumerate (Range'0.t_range usize)) (return'  (ret:Enumerate'0.t_enumerate (Range'0.t_range usize)))= {[@expl:precondition] [%#span60] inv'0 self}
-    {[@expl:precondition] [%#span59] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Enumerate'0.t_enumerate (Range'0.t_range usize)) (return'  (ret:Enumerate'0.t_enumerate (Range'0.t_range usize)))= {[@expl:precondition] [%#span49] inv'0 self}
+    {[@expl:precondition] [%#span48] into_iter_pre'0 self}
     any
-    [ return' (result:Enumerate'0.t_enumerate (Range'0.t_range usize))-> {[%#span61] inv'0 result}
-      {[%#span59] into_iter_post'0 self result}
+    [ return' (result:Enumerate'0.t_enumerate (Range'0.t_range usize))-> {[%#span50] inv'0 result}
+      {[%#span48] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec enumerate'0 (self:Range'0.t_range usize) (return'  (ret:Enumerate'0.t_enumerate (Range'0.t_range usize)))= {[@expl:precondition] [%#span62] inv'2 self}
+  let rec enumerate'0 (self:Range'0.t_range usize) (return'  (ret:Enumerate'0.t_enumerate (Range'0.t_range usize)))= {[@expl:precondition] [%#span51] inv'2 self}
     any
-    [ return' (result:Enumerate'0.t_enumerate (Range'0.t_range usize))-> {[%#span63] inv'0 result}
-      {[%#span59] iter'0 result = self /\ n'0 result = 0}
+    [ return' (result:Enumerate'0.t_enumerate (Range'0.t_range usize))-> {[%#span52] inv'0 result}
+      {[%#span48] iter'0 result = self /\ n'0 result = 0}
       (! return' {result}) ]
     
   
@@ -3927,252 +3509,202 @@ module C03StdIterators_MyReverse
   
   let%span span20 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span24 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span25 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span26 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span27 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span28 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span31 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span32 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span33 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 44 8 50 9
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span36 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 60 15 60 32
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span37 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 61 15 61 32
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span38 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 22 63 23
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span39 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 52 63 53
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span40 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 82 63 83
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span41 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 62 14 62 42
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 56 21 56 25
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 44 8 50 9
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 55 14 55 45
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 60 15 60 32
+  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 61 15 61 32
+  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 22 63 23
+  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 114 14 114 40
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 31 63 33
+  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 100
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 52 63 53
+  let%span span48 = "" 0 0 0 0
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 61 63 63
+  let%span span49 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 63 82 63 83
+  let%span span50 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span51 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 62 14 62 42
+  let%span span51 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 56 21 56 25
+  let%span span52 = "../../../../../creusot-contracts/src/logic/ops.rs" 54 8 54 32
   
-  let%span span53 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 55 14 55 45
+  let%span span53 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 135 8 142 110
   
-  let%span span55 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span55 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span56 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span56 = "../../../../../creusot-contracts/src/std/slice.rs" 235 19 235 35
   
-  let%span span57 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span57 = "../../../../../creusot-contracts/src/std/slice.rs" 236 19 236 35
   
-  let%span span58 = "../../../../../creusot-contracts/src/logic/seq2.rs" 115 19 115 23
+  let%span span58 = "" 0 0 0 0
   
-  let%span span59 = "../../../../../creusot-contracts/src/logic/seq2.rs" 113 14 113 40
+  let%span span59 = "../../../../../creusot-contracts/src/std/slice.rs" 237 8 237 52
   
-  let%span span60 = "../../../../../creusot-contracts/src/logic/seq2.rs" 114 4 114 100
+  let%span span60 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span61 = "../../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 32
+  let%span span61 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
   
-  let%span span62 = "" 0 0 0 0
+  let%span span62 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span63 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span63 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span64 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span64 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span65 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span65 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span66 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span66 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 31 8 38 9
   
-  let%span span67 = "../../../../../creusot-contracts/src/logic/ops.rs" 54 8 54 32
+  let%span span67 = "" 0 0 0 0
   
-  let%span span68 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span68 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span69 = "../../../../../creusot-contracts/src/logic/seq2.rs" 134 8 141 110
+  let%span span69 = "" 0 0 0 0
   
-  let%span span70 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span70 = "../03_std_iterators.rs" 88 4 90 5
   
-  let%span span71 = "../../../../../creusot-contracts/src/std/slice.rs" 235 19 235 35
+  let%span span71 = "../03_std_iterators.rs" 81 4 83 5
   
-  let%span span72 = "../../../../../creusot-contracts/src/std/slice.rs" 236 19 236 35
+  let%span span72 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span73 = "" 0 0 0 0
+  let%span span73 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span74 = "../../../../../creusot-contracts/src/std/slice.rs" 237 8 237 52
+  let%span span74 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span75 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span75 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span76 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
+  let%span span76 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span77 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span77 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span78 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span78 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span79 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span79 = "" 0 0 0 0
   
-  let%span span80 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span80 = "" 0 0 0 0
   
-  let%span span81 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span81 = "../../../../../creusot-contracts/src/std/iter.rs" 129 27 129 48
   
-  let%span span82 = "../../../../../creusot-contracts/src/std/iter/zip.rs" 31 8 38 9
+  let%span span82 = "" 0 0 0 0
   
   let%span span83 = "" 0 0 0 0
   
-  let%span span84 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span84 = "../../../../../creusot-contracts/src/std/iter.rs" 131 26 131 62
   
   let%span span85 = "" 0 0 0 0
   
-  let%span span86 = "../03_std_iterators.rs" 88 4 90 5
-  
-  let%span span87 = "../03_std_iterators.rs" 81 4 83 5
-  
-  let%span span88 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span89 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
+  let%span span86 = "" 0 0 0 0
   
-  let%span span90 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span91 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span92 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span93 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span94 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span95 = "" 0 0 0 0
-  
-  let%span span96 = "" 0 0 0 0
-  
-  let%span span97 = "../../../../../creusot-contracts/src/std/iter.rs" 129 27 129 48
-  
-  let%span span98 = "" 0 0 0 0
-  
-  let%span span99 = "" 0 0 0 0
-  
-  let%span span100 = "../../../../../creusot-contracts/src/std/iter.rs" 131 26 131 62
-  
-  let%span span101 = "" 0 0 0 0
-  
-  let%span span102 = "" 0 0 0 0
-  
-  let%span span103 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span87 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
   use prelude.prelude.UIntSize
   
-  predicate invariant'12 (self : usize) =
+  predicate invariant'10 (self : usize) =
     [%#span20] true
   
-  predicate inv'12 (_x : usize)
+  predicate inv'10 (_x : usize)
   
-  axiom inv'12 : forall x : usize . inv'12 x = true
+  axiom inv'10 : forall x : usize . inv'10 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'11 (self : borrowed (Range'0.t_range usize)) =
+  predicate invariant'9 (self : borrowed (Range'0.t_range usize)) =
     [%#span20] true
   
-  predicate inv'11 (_x : borrowed (Range'0.t_range usize))
+  predicate inv'9 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'11 : forall x : borrowed (Range'0.t_range usize) . inv'11 x = true
+  axiom inv'9 : forall x : borrowed (Range'0.t_range usize) . inv'9 x = true
   
-  predicate invariant'10 (self : (usize, usize)) =
+  predicate invariant'8 (self : (usize, usize)) =
     [%#span20] true
   
-  predicate inv'10 (_x : (usize, usize))
+  predicate inv'8 (_x : (usize, usize))
   
-  axiom inv'10 : forall x : (usize, usize) . inv'10 x = true
+  axiom inv'8 : forall x : (usize, usize) . inv'8 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'9 (self : Option'0.t_option (usize, usize)) =
+  predicate invariant'7 (self : Option'0.t_option (usize, usize)) =
     [%#span20] true
   
-  predicate inv'9 (_x : Option'0.t_option (usize, usize))
+  predicate inv'7 (_x : Option'0.t_option (usize, usize))
   
-  axiom inv'9 : forall x : Option'0.t_option (usize, usize) . inv'9 x = true
+  axiom inv'7 : forall x : Option'0.t_option (usize, usize) . inv'7 x = true
   
   use Core_Iter_Adapters_Zip_Zip_Type as Zip'0
   
-  predicate invariant'8 (self : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))) =
+  predicate invariant'6 (self : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))) =
     [%#span20] true
   
-  predicate inv'8 (_x : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)))
+  predicate inv'6 (_x : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)))
   
-  axiom inv'8 : forall x : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) . inv'8 x = true
+  axiom inv'6 : forall x : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) . inv'6 x = true
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'7 (self : Seq'0.t_seq t)
-  
-  predicate inv'7 (_x : Seq'0.t_seq t)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq t . inv'7 x = true
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'3 (self : Seq'0.t_seq usize) (x : int) : usize
-  
-  use seq.Seq
-  
-  predicate inv'6 (_x : Seq'0.t_seq usize)
+  function index_logic'3 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function len'3 (self : Seq'0.t_seq usize) : int
   
-  axiom len'3_spec : forall self : Seq'0.t_seq usize . ([%#span21] inv'6 self)  -> ([%#span22] len'3 self >= 0)
+  axiom len'3_spec : forall self : Seq'0.t_seq usize . [%#span21] len'3 self >= 0
   
   function concat'1 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span23] inv'6 self)
-   -> ([%#span24] inv'6 other)
-   -> ([%#span27] inv'6 (concat'1 self other))
-  && ([%#span26] forall i : int . 0 <= i /\ i < len'3 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span23] forall i : int . 0 <= i
+  /\ i < len'3 (concat'1 self other)
    -> index_logic'3 (concat'1 self other) i
   = (if i < len'3 self then index_logic'3 self i else index_logic'3 other (i - len'3 self)))
-  && ([%#span25] len'3 (concat'1 self other) = len'3 self + len'3 other)
+  && ([%#span22] len'3 (concat'1 self other) = len'3 self + len'3 other)
   
   predicate inv'4 (_x : Range'0.t_range usize)
   
@@ -4181,12 +3713,12 @@ module C03StdIterators_MyReverse
   use prelude.prelude.UIntSize
   
   function deep_model'0 (self : usize) : int =
-    [%#span28] UIntSize.to_int self
+    [%#span24] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'1 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span29] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span25] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'3 visited > 0
@@ -4199,29 +3731,21 @@ module C03StdIterators_MyReverse
   function produces_trans'1 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span30] produces'1 a ab b)
-   -> ([%#span31] produces'1 b bc c)
-   -> ([%#span32] inv'4 a)
-   -> ([%#span33] inv'6 ab)
-   -> ([%#span34] inv'4 b)
-   -> ([%#span35] inv'6 bc)  -> ([%#span36] inv'4 c)  -> ([%#span37] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span26] produces'1 a ab b)
+   -> ([%#span27] produces'1 b bc c)
+   -> ([%#span28] inv'4 a)
+   -> ([%#span29] inv'4 b)  -> ([%#span30] inv'4 c)  -> ([%#span31] produces'1 a (concat'1 ab bc) c)
   
-  constant empty'2 : Seq'0.t_seq usize = [%#span38] ()
+  constant empty'2 : Seq'0.t_seq usize
   
   function produces_refl'1 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span39] inv'4 self)
-   -> ([%#span40] produces'1 self (empty'2 : Seq'0.t_seq usize) self)
+  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span32] inv'4 self)
+   -> ([%#span33] produces'1 self (empty'2 : Seq'0.t_seq usize) self)
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span42] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span41] len'3 (empty'2 : Seq'0.t_seq usize) = 0
-  
-  predicate invariant'6 (self : Seq'0.t_seq usize) =
-    [%#span20] true
-  
-  axiom inv'6 : forall x : Seq'0.t_seq usize . inv'6 x = true
+  axiom empty_len'2_spec : forall _1 : () . [%#span34] len'3 (empty'2 : Seq'0.t_seq usize) = 0
   
   predicate invariant'5 (self : Seq'0.t_seq (usize, usize)) =
     [%#span20] true
@@ -4255,41 +3779,31 @@ module C03StdIterators_MyReverse
   
   axiom inv'1 : forall x : slice t . inv'1 x = true
   
-  use seq.Seq
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span21] inv'7 self)  -> ([%#span22] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span38] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span42] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span21] len'1 self >= 0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span41] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  constant empty'1 : Seq'0.t_seq t
   
-  use seq.Seq
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span34] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
-  function index_logic'2 (self : Seq'0.t_seq (usize, usize)) (x : int) : (usize, usize)
-  
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq (usize, usize)) (_2 : int) : (usize, usize)
   
   function len'2 (self : Seq'0.t_seq (usize, usize)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (usize, usize) . ([%#span21] inv'5 self)  -> ([%#span22] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (usize, usize) . [%#span21] len'2 self >= 0
   
   function concat'0 (self : Seq'0.t_seq (usize, usize)) (other : Seq'0.t_seq (usize, usize)) : Seq'0.t_seq (usize, usize)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, usize), other : Seq'0.t_seq (usize, usize) . ([%#span23] inv'5 self)
-   -> ([%#span24] inv'5 other)
-   -> ([%#span27] inv'5 (concat'0 self other))
-  && ([%#span26] forall i : int . 0 <= i /\ i < len'2 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, usize), other : Seq'0.t_seq (usize, usize) . ([%#span23] forall i : int . 0
+  <= i
+  /\ i < len'2 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'2 self then index_logic'2 self i else index_logic'2 other (i - len'2 self)))
-  && ([%#span25] len'2 (concat'0 self other) = len'2 self + len'2 other)
+  && ([%#span22] len'2 (concat'0 self other) = len'2 self + len'2 other)
   
   predicate inv'0 (_x : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))
   
@@ -4300,9 +3814,7 @@ module C03StdIterators_MyReverse
   predicate produces'0 (self : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) (visited : Seq'0.t_seq (usize, usize)) (o : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))
     
    =
-    [%#span43] exists p2 : Seq'0.t_seq usize . exists p1 : Seq'0.t_seq usize . inv'6 p2
-    /\ inv'6 p1
-    /\ len'3 p1 = len'3 p2
+    [%#span35] exists p2 : Seq'0.t_seq usize . exists p1 : Seq'0.t_seq usize . len'3 p1 = len'3 p2
     /\ len'3 p2 = len'2 visited
     /\ (forall i : int . 0 <= i /\ i < len'2 visited
      -> index_logic'2 visited i = (index_logic'3 p1 i, index_logic'3 p2 i))
@@ -4311,77 +3823,63 @@ module C03StdIterators_MyReverse
   function produces_trans'0 (a : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) (ab : Seq'0.t_seq (usize, usize)) (b : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) (bc : Seq'0.t_seq (usize, usize)) (c : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize), ab : Seq'0.t_seq (usize, usize), b : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize), bc : Seq'0.t_seq (usize, usize), c : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize) . ([%#span44] produces'0 a ab b)
-   -> ([%#span45] produces'0 b bc c)
-   -> ([%#span46] inv'0 a)
-   -> ([%#span47] inv'5 ab)
-   -> ([%#span48] inv'0 b)
-   -> ([%#span49] inv'5 bc)  -> ([%#span50] inv'0 c)  -> ([%#span51] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize), ab : Seq'0.t_seq (usize, usize), b : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize), bc : Seq'0.t_seq (usize, usize), c : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize) . ([%#span36] produces'0 a ab b)
+   -> ([%#span37] produces'0 b bc c)
+   -> ([%#span38] inv'0 a)
+   -> ([%#span39] inv'0 b)  -> ([%#span40] inv'0 c)  -> ([%#span41] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq (usize, usize) = [%#span38] ()
+  constant empty'0 : Seq'0.t_seq (usize, usize)
   
   function produces_refl'0 (self : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) : ()
   
-  axiom produces_refl'0_spec : forall self : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize) . ([%#span52] inv'0 self)
-   -> ([%#span53] produces'0 self (empty'0 : Seq'0.t_seq (usize, usize)) self)
+  axiom produces_refl'0_spec : forall self : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize) . ([%#span42] inv'0 self)
+   -> ([%#span43] produces'0 self (empty'0 : Seq'0.t_seq (usize, usize)) self)
   
   predicate invariant'0 (self : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) =
     [%#span20] true
   
   axiom inv'0 : forall x : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize) . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span42] ()
-  
-  axiom empty_len'0_spec : forall _1 : () . [%#span41] len'2 (empty'0 : Seq'0.t_seq (usize, usize)) = 0
-  
-  use seq.Seq
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span34] len'2 (empty'0 : Seq'0.t_seq (usize, usize)) = 0
   
-  function index_logic'4 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'4 (self : Seq'0.t_seq t) (_2 : int) : t
   
   predicate ext_eq'0 (self : Seq'0.t_seq t) (oth : Seq'0.t_seq t)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span54] inv'7 self)
-   -> ([%#span55] inv'7 oth)
-   -> ([%#span57] len'1 self = len'1 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span45] len'1 self = len'1 oth
   /\ (forall i : int . 0 <= i /\ i < len'1 self  -> index_logic'4 self i = index_logic'4 oth i)  -> ext_eq'0 self oth)
-  && ([%#span56] ext_eq'0 self oth  -> self = oth)
-  
-  use seq.Reverse
+  && ([%#span44] ext_eq'0 self oth  -> self = oth)
   
   function reverse'0 (self : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom reverse'0_spec : forall self : Seq'0.t_seq t . ([%#span58] inv'7 self)
-   -> ([%#span61] inv'7 (reverse'0 self))
-  && ([%#span60] forall i : int . 0 <= i /\ i < len'1 (reverse'0 self)
+  axiom reverse'0_spec : forall self : Seq'0.t_seq t . ([%#span47] forall i : int . 0 <= i /\ i < len'1 (reverse'0 self)
    -> index_logic'4 (reverse'0 self) i = index_logic'4 self (len'1 self - 1 - i))
-  && ([%#span59] len'1 (reverse'0 self) = len'1 self)
+  && ([%#span46] len'1 (reverse'0 self) = len'1 self)
   
-  constant max'0 : usize = [%#span62] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span48] (18446744073709551615 : usize)
   
   function shallow_model'2 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : slice t . ([%#span63] inv'1 self)
-   -> ([%#span65] inv'7 (shallow_model'2 self))
-  && ([%#span64] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : slice t . ([%#span49] inv'1 self)
+   -> ([%#span50] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'3 (self : borrowed (slice t)) =
-    [%#span66]  ^ self =  * self
+    [%#span51]  ^ self =  * self
   
   function index_logic'1 [@inline:trivial] (self : slice t) (ix : usize) : t =
-    [%#span67] index_logic'4 (shallow_model'2 self) (UIntSize.to_int ix)
+    [%#span52] index_logic'4 (shallow_model'2 self) (UIntSize.to_int ix)
   
   function index_logic'0 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span68] index_logic'4 (shallow_model'2 self) ix
+    [%#span53] index_logic'4 (shallow_model'2 self) ix
   
   predicate exchange'0 (self : Seq'0.t_seq t) (oth : Seq'0.t_seq t) (i : int) (j : int) =
-    [%#span69] len'1 self = len'1 oth
+    [%#span54] len'1 self = len'1 oth
     /\ 0 <= i
     /\ i < len'1 self
     /\ 0 <= j
@@ -4391,63 +3889,57 @@ module C03StdIterators_MyReverse
     /\ (forall k : int . 0 <= k /\ k < len'1 self  -> k <> i  -> k <> j  -> index_logic'4 self k = index_logic'4 oth k)
   
   function shallow_model'0 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span70] shallow_model'2 ( * self)
+    [%#span55] shallow_model'2 ( * self)
   
-  let rec swap'0 (self:borrowed (slice t)) (a:usize) (b:usize) (return'  (ret:()))= {[@expl:precondition] [%#span73] inv'2 self}
-    {[@expl:precondition] [%#span72] UIntSize.to_int b < len'1 (shallow_model'0 self)}
-    {[@expl:precondition] [%#span71] UIntSize.to_int a < len'1 (shallow_model'0 self)}
+  let rec swap'0 (self:borrowed (slice t)) (a:usize) (b:usize) (return'  (ret:()))= {[@expl:precondition] [%#span58] inv'2 self}
+    {[@expl:precondition] [%#span57] UIntSize.to_int b < len'1 (shallow_model'0 self)}
+    {[@expl:precondition] [%#span56] UIntSize.to_int a < len'1 (shallow_model'0 self)}
     any
-    [ return' (result:())-> {[%#span74] exchange'0 (shallow_model'2 ( ^ self)) (shallow_model'0 self) (UIntSize.to_int a) (UIntSize.to_int b)}
+    [ return' (result:())-> {[%#span59] exchange'0 (shallow_model'2 ( ^ self)) (shallow_model'0 self) (UIntSize.to_int a) (UIntSize.to_int b)}
       (! return' {result}) ]
     
   
   predicate resolve'4 (self : usize) =
-    [%#span75] true
+    [%#span60] true
   
   predicate resolve'2 (self : (usize, usize)) =
-    [%#span76] resolve'4 (let (a, _) = self in a) /\ resolve'4 (let (_, a) = self in a)
-  
-  use seq.Seq
+    [%#span61] resolve'4 (let (a, _) = self in a) /\ resolve'4 (let (_, a) = self in a)
   
   function singleton'0 (v : (usize, usize)) : Seq'0.t_seq (usize, usize)
   
-  axiom singleton'0_spec : forall v : (usize, usize) . ([%#span77] inv'10 v)
-   -> ([%#span80] inv'5 (singleton'0 v))
-  && ([%#span79] index_logic'2 (singleton'0 v) 0 = v) && ([%#span78] len'2 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (usize, usize) . ([%#span62] inv'8 v)
+   -> ([%#span64] index_logic'2 (singleton'0 v) 0 = v) && ([%#span63] len'2 (singleton'0 v) = 1)
   
   predicate resolve'1 (self : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))) =
-    [%#span66]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span51]  ^ self =  * self
   
   function singleton'1 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'1_spec : forall v : usize . ([%#span77] inv'12 v)
-   -> ([%#span80] inv'6 (singleton'1 v))
-  && ([%#span79] index_logic'3 (singleton'1 v) 0 = v) && ([%#span78] len'3 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : usize . ([%#span62] inv'10 v)
+   -> ([%#span64] index_logic'3 (singleton'1 v) 0 = v) && ([%#span63] len'3 (singleton'1 v) = 1)
   
   predicate resolve'5 (self : borrowed (Range'0.t_range usize)) =
-    [%#span66]  ^ self =  * self
+    [%#span51]  ^ self =  * self
   
   predicate completed'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span81] resolve'5 self
+    [%#span65] resolve'5 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
   predicate completed'0 (self : borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))) =
-    [%#span82] exists b : borrowed (Range'0.t_range usize) . exists a : borrowed (Range'0.t_range usize) . inv'11 b
-    /\ inv'11 a
+    [%#span66] exists b : borrowed (Range'0.t_range usize) . exists a : borrowed (Range'0.t_range usize) . inv'9 b
+    /\ inv'9 a
     /\  * a = itera'0 ( * self)
     /\  * b = iterb'0 ( * self)
     /\  ^ a = itera'0 ( ^ self)
     /\  ^ b = iterb'0 ( ^ self)
     /\ (completed'1 a /\ resolve'5 b
-    \/ (exists x : usize . inv'12 x /\ produces'1 ( * a) (singleton'1 x) ( ^ a) /\ resolve'4 x /\ completed'1 b))
+    \/ (exists x : usize . inv'10 x /\ produces'1 ( * a) (singleton'1 x) ( ^ a) /\ resolve'4 x /\ completed'1 b))
   
-  let rec next'0 (self:borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))) (return'  (ret:Option'0.t_option (usize, usize)))= {[@expl:precondition] [%#span83] inv'8 self}
+  let rec next'0 (self:borrowed (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))) (return'  (ret:Option'0.t_option (usize, usize)))= {[@expl:precondition] [%#span67] inv'6 self}
     any
-    [ return' (result:Option'0.t_option (usize, usize))-> {[%#span85] inv'9 result}
-      {[%#span84] match result with
+    [ return' (result:Option'0.t_option (usize, usize))-> {[%#span69] inv'7 result}
+      {[%#span68] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -4457,22 +3949,22 @@ module C03StdIterators_MyReverse
   predicate equiv_reverse_range'0 [#"../03_std_iterators.rs" 87 0 87 81] (s1 : Seq'0.t_seq t) (s2 : Seq'0.t_seq t) (l : int) (u : int) (n : int)
     
    =
-    [%#span86] forall i : int . l <= i /\ i < u  -> index_logic'4 s1 i = index_logic'4 s2 (n - i)
+    [%#span70] forall i : int . l <= i /\ i < u  -> index_logic'4 s1 i = index_logic'4 s2 (n - i)
   
   predicate equiv_range'0 [#"../03_std_iterators.rs" 80 0 80 65] (s1 : Seq'0.t_seq t) (s2 : Seq'0.t_seq t) (l : int) (u : int)
     
    =
-    [%#span87] forall i : int . l <= i /\ i < u  -> index_logic'4 s1 i = index_logic'4 s2 i
+    [%#span71] forall i : int . l <= i /\ i < u  -> index_logic'4 s1 i = index_logic'4 s2 i
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, usize))) : Seq'0.t_seq (usize, usize)
   
   function shallow_model'4 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span88] shallow_model'0 self
+    [%#span72] shallow_model'0 self
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (slice t))) : borrowed (slice t)
   
   function shallow_model'1 (self : Snapshot'0.t_snapshot (borrowed (slice t))) : Seq'0.t_seq t =
-    [%#span89] shallow_model'4 (deref'0 self)
+    [%#span73] shallow_model'4 (deref'0 self)
   
   function inner'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, usize))) : Seq'0.t_seq (usize, usize)
   
@@ -4484,43 +3976,43 @@ module C03StdIterators_MyReverse
   
   function new'2 (x : Seq'0.t_seq (usize, usize)) : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, usize))
   
-  axiom new'2_spec : forall x : Seq'0.t_seq (usize, usize) . ([%#span90] inv'5 x)  -> ([%#span91] deref'1 (new'2 x) = x)
+  axiom new'2_spec : forall x : Seq'0.t_seq (usize, usize) . ([%#span74] inv'5 x)  -> ([%#span75] deref'1 (new'2 x) = x)
   
   function new'1 (x : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) : Snapshot'0.t_snapshot (Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))
     
   
-  axiom new'1_spec : forall x : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize) . ([%#span90] inv'0 x)
-   -> ([%#span91] deref'2 (new'1 x) = x)
+  axiom new'1_spec : forall x : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize) . ([%#span74] inv'0 x)
+   -> ([%#span75] deref'2 (new'1 x) = x)
   
   predicate into_iter_post'1 (self : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) (res : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))
     
    =
-    [%#span92] self = res
+    [%#span76] self = res
   
   predicate into_iter_pre'1 (self : Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) =
-    [%#span93] true
+    [%#span77] true
   
-  let rec into_iter'0 (self:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) (return'  (ret:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)))= {[@expl:precondition] [%#span95] inv'0 self}
-    {[@expl:precondition] [%#span94] into_iter_pre'1 self}
+  let rec into_iter'0 (self:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)) (return'  (ret:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)))= {[@expl:precondition] [%#span79] inv'0 self}
+    {[@expl:precondition] [%#span78] into_iter_pre'1 self}
     any
-    [ return' (result:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))-> {[%#span96] inv'0 result}
-      {[%#span94] into_iter_post'1 self result}
+    [ return' (result:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))-> {[%#span80] inv'0 result}
+      {[%#span78] into_iter_post'1 self result}
       (! return' {result}) ]
     
   
   predicate into_iter_post'0 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span92] self = res
+    [%#span76] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range usize) =
-    [%#span93] true
+    [%#span77] true
   
-  let rec zip'0 (self:Range'0.t_range usize) (other:Range'0.t_range usize) (return'  (ret:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)))= {[@expl:precondition] [%#span99] inv'4 other}
-    {[@expl:precondition] [%#span98] inv'4 self}
-    {[@expl:precondition] [%#span97] into_iter_pre'0 other}
+  let rec zip'0 (self:Range'0.t_range usize) (other:Range'0.t_range usize) (return'  (ret:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize)))= {[@expl:precondition] [%#span83] inv'4 other}
+    {[@expl:precondition] [%#span82] inv'4 self}
+    {[@expl:precondition] [%#span81] into_iter_pre'0 other}
     any
-    [ return' (result:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))-> {[%#span101] inv'0 result}
-      {[%#span100] into_iter_post'0 other (iterb'0 result)}
-      {[%#span94] itera'0 result = self}
+    [ return' (result:Zip'0.t_zip (Range'0.t_range usize) (Range'0.t_range usize))-> {[%#span85] inv'0 result}
+      {[%#span84] into_iter_post'0 other (iterb'0 result)}
+      {[%#span78] itera'0 result = self}
       (! return' {result}) ]
     
   
@@ -4528,15 +4020,14 @@ module C03StdIterators_MyReverse
   
   function new'0 (x : borrowed (slice t)) : Snapshot'0.t_snapshot (borrowed (slice t))
   
-  axiom new'0_spec : forall x : borrowed (slice t) . ([%#span90] inv'2 x)  -> ([%#span91] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (slice t) . ([%#span74] inv'2 x)  -> ([%#span75] deref'0 (new'0 x) = x)
   
   function shallow_model'3 (self : slice t) : Seq'0.t_seq t =
-    [%#span88] shallow_model'2 self
+    [%#span72] shallow_model'2 self
   
-  let rec len'0 (self:slice t) (return'  (ret:usize))= {[@expl:precondition] [%#span102] inv'3 self}
+  let rec len'0 (self:slice t) (return'  (ret:usize))= {[@expl:precondition] [%#span86] inv'3 self}
     any
-    [ return' (result:usize)-> {[%#span103] len'1 (shallow_model'3 self) = UIntSize.to_int result}
-      (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span87] len'1 (shallow_model'3 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
   let rec my_reverse (slice:borrowed (slice t)) (return'  (ret:()))= {[%#s03_std_iterators18] inv'2 slice}
diff --git a/creusot/tests/should_succeed/iterators/04_skip.coma b/creusot/tests/should_succeed/iterators/04_skip.coma
index 8d75694f06..2176f2680d 100644
--- a/creusot/tests/should_succeed/iterators/04_skip.coma
+++ b/creusot/tests/should_succeed/iterators/04_skip.coma
@@ -25,22 +25,7 @@ module C04Skip_Skip_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C04Skip_Impl0_ProducesRefl_Impl
   type i
@@ -49,113 +34,79 @@ module C04Skip_Impl0_ProducesRefl_Impl
   
   let%span s04_skip1 = "../04_skip.rs" 49 14 49 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span9 = "../common.rs" 18 15 18 32
-  
-  let%span span10 = "../common.rs" 19 15 19 32
-  
-  let%span span11 = "../common.rs" 21 22 21 23
-  
-  let%span span12 = "../common.rs" 21 31 21 33
+  let%span span5 = "../common.rs" 18 15 18 32
   
-  let%span span13 = "../common.rs" 21 52 21 53
+  let%span span6 = "../common.rs" 19 15 19 32
   
-  let%span span14 = "../common.rs" 21 61 21 63
+  let%span span7 = "../common.rs" 21 22 21 23
   
-  let%span span15 = "../common.rs" 21 82 21 83
+  let%span span8 = "../common.rs" 21 52 21 53
   
-  let%span span16 = "../common.rs" 20 14 20 42
+  let%span span9 = "../common.rs" 21 82 21 83
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span10 = "../common.rs" 20 14 20 42
   
-  let%span span18 = "../common.rs" 15 21 15 25
+  let%span span11 = "../common.rs" 15 21 15 25
   
-  let%span span19 = "../common.rs" 14 14 14 45
+  let%span span12 = "../common.rs" 14 14 14 45
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span14 = "../04_skip.rs" 37 8 44 9
   
-  let%span span22 = "../04_skip.rs" 37 8 44 9
-  
-  predicate invariant'2 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'2 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'2 : forall x : i . inv'2 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] inv'1 self)
-   -> ([%#span5] inv'1 other)
-   -> ([%#span8] inv'1 (concat'0 self other))
-  && ([%#span7] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span6] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span3] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'1 a ab b)
-   -> ([%#span10] produces'1 b bc c)
-   -> ([%#span11] inv'2 a)
-   -> ([%#span12] inv'1 ab)
-   -> ([%#span13] inv'2 b)
-   -> ([%#span14] inv'1 bc)  -> ([%#span15] inv'2 c)  -> ([%#span16] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span5] produces'1 a ab b)
+   -> ([%#span6] produces'1 b bc c)
+   -> ([%#span7] inv'1 a)
+   -> ([%#span8] inv'1 b)  -> ([%#span9] inv'1 c)  -> ([%#span10] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span18] inv'2 self)
-   -> ([%#span19] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span11] inv'1 self)
+   -> ([%#span12] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span21] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C04Skip_Skip_Type as Skip'0
   
@@ -174,11 +125,10 @@ module C04Skip_Impl0_ProducesRefl_Impl
   predicate produces'0 [#"../04_skip.rs" 36 4 36 64] (self : Skip'0.t_skip i) (visited : Seq'0.t_seq item'0) (o : Skip'0.t_skip i)
     
    =
-    [%#span22] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
+    [%#span14] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
     \/ UIntSize.to_int (C04Skip_Skip_Type.skip_n o) = 0
     /\ len'0 visited > 0
-    /\ (exists s : Seq'0.t_seq item'0 . inv'1 s
-    /\ len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
     /\ produces'1 (C04Skip_Skip_Type.skip_iter self) (concat'0 s visited) (C04Skip_Skip_Type.skip_iter o)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'0 (index_logic'0 s i)))
   
@@ -198,123 +148,85 @@ module C04Skip_Impl0_ProducesTrans_Impl
   
   let%span s04_skip2 = "../04_skip.rs" 57 22 57 23
   
-  let%span s04_skip3 = "../04_skip.rs" 57 31 57 33
-  
-  let%span s04_skip4 = "../04_skip.rs" 57 52 57 53
-  
-  let%span s04_skip5 = "../04_skip.rs" 57 61 57 63
-  
-  let%span s04_skip6 = "../04_skip.rs" 57 82 57 83
-  
-  let%span s04_skip7 = "../04_skip.rs" 56 14 56 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span s04_skip3 = "../04_skip.rs" 57 52 57 53
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s04_skip4 = "../04_skip.rs" 57 82 57 83
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span s04_skip5 = "../04_skip.rs" 56 14 56 42
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../common.rs" 18 15 18 32
-  
-  let%span span16 = "../common.rs" 19 15 19 32
-  
-  let%span span17 = "../common.rs" 21 22 21 23
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span18 = "../common.rs" 21 31 21 33
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span19 = "../common.rs" 21 52 21 53
+  let%span span9 = "../common.rs" 18 15 18 32
   
-  let%span span20 = "../common.rs" 21 61 21 63
+  let%span span10 = "../common.rs" 19 15 19 32
   
-  let%span span21 = "../common.rs" 21 82 21 83
+  let%span span11 = "../common.rs" 21 22 21 23
   
-  let%span span22 = "../common.rs" 20 14 20 42
+  let%span span12 = "../common.rs" 21 52 21 53
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span13 = "../common.rs" 21 82 21 83
   
-  let%span span24 = "../common.rs" 15 21 15 25
+  let%span span14 = "../common.rs" 20 14 20 42
   
-  let%span span25 = "../common.rs" 14 14 14 45
+  let%span span15 = "../common.rs" 15 21 15 25
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span16 = "../common.rs" 14 14 14 45
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span28 = "../04_skip.rs" 37 8 44 9
+  let%span span18 = "../04_skip.rs" 37 8 44 9
   
-  predicate invariant'2 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'2 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'2 : forall x : i . inv'2 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] inv'1 self)
-   -> ([%#span11] inv'1 other)
-   -> ([%#span14] inv'1 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span15] produces'1 a ab b)
-   -> ([%#span16] produces'1 b bc c)
-   -> ([%#span17] inv'2 a)
-   -> ([%#span18] inv'1 ab)
-   -> ([%#span19] inv'2 b)
-   -> ([%#span20] inv'1 bc)  -> ([%#span21] inv'2 c)  -> ([%#span22] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'1 a ab b)
+   -> ([%#span10] produces'1 b bc c)
+   -> ([%#span11] inv'1 a)
+   -> ([%#span12] inv'1 b)  -> ([%#span13] inv'1 c)  -> ([%#span14] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span23] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span24] inv'2 self)
-   -> ([%#span25] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span27] ()
+  axiom produces_refl'0_spec : forall self : i . ([%#span15] inv'1 self)
+   -> ([%#span16] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span26] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C04Skip_Skip_Type as Skip'0
   
@@ -333,11 +245,10 @@ module C04Skip_Impl0_ProducesTrans_Impl
   predicate produces'0 [#"../04_skip.rs" 36 4 36 64] (self : Skip'0.t_skip i) (visited : Seq'0.t_seq item'0) (o : Skip'0.t_skip i)
     
    =
-    [%#span28] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
+    [%#span18] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
     \/ UIntSize.to_int (C04Skip_Skip_Type.skip_n o) = 0
     /\ len'0 visited > 0
-    /\ (exists s : Seq'0.t_seq item'0 . inv'1 s
-    /\ len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
     /\ produces'1 (C04Skip_Skip_Type.skip_iter self) (concat'0 s visited) (C04Skip_Skip_Type.skip_iter o)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'0 (index_logic'0 s i)))
   
@@ -354,13 +265,11 @@ module C04Skip_Impl0_ProducesTrans_Impl
   function produces_trans [#"../04_skip.rs" 57 4 57 90] (a : Skip'0.t_skip i) (ab : Seq'0.t_seq item'0) (b : Skip'0.t_skip i) (bc : Seq'0.t_seq item'0) (c : Skip'0.t_skip i) : ()
     
   
-  goal vc_produces_trans : ([%#s04_skip6] inv'0 c)
-   -> ([%#s04_skip5] inv'1 bc)
-   -> ([%#s04_skip4] inv'0 b)
-   -> ([%#s04_skip3] inv'1 ab)
+  goal vc_produces_trans : ([%#s04_skip4] inv'0 c)
+   -> ([%#s04_skip3] inv'0 b)
    -> ([%#s04_skip2] inv'0 a)
    -> ([%#s04_skip1] produces'0 b bc c)
-   -> ([%#s04_skip0] produces'0 a ab b)  -> ([%#s04_skip7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s04_skip0] produces'0 a ab b)  -> ([%#s04_skip5] produces'0 a (concat'0 ab bc) c)
 end
 module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
@@ -412,81 +321,63 @@ module C04Skip_Impl0_Next
   
   let%span span13 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span21 = "../common.rs" 18 15 18 32
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span22 = "../common.rs" 19 15 19 32
+  let%span span17 = "../common.rs" 18 15 18 32
   
-  let%span span23 = "../common.rs" 21 22 21 23
+  let%span span18 = "../common.rs" 19 15 19 32
   
-  let%span span24 = "../common.rs" 21 31 21 33
+  let%span span19 = "../common.rs" 21 22 21 23
   
-  let%span span25 = "../common.rs" 21 52 21 53
+  let%span span20 = "../common.rs" 21 52 21 53
   
-  let%span span26 = "../common.rs" 21 61 21 63
-  
-  let%span span27 = "../common.rs" 21 82 21 83
-  
-  let%span span28 = "../common.rs" 20 14 20 42
-  
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span30 = "../common.rs" 15 21 15 25
+  let%span span21 = "../common.rs" 21 82 21 83
   
-  let%span span31 = "../common.rs" 14 14 14 45
+  let%span span22 = "../common.rs" 20 14 20 42
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span23 = "../common.rs" 15 21 15 25
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span24 = "../common.rs" 14 14 14 45
   
-  let%span span34 = "../04_skip.rs" 37 8 44 9
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span35 = "../04_skip.rs" 23 8 31 9
+  let%span span26 = "../04_skip.rs" 37 8 44 9
   
-  let%span span36 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span27 = "../04_skip.rs" 23 8 31 9
   
-  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span28 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span41 = "../common.rs" 27 17 27 21
+  let%span span32 = "../common.rs" 27 17 27 21
   
-  let%span span42 = "../common.rs" 23 14 26 5
+  let%span span33 = "../common.rs" 23 14 26 5
   
-  let%span span43 = "../common.rs" 27 26 27 44
+  let%span span34 = "../common.rs" 27 26 27 44
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
+  let%span span35 = "../../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
   
-  let%span span45 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span36 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span46 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span37 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/num.rs" 30 28 30 32
+  let%span span38 = "../../../../../creusot-contracts/src/std/num.rs" 30 28 30 32
   
-  let%span span48 = "" 0 0 0 0
+  let%span span39 = "" 0 0 0 0
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/mem.rs" 17 22 17 37
+  let%span span40 = "../../../../../creusot-contracts/src/std/mem.rs" 17 22 17 37
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/mem.rs" 18 22 18 42
+  let%span span41 = "../../../../../creusot-contracts/src/std/mem.rs" 18 22 18 42
   
-  let%span span51 = "" 0 0 0 0
+  let%span span42 = "" 0 0 0 0
   
   use prelude.prelude.Borrow
   
@@ -550,55 +441,43 @@ module C04Skip_Impl0_Next
   
   axiom inv'0 : forall x : borrowed (Skip'0.t_skip i) . inv'0 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span14] inv'6 self)  -> ([%#span15] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span14] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span16] inv'6 self)
-   -> ([%#span17] inv'6 other)
-   -> ([%#span20] inv'6 (concat'0 self other))
-  && ([%#span19] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span16] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span18] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span21] produces'0 a ab b)
-   -> ([%#span22] produces'0 b bc c)
-   -> ([%#span23] inv'1 a)
-   -> ([%#span24] inv'6 ab)
-   -> ([%#span25] inv'1 b)
-   -> ([%#span26] inv'6 bc)  -> ([%#span27] inv'1 c)  -> ([%#span28] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span17] produces'0 a ab b)
+   -> ([%#span18] produces'0 b bc c)
+   -> ([%#span19] inv'1 a)
+   -> ([%#span20] inv'1 b)  -> ([%#span21] inv'1 c)  -> ([%#span22] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span29] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span30] inv'1 self)
-   -> ([%#span31] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span23] inv'1 self)
+   -> ([%#span24] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span33] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span32] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span25] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate resolve'3 (self : item'0)
   
@@ -609,20 +488,18 @@ module C04Skip_Impl0_Next
   predicate produces'1 [#"../04_skip.rs" 36 4 36 64] (self : Skip'0.t_skip i) (visited : Seq'0.t_seq item'0) (o : Skip'0.t_skip i)
     
    =
-    [%#span34] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
+    [%#span26] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
     \/ UIntSize.to_int (C04Skip_Skip_Type.skip_n o) = 0
     /\ len'0 visited > 0
-    /\ (exists s : Seq'0.t_seq item'0 . inv'6 s
-    /\ len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
     /\ produces'0 (C04Skip_Skip_Type.skip_iter self) (concat'0 s visited) (C04Skip_Skip_Type.skip_iter o)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'3 (index_logic'1 s i)))
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate completed'0 [#"../04_skip.rs" 22 4 22 35] (self : borrowed (Skip'0.t_skip i)) =
-    [%#span35] UIntSize.to_int (C04Skip_Skip_Type.skip_n ( ^ self)) = 0
+    [%#span27] UIntSize.to_int (C04Skip_Skip_Type.skip_n ( ^ self)) = 0
     /\ (exists i : borrowed i . exists s : Seq'0.t_seq item'0 . inv'7 i
-    /\ inv'6 s
     /\ len'0 s <= UIntSize.to_int (C04Skip_Skip_Type.skip_n ( * self))
     /\ produces'0 (C04Skip_Skip_Type.skip_iter ( * self)) s ( * i)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'3 (index_logic'1 s i))
@@ -633,22 +510,19 @@ module C04Skip_Impl0_Next
   use prelude.prelude.Intrinsic
   
   predicate resolve'5 (self : borrowed (Skip'0.t_skip i)) =
-    [%#span36]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span28]  ^ self =  * self
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span37] inv'2 v)
-   -> ([%#span40] inv'6 (singleton'0 v))
-  && ([%#span39] index_logic'1 (singleton'0 v) 0 = v) && ([%#span38] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span29] inv'2 v)
+   -> ([%#span31] index_logic'1 (singleton'0 v) 0 = v) && ([%#span30] len'0 (singleton'0 v) = 1)
   
   predicate resolve'4 (self : Option'0.t_option item'0)
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span41] inv'7 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span32] inv'7 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span43] inv'3 result}
-      {[%#span42] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span34] inv'3 result}
+      {[%#span33] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -658,7 +532,7 @@ module C04Skip_Impl0_Next
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
   function index_logic'0 [@inline:trivial] (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) (ix : int) : item'0 =
-    [%#span44] index_logic'1 (deref'0 self) ix
+    [%#span35] index_logic'1 (deref'0 self) ix
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
@@ -668,19 +542,19 @@ module C04Skip_Impl0_Next
   
   function new'1 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq item'0 . ([%#span45] inv'6 x)  -> ([%#span46] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq item'0 . ([%#span36] inv'6 x)  -> ([%#span37] deref'0 (new'1 x) = x)
   
   predicate resolve'1 (self : borrowed usize) =
-    [%#span36]  ^ self =  * self
+    [%#span28]  ^ self =  * self
   
   predicate is_default'0 (self : usize) =
-    [%#span47] self = (0 : usize)
+    [%#span38] self = (0 : usize)
   
-  let rec take'0 (dest:borrowed usize) (return'  (ret:usize))= {[@expl:precondition] [%#span48] inv'4 dest}
+  let rec take'0 (dest:borrowed usize) (return'  (ret:usize))= {[@expl:precondition] [%#span39] inv'4 dest}
     any
-    [ return' (result:usize)-> {[%#span51] inv'5 result}
-      {[%#span50] is_default'0 ( ^ dest)}
-      {[%#span49] result =  * dest}
+    [ return' (result:usize)-> {[%#span42] inv'5 result}
+      {[%#span41] is_default'0 ( ^ dest)}
+      {[%#span40] result =  * dest}
       (! return' {result}) ]
     
   
@@ -688,7 +562,7 @@ module C04Skip_Impl0_Next
   
   function new'0 (x : borrowed (Skip'0.t_skip i)) : Snapshot'0.t_snapshot (borrowed (Skip'0.t_skip i))
   
-  axiom new'0_spec : forall x : borrowed (Skip'0.t_skip i) . ([%#span45] inv'0 x)  -> ([%#span46] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (Skip'0.t_skip i) . ([%#span36] inv'0 x)  -> ([%#span37] deref'1 (new'0 x) = x)
   
   let rec next (self:borrowed (Skip'0.t_skip i)) (return'  (ret:Option'0.t_option item'0))= {[%#s04_skip10] inv'0 self}
     (! bb0
@@ -818,57 +692,37 @@ module C04Skip_Impl0
   
   let%span s04_skip2 = "../04_skip.rs" 57 4 57 90
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span11 = "../04_skip.rs" 37 8 44 9
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span6 = "../04_skip.rs" 37 8 44 9
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span16 = "../04_skip.rs" 23 8 31 9
+  let%span span10 = "../04_skip.rs" 23 8 31 9
   
   type item'0
   
-  predicate invariant'5 (self : item'0)
+  predicate invariant'4 (self : item'0)
   
-  predicate inv'5 (_x : item'0)
+  predicate inv'4 (_x : item'0)
   
-  axiom inv'5 : forall x : item'0 . inv'5 x = true
+  axiom inv'4 : forall x : item'0 . inv'4 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'4 (self : borrowed i)
-  
-  predicate inv'4 (_x : borrowed i)
-  
-  axiom inv'4 : forall x : borrowed i . inv'4 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'3 (self : Seq'0.t_seq item'0)
+  predicate invariant'3 (self : borrowed i)
   
-  predicate inv'3 (_x : Seq'0.t_seq item'0)
+  predicate inv'3 (_x : borrowed i)
   
-  axiom inv'3 : forall x : Seq'0.t_seq item'0 . inv'3 x = true
+  axiom inv'3 : forall x : borrowed i . inv'3 x = true
   
   use C04Skip_Skip_Type as Skip'0
   
@@ -892,35 +746,28 @@ module C04Skip_Impl0
   
   axiom inv'0 : forall x : borrowed (Skip'0.t_skip i) . inv'0 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span3] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span5] inv'3 self)
-   -> ([%#span6] inv'3 other)
-   -> ([%#span9] inv'3 (concat'0 self other))
-  && ([%#span8] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span5] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span4] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   predicate resolve'0 (self : item'0)
   
@@ -933,28 +780,23 @@ module C04Skip_Impl0
   predicate produces'0 [#"../04_skip.rs" 36 4 36 64] (self : Skip'0.t_skip i) (visited : Seq'0.t_seq item'0) (o : Skip'0.t_skip i)
     
    =
-    [%#span11] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
+    [%#span6] visited = (empty'0 : Seq'0.t_seq item'0) /\ self = o
     \/ UIntSize.to_int (C04Skip_Skip_Type.skip_n o) = 0
     /\ len'0 visited > 0
-    /\ (exists s : Seq'0.t_seq item'0 . inv'3 s
-    /\ len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = UIntSize.to_int (C04Skip_Skip_Type.skip_n self)
     /\ produces'1 (C04Skip_Skip_Type.skip_iter self) (concat'0 s visited) (C04Skip_Skip_Type.skip_iter o)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'0 (index_logic'0 s i)))
   
-  use seq.Seq
-  
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span12] inv'5 v)
-   -> ([%#span15] inv'3 (singleton'0 v))
-  && ([%#span14] index_logic'0 (singleton'0 v) 0 = v) && ([%#span13] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span7] inv'4 v)
+   -> ([%#span9] index_logic'0 (singleton'0 v) 0 = v) && ([%#span8] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate completed'0 [#"../04_skip.rs" 22 4 22 35] (self : borrowed (Skip'0.t_skip i)) =
-    [%#span16] UIntSize.to_int (C04Skip_Skip_Type.skip_n ( ^ self)) = 0
-    /\ (exists i : borrowed i . exists s : Seq'0.t_seq item'0 . inv'4 i
-    /\ inv'3 s
+    [%#span10] UIntSize.to_int (C04Skip_Skip_Type.skip_n ( ^ self)) = 0
+    /\ (exists i : borrowed i . exists s : Seq'0.t_seq item'0 . inv'3 i
     /\ len'0 s <= UIntSize.to_int (C04Skip_Skip_Type.skip_n ( * self))
     /\ produces'1 (C04Skip_Skip_Type.skip_iter ( * self)) s ( * i)
     /\ (forall i : int . 0 <= i /\ i < len'0 s  -> resolve'0 (index_logic'0 s i))
@@ -979,11 +821,9 @@ module C04Skip_Impl0
    -> produces'0 self (empty'1 : Seq'0.t_seq item'0) self)
   
   goal produces_trans_refn : [%#s04_skip2] forall a : Skip'0.t_skip i . forall ab : Seq'0.t_seq item'0 . forall b : Skip'0.t_skip i . forall bc : Seq'0.t_seq item'0 . forall c : Skip'0.t_skip i . inv'2 c
-  /\ inv'3 bc /\ inv'2 b /\ inv'3 ab /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'2 b /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'2 c
-  /\ inv'3 bc
   /\ inv'2 b
-  /\ inv'3 ab
   /\ inv'2 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
diff --git a/creusot/tests/should_succeed/iterators/05_map.coma b/creusot/tests/should_succeed/iterators/05_map.coma
index 9d4d196116..e36a3e366f 100644
--- a/creusot/tests/should_succeed/iterators/05_map.coma
+++ b/creusot/tests/should_succeed/iterators/05_map.coma
@@ -21,22 +21,7 @@ module C05Map_Map_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C05Map_Impl0_ProducesRefl_Impl
   type i
@@ -49,222 +34,177 @@ module C05Map_Impl0_ProducesRefl_Impl
   
   let%span s05_map1 = "../05_map.rs" 28 14 28 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span6 = "../common.rs" 18 15 18 32
   
-  let%span span12 = "../common.rs" 18 15 18 32
+  let%span span7 = "../common.rs" 19 15 19 32
   
-  let%span span13 = "../common.rs" 19 15 19 32
+  let%span span8 = "../common.rs" 21 22 21 23
   
-  let%span span14 = "../common.rs" 21 22 21 23
+  let%span span9 = "../common.rs" 21 52 21 53
   
-  let%span span15 = "../common.rs" 21 31 21 33
+  let%span span10 = "../common.rs" 21 82 21 83
   
-  let%span span16 = "../common.rs" 21 52 21 53
+  let%span span11 = "../common.rs" 20 14 20 42
   
-  let%span span17 = "../common.rs" 21 61 21 63
+  let%span span12 = "../common.rs" 15 21 15 25
   
-  let%span span18 = "../common.rs" 21 82 21 83
+  let%span span13 = "../common.rs" 14 14 14 45
   
-  let%span span19 = "../common.rs" 20 14 20 42
-  
-  let%span span20 = "../common.rs" 15 21 15 25
-  
-  let%span span21 = "../common.rs" 14 14 14 45
-  
-  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
-  
-  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span43 = "../05_map.rs" 75 8 77 9
+  let%span span34 = "../05_map.rs" 75 8 77 9
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span45 = "../05_map.rs" 82 8 89 9
+  let%span span36 = "../05_map.rs" 82 8 89 9
   
-  let%span span46 = "../05_map.rs" 94 8 98 9
+  let%span span37 = "../05_map.rs" 94 8 98 9
   
-  let%span span47 = "../05_map.rs" 133 12 135 57
+  let%span span38 = "../05_map.rs" 133 12 135 57
   
-  let%span span48 = "../05_map.rs" 42 8 53 9
+  let%span span39 = "../05_map.rs" 42 8 53 9
   
   type item'0
   
-  predicate invariant'10 (self : item'0)
+  predicate invariant'7 (self : item'0)
   
-  predicate inv'10 (_x : item'0)
+  predicate inv'7 (_x : item'0)
   
-  axiom inv'10 : forall x : item'0 . inv'10 x = true
+  axiom inv'7 : forall x : item'0 . inv'7 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'9 (self : borrowed i)
+  predicate invariant'6 (self : borrowed i)
   
-  predicate inv'9 (_x : borrowed i)
+  predicate inv'6 (_x : borrowed i)
   
-  axiom inv'9 : forall x : borrowed i . inv'9 x = true
+  axiom inv'6 : forall x : borrowed i . inv'6 x = true
   
-  predicate invariant'8 (self : b)
+  predicate invariant'5 (self : b)
   
-  predicate inv'8 (_x : b)
+  predicate inv'5 (_x : b)
   
-  axiom inv'8 : forall x : b . inv'8 x = true
+  axiom inv'5 : forall x : b . inv'5 x = true
   
-  predicate invariant'7 (self : item'0)
+  predicate invariant'4 (self : item'0)
   
-  predicate inv'7 (_x : item'0)
+  predicate inv'4 (_x : item'0)
   
-  axiom inv'7 : forall x : item'0 . inv'7 x = true
+  axiom inv'4 : forall x : item'0 . inv'4 x = true
   
-  predicate invariant'6 (self : borrowed f)
+  predicate invariant'3 (self : borrowed f)
   
-  predicate inv'6 (_x : borrowed f)
+  predicate inv'3 (_x : borrowed f)
   
-  axiom inv'6 : forall x : borrowed f . inv'6 x = true
+  axiom inv'3 : forall x : borrowed f . inv'3 x = true
   
-  predicate invariant'5 (self : f)
+  predicate invariant'2 (self : f)
   
-  predicate inv'5 (_x : f)
+  predicate inv'2 (_x : f)
   
-  axiom inv'5 : forall x : f . inv'5 x = true
+  axiom inv'2 : forall x : f . inv'2 x = true
   
-  predicate invariant'4 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'4 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'4 : forall x : i . inv'4 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'3 (_x : Seq'0.t_seq (borrowed f))
-  
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span2] inv'3 self)  -> ([%#span3] len'2 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span4] ()
-  
-  function empty_len'2 (_1 : ()) : () =
-    [%#span6] ()
-  
-  axiom empty_len'2_spec : forall _1 : () . [%#span5] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span2] len'2 self >= 0
   
-  predicate invariant'3 (self : Seq'0.t_seq (borrowed f))
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  axiom inv'3 : forall x : Seq'0.t_seq (borrowed f) . inv'3 x = true
+  function empty_len'2 (_1 : ()) : ()
   
-  use seq.Seq
-  
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
+  axiom empty_len'2_spec : forall _1 : () . [%#span3] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'2 self)  -> ([%#span3] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span4] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span6] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span5] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
+  constant empty'1 : Seq'0.t_seq item'0
   
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
+  axiom empty_len'1_spec : forall _1 : () . [%#span3] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span7] inv'2 self)
-   -> ([%#span8] inv'2 other)
-   -> ([%#span11] inv'2 (concat'0 self other))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span5] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span4] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span12] produces'1 a ab b)
-   -> ([%#span13] produces'1 b bc c)
-   -> ([%#span14] inv'4 a)
-   -> ([%#span15] inv'2 ab)
-   -> ([%#span16] inv'4 b)
-   -> ([%#span17] inv'2 bc)  -> ([%#span18] inv'4 c)  -> ([%#span19] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span6] produces'1 a ab b)
+   -> ([%#span7] produces'1 b bc c)
+   -> ([%#span8] inv'1 a)
+   -> ([%#span9] inv'1 b)  -> ([%#span10] inv'1 c)  -> ([%#span11] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span20] inv'4 self)
-   -> ([%#span21] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span12] inv'1 self)
+   -> ([%#span13] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   predicate resolve'0 (self : f)
   
@@ -274,73 +214,60 @@ module C05Map_Impl0_ProducesRefl_Impl
   
   function fn_mut_once'0 (self : f) (args : item'0) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span22] inv'5 self)
-   -> ([%#span23] inv'7 args)
-   -> ([%#span24] inv'8 res)
-   -> ([%#span25] postcondition_once'0 self args res
-  = (exists s : borrowed f . inv'6 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
+  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span14] inv'2 self)
+   -> ([%#span15] inv'4 args)
+   -> ([%#span16] inv'5 res)
+   -> ([%#span17] postcondition_once'0 self args res
+  = (exists s : borrowed f . inv'3 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span26] unnest'0 self b)
-   -> ([%#span27] unnest'0 b c)
-   -> ([%#span28] inv'5 self)  -> ([%#span29] inv'5 b)  -> ([%#span30] inv'5 c)  -> ([%#span31] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span18] unnest'0 self b)
+   -> ([%#span19] unnest'0 b c)
+   -> ([%#span20] inv'2 self)  -> ([%#span21] inv'2 b)  -> ([%#span22] inv'2 c)  -> ([%#span23] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span32] inv'5 self)  -> ([%#span33] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span24] inv'2 self)  -> ([%#span25] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : item'0) (res : b) : ()
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span34] postcondition_mut'0 self args res)
-   -> ([%#span35] inv'6 self)
-   -> ([%#span36] inv'7 args)  -> ([%#span37] inv'8 res)  -> ([%#span38] unnest'0 ( * self) ( ^ self))
-  
-  predicate invariant'1 (self : Seq'0.t_seq b)
-  
-  predicate inv'1 (_x : Seq'0.t_seq b)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq b . inv'1 x = true
-  
-  use seq.Seq
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span26] postcondition_mut'0 self args res)
+   -> ([%#span27] inv'3 self)
+   -> ([%#span28] inv'4 args)  -> ([%#span29] inv'5 res)  -> ([%#span30] unnest'0 ( * self) ( ^ self))
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span2] inv'1 self)  -> ([%#span3] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span2] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq b = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq b
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'1 (empty'0 : Seq'0.t_seq b) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'1 (empty'0 : Seq'0.t_seq b) = 0
   
   predicate precondition'0 (self : f) (_2 : item'0)
   
-  use seq.Seq
-  
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span39] inv'10 v)
-   -> ([%#span42] inv'2 (singleton'0 v))
-  && ([%#span41] index_logic'1 (singleton'0 v) 0 = v) && ([%#span40] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span31] inv'7 v)
+   -> ([%#span33] index_logic'1 (singleton'0 v) 0 = v) && ([%#span32] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../05_map.rs" 74 4 74 50] (iter : i) (func : f) =
-    [%#span43] forall i : i . forall e : item'0 . inv'4 i
-     -> inv'10 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e)
+    [%#span34] forall i : i . forall e : item'0 . inv'1 i
+     -> inv'7 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span44] concat'0 self (singleton'0 v)
+    [%#span35] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../05_map.rs" 81 4 81 45] (iter : i) (func : f) =
-    [%#span45] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
-     -> inv'8 b
-     -> inv'6 f
-     -> inv'10 e2
-     -> inv'10 e1
-     -> inv'2 s
+    [%#span36] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
+     -> inv'5 b
+     -> inv'3 f
+     -> inv'7 e2
+     -> inv'7 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1)  -> postcondition_mut'0 f (e1) b  -> precondition'0 ( ^ f) (e2)
@@ -350,13 +277,13 @@ module C05Map_Impl0_ProducesRefl_Impl
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../05_map.rs" 93 4 93 29] (_1 : ()) =
-    [%#span46] forall func : f . forall iter : borrowed i . inv'5 func
-     -> inv'9 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
+    [%#span37] forall func : f . forall iter : borrowed i . inv'2 func
+     -> inv'6 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
   
   use C05Map_Map_Type as Map'0
   
   predicate invariant'0 [#"../05_map.rs" 131 4 131 30] (self : Map'0.t_map i b f) =
-    [%#span47] reinitialize'0 ()
+    [%#span38] reinitialize'0 ()
     /\ preservation'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
     /\ next_precondition'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
   
@@ -368,23 +295,17 @@ module C05Map_Impl0_ProducesRefl_Impl
     | Map'0.C_Map iter func -> true
     end)
   
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq b) (_2 : int) : b
   
-  function index_logic'2 (self : Seq'0.t_seq b) (x : int) : b
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   predicate produces'0 [@inline:trivial] [#"../05_map.rs" 41 4 41 67] (self : Map'0.t_map i b f) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f)
     
    =
-    [%#span48] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'2 s
-    /\ len'0 s = len'1 visited
+    [%#span39] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'1 (C05Map_Map_Type.map_iter self) s (C05Map_Map_Type.map_iter succ)
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'3 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'0 fs (i - 1) =  * index_logic'0 fs i)
     /\ (if len'1 visited = 0 then
       C05Map_Map_Type.map_func self = C05Map_Map_Type.map_func succ
@@ -416,232 +337,183 @@ module C05Map_Impl0_ProducesTrans_Impl
   
   let%span s05_map2 = "../05_map.rs" 36 22 36 23
   
-  let%span s05_map3 = "../05_map.rs" 36 31 36 33
-  
-  let%span s05_map4 = "../05_map.rs" 36 52 36 53
-  
-  let%span s05_map5 = "../05_map.rs" 36 61 36 63
-  
-  let%span s05_map6 = "../05_map.rs" 36 82 36 83
-  
-  let%span s05_map7 = "../05_map.rs" 35 14 35 42
+  let%span s05_map3 = "../05_map.rs" 36 52 36 53
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span s05_map4 = "../05_map.rs" 36 82 36 83
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s05_map5 = "../05_map.rs" 35 14 35 42
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span10 = "../common.rs" 18 15 18 32
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span11 = "../common.rs" 19 15 19 32
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span12 = "../common.rs" 21 22 21 23
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span13 = "../common.rs" 21 52 21 53
   
-  let%span span18 = "../common.rs" 18 15 18 32
+  let%span span14 = "../common.rs" 21 82 21 83
   
-  let%span span19 = "../common.rs" 19 15 19 32
+  let%span span15 = "../common.rs" 20 14 20 42
   
-  let%span span20 = "../common.rs" 21 22 21 23
+  let%span span16 = "../common.rs" 15 21 15 25
   
-  let%span span21 = "../common.rs" 21 31 21 33
+  let%span span17 = "../common.rs" 14 14 14 45
   
-  let%span span22 = "../common.rs" 21 52 21 53
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span23 = "../common.rs" 21 61 21 63
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span24 = "../common.rs" 21 82 21 83
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span25 = "../common.rs" 20 14 20 42
+  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span26 = "../common.rs" 15 21 15 25
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span27 = "../common.rs" 14 14 14 45
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span38 = "../05_map.rs" 75 8 77 9
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span40 = "../05_map.rs" 82 8 89 9
   
-  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span41 = "../05_map.rs" 94 8 98 9
   
-  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span42 = "../05_map.rs" 133 12 135 57
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span49 = "../05_map.rs" 75 8 77 9
-  
-  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
-  
-  let%span span51 = "../05_map.rs" 82 8 89 9
-  
-  let%span span52 = "../05_map.rs" 94 8 98 9
-  
-  let%span span53 = "../05_map.rs" 133 12 135 57
-  
-  let%span span54 = "../05_map.rs" 42 8 53 9
+  let%span span43 = "../05_map.rs" 42 8 53 9
   
   type item'0
   
-  predicate invariant'10 (self : item'0)
+  predicate invariant'7 (self : item'0)
   
-  predicate inv'10 (_x : item'0)
+  predicate inv'7 (_x : item'0)
   
-  axiom inv'10 : forall x : item'0 . inv'10 x = true
+  axiom inv'7 : forall x : item'0 . inv'7 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'9 (self : borrowed i)
+  predicate invariant'6 (self : borrowed i)
   
-  predicate inv'9 (_x : borrowed i)
+  predicate inv'6 (_x : borrowed i)
   
-  axiom inv'9 : forall x : borrowed i . inv'9 x = true
+  axiom inv'6 : forall x : borrowed i . inv'6 x = true
   
-  predicate invariant'8 (self : b)
+  predicate invariant'5 (self : b)
   
-  predicate inv'8 (_x : b)
+  predicate inv'5 (_x : b)
   
-  axiom inv'8 : forall x : b . inv'8 x = true
+  axiom inv'5 : forall x : b . inv'5 x = true
   
-  predicate invariant'7 (self : item'0)
+  predicate invariant'4 (self : item'0)
   
-  predicate inv'7 (_x : item'0)
+  predicate inv'4 (_x : item'0)
   
-  axiom inv'7 : forall x : item'0 . inv'7 x = true
+  axiom inv'4 : forall x : item'0 . inv'4 x = true
   
-  predicate invariant'6 (self : borrowed f)
+  predicate invariant'3 (self : borrowed f)
   
-  predicate inv'6 (_x : borrowed f)
+  predicate inv'3 (_x : borrowed f)
   
-  axiom inv'6 : forall x : borrowed f . inv'6 x = true
+  axiom inv'3 : forall x : borrowed f . inv'3 x = true
   
-  predicate invariant'5 (self : f)
+  predicate invariant'2 (self : f)
   
-  predicate inv'5 (_x : f)
+  predicate inv'2 (_x : f)
   
-  axiom inv'5 : forall x : f . inv'5 x = true
+  axiom inv'2 : forall x : f . inv'2 x = true
   
-  predicate invariant'4 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'4 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'4 : forall x : i . inv'4 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'3 (_x : Seq'0.t_seq (borrowed f))
-  
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span8] inv'3 self)  -> ([%#span9] len'2 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span10] ()
-  
-  function empty_len'2 (_1 : ()) : () =
-    [%#span12] ()
-  
-  axiom empty_len'2_spec : forall _1 : () . [%#span11] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span6] len'2 self >= 0
   
-  predicate invariant'3 (self : Seq'0.t_seq (borrowed f))
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  axiom inv'3 : forall x : Seq'0.t_seq (borrowed f) . inv'3 x = true
+  function empty_len'2 (_1 : ()) : ()
   
-  use seq.Seq
-  
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
+  axiom empty_len'2_spec : forall _1 : () . [%#span7] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'2 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span10] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
-  
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
+  constant empty'1 : Seq'0.t_seq item'0
   
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'1 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span13] inv'2 self)
-   -> ([%#span14] inv'2 other)
-   -> ([%#span17] inv'2 (concat'1 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'1 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'1 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span18] produces'1 a ab b)
-   -> ([%#span19] produces'1 b bc c)
-   -> ([%#span20] inv'4 a)
-   -> ([%#span21] inv'2 ab)
-   -> ([%#span22] inv'4 b)
-   -> ([%#span23] inv'2 bc)  -> ([%#span24] inv'4 c)  -> ([%#span25] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span10] produces'1 a ab b)
+   -> ([%#span11] produces'1 b bc c)
+   -> ([%#span12] inv'1 a)
+   -> ([%#span13] inv'1 b)  -> ([%#span14] inv'1 c)  -> ([%#span15] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span26] inv'4 self)
-   -> ([%#span27] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span16] inv'1 self)
+   -> ([%#span17] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   predicate resolve'0 (self : f)
   
@@ -651,73 +523,60 @@ module C05Map_Impl0_ProducesTrans_Impl
   
   function fn_mut_once'0 (self : f) (args : item'0) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span28] inv'5 self)
-   -> ([%#span29] inv'7 args)
-   -> ([%#span30] inv'8 res)
-   -> ([%#span31] postcondition_once'0 self args res
-  = (exists s : borrowed f . inv'6 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
+  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span18] inv'2 self)
+   -> ([%#span19] inv'4 args)
+   -> ([%#span20] inv'5 res)
+   -> ([%#span21] postcondition_once'0 self args res
+  = (exists s : borrowed f . inv'3 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span32] unnest'0 self b)
-   -> ([%#span33] unnest'0 b c)
-   -> ([%#span34] inv'5 self)  -> ([%#span35] inv'5 b)  -> ([%#span36] inv'5 c)  -> ([%#span37] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span22] unnest'0 self b)
+   -> ([%#span23] unnest'0 b c)
+   -> ([%#span24] inv'2 self)  -> ([%#span25] inv'2 b)  -> ([%#span26] inv'2 c)  -> ([%#span27] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span38] inv'5 self)  -> ([%#span39] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span28] inv'2 self)  -> ([%#span29] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : item'0) (res : b) : ()
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span40] postcondition_mut'0 self args res)
-   -> ([%#span41] inv'6 self)
-   -> ([%#span42] inv'7 args)  -> ([%#span43] inv'8 res)  -> ([%#span44] unnest'0 ( * self) ( ^ self))
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq b)
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span30] postcondition_mut'0 self args res)
+   -> ([%#span31] inv'3 self)
+   -> ([%#span32] inv'4 args)  -> ([%#span33] inv'5 res)  -> ([%#span34] unnest'0 ( * self) ( ^ self))
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span8] inv'1 self)  -> ([%#span9] len'1 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq b = [%#span10] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span6] len'1 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'0 : Seq'0.t_seq b
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'1 (empty'0 : Seq'0.t_seq b) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq b)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq b . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'1 (empty'0 : Seq'0.t_seq b) = 0
   
   predicate precondition'0 (self : f) (_2 : item'0)
   
-  use seq.Seq
-  
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span45] inv'10 v)
-   -> ([%#span48] inv'2 (singleton'0 v))
-  && ([%#span47] index_logic'1 (singleton'0 v) 0 = v) && ([%#span46] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span35] inv'7 v)
+   -> ([%#span37] index_logic'1 (singleton'0 v) 0 = v) && ([%#span36] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../05_map.rs" 74 4 74 50] (iter : i) (func : f) =
-    [%#span49] forall i : i . forall e : item'0 . inv'4 i
-     -> inv'10 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e)
+    [%#span38] forall i : i . forall e : item'0 . inv'1 i
+     -> inv'7 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span50] concat'1 self (singleton'0 v)
+    [%#span39] concat'1 self (singleton'0 v)
   
   predicate preservation'0 [#"../05_map.rs" 81 4 81 45] (iter : i) (func : f) =
-    [%#span51] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
-     -> inv'8 b
-     -> inv'6 f
-     -> inv'10 e2
-     -> inv'10 e1
-     -> inv'2 s
+    [%#span40] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
+     -> inv'5 b
+     -> inv'3 f
+     -> inv'7 e2
+     -> inv'7 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1)  -> postcondition_mut'0 f (e1) b  -> precondition'0 ( ^ f) (e2)
@@ -727,13 +586,13 @@ module C05Map_Impl0_ProducesTrans_Impl
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../05_map.rs" 93 4 93 29] (_1 : ()) =
-    [%#span52] forall func : f . forall iter : borrowed i . inv'5 func
-     -> inv'9 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
+    [%#span41] forall func : f . forall iter : borrowed i . inv'2 func
+     -> inv'6 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
   
   use C05Map_Map_Type as Map'0
   
   predicate invariant'0 [#"../05_map.rs" 131 4 131 30] (self : Map'0.t_map i b f) =
-    [%#span53] reinitialize'0 ()
+    [%#span42] reinitialize'0 ()
     /\ preservation'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
     /\ next_precondition'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
   
@@ -745,35 +604,25 @@ module C05Map_Impl0_ProducesTrans_Impl
     | Map'0.C_Map iter func -> true
     end)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq b) (x : int) : b
+  function index_logic'2 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function concat'0 (self : Seq'0.t_seq b) (other : Seq'0.t_seq b) : Seq'0.t_seq b
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span15] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span8] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   predicate produces'0 [@inline:trivial] [#"../05_map.rs" 41 4 41 67] (self : Map'0.t_map i b f) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f)
     
    =
-    [%#span54] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'2 s
-    /\ len'0 s = len'1 visited
+    [%#span43] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'1 (C05Map_Map_Type.map_iter self) s (C05Map_Map_Type.map_iter succ)
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'3 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'0 fs (i - 1) =  * index_logic'0 fs i)
     /\ (if len'1 visited = 0 then
       C05Map_Map_Type.map_func self = C05Map_Map_Type.map_func succ
@@ -799,13 +648,11 @@ module C05Map_Impl0_ProducesTrans_Impl
   function produces_trans [#"../05_map.rs" 36 4 36 90] (a : Map'0.t_map i b f) (ab : Seq'0.t_seq b) (b : Map'0.t_map i b f) (bc : Seq'0.t_seq b) (c : Map'0.t_map i b f) : ()
     
   
-  goal vc_produces_trans : ([%#s05_map6] inv'0 c)
-   -> ([%#s05_map5] inv'1 bc)
-   -> ([%#s05_map4] inv'0 b)
-   -> ([%#s05_map3] inv'1 ab)
+  goal vc_produces_trans : ([%#s05_map4] inv'0 c)
+   -> ([%#s05_map3] inv'0 b)
    -> ([%#s05_map2] inv'0 a)
    -> ([%#s05_map1] produces'0 b bc c)
-   -> ([%#s05_map0] produces'0 a ab b)  -> ([%#s05_map7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s05_map0] produces'0 a ab b)  -> ([%#s05_map5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -841,184 +688,145 @@ module C05Map_Impl1_ProducesOne_Impl
   
   let%span s05_map3 = "../05_map.rs" 116 14 116 68
   
-  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span sseq25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span sseq25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span sseq26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span sseq26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span sseq27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span s05_map7 = "../05_map.rs" 118 8 123 9
   
-  let%span s05_map8 = "../05_map.rs" 118 8 123 9
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span10 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span11 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span12 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
-  
-  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
-  
-  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
-  
-  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
-  
-  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
-  
-  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
-  
-  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
-  
-  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
-  
-  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
-  
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span36 = "../common.rs" 18 15 18 32
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span37 = "../common.rs" 19 15 19 32
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span38 = "../common.rs" 21 22 21 23
+  let%span span29 = "../common.rs" 18 15 18 32
   
-  let%span span39 = "../common.rs" 21 31 21 33
+  let%span span30 = "../common.rs" 19 15 19 32
   
-  let%span span40 = "../common.rs" 21 52 21 53
+  let%span span31 = "../common.rs" 21 22 21 23
   
-  let%span span41 = "../common.rs" 21 61 21 63
+  let%span span32 = "../common.rs" 21 52 21 53
   
-  let%span span42 = "../common.rs" 21 82 21 83
+  let%span span33 = "../common.rs" 21 82 21 83
   
-  let%span span43 = "../common.rs" 20 14 20 42
+  let%span span34 = "../common.rs" 20 14 20 42
   
-  let%span span44 = "../common.rs" 15 21 15 25
+  let%span span35 = "../common.rs" 15 21 15 25
   
-  let%span span45 = "../common.rs" 14 14 14 45
+  let%span span36 = "../common.rs" 14 14 14 45
   
-  let%span span46 = "../05_map.rs" 42 8 53 9
+  let%span span37 = "../05_map.rs" 42 8 53 9
   
-  let%span span47 = "../05_map.rs" 33 15 33 32
+  let%span span38 = "../05_map.rs" 33 15 33 32
   
-  let%span span48 = "../05_map.rs" 34 15 34 32
+  let%span span39 = "../05_map.rs" 34 15 34 32
   
-  let%span span49 = "../05_map.rs" 36 22 36 23
+  let%span span40 = "../05_map.rs" 36 22 36 23
   
-  let%span span50 = "../05_map.rs" 36 31 36 33
+  let%span span41 = "../05_map.rs" 36 52 36 53
   
-  let%span span51 = "../05_map.rs" 36 52 36 53
+  let%span span42 = "../05_map.rs" 36 82 36 83
   
-  let%span span52 = "../05_map.rs" 36 61 36 63
+  let%span span43 = "../05_map.rs" 35 14 35 42
   
-  let%span span53 = "../05_map.rs" 36 82 36 83
+  let%span span44 = "../05_map.rs" 31 4 31 10
   
-  let%span span54 = "../05_map.rs" 35 14 35 42
+  let%span span45 = "../05_map.rs" 29 21 29 25
   
-  let%span span55 = "../05_map.rs" 31 4 31 10
+  let%span span46 = "../05_map.rs" 28 14 28 45
   
-  let%span span56 = "../05_map.rs" 29 21 29 25
+  let%span span47 = "../05_map.rs" 26 4 26 10
   
-  let%span span57 = "../05_map.rs" 28 14 28 45
+  let%span span48 = "../05_map.rs" 75 8 77 9
   
-  let%span span58 = "../05_map.rs" 26 4 26 10
+  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span59 = "../05_map.rs" 75 8 77 9
+  let%span span50 = "../05_map.rs" 82 8 89 9
   
-  let%span span60 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span51 = "../05_map.rs" 94 8 98 9
   
-  let%span span61 = "../05_map.rs" 82 8 89 9
-  
-  let%span span62 = "../05_map.rs" 94 8 98 9
-  
-  let%span span63 = "../05_map.rs" 133 12 135 57
+  let%span span52 = "../05_map.rs" 133 12 135 57
   
   use prelude.prelude.Borrow
   
-  predicate invariant'10 (self : borrowed i)
+  predicate invariant'7 (self : borrowed i)
   
-  predicate inv'10 (_x : borrowed i)
+  predicate inv'7 (_x : borrowed i)
   
-  axiom inv'10 : forall x : borrowed i . inv'10 x = true
+  axiom inv'7 : forall x : borrowed i . inv'7 x = true
   
   type item'0
   
-  predicate invariant'9 (self : item'0)
+  predicate invariant'6 (self : item'0)
   
-  predicate inv'9 (_x : item'0)
+  predicate inv'6 (_x : item'0)
   
-  axiom inv'9 : forall x : item'0 . inv'9 x = true
+  axiom inv'6 : forall x : item'0 . inv'6 x = true
   
-  predicate invariant'8 (self : f)
+  predicate invariant'5 (self : f)
   
-  predicate inv'8 (_x : f)
+  predicate inv'5 (_x : f)
   
-  axiom inv'8 : forall x : f . inv'8 x = true
+  axiom inv'5 : forall x : f . inv'5 x = true
   
-  predicate invariant'7 (self : i)
+  predicate invariant'4 (self : i)
   
-  predicate inv'7 (_x : i)
+  predicate inv'4 (_x : i)
   
-  axiom inv'7 : forall x : i . inv'7 x = true
+  axiom inv'4 : forall x : i . inv'4 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'6 (_x : Seq'0.t_seq (borrowed f))
-  
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span9] inv'6 self)  -> ([%#span10] len'2 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span11] ()
-  
-  function empty_len'2 (_1 : ()) : () =
-    [%#span13] ()
-  
-  axiom empty_len'2_spec : forall _1 : () . [%#span12] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
-  
-  predicate invariant'6 (self : Seq'0.t_seq (borrowed f))
-  
-  axiom inv'6 : forall x : Seq'0.t_seq (borrowed f) . inv'6 x = true
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span8] len'2 self >= 0
   
-  predicate invariant'5 (self : Seq'0.t_seq b)
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  predicate inv'5 (_x : Seq'0.t_seq b)
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom inv'5 : forall x : Seq'0.t_seq b . inv'5 x = true
+  axiom empty_len'2_spec : forall _1 : () . [%#span9] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   predicate resolve'0 (self : f)
   
@@ -1032,81 +840,65 @@ module C05Map_Impl1_ProducesOne_Impl
   
   function fn_mut_once'0 (self : f) (args : item'0) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span14] inv'8 self)
-   -> ([%#span15] inv'9 args)
-   -> ([%#span16] inv'1 res)
-   -> ([%#span17] postcondition_once'0 self args res
+  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span10] inv'5 self)
+   -> ([%#span11] inv'6 args)
+   -> ([%#span12] inv'1 res)
+   -> ([%#span13] postcondition_once'0 self args res
   = (exists s : borrowed f . inv'2 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span18] unnest'0 self b)
-   -> ([%#span19] unnest'0 b c)
-   -> ([%#span20] inv'8 self)  -> ([%#span21] inv'8 b)  -> ([%#span22] inv'8 c)  -> ([%#span23] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span14] unnest'0 self b)
+   -> ([%#span15] unnest'0 b c)
+   -> ([%#span16] inv'5 self)  -> ([%#span17] inv'5 b)  -> ([%#span18] inv'5 c)  -> ([%#span19] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span24] inv'8 self)  -> ([%#span25] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span20] inv'5 self)  -> ([%#span21] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : item'0) (res : b) : ()
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span26] postcondition_mut'0 self args res)
-   -> ([%#span27] inv'2 self)
-   -> ([%#span28] inv'9 args)  -> ([%#span29] inv'1 res)  -> ([%#span30] unnest'0 ( * self) ( ^ self))
-  
-  predicate invariant'4 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'4 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'4 : forall x : Seq'0.t_seq item'0 . inv'4 x = true
-  
-  use seq.Seq
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span22] postcondition_mut'0 self args res)
+   -> ([%#span23] inv'2 self)
+   -> ([%#span24] inv'6 args)  -> ([%#span25] inv'1 res)  -> ([%#span26] unnest'0 ( * self) ( ^ self))
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span9] inv'4 self)  -> ([%#span10] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span11] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span8] len'0 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span13] ()
+  constant empty'1 : Seq'0.t_seq item'0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span12] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span9] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'1 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span31] inv'4 self)
-   -> ([%#span32] inv'4 other)
-   -> ([%#span35] inv'4 (concat'1 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'0 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span28] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'1 self other)
    -> index_logic'0 (concat'1 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span33] len'0 (concat'1 self other) = len'0 self + len'0 other)
+  && ([%#span27] len'0 (concat'1 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'1 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'1_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span36] produces'1 a ab b)
-   -> ([%#span37] produces'1 b bc c)
-   -> ([%#span38] inv'7 a)
-   -> ([%#span39] inv'4 ab)
-   -> ([%#span40] inv'7 b)
-   -> ([%#span41] inv'4 bc)  -> ([%#span42] inv'7 c)  -> ([%#span43] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'1_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span29] produces'1 a ab b)
+   -> ([%#span30] produces'1 b bc c)
+   -> ([%#span31] inv'4 a)
+   -> ([%#span32] inv'4 b)  -> ([%#span33] inv'4 c)  -> ([%#span34] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'1 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'1_spec : forall self : i . ([%#span44] inv'7 self)
-   -> ([%#span45] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'1_spec : forall self : i . ([%#span35] inv'4 self)
+   -> ([%#span36] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   predicate invariant'3 (self : item'0)
   
@@ -1120,47 +912,35 @@ module C05Map_Impl1_ProducesOne_Impl
   
   use C05Map_Map_Type as Map'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq b) (x : int) : b
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span9] inv'5 self)  -> ([%#span10] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span8] len'1 self >= 0
   
   function concat'0 (self : Seq'0.t_seq b) (other : Seq'0.t_seq b) : Seq'0.t_seq b
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span31] inv'5 self)
-   -> ([%#span32] inv'5 other)
-   -> ([%#span35] inv'5 (concat'0 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span28] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span33] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span27] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : Map'0.t_map i b f)
   
   predicate precondition'0 (self : f) (_2 : item'0)
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   use C05Map_Map_Type as C05Map_Map_Type
   
   predicate produces'0 [@inline:trivial] [#"../05_map.rs" 41 4 41 67] (self : Map'0.t_map i b f) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f)
     
    =
-    [%#span46] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'4 s
-    /\ len'0 s = len'1 visited
+    [%#span37] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'1 (C05Map_Map_Type.map_iter self) s (C05Map_Map_Type.map_iter succ)
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'6 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'2 fs (i - 1) =  * index_logic'2 fs i)
     /\ (if len'1 visited = 0 then
       C05Map_Map_Type.map_func self = C05Map_Map_Type.map_func succ
@@ -1176,54 +956,47 @@ module C05Map_Impl1_ProducesOne_Impl
   function produces_trans'0 [#"../05_map.rs" 36 4 36 90] (a : Map'0.t_map i b f) (ab : Seq'0.t_seq b) (b : Map'0.t_map i b f) (bc : Seq'0.t_seq b) (c : Map'0.t_map i b f) : ()
     
    =
-    [%#span55] ()
+    [%#span44] ()
   
-  axiom produces_trans'0_spec : forall a : Map'0.t_map i b f, ab : Seq'0.t_seq b, b : Map'0.t_map i b f, bc : Seq'0.t_seq b, c : Map'0.t_map i b f . ([%#span47] produces'0 a ab b)
-   -> ([%#span48] produces'0 b bc c)
-   -> ([%#span49] inv'0 a)
-   -> ([%#span50] inv'5 ab)
-   -> ([%#span51] inv'0 b)
-   -> ([%#span52] inv'5 bc)  -> ([%#span53] inv'0 c)  -> ([%#span54] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Map'0.t_map i b f, ab : Seq'0.t_seq b, b : Map'0.t_map i b f, bc : Seq'0.t_seq b, c : Map'0.t_map i b f . ([%#span38] produces'0 a ab b)
+   -> ([%#span39] produces'0 b bc c)
+   -> ([%#span40] inv'0 a)
+   -> ([%#span41] inv'0 b)  -> ([%#span42] inv'0 c)  -> ([%#span43] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq b = [%#span11] ()
+  constant empty'0 : Seq'0.t_seq b
   
   function produces_refl'0 [#"../05_map.rs" 29 4 29 26] (self : Map'0.t_map i b f) : () =
-    [%#span58] ()
+    [%#span47] ()
   
-  axiom produces_refl'0_spec : forall self : Map'0.t_map i b f . ([%#span56] inv'0 self)
-   -> ([%#span57] produces'0 self (empty'0 : Seq'0.t_seq b) self)
+  axiom produces_refl'0_spec : forall self : Map'0.t_map i b f . ([%#span45] inv'0 self)
+   -> ([%#span46] produces'0 self (empty'0 : Seq'0.t_seq b) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span13] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span12] len'1 (empty'0 : Seq'0.t_seq b) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'1 (empty'0 : Seq'0.t_seq b) = 0
   
   predicate invariant'1 (self : b)
   
   axiom inv'1 : forall x : b . inv'1 x = true
   
-  use seq.Seq
-  
   function singleton'1 (v : item'0) : Seq'0.t_seq item'0
   
   axiom singleton'1_spec : forall v : item'0 . ([%#sseq24] inv'3 v)
-   -> ([%#sseq27] inv'4 (singleton'1 v))
-  && ([%#sseq26] index_logic'0 (singleton'1 v) 0 = v) && ([%#sseq25] len'0 (singleton'1 v) = 1)
+   -> ([%#sseq26] index_logic'0 (singleton'1 v) 0 = v) && ([%#sseq25] len'0 (singleton'1 v) = 1)
   
   predicate next_precondition'0 [#"../05_map.rs" 74 4 74 50] (iter : i) (func : f) =
-    [%#span59] forall i : i . forall e : item'0 . inv'7 i
+    [%#span48] forall i : i . forall e : item'0 . inv'4 i
      -> inv'3 e  -> produces'1 iter (singleton'1 e) i  -> precondition'0 func (e)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span60] concat'1 self (singleton'1 v)
+    [%#span49] concat'1 self (singleton'1 v)
   
   predicate preservation'0 [#"../05_map.rs" 81 4 81 45] (iter : i) (func : f) =
-    [%#span61] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'7 i
+    [%#span50] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
      -> inv'1 b
      -> inv'2 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1)  -> postcondition_mut'0 f (e1) b  -> precondition'0 ( ^ f) (e2)
@@ -1231,11 +1004,11 @@ module C05Map_Impl1_ProducesOne_Impl
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../05_map.rs" 93 4 93 29] (_1 : ()) =
-    [%#span62] forall func : f . forall iter : borrowed i . inv'8 func
-     -> inv'10 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
+    [%#span51] forall func : f . forall iter : borrowed i . inv'5 func
+     -> inv'7 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
   
   predicate invariant'0 [#"../05_map.rs" 131 4 131 30] (self : Map'0.t_map i b f) =
-    [%#span63] reinitialize'0 ()
+    [%#span52] reinitialize'0 ()
     /\ preservation'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
     /\ next_precondition'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
   
@@ -1245,13 +1018,10 @@ module C05Map_Impl1_ProducesOne_Impl
     | Map'0.C_Map iter func -> true
     end)
   
-  use seq.Seq
-  
   function singleton'0 (v : b) : Seq'0.t_seq b
   
   axiom singleton'0_spec : forall v : b . ([%#sseq24] inv'1 v)
-   -> ([%#sseq27] inv'5 (singleton'0 v))
-  && ([%#sseq26] index_logic'1 (singleton'0 v) 0 = v) && ([%#sseq25] len'1 (singleton'0 v) = 1)
+   -> ([%#sseq26] index_logic'1 (singleton'0 v) 0 = v) && ([%#sseq25] len'1 (singleton'0 v) = 1)
   
   constant self  : Map'0.t_map i b f
   
@@ -1278,7 +1048,7 @@ module C05Map_Impl1_ProducesOne_Impl
   else
     true
   )
-  /\ ([%#s05_map3] ([%#s05_map8] exists f : borrowed f . inv'2 f
+  /\ ([%#s05_map3] ([%#s05_map7] exists f : borrowed f . inv'2 f
   /\  * f = C05Map_Map_Type.map_func self
   /\  ^ f = C05Map_Map_Type.map_func succ
   /\ (exists e : item'0 . inv'3 e
@@ -1313,129 +1083,103 @@ module C05Map_Impl1_ProducesOneInvariant_Impl
   
   let%span s05_map9 = "../05_map.rs" 106 14 106 47
   
-  let%span sseq210 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span sseq211 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span sseq212 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span sseq210 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span sseq213 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span sseq211 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span sseq214 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span sseq212 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span sseq215 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span sseq213 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span sseq216 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span sseq214 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span sseq217 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span s05_map15 = "../05_map.rs" 101 4 101 12
   
-  let%span sseq218 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span s05_map19 = "../05_map.rs" 101 4 101 12
+  let%span span17 = "../05_map.rs" 75 8 77 9
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span19 = "../05_map.rs" 82 8 89 9
   
-  let%span span22 = "../05_map.rs" 75 8 77 9
+  let%span span20 = "../05_map.rs" 94 8 98 9
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span21 = "../05_map.rs" 133 12 135 57
   
-  let%span span24 = "../05_map.rs" 82 8 89 9
-  
-  let%span span25 = "../05_map.rs" 94 8 98 9
-  
-  let%span span26 = "../05_map.rs" 133 12 135 57
-  
-  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
-  
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
-  
-  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
-  
-  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
-  
-  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span44 = "../common.rs" 18 15 18 32
+  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span45 = "../common.rs" 19 15 19 32
+  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span46 = "../common.rs" 21 22 21 23
+  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span47 = "../common.rs" 21 31 21 33
+  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span48 = "../common.rs" 21 52 21 53
+  let%span span39 = "../common.rs" 18 15 18 32
   
-  let%span span49 = "../common.rs" 21 61 21 63
+  let%span span40 = "../common.rs" 19 15 19 32
   
-  let%span span50 = "../common.rs" 21 82 21 83
+  let%span span41 = "../common.rs" 21 22 21 23
   
-  let%span span51 = "../common.rs" 20 14 20 42
+  let%span span42 = "../common.rs" 21 52 21 53
   
-  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span43 = "../common.rs" 21 82 21 83
   
-  let%span span53 = "../common.rs" 15 21 15 25
+  let%span span44 = "../common.rs" 20 14 20 42
   
-  let%span span54 = "../common.rs" 14 14 14 45
+  let%span span45 = "../common.rs" 15 21 15 25
   
-  let%span span55 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span46 = "../common.rs" 14 14 14 45
   
-  let%span span56 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
   use prelude.prelude.Borrow
   
-  predicate invariant'8 (self : borrowed i)
+  predicate invariant'7 (self : borrowed i)
   
-  predicate inv'8 (_x : borrowed i)
+  predicate inv'7 (_x : borrowed i)
   
-  axiom inv'8 : forall x : borrowed i . inv'8 x = true
+  axiom inv'7 : forall x : borrowed i . inv'7 x = true
   
-  predicate invariant'7 (self : f)
+  predicate invariant'6 (self : f)
   
-  predicate inv'7 (_x : f)
+  predicate inv'6 (_x : f)
   
-  axiom inv'7 : forall x : f . inv'7 x = true
+  axiom inv'6 : forall x : f . inv'6 x = true
   
   type item'0
   
-  predicate invariant'6 (self : item'0)
-  
-  predicate inv'6 (_x : item'0)
-  
-  axiom inv'6 : forall x : item'0 . inv'6 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate invariant'5 (self : item'0)
   
-  predicate invariant'5 (self : Seq'0.t_seq item'0)
+  predicate inv'5 (_x : item'0)
   
-  predicate inv'5 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'5 : forall x : Seq'0.t_seq item'0 . inv'5 x = true
+  axiom inv'5 : forall x : item'0 . inv'5 x = true
   
   predicate invariant'4 (self : i)
   
@@ -1461,62 +1205,51 @@ module C05Map_Impl1_ProducesOneInvariant_Impl
   
   axiom inv'1 : forall x : item'0 . inv'1 x = true
   
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  
   predicate precondition'0 (self : f) (_2 : item'0)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span20] inv'5 self)  -> ([%#span21] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span16] len'0 self >= 0
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
   axiom singleton'0_spec : forall v : item'0 . ([%#sseq210] inv'1 v)
-   -> ([%#sseq213] inv'5 (singleton'0 v))
-  && ([%#sseq212] index_logic'0 (singleton'0 v) 0 = v) && ([%#sseq211] len'0 (singleton'0 v) = 1)
+   -> ([%#sseq212] index_logic'0 (singleton'0 v) 0 = v) && ([%#sseq211] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../05_map.rs" 74 4 74 50] (iter : i) (func : f) =
-    [%#span22] forall i : i . forall e : item'0 . inv'4 i
+    [%#span17] forall i : i . forall e : item'0 . inv'4 i
      -> inv'1 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e)
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : item'0) (_3 : b)
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#sseq214] inv'5 self)
-   -> ([%#sseq215] inv'5 other)
-   -> ([%#sseq218] inv'5 (concat'0 self other))
-  && ([%#sseq217] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#sseq214] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#sseq216] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#sseq213] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span23] concat'0 self (singleton'0 v)
+    [%#span18] concat'0 self (singleton'0 v)
   
   predicate unnest'0 (self : f) (_2 : f)
   
   predicate preservation'0 [#"../05_map.rs" 81 4 81 45] (iter : i) (func : f) =
-    [%#span24] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
+    [%#span19] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
      -> inv'2 b
      -> inv'3 f
      -> inv'1 e2
      -> inv'1 e1
-     -> inv'5 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1)  -> postcondition_mut'0 f (e1) b  -> precondition'0 ( ^ f) (e2)
@@ -1526,13 +1259,13 @@ module C05Map_Impl1_ProducesOneInvariant_Impl
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../05_map.rs" 93 4 93 29] (_1 : ()) =
-    [%#span25] forall func : f . forall iter : borrowed i . inv'7 func
-     -> inv'8 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
+    [%#span20] forall func : f . forall iter : borrowed i . inv'6 func
+     -> inv'7 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
   
   use C05Map_Map_Type as Map'0
   
   predicate invariant'0 [#"../05_map.rs" 131 4 131 30] (self : Map'0.t_map i b f) =
-    [%#span26] reinitialize'0 ()
+    [%#span21] reinitialize'0 ()
     /\ preservation'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
     /\ next_precondition'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
   
@@ -1550,49 +1283,46 @@ module C05Map_Impl1_ProducesOneInvariant_Impl
   
   function fn_mut_once'0 (self : f) (args : item'0) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span27] inv'7 self)
-   -> ([%#span28] inv'6 args)
-   -> ([%#span29] inv'2 res)
-   -> ([%#span30] postcondition_once'0 self args res
+  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span22] inv'6 self)
+   -> ([%#span23] inv'5 args)
+   -> ([%#span24] inv'2 res)
+   -> ([%#span25] postcondition_once'0 self args res
   = (exists s : borrowed f . inv'3 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span31] unnest'0 self b)
-   -> ([%#span32] unnest'0 b c)
-   -> ([%#span33] inv'7 self)  -> ([%#span34] inv'7 b)  -> ([%#span35] inv'7 c)  -> ([%#span36] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span26] unnest'0 self b)
+   -> ([%#span27] unnest'0 b c)
+   -> ([%#span28] inv'6 self)  -> ([%#span29] inv'6 b)  -> ([%#span30] inv'6 c)  -> ([%#span31] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span37] inv'7 self)  -> ([%#span38] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span32] inv'6 self)  -> ([%#span33] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : item'0) (res : b) : ()
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span39] postcondition_mut'0 self args res)
-   -> ([%#span40] inv'3 self)
-   -> ([%#span41] inv'6 args)  -> ([%#span42] inv'2 res)  -> ([%#span43] unnest'0 ( * self) ( ^ self))
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span34] postcondition_mut'0 self args res)
+   -> ([%#span35] inv'3 self)
+   -> ([%#span36] inv'5 args)  -> ([%#span37] inv'2 res)  -> ([%#span38] unnest'0 ( * self) ( ^ self))
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span44] produces'0 a ab b)
-   -> ([%#span45] produces'0 b bc c)
-   -> ([%#span46] inv'4 a)
-   -> ([%#span47] inv'5 ab)
-   -> ([%#span48] inv'4 b)
-   -> ([%#span49] inv'5 bc)  -> ([%#span50] inv'4 c)  -> ([%#span51] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span39] produces'0 a ab b)
+   -> ([%#span40] produces'0 b bc c)
+   -> ([%#span41] inv'4 a)
+   -> ([%#span42] inv'4 b)  -> ([%#span43] inv'4 c)  -> ([%#span44] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span52] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span53] inv'4 self)
-   -> ([%#span54] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span45] inv'4 self)
+   -> ([%#span46] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span56] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span55] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span47] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   constant self  : Map'0.t_map i b f
   
@@ -1617,32 +1347,16 @@ module C05Map_Impl1_ProducesOneInvariant_Impl
    -> ([%#s05_map0] produces'0 (C05Map_Map_Type.map_iter self) (singleton'0 e) iter)
    -> (forall i : i . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . if inv'4 i then
     if inv'1 e2 then
-      if inv'1 e1 then
-        if inv'5 s then
-          if produces'0 iter (push'0 (push'0 s e1) e2) i then
-            ([%#sseq210] inv'1 e)
-            /\ (([%#sseq213] inv'5 (singleton'0 e))
-            && ([%#sseq212] index_logic'0 (singleton'0 e) 0 = e) && ([%#sseq211] len'0 (singleton'0 e) = 1)
-             -> ([%#sseq215] inv'5 s) && ([%#sseq214] inv'5 (singleton'0 e)))
-          else
-            true
-          
-        else
-          true
-        
-      else
-        true
-      
+      if inv'1 e1 then if produces'0 iter (push'0 (push'0 s e1) e2) i then [%#sseq210] inv'1 e else true else true
     else
       true
     
   else
     true
   )
-  /\ ([%#s05_map19] forall i : i . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
+  /\ ([%#s05_map15] forall i : i . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
    -> inv'1 e2
    -> inv'1 e1
-   -> inv'5 s
    -> produces'0 iter (push'0 (push'0 s e1) e2) i
    -> produces'0 (C05Map_Map_Type.map_iter self) (push'0 (push'0 (concat'0 (singleton'0 e) s) e1) e2) i)
   && (let _ = () in ([%#s05_map9] next_precondition'0 iter ( ^ f)) && ([%#s05_map8] preservation'0 iter ( ^ f)))
@@ -1666,221 +1380,177 @@ module C05Map_Impl0_Next
   
   let%span s05_map5 = "../05_map.rs" 60 26 60 44
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span15 = "../05_map.rs" 75 8 77 9
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span11 = "../05_map.rs" 75 8 77 9
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span22 = "../05_map.rs" 82 8 89 9
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span23 = "../05_map.rs" 94 8 98 9
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span24 = "../05_map.rs" 133 12 135 57
+  let%span span15 = "../05_map.rs" 82 8 89 9
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span span16 = "../05_map.rs" 94 8 98 9
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span17 = "../05_map.rs" 133 12 135 57
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span42 = "../common.rs" 18 15 18 32
+  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span43 = "../common.rs" 19 15 19 32
+  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span44 = "../common.rs" 21 22 21 23
+  let%span span35 = "../common.rs" 18 15 18 32
   
-  let%span span45 = "../common.rs" 21 31 21 33
+  let%span span36 = "../common.rs" 19 15 19 32
   
-  let%span span46 = "../common.rs" 21 52 21 53
+  let%span span37 = "../common.rs" 21 22 21 23
   
-  let%span span47 = "../common.rs" 21 61 21 63
+  let%span span38 = "../common.rs" 21 52 21 53
   
-  let%span span48 = "../common.rs" 21 82 21 83
+  let%span span39 = "../common.rs" 21 82 21 83
   
-  let%span span49 = "../common.rs" 20 14 20 42
+  let%span span40 = "../common.rs" 20 14 20 42
   
-  let%span span50 = "../common.rs" 15 21 15 25
+  let%span span41 = "../common.rs" 15 21 15 25
   
-  let%span span51 = "../common.rs" 14 14 14 45
+  let%span span42 = "../common.rs" 14 14 14 45
   
-  let%span span52 = "../05_map.rs" 42 8 53 9
+  let%span span43 = "../05_map.rs" 42 8 53 9
   
-  let%span span53 = "../05_map.rs" 117 20 117 24
+  let%span span44 = "../05_map.rs" 117 20 117 24
   
-  let%span span54 = "../05_map.rs" 117 26 117 33
+  let%span span45 = "../05_map.rs" 117 26 117 33
   
-  let%span span55 = "../05_map.rs" 117 38 117 42
+  let%span span46 = "../05_map.rs" 117 38 117 42
   
-  let%span span56 = "../05_map.rs" 116 14 116 68
+  let%span span47 = "../05_map.rs" 116 14 116 68
   
-  let%span span57 = "../05_map.rs" 118 8 123 9
+  let%span span48 = "../05_map.rs" 118 8 123 9
   
-  let%span span58 = "../05_map.rs" 23 8 23 75
+  let%span span49 = "../05_map.rs" 23 8 23 75
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/ops.rs" 160 27 160 52
+  let%span span50 = "../../../../../creusot-contracts/src/std/ops.rs" 160 27 160 52
   
-  let%span span60 = "" 0 0 0 0
+  let%span span51 = "" 0 0 0 0
   
-  let%span span61 = "" 0 0 0 0
+  let%span span52 = "" 0 0 0 0
   
-  let%span span62 = "../../../../../creusot-contracts/src/std/ops.rs" 148 0 172 1
+  let%span span53 = "../../../../../creusot-contracts/src/std/ops.rs" 148 0 172 1
   
-  let%span span63 = "" 0 0 0 0
+  let%span span54 = "" 0 0 0 0
   
-  let%span span64 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span55 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span65 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span56 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span66 = "../05_map.rs" 102 4 102 60
+  let%span span57 = "../05_map.rs" 102 4 102 60
   
-  let%span span67 = "../05_map.rs" 103 15 103 30
+  let%span span58 = "../05_map.rs" 103 15 103 30
   
-  let%span span68 = "../05_map.rs" 104 15 104 43
+  let%span span59 = "../05_map.rs" 104 15 104 43
   
-  let%span span69 = "../05_map.rs" 107 30 107 34
+  let%span span60 = "../05_map.rs" 107 30 107 34
   
-  let%span span70 = "../05_map.rs" 107 36 107 37
+  let%span span61 = "../05_map.rs" 107 36 107 37
   
-  let%span span71 = "../05_map.rs" 107 48 107 49
+  let%span span62 = "../05_map.rs" 107 48 107 49
   
-  let%span span72 = "../05_map.rs" 107 54 107 55
+  let%span span63 = "../05_map.rs" 107 54 107 55
   
-  let%span span73 = "../05_map.rs" 107 65 107 69
+  let%span span64 = "../05_map.rs" 107 65 107 69
   
-  let%span span74 = "../05_map.rs" 105 14 105 42
+  let%span span65 = "../05_map.rs" 105 14 105 42
   
-  let%span span75 = "../05_map.rs" 106 14 106 47
+  let%span span66 = "../05_map.rs" 106 14 106 47
   
-  let%span span76 = "../05_map.rs" 101 4 101 12
+  let%span span67 = "../05_map.rs" 101 4 101 12
   
-  let%span span77 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span68 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span78 = "../common.rs" 27 17 27 21
+  let%span span69 = "../common.rs" 27 17 27 21
   
-  let%span span79 = "../common.rs" 23 14 26 5
+  let%span span70 = "../common.rs" 23 14 26 5
   
-  let%span span80 = "../common.rs" 27 26 27 44
+  let%span span71 = "../common.rs" 27 26 27 44
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   use prelude.prelude.Borrow
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'14 (_x : Seq'0.t_seq (borrowed f))
-  
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span6] inv'14 self)  -> ([%#span7] len'2 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span8] ()
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span6] len'2 self >= 0
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span10] ()
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span9] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
+  function empty_len'2 (_1 : ()) : ()
   
-  predicate invariant'14 (self : Seq'0.t_seq (borrowed f))
-  
-  axiom inv'14 : forall x : Seq'0.t_seq (borrowed f) . inv'14 x = true
-  
-  predicate invariant'13 (self : Seq'0.t_seq b)
-  
-  predicate inv'13 (_x : Seq'0.t_seq b)
-  
-  axiom inv'13 : forall x : Seq'0.t_seq b . inv'13 x = true
-  
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span7] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span6] inv'13 self)  -> ([%#span7] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span6] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq b = [%#span8] ()
+  constant empty'1 : Seq'0.t_seq b
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span9] len'1 (empty'1 : Seq'0.t_seq b) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'1 (empty'1 : Seq'0.t_seq b) = 0
   
   type item'0
   
-  predicate invariant'12 (self : item'0)
-  
-  predicate inv'12 (_x : item'0)
+  predicate invariant'11 (self : item'0)
   
-  axiom inv'12 : forall x : item'0 . inv'12 x = true
+  predicate inv'11 (_x : item'0)
   
-  predicate invariant'11 (self : ())
+  axiom inv'11 : forall x : item'0 . inv'11 x = true
   
-  predicate inv'11 (_x : ())
+  predicate invariant'10 (self : ())
   
-  axiom inv'11 : forall x : () . inv'11 x = true
+  predicate inv'10 (_x : ())
   
-  predicate invariant'10 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'10 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'10 : forall x : Seq'0.t_seq item'0 . inv'10 x = true
+  axiom inv'10 : forall x : () . inv'10 x = true
   
   predicate invariant'9 (self : borrowed f)
   
@@ -1908,54 +1578,43 @@ module C05Map_Impl0_Next
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span6] inv'10 self)  -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span11] inv'7 v)
-   -> ([%#span14] inv'10 (singleton'0 v))
-  && ([%#span13] index_logic'0 (singleton'0 v) 0 = v) && ([%#span12] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span8] inv'7 v)
+   -> ([%#span10] index_logic'0 (singleton'0 v) 0 = v) && ([%#span9] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../05_map.rs" 74 4 74 50] (iter : i) (func : f) =
-    [%#span15] forall i : i . forall e : item'0 . inv'0 i
+    [%#span11] forall i : i . forall e : item'0 . inv'0 i
      -> inv'7 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e)
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : item'0) (_3 : b)
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span16] inv'10 self)
-   -> ([%#span17] inv'10 other)
-   -> ([%#span20] inv'10 (concat'0 self other))
-  && ([%#span19] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span13] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span18] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span21] concat'0 self (singleton'0 v)
+    [%#span14] concat'0 self (singleton'0 v)
   
   predicate unnest'0 (self : f) (_2 : f)
   
   predicate preservation'0 [#"../05_map.rs" 81 4 81 45] (iter : i) (func : f) =
-    [%#span22] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+    [%#span15] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
      -> inv'8 b
      -> inv'9 f
      -> inv'7 e2
      -> inv'7 e1
-     -> inv'10 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1)  -> postcondition_mut'0 f (e1) b  -> precondition'0 ( ^ f) (e2)
@@ -1967,13 +1626,13 @@ module C05Map_Impl0_Next
   predicate inv'5 (_x : borrowed i)
   
   predicate reinitialize'0 [#"../05_map.rs" 93 4 93 29] (_1 : ()) =
-    [%#span23] forall func : f . forall iter : borrowed i . inv'3 func
+    [%#span16] forall func : f . forall iter : borrowed i . inv'3 func
      -> inv'5 iter  -> completed'1 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
   
   use C05Map_Map_Type as Map'0
   
   predicate invariant'6 [#"../05_map.rs" 131 4 131 30] (self : Map'0.t_map i b f) =
-    [%#span24] reinitialize'0 ()
+    [%#span17] reinitialize'0 ()
     /\ preservation'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
     /\ next_precondition'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
   
@@ -1991,34 +1650,33 @@ module C05Map_Impl0_Next
   
   function fn_mut_once'0 (self : f) (args : item'0) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span25] inv'3 self)
-   -> ([%#span26] inv'12 args)
-   -> ([%#span27] inv'8 res)
-   -> ([%#span28] postcondition_once'0 self args res
+  axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span18] inv'3 self)
+   -> ([%#span19] inv'11 args)
+   -> ([%#span20] inv'8 res)
+   -> ([%#span21] postcondition_once'0 self args res
   = (exists s : borrowed f . inv'9 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'3 ( ^ s)))
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span29] unnest'0 self b)
-   -> ([%#span30] unnest'0 b c)
-   -> ([%#span31] inv'3 self)  -> ([%#span32] inv'3 b)  -> ([%#span33] inv'3 c)  -> ([%#span34] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span22] unnest'0 self b)
+   -> ([%#span23] unnest'0 b c)
+   -> ([%#span24] inv'3 self)  -> ([%#span25] inv'3 b)  -> ([%#span26] inv'3 c)  -> ([%#span27] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span35] inv'3 self)  -> ([%#span36] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span28] inv'3 self)  -> ([%#span29] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : item'0) (res : b) : ()
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span37] postcondition_mut'0 self args res)
-   -> ([%#span38] inv'9 self)
-   -> ([%#span39] inv'12 args)  -> ([%#span40] inv'8 res)  -> ([%#span41] unnest'0 ( * self) ( ^ self))
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span30] postcondition_mut'0 self args res)
+   -> ([%#span31] inv'9 self)
+   -> ([%#span32] inv'11 args)  -> ([%#span33] inv'8 res)  -> ([%#span34] unnest'0 ( * self) ( ^ self))
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span8] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'5 (self : borrowed i)
   
@@ -2051,39 +1709,31 @@ module C05Map_Impl0_Next
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span42] produces'0 a ab b)
-   -> ([%#span43] produces'0 b bc c)
-   -> ([%#span44] inv'0 a)
-   -> ([%#span45] inv'10 ab)
-   -> ([%#span46] inv'0 b)
-   -> ([%#span47] inv'10 bc)  -> ([%#span48] inv'0 c)  -> ([%#span49] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span35] produces'0 a ab b)
+   -> ([%#span36] produces'0 b bc c)
+   -> ([%#span37] inv'0 a)
+   -> ([%#span38] inv'0 b)  -> ([%#span39] inv'0 c)  -> ([%#span40] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span50] inv'0 self)
-   -> ([%#span51] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span41] inv'0 self)
+   -> ([%#span42] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'0 (self : i)
   
   axiom inv'0 : forall x : i . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq b) (x : int) : b
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq b) (_2 : int) : b
   
-  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   predicate produces'1 [@inline:trivial] [#"../05_map.rs" 41 4 41 67] (self : Map'0.t_map i b f) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f)
     
    =
-    [%#span52] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'10 s
-    /\ len'0 s = len'1 visited
+    [%#span43] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'0 (C05Map_Map_Type.map_iter self) s (C05Map_Map_Type.map_iter succ)
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'14 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'2 fs (i - 1) =  * index_logic'2 fs i)
     /\ (if len'1 visited = 0 then
       C05Map_Map_Type.map_func self = C05Map_Map_Type.map_func succ
@@ -2096,43 +1746,40 @@ module C05Map_Impl0_Next
     /\ precondition'0 ( * index_logic'2 fs i) (index_logic'0 s i)
     /\ postcondition_mut'0 (index_logic'2 fs i) (index_logic'0 s i) (index_logic'1 visited i))))
   
-  use seq.Seq
-  
   function singleton'1 (v : b) : Seq'0.t_seq b
   
-  axiom singleton'1_spec : forall v : b . ([%#span11] inv'8 v)
-   -> ([%#span14] inv'13 (singleton'1 v))
-  && ([%#span13] index_logic'1 (singleton'1 v) 0 = v) && ([%#span12] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : b . ([%#span8] inv'8 v)
+   -> ([%#span10] index_logic'1 (singleton'1 v) 0 = v) && ([%#span9] len'1 (singleton'1 v) = 1)
   
   predicate produces_one'0 [#"../05_map.rs" 117 4 117 57] (self : Map'0.t_map i b f) (visited : b) (succ : Map'0.t_map i b f)
     
    =
-    [%#span57] exists f : borrowed f . inv'9 f
+    [%#span48] exists f : borrowed f . inv'9 f
     /\  * f = C05Map_Map_Type.map_func self
     /\  ^ f = C05Map_Map_Type.map_func succ
     /\ (exists e : item'0 . inv'7 e
     /\ produces'0 (C05Map_Map_Type.map_iter self) (singleton'0 e) (C05Map_Map_Type.map_iter succ)
     /\ precondition'0 ( * f) (e) /\ postcondition_mut'0 f (e) visited)
   
-  axiom produces_one'0_spec : forall self : Map'0.t_map i b f, visited : b, succ : Map'0.t_map i b f . ([%#span53] inv'6 self)
-   -> ([%#span54] inv'8 visited)
-   -> ([%#span55] inv'6 succ)
-   -> ([%#span56] produces_one'0 self visited succ = produces'1 self (singleton'1 visited) succ)
+  axiom produces_one'0_spec : forall self : Map'0.t_map i b f, visited : b, succ : Map'0.t_map i b f . ([%#span44] inv'6 self)
+   -> ([%#span45] inv'8 visited)
+   -> ([%#span46] inv'6 succ)
+   -> ([%#span47] produces_one'0 self visited succ = produces'1 self (singleton'1 visited) succ)
   
   predicate completed'0 [#"../05_map.rs" 22 4 22 35] (self : borrowed (Map'0.t_map i b f)) =
-    [%#span58] completed'1 (Borrow.borrow_logic (C05Map_Map_Type.map_iter ( * self)) (C05Map_Map_Type.map_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span49] completed'1 (Borrow.borrow_logic (C05Map_Map_Type.map_iter ( * self)) (C05Map_Map_Type.map_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ C05Map_Map_Type.map_func ( * self) = C05Map_Map_Type.map_func ( ^ self)
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  let rec call_mut'0 (self:borrowed f) (args:item'0) (return'  (ret:b))= {[@expl:precondition] [%#span61] inv'12 args}
-    {[@expl:precondition] [%#span60] inv'9 self}
-    {[@expl:precondition] [%#span59] precondition'0 ( * self) args}
+  let rec call_mut'0 (self:borrowed f) (args:item'0) (return'  (ret:b))= {[@expl:precondition] [%#span52] inv'11 args}
+    {[@expl:precondition] [%#span51] inv'9 self}
+    {[@expl:precondition] [%#span50] precondition'0 ( * self) args}
     any
-    [ return' (result:b)-> {[%#span63] inv'8 result}
-      {[%#span62] postcondition_mut'0 self args result}
+    [ return' (result:b)-> {[%#span54] inv'8 result}
+      {[%#span53] postcondition_mut'0 self args result}
       (! return' {result}) ]
     
   
@@ -2142,30 +1789,30 @@ module C05Map_Impl0_Next
   
   function new'0 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'0_spec : forall x : () . ([%#span64] inv'11 x)  -> ([%#span65] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : () . ([%#span55] inv'10 x)  -> ([%#span56] deref'0 (new'0 x) = x)
   
   function produces_one_invariant'0 [#"../05_map.rs" 107 4 107 73] (self : Map'0.t_map i b f) (e : item'0) (r : b) (f : borrowed f) (iter : i) : ()
     
   
-  axiom produces_one_invariant'0_spec : forall self : Map'0.t_map i b f, e : item'0, r : b, f : borrowed f, iter : i . ([%#span66] produces'0 (C05Map_Map_Type.map_iter self) (singleton'0 e) iter)
-   -> ([%#span67]  * f = C05Map_Map_Type.map_func self)
-   -> ([%#span68] postcondition_mut'0 f (e) r)
-   -> ([%#span69] inv'6 self)
-   -> ([%#span70] inv'7 e)
-   -> ([%#span71] inv'8 r)
-   -> ([%#span72] inv'9 f)
-   -> ([%#span73] inv'0 iter)
-   -> ([%#span75] next_precondition'0 iter ( ^ f)) && ([%#span74] preservation'0 iter ( ^ f))
+  axiom produces_one_invariant'0_spec : forall self : Map'0.t_map i b f, e : item'0, r : b, f : borrowed f, iter : i . ([%#span57] produces'0 (C05Map_Map_Type.map_iter self) (singleton'0 e) iter)
+   -> ([%#span58]  * f = C05Map_Map_Type.map_func self)
+   -> ([%#span59] postcondition_mut'0 f (e) r)
+   -> ([%#span60] inv'6 self)
+   -> ([%#span61] inv'7 e)
+   -> ([%#span62] inv'8 r)
+   -> ([%#span63] inv'9 f)
+   -> ([%#span64] inv'0 iter)
+   -> ([%#span66] next_precondition'0 iter ( ^ f)) && ([%#span65] preservation'0 iter ( ^ f))
   
   predicate resolve'1 (self : Option'0.t_option item'0)
   
   predicate resolve'0 (self : borrowed (Map'0.t_map i b f)) =
-    [%#span77]  ^ self =  * self
+    [%#span68]  ^ self =  * self
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span78] inv'5 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span69] inv'5 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span80] inv'2 result}
-      {[%#span79] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span71] inv'2 result}
+      {[%#span70] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -2320,71 +1967,53 @@ module C05Map_Map
   
   let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span30 = "../05_map.rs" 75 8 77 9
+  let%span span28 = "../05_map.rs" 75 8 77 9
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span32 = "../05_map.rs" 82 8 89 9
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span33 = "../05_map.rs" 94 8 98 9
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span34 = "../05_map.rs" 133 12 135 57
   
-  let%span span37 = "../05_map.rs" 82 8 89 9
+  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span38 = "../05_map.rs" 94 8 98 9
-  
-  let%span span39 = "../05_map.rs" 133 12 135 57
-  
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span43 = "../common.rs" 18 15 18 32
-  
-  let%span span44 = "../common.rs" 19 15 19 32
-  
-  let%span span45 = "../common.rs" 21 22 21 23
+  let%span span36 = "../common.rs" 18 15 18 32
   
-  let%span span46 = "../common.rs" 21 31 21 33
+  let%span span37 = "../common.rs" 19 15 19 32
   
-  let%span span47 = "../common.rs" 21 52 21 53
+  let%span span38 = "../common.rs" 21 22 21 23
   
-  let%span span48 = "../common.rs" 21 61 21 63
+  let%span span39 = "../common.rs" 21 52 21 53
   
-  let%span span49 = "../common.rs" 21 82 21 83
+  let%span span40 = "../common.rs" 21 82 21 83
   
-  let%span span50 = "../common.rs" 20 14 20 42
+  let%span span41 = "../common.rs" 20 14 20 42
   
-  let%span span51 = "../common.rs" 15 21 15 25
+  let%span span42 = "../common.rs" 15 21 15 25
   
-  let%span span52 = "../common.rs" 14 14 14 45
+  let%span span43 = "../common.rs" 14 14 14 45
   
   type item'0
   
-  predicate invariant'8 (self : item'0)
+  predicate invariant'7 (self : item'0)
   
-  predicate inv'8 (_x : item'0)
+  predicate inv'7 (_x : item'0)
   
-  axiom inv'8 : forall x : item'0 . inv'8 x = true
+  axiom inv'7 : forall x : item'0 . inv'7 x = true
   
   predicate resolve'0 (self : f)
   
@@ -2392,21 +2021,21 @@ module C05Map_Map
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : item'0) (_3 : b)
   
-  predicate inv'7 (_x : borrowed f)
+  predicate inv'6 (_x : borrowed f)
   
   predicate postcondition_once'0 (self : f) (_2 : item'0) (_3 : b)
   
-  predicate inv'6 (_x : b)
+  predicate inv'5 (_x : b)
   
   predicate inv'2 (_x : f)
   
   function fn_mut_once'0 (self : f) (args : item'0) (res : b) : ()
   
   axiom fn_mut_once'0_spec : forall self : f, args : item'0, res : b . ([%#span7] inv'2 self)
-   -> ([%#span8] inv'8 args)
-   -> ([%#span9] inv'6 res)
+   -> ([%#span8] inv'7 args)
+   -> ([%#span9] inv'5 res)
    -> ([%#span10] postcondition_once'0 self args res
-  = (exists s : borrowed f . inv'7 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
+  = (exists s : borrowed f . inv'6 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
@@ -2423,87 +2052,68 @@ module C05Map_Map
   function postcondition_mut_unnest'0 (self : borrowed f) (args : item'0) (res : b) : ()
   
   axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : item'0, res : b . ([%#span19] postcondition_mut'0 self args res)
-   -> ([%#span20] inv'7 self)
-   -> ([%#span21] inv'8 args)  -> ([%#span22] inv'6 res)  -> ([%#span23] unnest'0 ( * self) ( ^ self))
-  
-  predicate invariant'7 (self : borrowed f)
-  
-  axiom inv'7 : forall x : borrowed f . inv'7 x = true
-  
-  predicate invariant'6 (self : b)
+   -> ([%#span20] inv'6 self)
+   -> ([%#span21] inv'7 args)  -> ([%#span22] inv'5 res)  -> ([%#span23] unnest'0 ( * self) ( ^ self))
   
-  axiom inv'6 : forall x : b . inv'6 x = true
-  
-  predicate invariant'5 (self : borrowed i)
+  predicate invariant'6 (self : borrowed f)
   
-  predicate inv'5 (_x : borrowed i)
+  axiom inv'6 : forall x : borrowed f . inv'6 x = true
   
-  axiom inv'5 : forall x : borrowed i . inv'5 x = true
+  predicate invariant'5 (self : b)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'5 : forall x : b . inv'5 x = true
   
-  predicate invariant'4 (self : Seq'0.t_seq item'0)
+  predicate invariant'4 (self : borrowed i)
   
-  predicate inv'4 (_x : Seq'0.t_seq item'0)
+  predicate inv'4 (_x : borrowed i)
   
-  axiom inv'4 : forall x : Seq'0.t_seq item'0 . inv'4 x = true
+  axiom inv'4 : forall x : borrowed i . inv'4 x = true
   
   predicate inv'0 (_x : i)
   
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  
   predicate precondition'0 (self : f) (_2 : item'0)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span24] inv'4 self)  -> ([%#span25] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span24] len'0 self >= 0
   
   predicate inv'1 (_x : item'0)
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span26] inv'1 v)
-   -> ([%#span29] inv'4 (singleton'0 v))
-  && ([%#span28] index_logic'0 (singleton'0 v) 0 = v) && ([%#span27] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span25] inv'1 v)
+   -> ([%#span27] index_logic'0 (singleton'0 v) 0 = v) && ([%#span26] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../05_map.rs" 74 4 74 50] (iter : i) (func : f) =
-    [%#span30] forall i : i . forall e : item'0 . inv'0 i
+    [%#span28] forall i : i . forall e : item'0 . inv'0 i
      -> inv'1 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e)
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span31] inv'4 self)
-   -> ([%#span32] inv'4 other)
-   -> ([%#span35] inv'4 (concat'0 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span30] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span33] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span29] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span36] concat'0 self (singleton'0 v)
+    [%#span31] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../05_map.rs" 81 4 81 45] (iter : i) (func : f) =
-    [%#span37] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
-     -> inv'6 b
-     -> inv'7 f
+    [%#span32] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+     -> inv'5 b
+     -> inv'6 f
      -> inv'1 e2
      -> inv'1 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1)  -> postcondition_mut'0 f (e1) b  -> precondition'0 ( ^ f) (e2)
@@ -2513,13 +2123,13 @@ module C05Map_Map
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../05_map.rs" 93 4 93 29] (_1 : ()) =
-    [%#span38] forall func : f . forall iter : borrowed i . inv'2 func
-     -> inv'5 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
+    [%#span33] forall func : f . forall iter : borrowed i . inv'2 func
+     -> inv'4 iter  -> completed'0 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
   
   use C05Map_Map_Type as Map'0
   
   predicate invariant'3 [#"../05_map.rs" 131 4 131 30] (self : Map'0.t_map i b f) =
-    [%#span39] reinitialize'0 ()
+    [%#span34] reinitialize'0 ()
     /\ preservation'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
     /\ next_precondition'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
   
@@ -2535,12 +2145,11 @@ module C05Map_Map
   
   axiom inv'2 : forall x : f . inv'2 x = true
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span40] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span42] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span41] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span35] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'1 (self : item'0)
   
@@ -2553,17 +2162,15 @@ module C05Map_Map
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span43] produces'0 a ab b)
-   -> ([%#span44] produces'0 b bc c)
-   -> ([%#span45] inv'0 a)
-   -> ([%#span46] inv'4 ab)
-   -> ([%#span47] inv'0 b)
-   -> ([%#span48] inv'4 bc)  -> ([%#span49] inv'0 c)  -> ([%#span50] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span36] produces'0 a ab b)
+   -> ([%#span37] produces'0 b bc c)
+   -> ([%#span38] inv'0 a)
+   -> ([%#span39] inv'0 b)  -> ([%#span40] inv'0 c)  -> ([%#span41] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span51] inv'0 self)
-   -> ([%#span52] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span42] inv'0 self)
+   -> ([%#span43] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   use prelude.prelude.Intrinsic
   
@@ -2605,113 +2212,83 @@ module C05Map_Impl0
   
   let%span s05_map2 = "../05_map.rs" 29 4 29 26
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span7 = "../05_map.rs" 75 8 77 9
   
-  let%span span9 = "../05_map.rs" 75 8 77 9
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span11 = "../05_map.rs" 82 8 89 9
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span12 = "../05_map.rs" 94 8 98 9
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span13 = "../05_map.rs" 133 12 135 57
   
-  let%span span16 = "../05_map.rs" 82 8 89 9
+  let%span span14 = "../05_map.rs" 42 8 53 9
   
-  let%span span17 = "../05_map.rs" 94 8 98 9
+  let%span span15 = "../05_map.rs" 117 20 117 24
   
-  let%span span18 = "../05_map.rs" 133 12 135 57
+  let%span span16 = "../05_map.rs" 117 26 117 33
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span17 = "../05_map.rs" 117 38 117 42
   
-  let%span span20 = "../05_map.rs" 42 8 53 9
+  let%span span18 = "../05_map.rs" 116 14 116 68
   
-  let%span span21 = "../05_map.rs" 117 20 117 24
+  let%span span19 = "../05_map.rs" 118 8 123 9
   
-  let%span span22 = "../05_map.rs" 117 26 117 33
-  
-  let%span span23 = "../05_map.rs" 117 38 117 42
-  
-  let%span span24 = "../05_map.rs" 116 14 116 68
-  
-  let%span span25 = "../05_map.rs" 118 8 123 9
-  
-  let%span span26 = "../05_map.rs" 23 8 23 75
+  let%span span20 = "../05_map.rs" 23 8 23 75
   
   use prelude.prelude.Borrow
   
-  predicate invariant'11 (self : borrowed i)
-  
-  predicate inv'11 (_x : borrowed i)
-  
-  axiom inv'11 : forall x : borrowed i . inv'11 x = true
-  
-  predicate invariant'10 (self : f)
-  
-  predicate inv'10 (_x : f)
+  predicate invariant'8 (self : borrowed i)
   
-  axiom inv'10 : forall x : f . inv'10 x = true
+  predicate inv'8 (_x : borrowed i)
   
-  predicate invariant'9 (self : i)
+  axiom inv'8 : forall x : borrowed i . inv'8 x = true
   
-  predicate inv'9 (_x : i)
+  predicate invariant'7 (self : f)
   
-  axiom inv'9 : forall x : i . inv'9 x = true
+  predicate inv'7 (_x : f)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'7 : forall x : f . inv'7 x = true
   
-  predicate invariant'8 (self : Seq'0.t_seq (borrowed f))
+  predicate invariant'6 (self : i)
   
-  predicate inv'8 (_x : Seq'0.t_seq (borrowed f))
+  predicate inv'6 (_x : i)
   
-  axiom inv'8 : forall x : Seq'0.t_seq (borrowed f) . inv'8 x = true
+  axiom inv'6 : forall x : i . inv'6 x = true
   
   type item'0
   
-  predicate invariant'7 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'7 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq item'0 . inv'7 x = true
-  
-  predicate invariant'6 (self : item'0)
-  
-  predicate inv'6 (_x : item'0)
+  predicate invariant'5 (self : item'0)
   
-  axiom inv'6 : forall x : item'0 . inv'6 x = true
-  
-  predicate invariant'5 (self : borrowed f)
+  predicate inv'5 (_x : item'0)
   
-  predicate inv'5 (_x : borrowed f)
+  axiom inv'5 : forall x : item'0 . inv'5 x = true
   
-  axiom inv'5 : forall x : borrowed f . inv'5 x = true
+  predicate invariant'4 (self : borrowed f)
   
-  predicate invariant'4 (self : b)
+  predicate inv'4 (_x : borrowed f)
   
-  predicate inv'4 (_x : b)
+  axiom inv'4 : forall x : borrowed f . inv'4 x = true
   
-  axiom inv'4 : forall x : b . inv'4 x = true
+  predicate invariant'3 (self : b)
   
-  predicate invariant'3 (self : Seq'0.t_seq b)
+  predicate inv'3 (_x : b)
   
-  predicate inv'3 (_x : Seq'0.t_seq b)
+  axiom inv'3 : forall x : b . inv'3 x = true
   
-  axiom inv'3 : forall x : Seq'0.t_seq b . inv'3 x = true
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   predicate precondition'0 (self : f) (_2 : item'0)
   
@@ -2719,56 +2296,43 @@ module C05Map_Impl0
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'2 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span3] inv'7 self)  -> ([%#span4] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span3] len'1 self >= 0
   
   function singleton'1 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'1_spec : forall v : item'0 . ([%#span5] inv'6 v)
-   -> ([%#span8] inv'7 (singleton'1 v))
-  && ([%#span7] index_logic'2 (singleton'1 v) 0 = v) && ([%#span6] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : item'0 . ([%#span4] inv'5 v)
+   -> ([%#span6] index_logic'2 (singleton'1 v) 0 = v) && ([%#span5] len'1 (singleton'1 v) = 1)
   
   predicate next_precondition'0 [#"../05_map.rs" 74 4 74 50] (iter : i) (func : f) =
-    [%#span9] forall i : i . forall e : item'0 . inv'9 i
-     -> inv'6 e  -> produces'1 iter (singleton'1 e) i  -> precondition'0 func (e)
+    [%#span7] forall i : i . forall e : item'0 . inv'6 i
+     -> inv'5 e  -> produces'1 iter (singleton'1 e) i  -> precondition'0 func (e)
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : item'0) (_3 : b)
   
-  use seq.Seq
-  
   function concat'1 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] inv'7 self)
-   -> ([%#span11] inv'7 other)
-   -> ([%#span14] inv'7 (concat'1 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'2 (concat'1 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span12] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span8] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span15] concat'1 self (singleton'1 v)
+    [%#span10] concat'1 self (singleton'1 v)
   
   predicate unnest'0 (self : f) (_2 : f)
   
   predicate preservation'0 [#"../05_map.rs" 81 4 81 45] (iter : i) (func : f) =
-    [%#span16] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'9 i
-     -> inv'4 b
-     -> inv'5 f
-     -> inv'6 e2
-     -> inv'6 e1
-     -> inv'7 s
+    [%#span11] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'6 i
+     -> inv'3 b
+     -> inv'4 f
+     -> inv'5 e2
+     -> inv'5 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1)  -> postcondition_mut'0 f (e1) b  -> precondition'0 ( ^ f) (e2)
@@ -2778,13 +2342,13 @@ module C05Map_Impl0
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../05_map.rs" 93 4 93 29] (_1 : ()) =
-    [%#span17] forall func : f . forall iter : borrowed i . inv'10 func
-     -> inv'11 iter  -> completed'1 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
+    [%#span12] forall func : f . forall iter : borrowed i . inv'7 func
+     -> inv'8 iter  -> completed'1 iter  -> next_precondition'0 ( ^ iter) func /\ preservation'0 ( ^ iter) func
   
   use C05Map_Map_Type as Map'0
   
   predicate invariant'2 [#"../05_map.rs" 131 4 131 30] (self : Map'0.t_map i b f) =
-    [%#span18] reinitialize'0 ()
+    [%#span13] reinitialize'0 ()
     /\ preservation'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
     /\ next_precondition'0 (C05Map_Map_Type.map_iter self) (C05Map_Map_Type.map_func self)
   
@@ -2810,51 +2374,37 @@ module C05Map_Impl0
   
   axiom inv'0 : forall x : borrowed (Map'0.t_map i b f) . inv'0 x = (inv'2 ( * x) /\ inv'2 ( ^ x))
   
-  constant empty'0 : Seq'0.t_seq b = [%#span19] ()
-  
-  constant empty'0 : Seq'0.t_seq b = [%#span19] ()
+  constant empty'0 : Seq'0.t_seq b
   
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq b
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq b) (x : int) : b
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function len'0 (self : Seq'0.t_seq b) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq b . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq b . [%#span3] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq b) (other : Seq'0.t_seq b) : Seq'0.t_seq b
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span10] inv'3 self)
-   -> ([%#span11] inv'3 other)
-   -> ([%#span14] inv'3 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span3] inv'8 self)  -> ([%#span4] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span3] len'2 self >= 0
   
   predicate produces'0 [@inline:trivial] [#"../05_map.rs" 41 4 41 67] (self : Map'0.t_map i b f) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f)
     
    =
-    [%#span20] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'7 s
-    /\ len'1 s = len'0 visited
+    [%#span14] unnest'0 (C05Map_Map_Type.map_func self) (C05Map_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'1 s = len'0 visited
     /\ produces'1 (C05Map_Map_Type.map_iter self) s (C05Map_Map_Type.map_iter succ)
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'8 fs
-    /\ len'2 fs = len'0 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'0 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'1 fs (i - 1) =  * index_logic'1 fs i)
     /\ (if len'0 visited = 0 then
       C05Map_Map_Type.map_func self = C05Map_Map_Type.map_func succ
@@ -2867,31 +2417,28 @@ module C05Map_Impl0
     /\ precondition'0 ( * index_logic'1 fs i) (index_logic'2 s i)
     /\ postcondition_mut'0 (index_logic'1 fs i) (index_logic'2 s i) (index_logic'0 visited i))))
   
-  use seq.Seq
-  
   function singleton'0 (v : b) : Seq'0.t_seq b
   
-  axiom singleton'0_spec : forall v : b . ([%#span5] inv'4 v)
-   -> ([%#span8] inv'3 (singleton'0 v))
-  && ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : b . ([%#span4] inv'3 v)
+   -> ([%#span6] index_logic'0 (singleton'0 v) 0 = v) && ([%#span5] len'0 (singleton'0 v) = 1)
   
   predicate produces_one'0 [#"../05_map.rs" 117 4 117 57] (self : Map'0.t_map i b f) (visited : b) (succ : Map'0.t_map i b f)
     
    =
-    [%#span25] exists f : borrowed f . inv'5 f
+    [%#span19] exists f : borrowed f . inv'4 f
     /\  * f = C05Map_Map_Type.map_func self
     /\  ^ f = C05Map_Map_Type.map_func succ
-    /\ (exists e : item'0 . inv'6 e
+    /\ (exists e : item'0 . inv'5 e
     /\ produces'1 (C05Map_Map_Type.map_iter self) (singleton'1 e) (C05Map_Map_Type.map_iter succ)
     /\ precondition'0 ( * f) (e) /\ postcondition_mut'0 f (e) visited)
   
-  axiom produces_one'0_spec : forall self : Map'0.t_map i b f, visited : b, succ : Map'0.t_map i b f . ([%#span21] inv'2 self)
-   -> ([%#span22] inv'4 visited)
-   -> ([%#span23] inv'2 succ)
-   -> ([%#span24] produces_one'0 self visited succ = produces'0 self (singleton'0 visited) succ)
+  axiom produces_one'0_spec : forall self : Map'0.t_map i b f, visited : b, succ : Map'0.t_map i b f . ([%#span15] inv'2 self)
+   -> ([%#span16] inv'3 visited)
+   -> ([%#span17] inv'2 succ)
+   -> ([%#span18] produces_one'0 self visited succ = produces'0 self (singleton'0 visited) succ)
   
   predicate completed'0 [#"../05_map.rs" 22 4 22 35] (self : borrowed (Map'0.t_map i b f)) =
-    [%#span26] completed'1 (Borrow.borrow_logic (C05Map_Map_Type.map_iter ( * self)) (C05Map_Map_Type.map_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span20] completed'1 (Borrow.borrow_logic (C05Map_Map_Type.map_iter ( * self)) (C05Map_Map_Type.map_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ C05Map_Map_Type.map_func ( * self) = C05Map_Map_Type.map_func ( ^ self)
   
   goal next_refn : [%#s05_map0] forall self : borrowed (Map'0.t_map i b f) . inv'0 self
@@ -2908,11 +2455,9 @@ module C05Map_Impl0
     end)
   
   goal produces_trans_refn : [%#s05_map1] forall a : Map'0.t_map i b f . forall ab : Seq'0.t_seq b . forall b : Map'0.t_map i b f . forall bc : Seq'0.t_seq b . forall c : Map'0.t_map i b f . inv'2 c
-  /\ inv'3 bc /\ inv'2 b /\ inv'3 ab /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'2 b /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'2 c
-  /\ inv'3 bc
   /\ inv'2 b
-  /\ inv'3 ab
   /\ inv'2 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
diff --git a/creusot/tests/should_succeed/iterators/06_map_precond.coma b/creusot/tests/should_succeed/iterators/06_map_precond.coma
index dcc24cbec2..dd9e9c325a 100644
--- a/creusot/tests/should_succeed/iterators/06_map_precond.coma
+++ b/creusot/tests/should_succeed/iterators/06_map_precond.coma
@@ -3,22 +3,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C06MapPrecond_Map_Type
   type item'0
@@ -68,101 +53,81 @@ module C06MapPrecond_Impl1_PreservationInv_Impl
   
   let%span s06_map_precond1 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span s06_map_precond2 = "../06_map_precond.rs" 93 42 93 50
-  
-  let%span s06_map_precond3 = "../06_map_precond.rs" 92 4 92 83
-  
-  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span sseq25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span sseq26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span s06_map_precond2 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span sseq27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span sseq23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span sseq28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span ssnapshot9 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span ssnapshot5 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span ssnapshot10 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span ssnapshot6 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span s06_map_precond11 = "../06_map_precond.rs" 94 8 101 9
+  let%span s06_map_precond7 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
-  
-  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
-  
-  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
-  
-  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
-  
-  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
-  
-  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span8 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span9 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span10 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span11 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span12 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span31 = "../common.rs" 18 15 18 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span32 = "../common.rs" 19 15 19 32
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span33 = "../common.rs" 21 22 21 23
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span34 = "../common.rs" 21 31 21 33
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span35 = "../common.rs" 21 52 21 53
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span36 = "../common.rs" 21 61 21 63
+  let%span span26 = "../common.rs" 18 15 18 32
   
-  let%span span37 = "../common.rs" 21 82 21 83
+  let%span span27 = "../common.rs" 19 15 19 32
   
-  let%span span38 = "../common.rs" 20 14 20 42
+  let%span span28 = "../common.rs" 21 22 21 23
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span29 = "../common.rs" 21 52 21 53
   
-  let%span span40 = "../common.rs" 15 21 15 25
+  let%span span30 = "../common.rs" 21 82 21 83
   
-  let%span span41 = "../common.rs" 14 14 14 45
+  let%span span31 = "../common.rs" 20 14 20 42
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span32 = "../common.rs" 15 21 15 25
   
-  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span33 = "../common.rs" 14 14 14 45
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span49 = "../06_map_precond.rs" 106 8 113 9
+  let%span span39 = "../06_map_precond.rs" 106 8 113 9
   
   type item'0
   
@@ -176,88 +141,83 @@ module C06MapPrecond_Impl1_PreservationInv_Impl
   
   axiom inv'6 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'6 x = true
   
+  predicate invariant'5 (self : Seq'0.t_seq item'0)
+  
+  predicate inv'5 (_x : Seq'0.t_seq item'0)
+  
+  axiom inv'5 : forall x : Seq'0.t_seq item'0 . inv'5 x = true
+  
   predicate resolve'0 (self : f)
   
   use prelude.prelude.Borrow
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (_3 : b)
   
-  predicate inv'4 (_x : borrowed f)
+  predicate inv'3 (_x : borrowed f)
   
   predicate postcondition_once'0 (self : f) (_2 : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (_3 : b)
   
-  predicate inv'3 (_x : b)
+  predicate inv'2 (_x : b)
   
   predicate inv'1 (_x : f)
   
   function fn_mut_once'0 (self : f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span12] inv'1 self)
-   -> ([%#span13] inv'6 args)
-   -> ([%#span14] inv'3 res)
-   -> ([%#span15] postcondition_once'0 self args res
-  = (exists s : borrowed f . inv'4 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
+  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span8] inv'1 self)
+   -> ([%#span9] inv'6 args)
+   -> ([%#span10] inv'2 res)
+   -> ([%#span11] postcondition_once'0 self args res
+  = (exists s : borrowed f . inv'3 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span16] unnest'0 self b)
-   -> ([%#span17] unnest'0 b c)
-   -> ([%#span18] inv'1 self)  -> ([%#span19] inv'1 b)  -> ([%#span20] inv'1 c)  -> ([%#span21] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span12] unnest'0 self b)
+   -> ([%#span13] unnest'0 b c)
+   -> ([%#span14] inv'1 self)  -> ([%#span15] inv'1 b)  -> ([%#span16] inv'1 c)  -> ([%#span17] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span22] inv'1 self)  -> ([%#span23] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span18] inv'1 self)  -> ([%#span19] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
     
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span24] postcondition_mut'0 self args res)
-   -> ([%#span25] inv'4 self)
-   -> ([%#span26] inv'6 args)  -> ([%#span27] inv'3 res)  -> ([%#span28] unnest'0 ( * self) ( ^ self))
-  
-  predicate invariant'5 (self : item'0)
-  
-  predicate inv'5 (_x : item'0)
-  
-  axiom inv'5 : forall x : item'0 . inv'5 x = true
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span20] postcondition_mut'0 self args res)
+   -> ([%#span21] inv'3 self)
+   -> ([%#span22] inv'6 args)  -> ([%#span23] inv'2 res)  -> ([%#span24] unnest'0 ( * self) ( ^ self))
   
-  predicate invariant'4 (self : borrowed f)
+  predicate invariant'4 (self : item'0)
   
-  axiom inv'4 : forall x : borrowed f . inv'4 x = true
+  predicate inv'4 (_x : item'0)
   
-  predicate invariant'3 (self : b)
+  axiom inv'4 : forall x : item'0 . inv'4 x = true
   
-  axiom inv'3 : forall x : b . inv'3 x = true
+  predicate invariant'3 (self : borrowed f)
   
-  use seq.Seq
+  axiom inv'3 : forall x : borrowed f . inv'3 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  predicate invariant'2 (self : b)
   
-  use seq.Seq
+  axiom inv'2 : forall x : b . inv'2 x = true
   
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
-  
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span29] inv'2 self)  -> ([%#span30] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span25] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#sseq24] inv'2 self)
-   -> ([%#sseq25] inv'2 other)
-   -> ([%#sseq28] inv'2 (concat'0 self other))
-  && ([%#sseq27] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#sseq24] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#sseq26] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#sseq23] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : i)
   
@@ -266,28 +226,21 @@ module C06MapPrecond_Impl1_PreservationInv_Impl
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span31] produces'0 a ab b)
-   -> ([%#span32] produces'0 b bc c)
-   -> ([%#span33] inv'0 a)
-   -> ([%#span34] inv'2 ab)
-   -> ([%#span35] inv'0 b)
-   -> ([%#span36] inv'2 bc)  -> ([%#span37] inv'0 c)  -> ([%#span38] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span26] produces'0 a ab b)
+   -> ([%#span27] produces'0 b bc c)
+   -> ([%#span28] inv'0 a)
+   -> ([%#span29] inv'0 b)  -> ([%#span30] inv'0 c)  -> ([%#span31] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span39] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span40] inv'0 self)
-   -> ([%#span41] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span43] ()
+  axiom produces_refl'0_spec : forall self : i . ([%#span32] inv'0 self)
+   -> ([%#span33] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span42] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span34] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'1 (self : f)
   
@@ -303,27 +256,22 @@ module C06MapPrecond_Impl1_PreservationInv_Impl
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#ssnapshot9] inv'2 x)
-   -> ([%#ssnapshot10] deref'0 (new'0 x) = x)
-  
-  use seq.Seq
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#ssnapshot5] inv'5 x)  -> ([%#ssnapshot6] deref'0 (new'0 x) = x)
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span44] inv'5 v)
-   -> ([%#span47] inv'2 (singleton'0 v))
-  && ([%#span46] index_logic'0 (singleton'0 v) 0 = v) && ([%#span45] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span35] inv'4 v)
+   -> ([%#span37] index_logic'0 (singleton'0 v) 0 = v) && ([%#span36] len'0 (singleton'0 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span48] concat'0 self (singleton'0 v)
+    [%#span38] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span49] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
-     -> inv'3 b
-     -> inv'4 f
-     -> inv'5 e2
-     -> inv'5 e1
-     -> inv'2 s
+    [%#span39] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+     -> inv'2 b
+     -> inv'3 f
+     -> inv'4 e2
+     -> inv'4 e1
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
@@ -337,51 +285,40 @@ module C06MapPrecond_Impl1_PreservationInv_Impl
   
   predicate preservation_inv [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
   
-  goal vc_preservation_inv : ([%#s06_map_precond2] inv'2 produced)
-   -> ([%#s06_map_precond1] inv'1 func)
+  goal vc_preservation_inv : ([%#s06_map_precond1] inv'1 func)
    -> ([%#s06_map_precond0] inv'0 iter)
    -> (forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . if inv'0 i then
-    if inv'3 b then
-      if inv'4 f then
-        if inv'5 e2 then
-          if inv'5 e1 then
-            if inv'2 s then
-              if unnest'0 func ( * f) then
-                if produces'0 iter (push'0 (push'0 s e1) e2) i then
-                  (([%#sseq25] inv'2 s) && ([%#sseq24] inv'2 produced))
-                  /\ (([%#sseq28] inv'2 (concat'0 produced s))
-                  && ([%#sseq27] forall i : int . 0 <= i /\ i < len'0 (concat'0 produced s)
+    if inv'2 b then
+      if inv'3 f then
+        if inv'4 e2 then
+          if inv'4 e1 then
+            if unnest'0 func ( * f) then
+              if produces'0 iter (push'0 (push'0 s e1) e2) i then
+                ([%#sseq24] forall i : int . 0 <= i /\ i < len'0 (concat'0 produced s)
+                 -> index_logic'0 (concat'0 produced s) i
+                = (if i < len'0 produced then index_logic'0 produced i else index_logic'0 s (i - len'0 produced)))
+                && ([%#sseq23] len'0 (concat'0 produced s) = len'0 produced + len'0 s)
+                 -> ([%#ssnapshot5] inv'5 (concat'0 produced s))
+                /\ (([%#ssnapshot6] deref'0 (new'0 (concat'0 produced s)) = concat'0 produced s)
+                 -> (if precondition'0 ( * f) (e1, new'0 (concat'0 produced s)) then
+                  ([%#sseq24] forall i : int . 0 <= i /\ i < len'0 (concat'0 produced s)
                    -> index_logic'0 (concat'0 produced s) i
                   = (if i < len'0 produced then index_logic'0 produced i else index_logic'0 s (i - len'0 produced)))
-                  && ([%#sseq26] len'0 (concat'0 produced s) = len'0 produced + len'0 s)
-                   -> ([%#ssnapshot9] inv'2 (concat'0 produced s))
-                  /\ (([%#ssnapshot10] deref'0 (new'0 (concat'0 produced s)) = concat'0 produced s)
-                   -> (if precondition'0 ( * f) (e1, new'0 (concat'0 produced s)) then
-                    (([%#sseq25] inv'2 s) && ([%#sseq24] inv'2 produced))
-                    /\ (([%#sseq28] inv'2 (concat'0 produced s))
-                    && ([%#sseq27] forall i : int . 0 <= i /\ i < len'0 (concat'0 produced s)
+                  && ([%#sseq23] len'0 (concat'0 produced s) = len'0 produced + len'0 s)
+                   -> ([%#ssnapshot5] inv'5 (concat'0 produced s))
+                  /\ (([%#ssnapshot6] deref'0 (new'0 (concat'0 produced s)) = concat'0 produced s)
+                   -> (if postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b then
+                    ([%#sseq24] forall i : int . 0 <= i /\ i < len'0 (concat'0 produced s)
                      -> index_logic'0 (concat'0 produced s) i
                     = (if i < len'0 produced then index_logic'0 produced i else index_logic'0 s (i - len'0 produced)))
-                    && ([%#sseq26] len'0 (concat'0 produced s) = len'0 produced + len'0 s)
-                     -> ([%#ssnapshot9] inv'2 (concat'0 produced s))
-                    /\ (([%#ssnapshot10] deref'0 (new'0 (concat'0 produced s)) = concat'0 produced s)
-                     -> (if postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b then
-                      (([%#sseq25] inv'2 s) && ([%#sseq24] inv'2 produced))
-                      /\ (([%#sseq28] inv'2 (concat'0 produced s))
-                      && ([%#sseq27] forall i : int . 0 <= i /\ i < len'0 (concat'0 produced s)
-                       -> index_logic'0 (concat'0 produced s) i
-                      = (if i < len'0 produced then index_logic'0 produced i else index_logic'0 s (i - len'0 produced)))
-                      && ([%#sseq26] len'0 (concat'0 produced s) = len'0 produced + len'0 s)
-                       -> ([%#ssnapshot9] inv'2 (push'0 (concat'0 produced s) e1)))
-                    else
-                      true
-                    )))
+                    && ([%#sseq23] len'0 (concat'0 produced s) = len'0 produced + len'0 s)
+                     -> ([%#ssnapshot5] inv'5 (push'0 (concat'0 produced s) e1))
                   else
                     true
-                  )))
+                  ))
                 else
                   true
-                
+                ))
               else
                 true
               
@@ -403,13 +340,12 @@ module C06MapPrecond_Impl1_PreservationInv_Impl
   else
     true
   )
-  /\ ([%#s06_map_precond3] produced = (empty'0 : Seq'0.t_seq item'0)
-   -> ([%#s06_map_precond11] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
-   -> inv'3 b
-   -> inv'4 f
-   -> inv'5 e2
-   -> inv'5 e1
-   -> inv'2 s
+  /\ ([%#s06_map_precond2] produced = (empty'0 : Seq'0.t_seq item'0)
+   -> ([%#s06_map_precond7] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+   -> inv'2 b
+   -> inv'3 f
+   -> inv'4 e2
+   -> inv'4 e1
    -> unnest'0 func ( * f)
    -> produces'0 iter (push'0 (push'0 s e1) e2) i
    -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
@@ -428,215 +364,177 @@ module C06MapPrecond_Impl0_ProducesRefl_Impl
   
   let%span s06_map_precond1 = "../06_map_precond.rs" 30 14 30 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span7 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span span6 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span7 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span8 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span9 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span10 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span11 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span12 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span23 = "../common.rs" 18 15 18 32
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span24 = "../common.rs" 19 15 19 32
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span25 = "../common.rs" 21 22 21 23
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span26 = "../common.rs" 21 52 21 53
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span29 = "../common.rs" 18 15 18 32
-  
-  let%span span30 = "../common.rs" 19 15 19 32
-  
-  let%span span31 = "../common.rs" 21 22 21 23
+  let%span span27 = "../common.rs" 21 82 21 83
   
-  let%span span32 = "../common.rs" 21 31 21 33
+  let%span span28 = "../common.rs" 20 14 20 42
   
-  let%span span33 = "../common.rs" 21 52 21 53
+  let%span span29 = "../common.rs" 15 21 15 25
   
-  let%span span34 = "../common.rs" 21 61 21 63
+  let%span span30 = "../common.rs" 14 14 14 45
   
-  let%span span35 = "../common.rs" 21 82 21 83
+  let%span span31 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span36 = "../common.rs" 20 14 20 42
+  let%span span32 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span37 = "../common.rs" 15 21 15 25
+  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span38 = "../common.rs" 14 14 14 45
+  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span39 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span40 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span36 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span38 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span39 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span40 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span45 = "../06_map_precond.rs" 84 8 88 9
+  let%span span41 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span42 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span47 = "../06_map_precond.rs" 106 8 113 9
+  let%span span43 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span48 = "../06_map_precond.rs" 93 24 93 28
+  let%span span44 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span49 = "../06_map_precond.rs" 93 33 93 37
+  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span50 = "../06_map_precond.rs" 93 42 93 50
+  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span51 = "../06_map_precond.rs" 92 4 92 83
+  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span52 = "../06_map_precond.rs" 94 8 101 9
-  
-  let%span span53 = "../06_map_precond.rs" 118 8 123 9
-  
-  let%span span54 = "../06_map_precond.rs" 159 12 161 73
-  
-  let%span span55 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
-  
-  let%span span56 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
-  
-  let%span span57 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
-  
-  let%span span58 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
-  
-  let%span span59 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
-  
-  let%span span60 = "../06_map_precond.rs" 44 8 56 9
+  let%span span48 = "../06_map_precond.rs" 44 8 56 9
   
   type item'0
   
-  predicate invariant'10 (self : item'0)
+  predicate invariant'8 (self : item'0)
   
-  predicate inv'10 (_x : item'0)
+  predicate inv'8 (_x : item'0)
   
-  axiom inv'10 : forall x : item'0 . inv'10 x = true
+  axiom inv'8 : forall x : item'0 . inv'8 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'9 (self : borrowed i)
+  predicate invariant'7 (self : borrowed i)
   
-  predicate inv'9 (_x : borrowed i)
+  predicate inv'7 (_x : borrowed i)
   
-  axiom inv'9 : forall x : borrowed i . inv'9 x = true
+  axiom inv'7 : forall x : borrowed i . inv'7 x = true
   
-  predicate invariant'8 (self : b)
+  predicate invariant'6 (self : b)
   
-  predicate inv'8 (_x : b)
+  predicate inv'6 (_x : b)
   
-  axiom inv'8 : forall x : b . inv'8 x = true
+  axiom inv'6 : forall x : b . inv'6 x = true
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
-  predicate invariant'7 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  predicate invariant'5 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  predicate inv'7 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  predicate inv'5 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  axiom inv'7 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'7 x = true
+  axiom inv'5 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'5 x = true
   
-  predicate invariant'6 (self : borrowed f)
+  predicate invariant'4 (self : borrowed f)
   
-  predicate inv'6 (_x : borrowed f)
+  predicate inv'4 (_x : borrowed f)
   
-  axiom inv'6 : forall x : borrowed f . inv'6 x = true
+  axiom inv'4 : forall x : borrowed f . inv'4 x = true
   
-  predicate invariant'5 (self : f)
+  predicate invariant'3 (self : Seq'0.t_seq item'0)
   
-  predicate inv'5 (_x : f)
+  predicate inv'3 (_x : Seq'0.t_seq item'0)
   
-  axiom inv'5 : forall x : f . inv'5 x = true
+  axiom inv'3 : forall x : Seq'0.t_seq item'0 . inv'3 x = true
   
-  predicate invariant'4 (self : i)
+  predicate invariant'2 (self : f)
   
-  predicate inv'4 (_x : i)
+  predicate inv'2 (_x : f)
   
-  axiom inv'4 : forall x : i . inv'4 x = true
+  axiom inv'2 : forall x : f . inv'2 x = true
   
-  use prelude.prelude.Int
+  predicate invariant'1 (self : i)
   
-  use seq.Seq
+  predicate inv'1 (_x : i)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  axiom inv'1 : forall x : i . inv'1 x = true
   
-  predicate inv'3 (_x : Seq'0.t_seq (borrowed f))
+  use prelude.prelude.Int
   
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span2] inv'3 self)  -> ([%#span3] len'2 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span4] ()
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span2] len'2 self >= 0
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span6] ()
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span5] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
+  function empty_len'2 (_1 : ()) : ()
   
-  predicate invariant'3 (self : Seq'0.t_seq (borrowed f))
-  
-  axiom inv'3 : forall x : Seq'0.t_seq (borrowed f) . inv'3 x = true
-  
-  use seq.Seq
-  
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
+  axiom empty_len'2_spec : forall _1 : () . [%#span3] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'2 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span4] ()
+  constant empty'1 : Seq'0.t_seq item'0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span5] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
-  
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
+  axiom empty_len'1_spec : forall _1 : () . [%#span3] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
   predicate resolve'0 (self : f)
   
@@ -646,82 +544,66 @@ module C06MapPrecond_Impl0_ProducesRefl_Impl
   
   function fn_mut_once'0 (self : f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span7] inv'5 self)
-   -> ([%#span8] inv'7 args)
-   -> ([%#span9] inv'8 res)
-   -> ([%#span10] postcondition_once'0 self args res
-  = (exists s : borrowed f . inv'6 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
+  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span4] inv'2 self)
+   -> ([%#span5] inv'5 args)
+   -> ([%#span6] inv'6 res)
+   -> ([%#span7] postcondition_once'0 self args res
+  = (exists s : borrowed f . inv'4 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span11] unnest'0 self b)
-   -> ([%#span12] unnest'0 b c)
-   -> ([%#span13] inv'5 self)  -> ([%#span14] inv'5 b)  -> ([%#span15] inv'5 c)  -> ([%#span16] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span8] unnest'0 self b)
+   -> ([%#span9] unnest'0 b c)
+   -> ([%#span10] inv'2 self)  -> ([%#span11] inv'2 b)  -> ([%#span12] inv'2 c)  -> ([%#span13] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span17] inv'5 self)  -> ([%#span18] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span14] inv'2 self)  -> ([%#span15] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
     
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span19] postcondition_mut'0 self args res)
-   -> ([%#span20] inv'6 self)
-   -> ([%#span21] inv'7 args)  -> ([%#span22] inv'8 res)  -> ([%#span23] unnest'0 ( * self) ( ^ self))
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span16] postcondition_mut'0 self args res)
+   -> ([%#span17] inv'4 self)
+   -> ([%#span18] inv'5 args)  -> ([%#span19] inv'6 res)  -> ([%#span20] unnest'0 ( * self) ( ^ self))
   
-  predicate invariant'1 (self : Seq'0.t_seq b)
-  
-  predicate inv'1 (_x : Seq'0.t_seq b)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq b . inv'1 x = true
-  
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span24] inv'2 self)
-   -> ([%#span25] inv'2 other)
-   -> ([%#span28] inv'2 (concat'0 self other))
-  && ([%#span27] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span22] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span26] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span21] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span29] produces'1 a ab b)
-   -> ([%#span30] produces'1 b bc c)
-   -> ([%#span31] inv'4 a)
-   -> ([%#span32] inv'2 ab)
-   -> ([%#span33] inv'4 b)
-   -> ([%#span34] inv'2 bc)  -> ([%#span35] inv'4 c)  -> ([%#span36] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span23] produces'1 a ab b)
+   -> ([%#span24] produces'1 b bc c)
+   -> ([%#span25] inv'1 a)
+   -> ([%#span26] inv'1 b)  -> ([%#span27] inv'1 c)  -> ([%#span28] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span37] inv'4 self)
-   -> ([%#span38] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
-  
-  use seq.Seq
+  axiom produces_refl'0_spec : forall self : i . ([%#span29] inv'1 self)
+   -> ([%#span30] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span2] inv'1 self)  -> ([%#span3] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span2] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq b = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq b
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'1 (empty'0 : Seq'0.t_seq b) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'1 (empty'0 : Seq'0.t_seq b) = 0
   
   predicate precondition'0 (self : f) (_2 : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
@@ -729,32 +611,28 @@ module C06MapPrecond_Impl0_ProducesRefl_Impl
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span39] inv'2 x)  -> ([%#span40] deref'0 (new'0 x) = x)
-  
-  use seq.Seq
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span31] inv'3 x)  -> ([%#span32] deref'0 (new'0 x) = x)
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span41] inv'10 v)
-   -> ([%#span44] inv'2 (singleton'0 v))
-  && ([%#span43] index_logic'1 (singleton'0 v) 0 = v) && ([%#span42] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span33] inv'8 v)
+   -> ([%#span35] index_logic'1 (singleton'0 v) 0 = v) && ([%#span34] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span45] forall i : i . forall e : item'0 . inv'4 i
-     -> inv'10 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
+    [%#span36] forall i : i . forall e : item'0 . inv'1 i
+     -> inv'8 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span46] concat'0 self (singleton'0 v)
+    [%#span37] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span47] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
-     -> inv'8 b
-     -> inv'6 f
-     -> inv'10 e2
-     -> inv'10 e1
-     -> inv'2 s
+    [%#span38] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
+     -> inv'6 b
+     -> inv'4 f
+     -> inv'8 e2
+     -> inv'8 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
@@ -763,22 +641,20 @@ module C06MapPrecond_Impl0_ProducesRefl_Impl
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span52] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
-     -> inv'8 b
-     -> inv'6 f
-     -> inv'10 e2
-     -> inv'10 e1
-     -> inv'2 s
+    [%#span42] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
+     -> inv'6 b
+     -> inv'4 f
+     -> inv'8 e2
+     -> inv'8 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span48] inv'4 iter)
-   -> ([%#span49] inv'5 func)
-   -> ([%#span50] inv'2 produced)
-   -> ([%#span51] produced = (empty'1 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span39] inv'1 iter)
+   -> ([%#span40] inv'2 func)
+   -> ([%#span41] produced = (empty'1 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -786,15 +662,15 @@ module C06MapPrecond_Impl0_ProducesRefl_Impl
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span53] forall func : f . forall iter : borrowed i . inv'5 func
-     -> inv'9 iter
+    [%#span43] forall func : f . forall iter : borrowed i . inv'2 func
+     -> inv'7 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'1 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
   
   use C06MapPrecond_Map_Type as Map'0
   
   predicate invariant'0 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i b f item'0) =
-    [%#span54] reinitialize'0 ()
+    [%#span44] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -806,39 +682,29 @@ module C06MapPrecond_Impl0_ProducesRefl_Impl
     | Map'0.C_Map iter func produced -> true
     end)
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq b) (x : int) : b
-  
-  use prelude.seq_ext.SeqExt
+  function index_logic'2 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function subsequence'0 (self : Seq'0.t_seq item'0) (n : int) (m : int) : Seq'0.t_seq item'0
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span55] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span45] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span56] inv'2 self)
-   -> ([%#span59] inv'2 (subsequence'0 self n m))
-  && ([%#span58] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span47] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span57] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span46] len'0 (subsequence'0 self n m) = m - n)
   
-  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
   predicate produces'0 [@inline:trivial] [#"../06_map_precond.rs" 43 4 43 67] (self : Map'0.t_map i b f item'0) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f item'0)
     
    =
-    [%#span60] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'2 s
-    /\ len'0 s = len'1 visited
+    [%#span48] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'1 (C06MapPrecond_Map_Type.map_iter self) s (C06MapPrecond_Map_Type.map_iter succ)
     /\ inner'0 (C06MapPrecond_Map_Type.map_produced succ)
     = concat'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'3 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'0 fs (i - 1) =  * index_logic'0 fs i)
     /\ (if len'1 visited = 0 then
       C06MapPrecond_Map_Type.map_func self = C06MapPrecond_Map_Type.map_func succ
@@ -871,225 +737,183 @@ module C06MapPrecond_Impl0_ProducesTrans_Impl
   
   let%span s06_map_precond2 = "../06_map_precond.rs" 38 22 38 23
   
-  let%span s06_map_precond3 = "../06_map_precond.rs" 38 31 38 33
-  
-  let%span s06_map_precond4 = "../06_map_precond.rs" 38 52 38 53
-  
-  let%span s06_map_precond5 = "../06_map_precond.rs" 38 61 38 63
-  
-  let%span s06_map_precond6 = "../06_map_precond.rs" 38 82 38 83
-  
-  let%span s06_map_precond7 = "../06_map_precond.rs" 37 14 37 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span s06_map_precond3 = "../06_map_precond.rs" 38 52 38 53
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span s06_map_precond4 = "../06_map_precond.rs" 38 82 38 83
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span s06_map_precond5 = "../06_map_precond.rs" 37 14 37 42
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
-  
-  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
-  
-  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
-  
-  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
-  
-  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span8 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span9 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span10 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span11 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span12 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span35 = "../common.rs" 18 15 18 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span36 = "../common.rs" 19 15 19 32
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span37 = "../common.rs" 21 22 21 23
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span38 = "../common.rs" 21 31 21 33
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span39 = "../common.rs" 21 52 21 53
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span40 = "../common.rs" 21 61 21 63
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span41 = "../common.rs" 21 82 21 83
+  let%span span27 = "../common.rs" 18 15 18 32
   
-  let%span span42 = "../common.rs" 20 14 20 42
+  let%span span28 = "../common.rs" 19 15 19 32
   
-  let%span span43 = "../common.rs" 15 21 15 25
+  let%span span29 = "../common.rs" 21 22 21 23
   
-  let%span span44 = "../common.rs" 14 14 14 45
+  let%span span30 = "../common.rs" 21 52 21 53
   
-  let%span span45 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span31 = "../common.rs" 21 82 21 83
   
-  let%span span46 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span32 = "../common.rs" 20 14 20 42
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span33 = "../common.rs" 15 21 15 25
   
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span34 = "../common.rs" 14 14 14 45
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span35 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span36 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span51 = "../06_map_precond.rs" 84 8 88 9
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span53 = "../06_map_precond.rs" 106 8 113 9
+  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span54 = "../06_map_precond.rs" 93 24 93 28
+  let%span span40 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span55 = "../06_map_precond.rs" 93 33 93 37
+  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span56 = "../06_map_precond.rs" 93 42 93 50
+  let%span span42 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span57 = "../06_map_precond.rs" 92 4 92 83
+  let%span span43 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span58 = "../06_map_precond.rs" 94 8 101 9
+  let%span span44 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span59 = "../06_map_precond.rs" 118 8 123 9
+  let%span span45 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span60 = "../06_map_precond.rs" 159 12 161 73
+  let%span span46 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span61 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span47 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span62 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span48 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span63 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span64 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span65 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span51 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span66 = "../06_map_precond.rs" 44 8 56 9
+  let%span span52 = "../06_map_precond.rs" 44 8 56 9
   
   type item'0
   
-  predicate invariant'10 (self : item'0)
+  predicate invariant'8 (self : item'0)
   
-  predicate inv'10 (_x : item'0)
+  predicate inv'8 (_x : item'0)
   
-  axiom inv'10 : forall x : item'0 . inv'10 x = true
+  axiom inv'8 : forall x : item'0 . inv'8 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'9 (self : borrowed i)
+  predicate invariant'7 (self : borrowed i)
   
-  predicate inv'9 (_x : borrowed i)
+  predicate inv'7 (_x : borrowed i)
   
-  axiom inv'9 : forall x : borrowed i . inv'9 x = true
+  axiom inv'7 : forall x : borrowed i . inv'7 x = true
   
-  predicate invariant'8 (self : b)
+  predicate invariant'6 (self : b)
   
-  predicate inv'8 (_x : b)
+  predicate inv'6 (_x : b)
   
-  axiom inv'8 : forall x : b . inv'8 x = true
+  axiom inv'6 : forall x : b . inv'6 x = true
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
-  predicate invariant'7 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  predicate invariant'5 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  predicate inv'7 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  predicate inv'5 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  axiom inv'7 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'7 x = true
+  axiom inv'5 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'5 x = true
   
-  predicate invariant'6 (self : borrowed f)
+  predicate invariant'4 (self : borrowed f)
   
-  predicate inv'6 (_x : borrowed f)
+  predicate inv'4 (_x : borrowed f)
   
-  axiom inv'6 : forall x : borrowed f . inv'6 x = true
+  axiom inv'4 : forall x : borrowed f . inv'4 x = true
   
-  predicate invariant'5 (self : f)
+  predicate invariant'3 (self : f)
   
-  predicate inv'5 (_x : f)
+  predicate inv'3 (_x : f)
   
-  axiom inv'5 : forall x : f . inv'5 x = true
+  axiom inv'3 : forall x : f . inv'3 x = true
   
-  predicate invariant'4 (self : i)
+  predicate invariant'2 (self : i)
   
-  predicate inv'4 (_x : i)
+  predicate inv'2 (_x : i)
   
-  axiom inv'4 : forall x : i . inv'4 x = true
+  axiom inv'2 : forall x : i . inv'2 x = true
   
-  use prelude.prelude.Int
+  predicate invariant'1 (self : Seq'0.t_seq item'0)
   
-  use seq.Seq
+  predicate inv'1 (_x : Seq'0.t_seq item'0)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
   
-  predicate inv'3 (_x : Seq'0.t_seq (borrowed f))
+  use prelude.prelude.Int
   
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span8] inv'3 self)  -> ([%#span9] len'2 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span10] ()
-  
-  function empty_len'2 (_1 : ()) : () =
-    [%#span12] ()
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span6] len'2 self >= 0
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span11] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  predicate invariant'3 (self : Seq'0.t_seq (borrowed f))
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom inv'3 : forall x : Seq'0.t_seq (borrowed f) . inv'3 x = true
-  
-  use seq.Seq
-  
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
+  axiom empty_len'2_spec : forall _1 : () . [%#span7] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'2 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span10] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'1 : Seq'0.t_seq item'0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
   predicate resolve'0 (self : f)
   
@@ -1099,82 +923,66 @@ module C06MapPrecond_Impl0_ProducesTrans_Impl
   
   function fn_mut_once'0 (self : f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span13] inv'5 self)
-   -> ([%#span14] inv'7 args)
-   -> ([%#span15] inv'8 res)
-   -> ([%#span16] postcondition_once'0 self args res
-  = (exists s : borrowed f . inv'6 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
+  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span8] inv'3 self)
+   -> ([%#span9] inv'5 args)
+   -> ([%#span10] inv'6 res)
+   -> ([%#span11] postcondition_once'0 self args res
+  = (exists s : borrowed f . inv'4 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span17] unnest'0 self b)
-   -> ([%#span18] unnest'0 b c)
-   -> ([%#span19] inv'5 self)  -> ([%#span20] inv'5 b)  -> ([%#span21] inv'5 c)  -> ([%#span22] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span12] unnest'0 self b)
+   -> ([%#span13] unnest'0 b c)
+   -> ([%#span14] inv'3 self)  -> ([%#span15] inv'3 b)  -> ([%#span16] inv'3 c)  -> ([%#span17] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span23] inv'5 self)  -> ([%#span24] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span18] inv'3 self)  -> ([%#span19] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
     
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span25] postcondition_mut'0 self args res)
-   -> ([%#span26] inv'6 self)
-   -> ([%#span27] inv'7 args)  -> ([%#span28] inv'8 res)  -> ([%#span29] unnest'0 ( * self) ( ^ self))
-  
-  use seq.Seq
-  
-  use seq.Seq
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span20] postcondition_mut'0 self args res)
+   -> ([%#span21] inv'4 self)
+   -> ([%#span22] inv'5 args)  -> ([%#span23] inv'6 res)  -> ([%#span24] unnest'0 ( * self) ( ^ self))
   
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'1 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span30] inv'2 self)
-   -> ([%#span31] inv'2 other)
-   -> ([%#span34] inv'2 (concat'1 self other))
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'0 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span26] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span32] len'0 (concat'1 self other) = len'0 self + len'0 other)
+  && ([%#span25] len'0 (concat'1 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span35] produces'1 a ab b)
-   -> ([%#span36] produces'1 b bc c)
-   -> ([%#span37] inv'4 a)
-   -> ([%#span38] inv'2 ab)
-   -> ([%#span39] inv'4 b)
-   -> ([%#span40] inv'2 bc)  -> ([%#span41] inv'4 c)  -> ([%#span42] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span27] produces'1 a ab b)
+   -> ([%#span28] produces'1 b bc c)
+   -> ([%#span29] inv'2 a)
+   -> ([%#span30] inv'2 b)  -> ([%#span31] inv'2 c)  -> ([%#span32] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span43] inv'4 self)
-   -> ([%#span44] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq b)
+  axiom produces_refl'0_spec : forall self : i . ([%#span33] inv'2 self)
+   -> ([%#span34] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span8] inv'1 self)  -> ([%#span9] len'1 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq b = [%#span10] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span6] len'1 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'0 : Seq'0.t_seq b
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'1 (empty'0 : Seq'0.t_seq b) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq b)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq b . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'1 (empty'0 : Seq'0.t_seq b) = 0
   
   predicate precondition'0 (self : f) (_2 : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
@@ -1182,32 +990,28 @@ module C06MapPrecond_Impl0_ProducesTrans_Impl
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span45] inv'2 x)  -> ([%#span46] deref'0 (new'0 x) = x)
-  
-  use seq.Seq
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span35] inv'1 x)  -> ([%#span36] deref'0 (new'0 x) = x)
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span47] inv'10 v)
-   -> ([%#span50] inv'2 (singleton'0 v))
-  && ([%#span49] index_logic'1 (singleton'0 v) 0 = v) && ([%#span48] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span37] inv'8 v)
+   -> ([%#span39] index_logic'1 (singleton'0 v) 0 = v) && ([%#span38] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span51] forall i : i . forall e : item'0 . inv'4 i
-     -> inv'10 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
+    [%#span40] forall i : i . forall e : item'0 . inv'2 i
+     -> inv'8 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span52] concat'1 self (singleton'0 v)
+    [%#span41] concat'1 self (singleton'0 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span53] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
-     -> inv'8 b
-     -> inv'6 f
-     -> inv'10 e2
-     -> inv'10 e1
-     -> inv'2 s
+    [%#span42] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'2 i
+     -> inv'6 b
+     -> inv'4 f
+     -> inv'8 e2
+     -> inv'8 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
@@ -1216,22 +1020,20 @@ module C06MapPrecond_Impl0_ProducesTrans_Impl
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span58] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
-     -> inv'8 b
-     -> inv'6 f
-     -> inv'10 e2
-     -> inv'10 e1
-     -> inv'2 s
+    [%#span46] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'2 i
+     -> inv'6 b
+     -> inv'4 f
+     -> inv'8 e2
+     -> inv'8 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'1 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'1 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'1 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span54] inv'4 iter)
-   -> ([%#span55] inv'5 func)
-   -> ([%#span56] inv'2 produced)
-   -> ([%#span57] produced = (empty'1 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span43] inv'2 iter)
+   -> ([%#span44] inv'3 func)
+   -> ([%#span45] produced = (empty'1 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -1239,15 +1041,15 @@ module C06MapPrecond_Impl0_ProducesTrans_Impl
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span59] forall func : f . forall iter : borrowed i . inv'5 func
-     -> inv'9 iter
+    [%#span47] forall func : f . forall iter : borrowed i . inv'3 func
+     -> inv'7 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'1 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
   
   use C06MapPrecond_Map_Type as Map'0
   
   predicate invariant'0 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i b f item'0) =
-    [%#span60] reinitialize'0 ()
+    [%#span48] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -1259,51 +1061,37 @@ module C06MapPrecond_Impl0_ProducesTrans_Impl
     | Map'0.C_Map iter func produced -> true
     end)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq b) (x : int) : b
+  function index_logic'2 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function concat'0 (self : Seq'0.t_seq b) (other : Seq'0.t_seq b) : Seq'0.t_seq b
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span30] inv'1 self)
-   -> ([%#span31] inv'1 other)
-   -> ([%#span34] inv'1 (concat'0 self other))
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span26] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span32] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use prelude.seq_ext.SeqExt
+  && ([%#span25] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function subsequence'0 (self : Seq'0.t_seq item'0) (n : int) (m : int) : Seq'0.t_seq item'0
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span61] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span49] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span62] inv'2 self)
-   -> ([%#span65] inv'2 (subsequence'0 self n m))
-  && ([%#span64] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span51] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span63] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span50] len'0 (subsequence'0 self n m) = m - n)
   
-  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'0 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
   predicate produces'0 [@inline:trivial] [#"../06_map_precond.rs" 43 4 43 67] (self : Map'0.t_map i b f item'0) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f item'0)
     
    =
-    [%#span66] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'2 s
-    /\ len'0 s = len'1 visited
+    [%#span52] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'1 (C06MapPrecond_Map_Type.map_iter self) s (C06MapPrecond_Map_Type.map_iter succ)
     /\ inner'0 (C06MapPrecond_Map_Type.map_produced succ)
     = concat'1 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'3 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'0 fs (i - 1) =  * index_logic'0 fs i)
     /\ (if len'1 visited = 0 then
       C06MapPrecond_Map_Type.map_func self = C06MapPrecond_Map_Type.map_func succ
@@ -1329,13 +1117,11 @@ module C06MapPrecond_Impl0_ProducesTrans_Impl
   function produces_trans [#"../06_map_precond.rs" 38 4 38 90] (a : Map'0.t_map i b f item'0) (ab : Seq'0.t_seq b) (b : Map'0.t_map i b f item'0) (bc : Seq'0.t_seq b) (c : Map'0.t_map i b f item'0) : ()
     
   
-  goal vc_produces_trans : ([%#s06_map_precond6] inv'0 c)
-   -> ([%#s06_map_precond5] inv'1 bc)
-   -> ([%#s06_map_precond4] inv'0 b)
-   -> ([%#s06_map_precond3] inv'1 ab)
+  goal vc_produces_trans : ([%#s06_map_precond4] inv'0 c)
+   -> ([%#s06_map_precond3] inv'0 b)
    -> ([%#s06_map_precond2] inv'0 a)
    -> ([%#s06_map_precond1] produces'0 b bc c)
-   -> ([%#s06_map_precond0] produces'0 a ab b)  -> ([%#s06_map_precond7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s06_map_precond0] produces'0 a ab b)  -> ([%#s06_map_precond5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -1368,157 +1154,129 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   
   let%span s06_map_precond3 = "../06_map_precond.rs" 141 14 141 68
   
-  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span sseq25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span sseq26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span sseq27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span s06_map_precond8 = "../06_map_precond.rs" 143 8 149 9
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span sseq25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span sseq26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span s06_map_precond7 = "../06_map_precond.rs" 143 8 149 9
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span10 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span11 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span12 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span13 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span14 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span15 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span16 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span17 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span18 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span19 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span20 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span21 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span22 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span23 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span24 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span25 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span36 = "../common.rs" 18 15 18 32
-  
-  let%span span37 = "../common.rs" 19 15 19 32
-  
-  let%span span38 = "../common.rs" 21 22 21 23
-  
-  let%span span39 = "../common.rs" 21 31 21 33
-  
-  let%span span40 = "../common.rs" 21 52 21 53
-  
-  let%span span41 = "../common.rs" 21 61 21 63
-  
-  let%span span42 = "../common.rs" 21 82 21 83
-  
-  let%span span43 = "../common.rs" 20 14 20 42
+  let%span span29 = "../common.rs" 18 15 18 32
   
-  let%span span44 = "../common.rs" 15 21 15 25
+  let%span span30 = "../common.rs" 19 15 19 32
   
-  let%span span45 = "../common.rs" 14 14 14 45
+  let%span span31 = "../common.rs" 21 22 21 23
   
-  let%span span46 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span32 = "../common.rs" 21 52 21 53
   
-  let%span span47 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span33 = "../common.rs" 21 82 21 83
   
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span34 = "../common.rs" 20 14 20 42
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span35 = "../common.rs" 15 21 15 25
   
-  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span36 = "../common.rs" 14 14 14 45
   
-  let%span span51 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span37 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span38 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span53 = "../06_map_precond.rs" 44 8 56 9
+  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span54 = "../06_map_precond.rs" 35 15 35 32
+  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span55 = "../06_map_precond.rs" 36 15 36 32
+  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span56 = "../06_map_precond.rs" 38 22 38 23
+  let%span span42 = "../06_map_precond.rs" 44 8 56 9
   
-  let%span span57 = "../06_map_precond.rs" 38 31 38 33
+  let%span span43 = "../06_map_precond.rs" 35 15 35 32
   
-  let%span span58 = "../06_map_precond.rs" 38 52 38 53
+  let%span span44 = "../06_map_precond.rs" 36 15 36 32
   
-  let%span span59 = "../06_map_precond.rs" 38 61 38 63
+  let%span span45 = "../06_map_precond.rs" 38 22 38 23
   
-  let%span span60 = "../06_map_precond.rs" 38 82 38 83
+  let%span span46 = "../06_map_precond.rs" 38 52 38 53
   
-  let%span span61 = "../06_map_precond.rs" 37 14 37 42
+  let%span span47 = "../06_map_precond.rs" 38 82 38 83
   
-  let%span span62 = "../06_map_precond.rs" 33 4 33 10
+  let%span span48 = "../06_map_precond.rs" 37 14 37 42
   
-  let%span span63 = "../06_map_precond.rs" 31 21 31 25
+  let%span span49 = "../06_map_precond.rs" 33 4 33 10
   
-  let%span span64 = "../06_map_precond.rs" 30 14 30 45
+  let%span span50 = "../06_map_precond.rs" 31 21 31 25
   
-  let%span span65 = "../06_map_precond.rs" 28 4 28 10
+  let%span span51 = "../06_map_precond.rs" 30 14 30 45
   
-  let%span span66 = "../06_map_precond.rs" 84 8 88 9
+  let%span span52 = "../06_map_precond.rs" 28 4 28 10
   
-  let%span span67 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span53 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span68 = "../06_map_precond.rs" 106 8 113 9
+  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span69 = "../06_map_precond.rs" 93 24 93 28
+  let%span span55 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span70 = "../06_map_precond.rs" 93 33 93 37
+  let%span span56 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span71 = "../06_map_precond.rs" 93 42 93 50
+  let%span span57 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span72 = "../06_map_precond.rs" 92 4 92 83
+  let%span span58 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span73 = "../06_map_precond.rs" 94 8 101 9
+  let%span span59 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span74 = "../06_map_precond.rs" 118 8 123 9
+  let%span span60 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span75 = "../06_map_precond.rs" 159 12 161 73
+  let%span span61 = "../06_map_precond.rs" 159 12 161 73
   
   use prelude.prelude.Borrow
   
-  predicate invariant'10 (self : borrowed i)
+  predicate invariant'8 (self : borrowed i)
   
-  predicate inv'10 (_x : borrowed i)
+  predicate inv'8 (_x : borrowed i)
   
-  axiom inv'10 : forall x : borrowed i . inv'10 x = true
+  axiom inv'8 : forall x : borrowed i . inv'8 x = true
   
   type item'0
   
@@ -1526,52 +1284,41 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
-  predicate invariant'9 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  predicate invariant'7 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  predicate inv'9 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  predicate inv'7 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  axiom inv'9 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'9 x = true
+  axiom inv'7 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'7 x = true
   
-  predicate invariant'8 (self : f)
+  predicate invariant'6 (self : Seq'0.t_seq item'0)
   
-  predicate inv'8 (_x : f)
+  predicate inv'6 (_x : Seq'0.t_seq item'0)
   
-  axiom inv'8 : forall x : f . inv'8 x = true
+  axiom inv'6 : forall x : Seq'0.t_seq item'0 . inv'6 x = true
   
-  predicate invariant'7 (self : i)
+  predicate invariant'5 (self : f)
   
-  predicate inv'7 (_x : i)
+  predicate inv'5 (_x : f)
   
-  axiom inv'7 : forall x : i . inv'7 x = true
+  axiom inv'5 : forall x : f . inv'5 x = true
   
-  use prelude.prelude.Int
+  predicate invariant'4 (self : i)
   
-  use seq.Seq
+  predicate inv'4 (_x : i)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  axiom inv'4 : forall x : i . inv'4 x = true
   
-  predicate inv'6 (_x : Seq'0.t_seq (borrowed f))
+  use prelude.prelude.Int
   
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span9] inv'6 self)  -> ([%#span10] len'2 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span11] ()
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span8] len'2 self >= 0
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span13] ()
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span12] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
+  function empty_len'2 (_1 : ()) : ()
   
-  predicate invariant'6 (self : Seq'0.t_seq (borrowed f))
-  
-  axiom inv'6 : forall x : Seq'0.t_seq (borrowed f) . inv'6 x = true
-  
-  predicate invariant'5 (self : Seq'0.t_seq b)
-  
-  predicate inv'5 (_x : Seq'0.t_seq b)
-  
-  axiom inv'5 : forall x : Seq'0.t_seq b . inv'5 x = true
+  axiom empty_len'2_spec : forall _1 : () . [%#span9] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   predicate resolve'0 (self : f)
   
@@ -1585,49 +1332,40 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   
   function fn_mut_once'0 (self : f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span14] inv'8 self)
-   -> ([%#span15] inv'9 args)
-   -> ([%#span16] inv'1 res)
-   -> ([%#span17] postcondition_once'0 self args res
+  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span10] inv'5 self)
+   -> ([%#span11] inv'7 args)
+   -> ([%#span12] inv'1 res)
+   -> ([%#span13] postcondition_once'0 self args res
   = (exists s : borrowed f . inv'2 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   predicate unnest'0 (self : f) (_2 : f)
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span18] unnest'0 self b)
-   -> ([%#span19] unnest'0 b c)
-   -> ([%#span20] inv'8 self)  -> ([%#span21] inv'8 b)  -> ([%#span22] inv'8 c)  -> ([%#span23] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span14] unnest'0 self b)
+   -> ([%#span15] unnest'0 b c)
+   -> ([%#span16] inv'5 self)  -> ([%#span17] inv'5 b)  -> ([%#span18] inv'5 c)  -> ([%#span19] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span24] inv'8 self)  -> ([%#span25] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span20] inv'5 self)  -> ([%#span21] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
     
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span26] postcondition_mut'0 self args res)
-   -> ([%#span27] inv'2 self)
-   -> ([%#span28] inv'9 args)  -> ([%#span29] inv'1 res)  -> ([%#span30] unnest'0 ( * self) ( ^ self))
-  
-  predicate invariant'4 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'4 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'4 : forall x : Seq'0.t_seq item'0 . inv'4 x = true
-  
-  use seq.Seq
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span22] postcondition_mut'0 self args res)
+   -> ([%#span23] inv'2 self)
+   -> ([%#span24] inv'7 args)  -> ([%#span25] inv'1 res)  -> ([%#span26] unnest'0 ( * self) ( ^ self))
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span9] inv'4 self)  -> ([%#span10] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span8] len'0 self >= 0
   
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span11] ()
+  constant empty'1 : Seq'0.t_seq item'0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span13] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span12] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span9] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'3 (self : item'0)
   
@@ -1639,62 +1377,47 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   
   axiom inv'2 : forall x : borrowed f . inv'2 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span31] inv'4 self)
-   -> ([%#span32] inv'4 other)
-   -> ([%#span35] inv'4 (concat'0 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span28] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span33] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span27] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'1 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'1_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span36] produces'1 a ab b)
-   -> ([%#span37] produces'1 b bc c)
-   -> ([%#span38] inv'7 a)
-   -> ([%#span39] inv'4 ab)
-   -> ([%#span40] inv'7 b)
-   -> ([%#span41] inv'4 bc)  -> ([%#span42] inv'7 c)  -> ([%#span43] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span29] produces'1 a ab b)
+   -> ([%#span30] produces'1 b bc c)
+   -> ([%#span31] inv'4 a)
+   -> ([%#span32] inv'4 b)  -> ([%#span33] inv'4 c)  -> ([%#span34] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'1 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'1_spec : forall self : i . ([%#span44] inv'7 self)
-   -> ([%#span45] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'1_spec : forall self : i . ([%#span35] inv'4 self)
+   -> ([%#span36] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   use C06MapPrecond_Map_Type as Map'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq b) (x : int) : b
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span9] inv'5 self)  -> ([%#span10] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span8] len'1 self >= 0
   
   function concat'1 (self : Seq'0.t_seq b) (other : Seq'0.t_seq b) : Seq'0.t_seq b
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span31] inv'5 self)
-   -> ([%#span32] inv'5 other)
-   -> ([%#span35] inv'5 (concat'1 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span28] forall i : int . 0 <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span33] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span27] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : Map'0.t_map i b f item'0)
   
@@ -1704,23 +1427,17 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span46] inv'4 x)  -> ([%#span47] deref'0 (new'0 x) = x)
-  
-  use prelude.seq_ext.SeqExt
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span37] inv'6 x)  -> ([%#span38] deref'0 (new'0 x) = x)
   
   function subsequence'0 (self : Seq'0.t_seq item'0) (n : int) (m : int) : Seq'0.t_seq item'0
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span48] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span39] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span49] inv'4 self)
-   -> ([%#span52] inv'4 (subsequence'0 self n m))
-  && ([%#span51] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span41] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#span50] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span40] len'0 (subsequence'0 self n m) = m - n)
   
-  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
@@ -1729,14 +1446,12 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   predicate produces'0 [@inline:trivial] [#"../06_map_precond.rs" 43 4 43 67] (self : Map'0.t_map i b f item'0) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f item'0)
     
    =
-    [%#span53] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'4 s
-    /\ len'0 s = len'1 visited
+    [%#span42] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'1 (C06MapPrecond_Map_Type.map_iter self) s (C06MapPrecond_Map_Type.map_iter succ)
     /\ inner'0 (C06MapPrecond_Map_Type.map_produced succ)
     = concat'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'6 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'2 fs (i - 1) =  * index_logic'2 fs i)
     /\ (if len'1 visited = 0 then
       C06MapPrecond_Map_Type.map_func self = C06MapPrecond_Map_Type.map_func succ
@@ -1752,56 +1467,49 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   function produces_trans'0 [#"../06_map_precond.rs" 38 4 38 90] (a : Map'0.t_map i b f item'0) (ab : Seq'0.t_seq b) (b : Map'0.t_map i b f item'0) (bc : Seq'0.t_seq b) (c : Map'0.t_map i b f item'0) : ()
     
    =
-    [%#span62] ()
+    [%#span49] ()
   
-  axiom produces_trans'0_spec : forall a : Map'0.t_map i b f item'0, ab : Seq'0.t_seq b, b : Map'0.t_map i b f item'0, bc : Seq'0.t_seq b, c : Map'0.t_map i b f item'0 . ([%#span54] produces'0 a ab b)
-   -> ([%#span55] produces'0 b bc c)
-   -> ([%#span56] inv'0 a)
-   -> ([%#span57] inv'5 ab)
-   -> ([%#span58] inv'0 b)
-   -> ([%#span59] inv'5 bc)  -> ([%#span60] inv'0 c)  -> ([%#span61] produces'0 a (concat'1 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Map'0.t_map i b f item'0, ab : Seq'0.t_seq b, b : Map'0.t_map i b f item'0, bc : Seq'0.t_seq b, c : Map'0.t_map i b f item'0 . ([%#span43] produces'0 a ab b)
+   -> ([%#span44] produces'0 b bc c)
+   -> ([%#span45] inv'0 a)
+   -> ([%#span46] inv'0 b)  -> ([%#span47] inv'0 c)  -> ([%#span48] produces'0 a (concat'1 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq b = [%#span11] ()
+  constant empty'0 : Seq'0.t_seq b
   
   function produces_refl'0 [#"../06_map_precond.rs" 31 4 31 26] (self : Map'0.t_map i b f item'0) : () =
-    [%#span65] ()
+    [%#span52] ()
   
-  axiom produces_refl'0_spec : forall self : Map'0.t_map i b f item'0 . ([%#span63] inv'0 self)
-   -> ([%#span64] produces'0 self (empty'0 : Seq'0.t_seq b) self)
+  axiom produces_refl'0_spec : forall self : Map'0.t_map i b f item'0 . ([%#span50] inv'0 self)
+   -> ([%#span51] produces'0 self (empty'0 : Seq'0.t_seq b) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span13] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span12] len'1 (empty'0 : Seq'0.t_seq b) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'1 (empty'0 : Seq'0.t_seq b) = 0
   
   predicate invariant'1 (self : b)
   
   axiom inv'1 : forall x : b . inv'1 x = true
   
-  use seq.Seq
-  
   function singleton'1 (v : item'0) : Seq'0.t_seq item'0
   
   axiom singleton'1_spec : forall v : item'0 . ([%#sseq24] inv'3 v)
-   -> ([%#sseq27] inv'4 (singleton'1 v))
-  && ([%#sseq26] index_logic'0 (singleton'1 v) 0 = v) && ([%#sseq25] len'0 (singleton'1 v) = 1)
+   -> ([%#sseq26] index_logic'0 (singleton'1 v) 0 = v) && ([%#sseq25] len'0 (singleton'1 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span66] forall i : i . forall e : item'0 . inv'7 i
+    [%#span53] forall i : i . forall e : item'0 . inv'4 i
      -> inv'3 e  -> produces'1 iter (singleton'1 e) i  -> precondition'0 func (e, new'0 produced)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span67] concat'0 self (singleton'1 v)
+    [%#span54] concat'0 self (singleton'1 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span68] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'7 i
+    [%#span55] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
      -> inv'1 b
      -> inv'2 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
@@ -1810,34 +1518,32 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span73] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'7 i
+    [%#span59] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
      -> inv'1 b
      -> inv'2 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span69] inv'7 iter)
-   -> ([%#span70] inv'8 func)
-   -> ([%#span71] inv'4 produced)
-   -> ([%#span72] produced = (empty'1 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span56] inv'4 iter)
+   -> ([%#span57] inv'5 func)
+   -> ([%#span58] produced = (empty'1 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span74] forall func : f . forall iter : borrowed i . inv'8 func
-     -> inv'10 iter
+    [%#span60] forall func : f . forall iter : borrowed i . inv'5 func
+     -> inv'8 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'1 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
   
   predicate invariant'0 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i b f item'0) =
-    [%#span75] reinitialize'0 ()
+    [%#span61] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -1847,13 +1553,10 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
     | Map'0.C_Map iter func produced -> true
     end)
   
-  use seq.Seq
-  
   function singleton'0 (v : b) : Seq'0.t_seq b
   
   axiom singleton'0_spec : forall v : b . ([%#sseq24] inv'1 v)
-   -> ([%#sseq27] inv'5 (singleton'0 v))
-  && ([%#sseq26] index_logic'1 (singleton'0 v) 0 = v) && ([%#sseq25] len'1 (singleton'0 v) = 1)
+   -> ([%#sseq26] index_logic'1 (singleton'0 v) 0 = v) && ([%#sseq25] len'1 (singleton'0 v) = 1)
   
   constant self  : Map'0.t_map i b f item'0
   
@@ -1880,7 +1583,7 @@ module C06MapPrecond_Impl1_ProducesOne_Impl
   else
     true
   )
-  /\ ([%#s06_map_precond3] ([%#s06_map_precond8] exists f : borrowed f . inv'2 f
+  /\ ([%#s06_map_precond3] ([%#s06_map_precond7] exists f : borrowed f . inv'2 f
   /\  * f = C06MapPrecond_Map_Type.map_func self
   /\  ^ f = C06MapPrecond_Map_Type.map_func succ
   /\ (exists e : item'0 . inv'3 e
@@ -1917,113 +1620,93 @@ module C06MapPrecond_Impl1_ProducesOneInvariant_Impl
   
   let%span s06_map_precond9 = "../06_map_precond.rs" 131 14 131 70
   
-  let%span sseq210 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span sseq210 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span sseq211 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span sseq211 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span sseq212 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span sseq212 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span sseq213 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span sseq213 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span sseq214 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span sseq214 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span sseq215 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span s06_map_precond15 = "../06_map_precond.rs" 126 4 126 12
   
-  let%span sseq216 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span16 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span sseq217 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span17 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span sseq218 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span s06_map_precond19 = "../06_map_precond.rs" 126 4 126 12
-  
-  let%span span20 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span21 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span24 = "../06_map_precond.rs" 84 8 88 9
-  
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
-  
-  let%span span26 = "../06_map_precond.rs" 106 8 113 9
-  
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span28 = "../06_map_precond.rs" 93 24 93 28
-  
-  let%span span29 = "../06_map_precond.rs" 93 33 93 37
+  let%span span19 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span30 = "../06_map_precond.rs" 93 42 93 50
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span31 = "../06_map_precond.rs" 92 4 92 83
+  let%span span21 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span32 = "../06_map_precond.rs" 94 8 101 9
+  let%span span22 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span33 = "../06_map_precond.rs" 118 8 123 9
+  let%span span23 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span34 = "../06_map_precond.rs" 159 12 161 73
+  let%span span24 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span span25 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span26 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span27 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span39 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span40 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span51 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span41 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span52 = "../common.rs" 18 15 18 32
+  let%span span42 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span53 = "../common.rs" 19 15 19 32
+  let%span span43 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span54 = "../common.rs" 21 22 21 23
+  let%span span44 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span55 = "../common.rs" 21 31 21 33
+  let%span span45 = "../common.rs" 18 15 18 32
   
-  let%span span56 = "../common.rs" 21 52 21 53
+  let%span span46 = "../common.rs" 19 15 19 32
   
-  let%span span57 = "../common.rs" 21 61 21 63
+  let%span span47 = "../common.rs" 21 22 21 23
   
-  let%span span58 = "../common.rs" 21 82 21 83
+  let%span span48 = "../common.rs" 21 52 21 53
   
-  let%span span59 = "../common.rs" 20 14 20 42
+  let%span span49 = "../common.rs" 21 82 21 83
   
-  let%span span60 = "../common.rs" 15 21 15 25
+  let%span span50 = "../common.rs" 20 14 20 42
   
-  let%span span61 = "../common.rs" 14 14 14 45
+  let%span span51 = "../common.rs" 15 21 15 25
   
-  let%span span62 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span52 = "../common.rs" 14 14 14 45
   
-  let%span span63 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span53 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
   use prelude.prelude.Borrow
   
@@ -2037,25 +1720,25 @@ module C06MapPrecond_Impl1_ProducesOneInvariant_Impl
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
+  predicate invariant'7 (self : Seq'0.t_seq item'0)
   
-  predicate invariant'7 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  predicate inv'7 (_x : Seq'0.t_seq item'0)
   
-  predicate inv'7 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
+  axiom inv'7 : forall x : Seq'0.t_seq item'0 . inv'7 x = true
   
-  axiom inv'7 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'7 x = true
+  use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
-  predicate invariant'6 (self : f)
+  predicate invariant'6 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  predicate inv'6 (_x : f)
+  predicate inv'6 (_x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
-  axiom inv'6 : forall x : f . inv'6 x = true
+  axiom inv'6 : forall x : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) . inv'6 x = true
   
-  predicate invariant'5 (self : Seq'0.t_seq item'0)
+  predicate invariant'5 (self : f)
   
-  predicate inv'5 (_x : Seq'0.t_seq item'0)
+  predicate inv'5 (_x : f)
   
-  axiom inv'5 : forall x : Seq'0.t_seq item'0 . inv'5 x = true
+  axiom inv'5 : forall x : f . inv'5 x = true
   
   predicate invariant'4 (self : i)
   
@@ -2087,90 +1770,75 @@ module C06MapPrecond_Impl1_ProducesOneInvariant_Impl
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span20] inv'5 x)  -> ([%#span21] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span16] inv'7 x)  -> ([%#span17] deref'0 (new'0 x) = x)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span22] inv'5 self)  -> ([%#span23] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span18] len'0 self >= 0
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
   axiom singleton'0_spec : forall v : item'0 . ([%#sseq210] inv'1 v)
-   -> ([%#sseq213] inv'5 (singleton'0 v))
-  && ([%#sseq212] index_logic'0 (singleton'0 v) 0 = v) && ([%#sseq211] len'0 (singleton'0 v) = 1)
+   -> ([%#sseq212] index_logic'0 (singleton'0 v) 0 = v) && ([%#sseq211] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span24] forall i : i . forall e : item'0 . inv'4 i
+    [%#span19] forall i : i . forall e : item'0 . inv'4 i
      -> inv'1 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (_3 : b)
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#sseq214] inv'5 self)
-   -> ([%#sseq215] inv'5 other)
-   -> ([%#sseq218] inv'5 (concat'0 self other))
-  && ([%#sseq217] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#sseq214] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#sseq216] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#sseq213] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span25] concat'0 self (singleton'0 v)
+    [%#span20] concat'0 self (singleton'0 v)
   
   predicate unnest'0 (self : f) (_2 : f)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span26] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
+    [%#span21] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
      -> inv'2 b
      -> inv'3 f
      -> inv'1 e2
      -> inv'1 e1
-     -> inv'5 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
      -> postcondition_mut'0 f (e1, new'0 s) b  -> precondition'0 ( ^ f) (e2, new'0 (push'0 s e1))
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span27] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span32] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
+    [%#span25] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
      -> inv'2 b
      -> inv'3 f
      -> inv'1 e2
      -> inv'1 e1
-     -> inv'5 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span28] inv'4 iter)
-   -> ([%#span29] inv'6 func)
-   -> ([%#span30] inv'5 produced)
-   -> ([%#span31] produced = (empty'0 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span22] inv'4 iter)
+   -> ([%#span23] inv'5 func)
+   -> ([%#span24] produced = (empty'0 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -2178,7 +1846,7 @@ module C06MapPrecond_Impl1_ProducesOneInvariant_Impl
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span33] forall func : f . forall iter : borrowed i . inv'6 func
+    [%#span26] forall func : f . forall iter : borrowed i . inv'5 func
      -> inv'8 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
@@ -2186,7 +1854,7 @@ module C06MapPrecond_Impl1_ProducesOneInvariant_Impl
   use C06MapPrecond_Map_Type as Map'0
   
   predicate invariant'0 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i b f item'0) =
-    [%#span34] reinitialize'0 ()
+    [%#span27] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -2204,48 +1872,45 @@ module C06MapPrecond_Impl1_ProducesOneInvariant_Impl
   
   function fn_mut_once'0 (self : f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span35] inv'6 self)
-   -> ([%#span36] inv'7 args)
-   -> ([%#span37] inv'2 res)
-   -> ([%#span38] postcondition_once'0 self args res
+  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span28] inv'5 self)
+   -> ([%#span29] inv'6 args)
+   -> ([%#span30] inv'2 res)
+   -> ([%#span31] postcondition_once'0 self args res
   = (exists s : borrowed f . inv'3 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'0 ( ^ s)))
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span39] unnest'0 self b)
-   -> ([%#span40] unnest'0 b c)
-   -> ([%#span41] inv'6 self)  -> ([%#span42] inv'6 b)  -> ([%#span43] inv'6 c)  -> ([%#span44] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span32] unnest'0 self b)
+   -> ([%#span33] unnest'0 b c)
+   -> ([%#span34] inv'5 self)  -> ([%#span35] inv'5 b)  -> ([%#span36] inv'5 c)  -> ([%#span37] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span45] inv'6 self)  -> ([%#span46] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span38] inv'5 self)  -> ([%#span39] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
     
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span47] postcondition_mut'0 self args res)
-   -> ([%#span48] inv'3 self)
-   -> ([%#span49] inv'7 args)  -> ([%#span50] inv'2 res)  -> ([%#span51] unnest'0 ( * self) ( ^ self))
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span40] postcondition_mut'0 self args res)
+   -> ([%#span41] inv'3 self)
+   -> ([%#span42] inv'6 args)  -> ([%#span43] inv'2 res)  -> ([%#span44] unnest'0 ( * self) ( ^ self))
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span52] produces'0 a ab b)
-   -> ([%#span53] produces'0 b bc c)
-   -> ([%#span54] inv'4 a)
-   -> ([%#span55] inv'5 ab)
-   -> ([%#span56] inv'4 b)
-   -> ([%#span57] inv'5 bc)  -> ([%#span58] inv'4 c)  -> ([%#span59] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span45] produces'0 a ab b)
+   -> ([%#span46] produces'0 b bc c)
+   -> ([%#span47] inv'4 a)
+   -> ([%#span48] inv'4 b)  -> ([%#span49] inv'4 c)  -> ([%#span50] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span60] inv'4 self)
-   -> ([%#span61] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span51] inv'4 self)
+   -> ([%#span52] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span63] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span62] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span53] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   constant self  : Map'0.t_map i b f item'0
   
@@ -2270,32 +1935,16 @@ module C06MapPrecond_Impl1_ProducesOneInvariant_Impl
    -> ([%#s06_map_precond0] produces'0 (C06MapPrecond_Map_Type.map_iter self) (singleton'0 e) iter)
    -> (forall i : i . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . if inv'4 i then
     if inv'1 e2 then
-      if inv'1 e1 then
-        if inv'5 s then
-          if produces'0 iter (push'0 (push'0 s e1) e2) i then
-            ([%#sseq210] inv'1 e)
-            /\ (([%#sseq213] inv'5 (singleton'0 e))
-            && ([%#sseq212] index_logic'0 (singleton'0 e) 0 = e) && ([%#sseq211] len'0 (singleton'0 e) = 1)
-             -> ([%#sseq215] inv'5 s) && ([%#sseq214] inv'5 (singleton'0 e)))
-          else
-            true
-          
-        else
-          true
-        
-      else
-        true
-      
+      if inv'1 e1 then if produces'0 iter (push'0 (push'0 s e1) e2) i then [%#sseq210] inv'1 e else true else true
     else
       true
     
   else
     true
   )
-  /\ ([%#s06_map_precond19] forall i : i . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
+  /\ ([%#s06_map_precond15] forall i : i . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'4 i
    -> inv'1 e2
    -> inv'1 e1
-   -> inv'5 s
    -> produces'0 iter (push'0 (push'0 s e1) e2) i
    -> produces'0 (C06MapPrecond_Map_Type.map_iter self) (push'0 (push'0 (concat'0 (singleton'0 e) s) e1) e2) i)
   && (let _ = () in ([%#s06_map_precond9] next_precondition'0 iter ( ^ f) (push'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) e))
@@ -2312,233 +1961,189 @@ module C06MapPrecond_Impl0_Next
   
   let%span s06_map_precond1 = "../06_map_precond.rs" 66 16 66 76
   
-  let%span s06_map_precond2 = "../06_map_precond.rs" 67 31 67 66
-  
-  let%span s06_map_precond3 = "../06_map_precond.rs" 70 16 70 58
-  
-  let%span s06_map_precond4 = "../06_map_precond.rs" 74 32 74 56
-  
-  let%span s06_map_precond5 = "../06_map_precond.rs" 63 17 63 21
-  
-  let%span s06_map_precond6 = "../06_map_precond.rs" 59 14 62 5
-  
-  let%span s06_map_precond7 = "../06_map_precond.rs" 63 26 63 44
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span13 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span14 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span s06_map_precond2 = "../06_map_precond.rs" 67 31 67 66
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span s06_map_precond3 = "../06_map_precond.rs" 70 16 70 58
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span s06_map_precond4 = "../06_map_precond.rs" 74 32 74 56
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span s06_map_precond5 = "../06_map_precond.rs" 63 17 63 21
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span s06_map_precond6 = "../06_map_precond.rs" 59 14 62 5
   
-  let%span span19 = "../06_map_precond.rs" 84 8 88 9
+  let%span s06_map_precond7 = "../06_map_precond.rs" 63 26 63 44
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span10 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span11 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span26 = "../06_map_precond.rs" 106 8 113 9
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span27 = "../06_map_precond.rs" 93 24 93 28
+  let%span span15 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span28 = "../06_map_precond.rs" 93 33 93 37
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span29 = "../06_map_precond.rs" 93 42 93 50
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span30 = "../06_map_precond.rs" 92 4 92 83
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span31 = "../06_map_precond.rs" 94 8 101 9
+  let%span span19 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span32 = "../06_map_precond.rs" 118 8 123 9
+  let%span span20 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span33 = "../06_map_precond.rs" 159 12 161 73
+  let%span span21 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
+  let%span span22 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
+  let%span span23 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
+  let%span span24 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
+  let%span span25 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
+  let%span span26 = "../../../../../creusot-contracts/src/std/ops.rs" 123 19 123 23
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
+  let%span span27 = "../../../../../creusot-contracts/src/std/ops.rs" 123 25 123 29
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
+  let%span span28 = "../../../../../creusot-contracts/src/std/ops.rs" 123 37 123 40
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
+  let%span span29 = "../../../../../creusot-contracts/src/std/ops.rs" 122 14 122 135
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
+  let%span span30 = "../../../../../creusot-contracts/src/std/ops.rs" 114 15 114 29
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
+  let%span span31 = "../../../../../creusot-contracts/src/std/ops.rs" 115 15 115 26
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
+  let%span span32 = "../../../../../creusot-contracts/src/std/ops.rs" 117 20 117 24
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
+  let%span span33 = "../../../../../creusot-contracts/src/std/ops.rs" 117 26 117 27
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
+  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 117 35 117 36
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
+  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 116 14 116 28
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
+  let%span span36 = "../../../../../creusot-contracts/src/std/ops.rs" 110 19 110 23
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
+  let%span span37 = "../../../../../creusot-contracts/src/std/ops.rs" 109 14 109 31
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
+  let%span span38 = "../../../../../creusot-contracts/src/std/ops.rs" 103 15 103 48
   
-  let%span span51 = "../common.rs" 18 15 18 32
+  let%span span39 = "../../../../../creusot-contracts/src/std/ops.rs" 105 37 105 41
   
-  let%span span52 = "../common.rs" 19 15 19 32
+  let%span span40 = "../../../../../creusot-contracts/src/std/ops.rs" 105 43 105 47
   
-  let%span span53 = "../common.rs" 21 22 21 23
+  let%span span41 = "../../../../../creusot-contracts/src/std/ops.rs" 105 55 105 58
   
-  let%span span54 = "../common.rs" 21 31 21 33
+  let%span span42 = "../../../../../creusot-contracts/src/std/ops.rs" 104 14 104 35
   
-  let%span span55 = "../common.rs" 21 52 21 53
+  let%span span43 = "../common.rs" 18 15 18 32
   
-  let%span span56 = "../common.rs" 21 61 21 63
+  let%span span44 = "../common.rs" 19 15 19 32
   
-  let%span span57 = "../common.rs" 21 82 21 83
+  let%span span45 = "../common.rs" 21 22 21 23
   
-  let%span span58 = "../common.rs" 20 14 20 42
+  let%span span46 = "../common.rs" 21 52 21 53
   
-  let%span span59 = "../common.rs" 15 21 15 25
+  let%span span47 = "../common.rs" 21 82 21 83
   
-  let%span span60 = "../common.rs" 14 14 14 45
+  let%span span48 = "../common.rs" 20 14 20 42
   
-  let%span span61 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span49 = "../common.rs" 15 21 15 25
   
-  let%span span62 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span50 = "../common.rs" 14 14 14 45
   
-  let%span span63 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span51 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span64 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span65 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span53 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span66 = "../06_map_precond.rs" 44 8 56 9
+  let%span span54 = "../06_map_precond.rs" 44 8 56 9
   
-  let%span span67 = "../06_map_precond.rs" 142 20 142 24
+  let%span span55 = "../06_map_precond.rs" 142 20 142 24
   
-  let%span span68 = "../06_map_precond.rs" 142 26 142 33
+  let%span span56 = "../06_map_precond.rs" 142 26 142 33
   
-  let%span span69 = "../06_map_precond.rs" 142 38 142 42
+  let%span span57 = "../06_map_precond.rs" 142 38 142 42
   
-  let%span span70 = "../06_map_precond.rs" 141 14 141 68
+  let%span span58 = "../06_map_precond.rs" 141 14 141 68
   
-  let%span span71 = "../06_map_precond.rs" 143 8 149 9
+  let%span span59 = "../06_map_precond.rs" 143 8 149 9
   
-  let%span span72 = "../06_map_precond.rs" 22 8 25 9
+  let%span span60 = "../06_map_precond.rs" 22 8 25 9
   
-  let%span span73 = "../06_map_precond.rs" 127 4 127 60
+  let%span span61 = "../06_map_precond.rs" 127 4 127 60
   
-  let%span span74 = "../06_map_precond.rs" 128 15 128 30
+  let%span span62 = "../06_map_precond.rs" 128 15 128 30
   
-  let%span span75 = "../06_map_precond.rs" 129 15 129 57
+  let%span span63 = "../06_map_precond.rs" 129 15 129 57
   
-  let%span span76 = "../06_map_precond.rs" 132 30 132 34
+  let%span span64 = "../06_map_precond.rs" 132 30 132 34
   
-  let%span span77 = "../06_map_precond.rs" 132 36 132 37
+  let%span span65 = "../06_map_precond.rs" 132 36 132 37
   
-  let%span span78 = "../06_map_precond.rs" 132 48 132 49
+  let%span span66 = "../06_map_precond.rs" 132 48 132 49
   
-  let%span span79 = "../06_map_precond.rs" 132 54 132 55
+  let%span span67 = "../06_map_precond.rs" 132 54 132 55
   
-  let%span span80 = "../06_map_precond.rs" 132 65 132 69
+  let%span span68 = "../06_map_precond.rs" 132 65 132 69
   
-  let%span span81 = "../06_map_precond.rs" 130 14 130 69
+  let%span span69 = "../06_map_precond.rs" 130 14 130 69
   
-  let%span span82 = "../06_map_precond.rs" 131 14 131 70
+  let%span span70 = "../06_map_precond.rs" 131 14 131 70
   
-  let%span span83 = "../06_map_precond.rs" 126 4 126 12
+  let%span span71 = "../06_map_precond.rs" 126 4 126 12
   
-  let%span span84 = "../../../../../creusot-contracts/src/std/ops.rs" 160 27 160 52
+  let%span span72 = "../../../../../creusot-contracts/src/std/ops.rs" 160 27 160 52
   
-  let%span span85 = "" 0 0 0 0
+  let%span span73 = "" 0 0 0 0
   
-  let%span span86 = "" 0 0 0 0
+  let%span span74 = "" 0 0 0 0
   
-  let%span span87 = "../../../../../creusot-contracts/src/std/ops.rs" 148 0 172 1
+  let%span span75 = "../../../../../creusot-contracts/src/std/ops.rs" 148 0 172 1
   
-  let%span span88 = "" 0 0 0 0
+  let%span span76 = "" 0 0 0 0
   
-  let%span span89 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span77 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span90 = "../common.rs" 27 17 27 21
+  let%span span78 = "../common.rs" 27 17 27 21
   
-  let%span span91 = "../common.rs" 23 14 26 5
+  let%span span79 = "../common.rs" 23 14 26 5
   
-  let%span span92 = "../common.rs" 27 26 27 44
+  let%span span80 = "../common.rs" 27 26 27 44
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   use prelude.prelude.Borrow
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'14 (_x : Seq'0.t_seq (borrowed f))
-  
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span8] inv'14 self)  -> ([%#span9] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span8] len'2 self >= 0
   
-  constant empty'2 : Seq'0.t_seq (borrowed f) = [%#span10] ()
+  constant empty'2 : Seq'0.t_seq (borrowed f)
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span11] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
-  
-  predicate invariant'14 (self : Seq'0.t_seq (borrowed f))
-  
-  axiom inv'14 : forall x : Seq'0.t_seq (borrowed f) . inv'14 x = true
-  
-  predicate invariant'13 (self : Seq'0.t_seq b)
-  
-  predicate inv'13 (_x : Seq'0.t_seq b)
-  
-  axiom inv'13 : forall x : Seq'0.t_seq b . inv'13 x = true
-  
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span9] len'2 (empty'2 : Seq'0.t_seq (borrowed f)) = 0
   
   function len'1 (self : Seq'0.t_seq b) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq b . ([%#span8] inv'13 self)  -> ([%#span9] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq b . [%#span8] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq b = [%#span10] ()
+  constant empty'1 : Seq'0.t_seq b
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq b) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span9] len'1 (empty'1 : Seq'0.t_seq b) = 0
   
   predicate invariant'12 (self : ())
   
@@ -2568,50 +2173,40 @@ module C06MapPrecond_Impl0_Next
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span13] inv'6 x)  -> ([%#span14] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span10] inv'6 x)  -> ([%#span11] deref'0 (new'0 x) = x)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'6 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span8] len'0 self >= 0
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span15] inv'11 v)
-   -> ([%#span18] inv'6 (singleton'0 v))
-  && ([%#span17] index_logic'0 (singleton'0 v) 0 = v) && ([%#span16] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span12] inv'11 v)
+   -> ([%#span14] index_logic'0 (singleton'0 v) 0 = v) && ([%#span13] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span19] forall i : i . forall e : item'0 . inv'0 i
+    [%#span15] forall i : i . forall e : item'0 . inv'0 i
      -> inv'11 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (_3 : b)
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span20] inv'6 self)
-   -> ([%#span21] inv'6 other)
-   -> ([%#span24] inv'6 (concat'0 self other))
-  && ([%#span23] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span17] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span22] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span16] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span25] concat'0 self (singleton'0 v)
+    [%#span18] concat'0 self (singleton'0 v)
   
   predicate unnest'0 (self : f) (_2 : f)
   
@@ -2620,38 +2215,35 @@ module C06MapPrecond_Impl0_Next
   predicate inv'9 (_x : b)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span26] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+    [%#span19] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
      -> inv'9 b
      -> inv'7 f
      -> inv'11 e2
      -> inv'11 e1
-     -> inv'6 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
      -> postcondition_mut'0 f (e1, new'0 s) b  -> precondition'0 ( ^ f) (e2, new'0 (push'0 s e1))
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span31] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+    [%#span23] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
      -> inv'9 b
      -> inv'7 f
      -> inv'11 e2
      -> inv'11 e1
-     -> inv'6 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span27] inv'0 iter)
-   -> ([%#span28] inv'3 func)
-   -> ([%#span29] inv'6 produced)
-   -> ([%#span30] produced = (empty'0 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span20] inv'0 iter)
+   -> ([%#span21] inv'3 func)
+   -> ([%#span22] produced = (empty'0 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -2661,7 +2253,7 @@ module C06MapPrecond_Impl0_Next
   predicate inv'5 (_x : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span32] forall func : f . forall iter : borrowed i . inv'3 func
+    [%#span24] forall func : f . forall iter : borrowed i . inv'3 func
      -> inv'5 iter
      -> completed'1 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
@@ -2669,7 +2261,7 @@ module C06MapPrecond_Impl0_Next
   use C06MapPrecond_Map_Type as Map'0
   
   predicate invariant'10 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i b f item'0) =
-    [%#span33] reinitialize'0 ()
+    [%#span25] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -2693,28 +2285,28 @@ module C06MapPrecond_Impl0_Next
   
   function fn_mut_once'0 (self : f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
   
-  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span34] inv'3 self)
-   -> ([%#span35] inv'8 args)
-   -> ([%#span36] inv'9 res)
-   -> ([%#span37] postcondition_once'0 self args res
+  axiom fn_mut_once'0_spec : forall self : f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span26] inv'3 self)
+   -> ([%#span27] inv'8 args)
+   -> ([%#span28] inv'9 res)
+   -> ([%#span29] postcondition_once'0 self args res
   = (exists s : borrowed f . inv'7 s /\  * s = self /\ postcondition_mut'0 s args res /\ resolve'4 ( ^ s)))
   
   function unnest_trans'0 (self : f) (b : f) (c : f) : ()
   
-  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span38] unnest'0 self b)
-   -> ([%#span39] unnest'0 b c)
-   -> ([%#span40] inv'3 self)  -> ([%#span41] inv'3 b)  -> ([%#span42] inv'3 c)  -> ([%#span43] unnest'0 self c)
+  axiom unnest_trans'0_spec : forall self : f, b : f, c : f . ([%#span30] unnest'0 self b)
+   -> ([%#span31] unnest'0 b c)
+   -> ([%#span32] inv'3 self)  -> ([%#span33] inv'3 b)  -> ([%#span34] inv'3 c)  -> ([%#span35] unnest'0 self c)
   
   function unnest_refl'0 (self : f) : ()
   
-  axiom unnest_refl'0_spec : forall self : f . ([%#span44] inv'3 self)  -> ([%#span45] unnest'0 self self)
+  axiom unnest_refl'0_spec : forall self : f . ([%#span36] inv'3 self)  -> ([%#span37] unnest'0 self self)
   
   function postcondition_mut_unnest'0 (self : borrowed f) (args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (res : b) : ()
     
   
-  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span46] postcondition_mut'0 self args res)
-   -> ([%#span47] inv'7 self)
-   -> ([%#span48] inv'8 args)  -> ([%#span49] inv'9 res)  -> ([%#span50] unnest'0 ( * self) ( ^ self))
+  axiom postcondition_mut_unnest'0_spec : forall self : borrowed f, args : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)), res : b . ([%#span38] postcondition_mut'0 self args res)
+   -> ([%#span39] inv'7 self)
+   -> ([%#span40] inv'8 args)  -> ([%#span41] inv'9 res)  -> ([%#span42] unnest'0 ( * self) ( ^ self))
   
   predicate invariant'8 (self : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0)))
   
@@ -2744,10 +2336,9 @@ module C06MapPrecond_Impl0_Next
   
   axiom inv'3 : forall x : f . inv'3 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'2 (self : Option'0.t_option item'0)
   
@@ -2768,51 +2359,39 @@ module C06MapPrecond_Impl0_Next
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span51] produces'0 a ab b)
-   -> ([%#span52] produces'0 b bc c)
-   -> ([%#span53] inv'0 a)
-   -> ([%#span54] inv'6 ab)
-   -> ([%#span55] inv'0 b)
-   -> ([%#span56] inv'6 bc)  -> ([%#span57] inv'0 c)  -> ([%#span58] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span43] produces'0 a ab b)
+   -> ([%#span44] produces'0 b bc c)
+   -> ([%#span45] inv'0 a)
+   -> ([%#span46] inv'0 b)  -> ([%#span47] inv'0 c)  -> ([%#span48] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span59] inv'0 self)
-   -> ([%#span60] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span49] inv'0 self)
+   -> ([%#span50] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq b) (x : int) : b
-  
-  use prelude.seq_ext.SeqExt
+  function index_logic'1 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function subsequence'0 (self : Seq'0.t_seq item'0) (n : int) (m : int) : Seq'0.t_seq item'0
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span61] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span51] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span62] inv'6 self)
-   -> ([%#span65] inv'6 (subsequence'0 self n m))
-  && ([%#span64] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span53] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#span63] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span52] len'0 (subsequence'0 self n m) = m - n)
   
-  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
+  function index_logic'2 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   predicate produces'1 [@inline:trivial] [#"../06_map_precond.rs" 43 4 43 67] (self : Map'0.t_map i b f item'0) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f item'0)
     
    =
-    [%#span66] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'6 s
-    /\ len'0 s = len'1 visited
+    [%#span54] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'0 s = len'1 visited
     /\ produces'0 (C06MapPrecond_Map_Type.map_iter self) s (C06MapPrecond_Map_Type.map_iter succ)
     /\ inner'0 (C06MapPrecond_Map_Type.map_produced succ)
     = concat'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'14 fs
-    /\ len'2 fs = len'1 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'1 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'2 fs (i - 1) =  * index_logic'2 fs i)
     /\ (if len'1 visited = 0 then
       C06MapPrecond_Map_Type.map_func self = C06MapPrecond_Map_Type.map_func succ
@@ -2825,18 +2404,15 @@ module C06MapPrecond_Impl0_Next
     /\ precondition'0 ( * index_logic'2 fs i) (index_logic'0 s i, new'0 (concat'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) (subsequence'0 s 0 i)))
     /\ postcondition_mut'0 (index_logic'2 fs i) (index_logic'0 s i, new'0 (concat'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) (subsequence'0 s 0 i))) (index_logic'1 visited i))))
   
-  use seq.Seq
-  
   function singleton'1 (v : b) : Seq'0.t_seq b
   
-  axiom singleton'1_spec : forall v : b . ([%#span15] inv'9 v)
-   -> ([%#span18] inv'13 (singleton'1 v))
-  && ([%#span17] index_logic'1 (singleton'1 v) 0 = v) && ([%#span16] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : b . ([%#span12] inv'9 v)
+   -> ([%#span14] index_logic'1 (singleton'1 v) 0 = v) && ([%#span13] len'1 (singleton'1 v) = 1)
   
   predicate produces_one'0 [#"../06_map_precond.rs" 142 4 142 57] (self : Map'0.t_map i b f item'0) (visited : b) (succ : Map'0.t_map i b f item'0)
     
    =
-    [%#span71] exists f : borrowed f . inv'7 f
+    [%#span59] exists f : borrowed f . inv'7 f
     /\  * f = C06MapPrecond_Map_Type.map_func self
     /\  ^ f = C06MapPrecond_Map_Type.map_func succ
     /\ (exists e : item'0 . inv'11 e
@@ -2846,13 +2422,13 @@ module C06MapPrecond_Impl0_Next
     /\ precondition'0 ( * f) (e, C06MapPrecond_Map_Type.map_produced self)
     /\ postcondition_mut'0 f (e, C06MapPrecond_Map_Type.map_produced self) visited)
   
-  axiom produces_one'0_spec : forall self : Map'0.t_map i b f item'0, visited : b, succ : Map'0.t_map i b f item'0 . ([%#span67] inv'10 self)
-   -> ([%#span68] inv'9 visited)
-   -> ([%#span69] inv'10 succ)
-   -> ([%#span70] produces_one'0 self visited succ = produces'1 self (singleton'1 visited) succ)
+  axiom produces_one'0_spec : forall self : Map'0.t_map i b f item'0, visited : b, succ : Map'0.t_map i b f item'0 . ([%#span55] inv'10 self)
+   -> ([%#span56] inv'9 visited)
+   -> ([%#span57] inv'10 succ)
+   -> ([%#span58] produces_one'0 self visited succ = produces'1 self (singleton'1 visited) succ)
   
   predicate completed'0 [#"../06_map_precond.rs" 21 4 21 35] (self : borrowed (Map'0.t_map i b f item'0)) =
-    [%#span72] deref'0 (C06MapPrecond_Map_Type.map_produced ( ^ self)) = (empty'0 : Seq'0.t_seq item'0)
+    [%#span60] deref'0 (C06MapPrecond_Map_Type.map_produced ( ^ self)) = (empty'0 : Seq'0.t_seq item'0)
     /\ completed'1 (Borrow.borrow_logic (C06MapPrecond_Map_Type.map_iter ( * self)) (C06MapPrecond_Map_Type.map_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ C06MapPrecond_Map_Type.map_func ( * self) = C06MapPrecond_Map_Type.map_func ( ^ self)
   
@@ -2864,42 +2440,42 @@ module C06MapPrecond_Impl0_Next
   
   function new'1 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'1_spec : forall x : () . ([%#span13] inv'12 x)  -> ([%#span14] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : () . ([%#span10] inv'12 x)  -> ([%#span11] deref'1 (new'1 x) = x)
   
   function produces_one_invariant'0 [#"../06_map_precond.rs" 132 4 132 73] (self : Map'0.t_map i b f item'0) (e : item'0) (r : b) (f : borrowed f) (iter : i) : ()
     
   
-  axiom produces_one_invariant'0_spec : forall self : Map'0.t_map i b f item'0, e : item'0, r : b, f : borrowed f, iter : i . ([%#span73] produces'0 (C06MapPrecond_Map_Type.map_iter self) (singleton'0 e) iter)
-   -> ([%#span74]  * f = C06MapPrecond_Map_Type.map_func self)
-   -> ([%#span75] postcondition_mut'0 f (e, C06MapPrecond_Map_Type.map_produced self) r)
-   -> ([%#span76] inv'10 self)
-   -> ([%#span77] inv'11 e)
-   -> ([%#span78] inv'9 r)
-   -> ([%#span79] inv'7 f)
-   -> ([%#span80] inv'0 iter)
-   -> ([%#span82] next_precondition'0 iter ( ^ f) (push'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) e))
-  && ([%#span81] preservation_inv'0 iter ( ^ f) (push'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) e))
+  axiom produces_one_invariant'0_spec : forall self : Map'0.t_map i b f item'0, e : item'0, r : b, f : borrowed f, iter : i . ([%#span61] produces'0 (C06MapPrecond_Map_Type.map_iter self) (singleton'0 e) iter)
+   -> ([%#span62]  * f = C06MapPrecond_Map_Type.map_func self)
+   -> ([%#span63] postcondition_mut'0 f (e, C06MapPrecond_Map_Type.map_produced self) r)
+   -> ([%#span64] inv'10 self)
+   -> ([%#span65] inv'11 e)
+   -> ([%#span66] inv'9 r)
+   -> ([%#span67] inv'7 f)
+   -> ([%#span68] inv'0 iter)
+   -> ([%#span70] next_precondition'0 iter ( ^ f) (push'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) e))
+  && ([%#span69] preservation_inv'0 iter ( ^ f) (push'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) e))
   
   predicate resolve'2 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0))
   
-  let rec call_mut'0 (self:borrowed f) (args:(item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (return'  (ret:b))= {[@expl:precondition] [%#span86] inv'8 args}
-    {[@expl:precondition] [%#span85] inv'7 self}
-    {[@expl:precondition] [%#span84] precondition'0 ( * self) args}
+  let rec call_mut'0 (self:borrowed f) (args:(item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (return'  (ret:b))= {[@expl:precondition] [%#span74] inv'8 args}
+    {[@expl:precondition] [%#span73] inv'7 self}
+    {[@expl:precondition] [%#span72] precondition'0 ( * self) args}
     any
-    [ return' (result:b)-> {[%#span88] inv'9 result}
-      {[%#span87] postcondition_mut'0 self args result}
+    [ return' (result:b)-> {[%#span76] inv'9 result}
+      {[%#span75] postcondition_mut'0 self args result}
       (! return' {result}) ]
     
   
   predicate resolve'1 (self : Option'0.t_option item'0)
   
   predicate resolve'0 (self : borrowed (Map'0.t_map i b f item'0)) =
-    [%#span89]  ^ self =  * self
+    [%#span77]  ^ self =  * self
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span90] inv'5 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span78] inv'5 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span92] inv'2 result}
-      {[%#span91] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span80] inv'2 result}
+      {[%#span79] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -3098,73 +2674,53 @@ module C06MapPrecond_Map
   
   let%span span26 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span33 = "../06_map_precond.rs" 84 8 88 9
-  
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span31 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
-  
-  let%span span40 = "../06_map_precond.rs" 106 8 113 9
-  
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span42 = "../06_map_precond.rs" 93 24 93 28
+  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span43 = "../06_map_precond.rs" 93 33 93 37
+  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span44 = "../06_map_precond.rs" 93 42 93 50
+  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span45 = "../06_map_precond.rs" 92 4 92 83
+  let%span span35 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span46 = "../06_map_precond.rs" 94 8 101 9
+  let%span span36 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span47 = "../06_map_precond.rs" 118 8 123 9
+  let%span span37 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span48 = "../06_map_precond.rs" 159 12 161 73
+  let%span span38 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span49 = "../common.rs" 18 15 18 32
+  let%span span39 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span50 = "../common.rs" 19 15 19 32
+  let%span span40 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span51 = "../common.rs" 21 22 21 23
+  let%span span41 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span52 = "../common.rs" 21 31 21 33
+  let%span span42 = "../common.rs" 18 15 18 32
   
-  let%span span53 = "../common.rs" 21 52 21 53
+  let%span span43 = "../common.rs" 19 15 19 32
   
-  let%span span54 = "../common.rs" 21 61 21 63
+  let%span span44 = "../common.rs" 21 22 21 23
   
-  let%span span55 = "../common.rs" 21 82 21 83
+  let%span span45 = "../common.rs" 21 52 21 53
   
-  let%span span56 = "../common.rs" 20 14 20 42
+  let%span span46 = "../common.rs" 21 82 21 83
   
-  let%span span57 = "../common.rs" 15 21 15 25
+  let%span span47 = "../common.rs" 20 14 20 42
   
-  let%span span58 = "../common.rs" 14 14 14 45
+  let%span span48 = "../common.rs" 15 21 15 25
   
-  let%span span59 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span49 = "../common.rs" 14 14 14 45
   
-  let%span span60 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
   type item'0
   
@@ -3253,82 +2809,67 @@ module C06MapPrecond_Map
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span27] inv'4 self)  -> ([%#span28] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span27] len'0 self >= 0
   
   predicate inv'1 (_x : item'0)
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span29] inv'1 v)
-   -> ([%#span32] inv'4 (singleton'0 v))
-  && ([%#span31] index_logic'0 (singleton'0 v) 0 = v) && ([%#span30] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span28] inv'1 v)
+   -> ([%#span30] index_logic'0 (singleton'0 v) 0 = v) && ([%#span29] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span33] forall i : i . forall e : item'0 . inv'0 i
+    [%#span31] forall i : i . forall e : item'0 . inv'0 i
      -> inv'1 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span34] inv'4 self)
-   -> ([%#span35] inv'4 other)
-   -> ([%#span38] inv'4 (concat'0 self other))
-  && ([%#span37] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span33] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span36] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span32] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span39] concat'0 self (singleton'0 v)
+    [%#span34] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span40] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+    [%#span35] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
      -> inv'6 b
      -> inv'7 f
      -> inv'1 e2
      -> inv'1 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
      -> postcondition_mut'0 f (e1, new'0 s) b  -> precondition'0 ( ^ f) (e2, new'0 (push'0 s e1))
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span41] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span46] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
+    [%#span39] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'0 i
      -> inv'6 b
      -> inv'7 f
      -> inv'1 e2
      -> inv'1 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span42] inv'0 iter)
-   -> ([%#span43] inv'2 func)
-   -> ([%#span44] inv'4 produced)
-   -> ([%#span45] produced = (empty'0 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span36] inv'0 iter)
+   -> ([%#span37] inv'2 func)
+   -> ([%#span38] produced = (empty'0 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -3336,7 +2877,7 @@ module C06MapPrecond_Map
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span47] forall func : f . forall iter : borrowed i . inv'2 func
+    [%#span40] forall func : f . forall iter : borrowed i . inv'2 func
      -> inv'5 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
@@ -3344,7 +2885,7 @@ module C06MapPrecond_Map
   use C06MapPrecond_Map_Type as Map'0
   
   predicate invariant'3 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i b f item'0) =
-    [%#span48] reinitialize'0 ()
+    [%#span41] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -3371,22 +2912,19 @@ module C06MapPrecond_Map
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span49] produces'0 a ab b)
-   -> ([%#span50] produces'0 b bc c)
-   -> ([%#span51] inv'0 a)
-   -> ([%#span52] inv'4 ab)
-   -> ([%#span53] inv'0 b)
-   -> ([%#span54] inv'4 bc)  -> ([%#span55] inv'0 c)  -> ([%#span56] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span42] produces'0 a ab b)
+   -> ([%#span43] produces'0 b bc c)
+   -> ([%#span44] inv'0 a)
+   -> ([%#span45] inv'0 b)  -> ([%#span46] inv'0 c)  -> ([%#span47] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span57] inv'0 self)
-   -> ([%#span58] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span48] inv'0 self)
+   -> ([%#span49] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span60] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span59] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span50] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use prelude.prelude.Intrinsic
   
@@ -3429,17 +2967,9 @@ module C06MapPrecond_Map
     
 end
 module C06MapPrecond_Identity_Closure0_Type
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
-  use seq.Seq
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
@@ -3460,74 +2990,47 @@ module C06MapPrecond_Identity_Closure0
   
   let%span s06_map_precond1 = "../06_map_precond.rs" 178 14 178 20
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span12 = "../common.rs" 18 15 18 32
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span13 = "../common.rs" 19 15 19 32
+  let%span span6 = "../common.rs" 18 15 18 32
   
-  let%span span14 = "../common.rs" 21 22 21 23
+  let%span span7 = "../common.rs" 19 15 19 32
   
-  let%span span15 = "../common.rs" 21 31 21 33
+  let%span span8 = "../common.rs" 21 22 21 23
   
-  let%span span16 = "../common.rs" 21 52 21 53
+  let%span span9 = "../common.rs" 21 52 21 53
   
-  let%span span17 = "../common.rs" 21 61 21 63
+  let%span span10 = "../common.rs" 21 82 21 83
   
-  let%span span18 = "../common.rs" 21 82 21 83
+  let%span span11 = "../common.rs" 20 14 20 42
   
-  let%span span19 = "../common.rs" 20 14 20 42
+  let%span span12 = "../common.rs" 15 21 15 25
   
-  let%span span20 = "../common.rs" 15 21 15 25
+  let%span span13 = "../common.rs" 14 14 14 45
   
-  let%span span21 = "../common.rs" 14 14 14 45
+  let%span span14 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span22 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  use prelude.prelude.Int
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'2 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'1 (self : i)
   
@@ -3541,38 +3044,31 @@ module C06MapPrecond_Identity_Closure0
   
   axiom inv'0 : forall x : item'0 . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span7] inv'2 self)
-   -> ([%#span8] inv'2 other)
-   -> ([%#span11] inv'2 (concat'0 self other))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span5] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span4] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span12] produces'0 a ab b)
-   -> ([%#span13] produces'0 b bc c)
-   -> ([%#span14] inv'1 a)
-   -> ([%#span15] inv'2 ab)
-   -> ([%#span16] inv'1 b)
-   -> ([%#span17] inv'2 bc)  -> ([%#span18] inv'1 c)  -> ([%#span19] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span6] produces'0 a ab b)
+   -> ([%#span7] produces'0 b bc c)
+   -> ([%#span8] inv'1 a)
+   -> ([%#span9] inv'1 b)  -> ([%#span10] inv'1 c)  -> ([%#span11] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span20] inv'1 self)
-   -> ([%#span21] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span12] inv'1 self)
+   -> ([%#span13] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   use prelude.prelude.Int16
   
@@ -3590,7 +3086,7 @@ module C06MapPrecond_Identity_Closure0
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Closure'0.c06mapprecond_identity_closure0 i)) =
-    [%#span22]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0))
   
@@ -3619,91 +3115,71 @@ module C06MapPrecond_Identity
   
   let%span s06_map_precond0 = "../06_map_precond.rs" 177 29 177 33
   
-  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span6 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span7 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span12 = "../06_map_precond.rs" 84 8 88 9
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span3 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span4 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span8 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span19 = "../06_map_precond.rs" 106 8 113 9
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span20 = "../06_map_precond.rs" 93 24 93 28
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span21 = "../06_map_precond.rs" 93 33 93 37
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span22 = "../06_map_precond.rs" 93 42 93 50
+  let%span span12 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span23 = "../06_map_precond.rs" 92 4 92 83
+  let%span span13 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span24 = "../06_map_precond.rs" 94 8 101 9
+  let%span span14 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span25 = "../06_map_precond.rs" 118 8 123 9
+  let%span span15 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span26 = "../06_map_precond.rs" 159 12 161 73
+  let%span span16 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span27 = "../common.rs" 18 15 18 32
+  let%span span17 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span28 = "../common.rs" 19 15 19 32
+  let%span span18 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span29 = "../common.rs" 21 22 21 23
+  let%span span19 = "../common.rs" 18 15 18 32
   
-  let%span span30 = "../common.rs" 21 31 21 33
+  let%span span20 = "../common.rs" 19 15 19 32
   
-  let%span span31 = "../common.rs" 21 52 21 53
+  let%span span21 = "../common.rs" 21 22 21 23
   
-  let%span span32 = "../common.rs" 21 61 21 63
+  let%span span22 = "../common.rs" 21 52 21 53
   
-  let%span span33 = "../common.rs" 21 82 21 83
+  let%span span23 = "../common.rs" 21 82 21 83
   
-  let%span span34 = "../common.rs" 20 14 20 42
+  let%span span24 = "../common.rs" 20 14 20 42
   
-  let%span span35 = "../common.rs" 15 21 15 25
+  let%span span25 = "../common.rs" 15 21 15 25
   
-  let%span span36 = "../common.rs" 14 14 14 45
+  let%span span26 = "../common.rs" 14 14 14 45
   
-  let%span span37 = "../06_map_precond.rs" 166 0 166 131
+  let%span span27 = "../06_map_precond.rs" 166 0 166 131
   
-  let%span span38 = "../06_map_precond.rs" 167 11 167 41
+  let%span span28 = "../06_map_precond.rs" 167 11 167 41
   
-  let%span span39 = "../06_map_precond.rs" 168 11 168 51
+  let%span span29 = "../06_map_precond.rs" 168 11 168 51
   
-  let%span span40 = "../06_map_precond.rs" 171 4 171 8
+  let%span span30 = "../06_map_precond.rs" 171 4 171 8
   
-  let%span span41 = "../06_map_precond.rs" 172 4 172 8
+  let%span span31 = "../06_map_precond.rs" 172 4 172 8
   
-  let%span span42 = "../06_map_precond.rs" 169 10 169 75
+  let%span span32 = "../06_map_precond.rs" 169 10 169 75
   
-  let%span span43 = "../06_map_precond.rs" 173 5 173 17
+  let%span span33 = "../06_map_precond.rs" 173 5 173 17
   
   type item'0
   
@@ -3743,20 +3219,15 @@ module C06MapPrecond_Identity
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span1] inv'4 self)  -> ([%#span2] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span1] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span3] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span5] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span2] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'2 (self : item'0)
   
@@ -3779,26 +3250,21 @@ module C06MapPrecond_Identity
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span6] inv'4 x)  -> ([%#span7] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span3] inv'4 x)  -> ([%#span4] deref'0 (new'0 x) = x)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span8] inv'2 v)
-   -> ([%#span11] inv'4 (singleton'0 v))
-  && ([%#span10] index_logic'0 (singleton'0 v) 0 = v) && ([%#span9] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span5] inv'2 v)
+   -> ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : Closure'0.c06mapprecond_identity_closure0 i) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span12] forall i : i . forall e : item'0 . inv'1 i
+    [%#span8] forall i : i . forall e : item'0 . inv'1 i
      -> inv'2 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   predicate unnest'0 [#"../06_map_precond.rs" 178 14 178 20] (self : Closure'0.c06mapprecond_identity_closure0 i) (_2 : Closure'0.c06mapprecond_identity_closure0 i)
@@ -3811,30 +3277,26 @@ module C06MapPrecond_Identity
    =
     (let (x, _3) = args in true) /\ unnest'0 ( * self) ( ^ self)
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span13] inv'4 self)
-   -> ([%#span14] inv'4 other)
-   -> ([%#span17] inv'4 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span18] concat'0 self (singleton'0 v)
+    [%#span11] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : Closure'0.c06mapprecond_identity_closure0 i)
     
    =
-    [%#span19] forall i : i . forall b : item'0 . forall f : borrowed (Closure'0.c06mapprecond_identity_closure0 i) . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
+    [%#span12] forall i : i . forall b : item'0 . forall f : borrowed (Closure'0.c06mapprecond_identity_closure0 i) . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
      -> inv'2 b
      -> inv'6 f
      -> inv'2 e2
      -> inv'2 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
@@ -3843,22 +3305,20 @@ module C06MapPrecond_Identity
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : Closure'0.c06mapprecond_identity_closure0 i) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span24] forall i : i . forall b : item'0 . forall f : borrowed (Closure'0.c06mapprecond_identity_closure0 i) . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
+    [%#span16] forall i : i . forall b : item'0 . forall f : borrowed (Closure'0.c06mapprecond_identity_closure0 i) . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'1 i
      -> inv'2 b
      -> inv'6 f
      -> inv'2 e2
      -> inv'2 e1
-     -> inv'4 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : Closure'0.c06mapprecond_identity_closure0 i, produced : Seq'0.t_seq item'0 . ([%#span20] inv'1 iter)
-   -> ([%#span21] inv'3 func)
-   -> ([%#span22] inv'4 produced)
-   -> ([%#span23] produced = (empty'0 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : Closure'0.c06mapprecond_identity_closure0 i, produced : Seq'0.t_seq item'0 . ([%#span13] inv'1 iter)
+   -> ([%#span14] inv'3 func)
+   -> ([%#span15] produced = (empty'0 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -3866,7 +3326,7 @@ module C06MapPrecond_Identity
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span25] forall func : Closure'0.c06mapprecond_identity_closure0 i . forall iter : borrowed i . inv'3 func
+    [%#span17] forall func : Closure'0.c06mapprecond_identity_closure0 i . forall iter : borrowed i . inv'3 func
      -> inv'5 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
@@ -3876,7 +3336,7 @@ module C06MapPrecond_Identity
   predicate invariant'0 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i item'0 (Closure'0.c06mapprecond_identity_closure0 i) item'0)
     
    =
-    [%#span26] reinitialize'0 ()
+    [%#span18] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -3891,32 +3351,30 @@ module C06MapPrecond_Identity
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span27] produces'0 a ab b)
-   -> ([%#span28] produces'0 b bc c)
-   -> ([%#span29] inv'1 a)
-   -> ([%#span30] inv'4 ab)
-   -> ([%#span31] inv'1 b)
-   -> ([%#span32] inv'4 bc)  -> ([%#span33] inv'1 c)  -> ([%#span34] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span19] produces'0 a ab b)
+   -> ([%#span20] produces'0 b bc c)
+   -> ([%#span21] inv'1 a)
+   -> ([%#span22] inv'1 b)  -> ([%#span23] inv'1 c)  -> ([%#span24] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span35] inv'1 self)
-   -> ([%#span36] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span25] inv'1 self)
+   -> ([%#span26] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : Map'0.t_map i item'0 (Closure'0.c06mapprecond_identity_closure0 i) item'0)
   
-  let rec map'0 (iter:i) (func:Closure'0.c06mapprecond_identity_closure0 i) (return'  (ret:Map'0.t_map i item'0 (Closure'0.c06mapprecond_identity_closure0 i) item'0))= {[@expl:precondition] [%#span41] inv'3 func}
-    {[@expl:precondition] [%#span40] inv'1 iter}
-    {[@expl:precondition] [%#span39] preservation'0 iter func}
-    {[@expl:precondition] [%#span38] reinitialize'0 ()}
-    {[@expl:precondition] [%#span37] forall i2 : i . forall e : item'0 . inv'1 i2
+  let rec map'0 (iter:i) (func:Closure'0.c06mapprecond_identity_closure0 i) (return'  (ret:Map'0.t_map i item'0 (Closure'0.c06mapprecond_identity_closure0 i) item'0))= {[@expl:precondition] [%#span31] inv'3 func}
+    {[@expl:precondition] [%#span30] inv'1 iter}
+    {[@expl:precondition] [%#span29] preservation'0 iter func}
+    {[@expl:precondition] [%#span28] reinitialize'0 ()}
+    {[@expl:precondition] [%#span27] forall i2 : i . forall e : item'0 . inv'1 i2
      -> inv'2 e
      -> produces'0 iter (singleton'0 e) i2  -> precondition'0 func (e, new'0 (empty'0 : Seq'0.t_seq item'0))}
     any
-    [ return' (result:Map'0.t_map i item'0 (Closure'0.c06mapprecond_identity_closure0 i) item'0)-> {[%#span43] inv'0 result}
-      {[%#span42] result = Map'0.C_Map iter func (new'0 (empty'0 : Seq'0.t_seq item'0))}
+    [ return' (result:Map'0.t_map i item'0 (Closure'0.c06mapprecond_identity_closure0 i) item'0)-> {[%#span33] inv'0 result}
+      {[%#span32] result = Map'0.C_Map iter func (new'0 (empty'0 : Seq'0.t_seq item'0))}
       (! return' {result}) ]
     
   
@@ -4029,129 +3487,101 @@ module C06MapPrecond_Increment
   
   let%span span4 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../common.rs" 18 15 18 32
-  
-  let%span span16 = "../common.rs" 19 15 19 32
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span17 = "../common.rs" 21 22 21 23
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span18 = "../common.rs" 21 31 21 33
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span19 = "../common.rs" 21 52 21 53
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span20 = "../common.rs" 21 61 21 63
+  let%span span9 = "../common.rs" 18 15 18 32
   
-  let%span span21 = "../common.rs" 21 82 21 83
+  let%span span10 = "../common.rs" 19 15 19 32
   
-  let%span span22 = "../common.rs" 20 14 20 42
+  let%span span11 = "../common.rs" 21 22 21 23
   
-  let%span span23 = "../common.rs" 15 21 15 25
+  let%span span12 = "../common.rs" 21 52 21 53
   
-  let%span span24 = "../common.rs" 14 14 14 45
+  let%span span13 = "../common.rs" 21 82 21 83
   
-  let%span span25 = "../06_map_precond.rs" 188 19 188 27
+  let%span span14 = "../common.rs" 20 14 20 42
   
-  let%span span26 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span15 = "../common.rs" 15 21 15 25
   
-  let%span span27 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span16 = "../common.rs" 14 14 14 45
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span17 = "../06_map_precond.rs" 188 19 188 27
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span18 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span19 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span33 = "../06_map_precond.rs" 44 8 56 9
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span34 = "../06_map_precond.rs" 35 15 35 32
+  let%span span23 = "../06_map_precond.rs" 44 8 56 9
   
-  let%span span35 = "../06_map_precond.rs" 36 15 36 32
+  let%span span24 = "../06_map_precond.rs" 35 15 35 32
   
-  let%span span36 = "../06_map_precond.rs" 38 22 38 23
+  let%span span25 = "../06_map_precond.rs" 36 15 36 32
   
-  let%span span37 = "../06_map_precond.rs" 38 31 38 33
+  let%span span26 = "../06_map_precond.rs" 38 22 38 23
   
-  let%span span38 = "../06_map_precond.rs" 38 52 38 53
+  let%span span27 = "../06_map_precond.rs" 38 52 38 53
   
-  let%span span39 = "../06_map_precond.rs" 38 61 38 63
+  let%span span28 = "../06_map_precond.rs" 38 82 38 83
   
-  let%span span40 = "../06_map_precond.rs" 38 82 38 83
+  let%span span29 = "../06_map_precond.rs" 37 14 37 42
   
-  let%span span41 = "../06_map_precond.rs" 37 14 37 42
+  let%span span30 = "../06_map_precond.rs" 33 4 33 10
   
-  let%span span42 = "../06_map_precond.rs" 33 4 33 10
+  let%span span31 = "../06_map_precond.rs" 31 21 31 25
   
-  let%span span43 = "../06_map_precond.rs" 31 21 31 25
+  let%span span32 = "../06_map_precond.rs" 30 14 30 45
   
-  let%span span44 = "../06_map_precond.rs" 30 14 30 45
+  let%span span33 = "../06_map_precond.rs" 28 4 28 10
   
-  let%span span45 = "../06_map_precond.rs" 28 4 28 10
+  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span37 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span50 = "../06_map_precond.rs" 84 8 88 9
+  let%span span39 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span51 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span40 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span52 = "../06_map_precond.rs" 106 8 113 9
+  let%span span41 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span53 = "../06_map_precond.rs" 93 24 93 28
+  let%span span42 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span54 = "../06_map_precond.rs" 93 33 93 37
+  let%span span43 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span55 = "../06_map_precond.rs" 93 42 93 50
+  let%span span44 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span56 = "../06_map_precond.rs" 92 4 92 83
+  let%span span45 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span57 = "../06_map_precond.rs" 94 8 101 9
+  let%span span46 = "../06_map_precond.rs" 166 0 166 131
   
-  let%span span58 = "../06_map_precond.rs" 118 8 123 9
+  let%span span47 = "../06_map_precond.rs" 167 11 167 41
   
-  let%span span59 = "../06_map_precond.rs" 159 12 161 73
+  let%span span48 = "../06_map_precond.rs" 168 11 168 51
   
-  let%span span60 = "../06_map_precond.rs" 166 0 166 131
+  let%span span49 = "../06_map_precond.rs" 171 4 171 8
   
-  let%span span61 = "../06_map_precond.rs" 167 11 167 41
+  let%span span50 = "../06_map_precond.rs" 172 4 172 8
   
-  let%span span62 = "../06_map_precond.rs" 168 11 168 51
+  let%span span51 = "../06_map_precond.rs" 169 10 169 75
   
-  let%span span63 = "../06_map_precond.rs" 171 4 171 8
-  
-  let%span span64 = "../06_map_precond.rs" 172 4 172 8
-  
-  let%span span65 = "../06_map_precond.rs" 169 10 169 75
-  
-  let%span span66 = "../06_map_precond.rs" 173 5 173 17
+  let%span span52 = "../06_map_precond.rs" 173 5 173 17
   
   use prelude.prelude.UInt32
   
@@ -4165,46 +3595,34 @@ module C06MapPrecond_Increment
   
   use prelude.prelude.Borrow
   
-  predicate invariant'7 (self : borrowed (Closure'0.c06mapprecond_increment_closure2 u)) =
+  predicate invariant'6 (self : borrowed (Closure'0.c06mapprecond_increment_closure2 u)) =
     [%#span4] true
   
-  predicate inv'7 (_x : borrowed (Closure'0.c06mapprecond_increment_closure2 u))
+  predicate inv'6 (_x : borrowed (Closure'0.c06mapprecond_increment_closure2 u))
   
-  axiom inv'7 : forall x : borrowed (Closure'0.c06mapprecond_increment_closure2 u) . inv'7 x = true
+  axiom inv'6 : forall x : borrowed (Closure'0.c06mapprecond_increment_closure2 u) . inv'6 x = true
   
-  use prelude.prelude.Int
+  predicate invariant'5 (self : Seq'0.t_seq uint32) =
+    [%#span4] true
   
-  use seq.Seq
+  predicate inv'5 (_x : Seq'0.t_seq uint32)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  axiom inv'5 : forall x : Seq'0.t_seq uint32 . inv'5 x = true
   
-  predicate inv'6 (_x : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)))
+  use prelude.prelude.Int
   
   function len'1 (self : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u))) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)) . ([%#span5] inv'6 self)
-   -> ([%#span6] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)) . [%#span5] len'1 self
+  >= 0
   
-  constant empty'1 : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)) = [%#span7] ()
+  constant empty'1 : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u))
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span8] len'1 (empty'1 : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)))
+  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'1 : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)))
   = 0
   
-  predicate invariant'6 (self : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u))) =
-    [%#span4] true
-  
-  axiom inv'6 : forall x : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)) . inv'6 x = true
-  
-  predicate invariant'5 (self : Seq'0.t_seq uint32) =
-    [%#span4] true
-  
-  predicate inv'5 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'5 : forall x : Seq'0.t_seq uint32 . inv'5 x = true
-  
   predicate invariant'4 (self : Closure'0.c06mapprecond_increment_closure2 u) =
     [%#span4] true
   
@@ -4225,46 +3643,37 @@ module C06MapPrecond_Increment
   
   axiom inv'2 : forall x : u . inv'2 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span5] inv'5 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span5] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span10] inv'5 self)
-   -> ([%#span11] inv'5 other)
-   -> ([%#span14] inv'5 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : u) (visited : Seq'0.t_seq uint32) (o : u)
   
   function produces_trans'1 [#"../common.rs" 21 4 21 91] (a : u) (ab : Seq'0.t_seq uint32) (b : u) (bc : Seq'0.t_seq uint32) (c : u) : ()
     
   
-  axiom produces_trans'1_spec : forall a : u, ab : Seq'0.t_seq uint32, b : u, bc : Seq'0.t_seq uint32, c : u . ([%#span15] produces'1 a ab b)
-   -> ([%#span16] produces'1 b bc c)
-   -> ([%#span17] inv'2 a)
-   -> ([%#span18] inv'5 ab)
-   -> ([%#span19] inv'2 b)
-   -> ([%#span20] inv'5 bc)  -> ([%#span21] inv'2 c)  -> ([%#span22] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : u, ab : Seq'0.t_seq uint32, b : u, bc : Seq'0.t_seq uint32, c : u . ([%#span9] produces'1 a ab b)
+   -> ([%#span10] produces'1 b bc c)
+   -> ([%#span11] inv'2 a)
+   -> ([%#span12] inv'2 b)  -> ([%#span13] inv'2 c)  -> ([%#span14] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   function produces_refl'1 [#"../common.rs" 15 4 15 27] (self : u) : ()
   
-  axiom produces_refl'1_spec : forall self : u . ([%#span23] inv'2 self)
-   -> ([%#span24] produces'1 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'1_spec : forall self : u . ([%#span15] inv'2 self)
+   -> ([%#span16] produces'1 self (empty'0 : Seq'0.t_seq uint32) self)
   
   predicate invariant'1 (self : borrowed u)
   
@@ -4272,10 +3681,9 @@ module C06MapPrecond_Increment
   
   axiom inv'1 : forall x : borrowed u . inv'1 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use C06MapPrecond_Map_Type as Map'0
   
@@ -4296,29 +3704,23 @@ module C06MapPrecond_Increment
   predicate precondition'0 [#"../06_map_precond.rs" 189 8 189 35] (self : Closure'0.c06mapprecond_increment_closure2 u) (args : (uint32, Snapshot'0.t_snapshot (Seq'0.t_seq uint32)))
     
    =
-    [%#span25] let (x, _3) = args in UInt32.to_int x <= 15
+    [%#span17] let (x, _3) = args in UInt32.to_int x <= 15
   
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) : Seq'0.t_seq uint32
   
   function new'0 (x : Seq'0.t_seq uint32) : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq uint32 . ([%#span26] inv'5 x)  -> ([%#span27] deref'0 (new'0 x) = x)
-  
-  use prelude.seq_ext.SeqExt
+  axiom new'0_spec : forall x : Seq'0.t_seq uint32 . ([%#span18] inv'5 x)  -> ([%#span19] deref'0 (new'0 x) = x)
   
   function subsequence'0 (self : Seq'0.t_seq uint32) (n : int) (m : int) : Seq'0.t_seq uint32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span28] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span20] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span29] inv'5 self)
-   -> ([%#span32] inv'5 (subsequence'0 self n m))
-  && ([%#span31] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span22] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#span30] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span21] len'0 (subsequence'0 self n m) = m - n)
   
-  function index_logic'1 (self : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u))) (x : int) : borrowed (Closure'0.c06mapprecond_increment_closure2 u)
+  function index_logic'1 (self : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u))) (_2 : int) : borrowed (Closure'0.c06mapprecond_increment_closure2 u)
     
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) : Seq'0.t_seq uint32
@@ -4328,14 +3730,12 @@ module C06MapPrecond_Increment
   predicate produces'0 [@inline:trivial] [#"../06_map_precond.rs" 43 4 43 67] (self : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32) (visited : Seq'0.t_seq uint32) (succ : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32)
     
    =
-    [%#span33] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq uint32 . inv'5 s
-    /\ len'0 s = len'0 visited
+    [%#span23] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq uint32 . len'0 s = len'0 visited
     /\ produces'1 (C06MapPrecond_Map_Type.map_iter self) s (C06MapPrecond_Map_Type.map_iter succ)
     /\ inner'0 (C06MapPrecond_Map_Type.map_produced succ)
     = concat'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)) . inv'6 fs
-    /\ len'1 fs = len'0 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed (Closure'0.c06mapprecond_increment_closure2 u)) . len'1 fs = len'0 visited
     /\ (forall i : int . 1 <= i /\ i < len'1 fs  ->  ^ index_logic'1 fs (i - 1) =  * index_logic'1 fs i)
     /\ (if len'0 visited = 0 then
       C06MapPrecond_Map_Type.map_func self = C06MapPrecond_Map_Type.map_func succ
@@ -4351,49 +3751,43 @@ module C06MapPrecond_Increment
   function produces_trans'0 [#"../06_map_precond.rs" 38 4 38 90] (a : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32) (ab : Seq'0.t_seq uint32) (b : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32) (bc : Seq'0.t_seq uint32) (c : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32) : ()
     
    =
-    [%#span42] ()
+    [%#span30] ()
   
-  axiom produces_trans'0_spec : forall a : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32, ab : Seq'0.t_seq uint32, b : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32, bc : Seq'0.t_seq uint32, c : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32 . ([%#span34] produces'0 a ab b)
-   -> ([%#span35] produces'0 b bc c)
-   -> ([%#span36] inv'0 a)
-   -> ([%#span37] inv'5 ab)
-   -> ([%#span38] inv'0 b)
-   -> ([%#span39] inv'5 bc)  -> ([%#span40] inv'0 c)  -> ([%#span41] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32, ab : Seq'0.t_seq uint32, b : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32, bc : Seq'0.t_seq uint32, c : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32 . ([%#span24] produces'0 a ab b)
+   -> ([%#span25] produces'0 b bc c)
+   -> ([%#span26] inv'0 a)
+   -> ([%#span27] inv'0 b)  -> ([%#span28] inv'0 c)  -> ([%#span29] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../06_map_precond.rs" 31 4 31 26] (self : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32) : ()
     
    =
-    [%#span45] ()
+    [%#span33] ()
   
-  axiom produces_refl'0_spec : forall self : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32 . ([%#span43] inv'0 self)
-   -> ([%#span44] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
-  
-  use seq.Seq
+  axiom produces_refl'0_spec : forall self : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32 . ([%#span31] inv'0 self)
+   -> ([%#span32] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span46] inv'3 v)
-   -> ([%#span49] inv'5 (singleton'0 v))
-  && ([%#span48] index_logic'0 (singleton'0 v) 0 = v) && ([%#span47] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span34] inv'3 v)
+   -> ([%#span36] index_logic'0 (singleton'0 v) 0 = v) && ([%#span35] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : u) (func : Closure'0.c06mapprecond_increment_closure2 u) (produced : Seq'0.t_seq uint32)
     
    =
-    [%#span50] forall i : u . forall e : uint32 . inv'2 i
+    [%#span37] forall i : u . forall e : uint32 . inv'2 i
      -> inv'3 e  -> produces'1 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq uint32) (v : uint32) : Seq'0.t_seq uint32 =
-    [%#span51] concat'0 self (singleton'0 v)
+    [%#span38] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : u) (func : Closure'0.c06mapprecond_increment_closure2 u)
     
    =
-    [%#span52] forall i : u . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_increment_closure2 u) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
+    [%#span39] forall i : u . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_increment_closure2 u) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
      -> inv'3 b
-     -> inv'7 f
+     -> inv'6 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'5 s
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
@@ -4402,28 +3796,26 @@ module C06MapPrecond_Increment
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : u) (func : Closure'0.c06mapprecond_increment_closure2 u) (produced : Seq'0.t_seq uint32)
     
    =
-    [%#span57] forall i : u . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_increment_closure2 u) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
+    [%#span43] forall i : u . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_increment_closure2 u) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
      -> inv'3 b
-     -> inv'7 f
+     -> inv'6 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'5 s
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : u, func : Closure'0.c06mapprecond_increment_closure2 u, produced : Seq'0.t_seq uint32 . ([%#span53] inv'2 iter)
-   -> ([%#span54] inv'4 func)
-   -> ([%#span55] inv'5 produced)
-   -> ([%#span56] produced = (empty'0 : Seq'0.t_seq uint32)
+  axiom preservation_inv'0_spec : forall iter : u, func : Closure'0.c06mapprecond_increment_closure2 u, produced : Seq'0.t_seq uint32 . ([%#span40] inv'2 iter)
+   -> ([%#span41] inv'4 func)
+   -> ([%#span42] produced = (empty'0 : Seq'0.t_seq uint32)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed u)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span58] forall func : Closure'0.c06mapprecond_increment_closure2 u . forall iter : borrowed u . inv'4 func
+    [%#span44] forall func : Closure'0.c06mapprecond_increment_closure2 u . forall iter : borrowed u . inv'4 func
      -> inv'1 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq uint32) /\ preservation'0 ( ^ iter) func
@@ -4431,7 +3823,7 @@ module C06MapPrecond_Increment
   predicate invariant'0 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32)
     
    =
-    [%#span59] reinitialize'0 ()
+    [%#span45] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -4445,16 +3837,16 @@ module C06MapPrecond_Increment
   
   predicate resolve'0 (self : Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32)
   
-  let rec map'0 (iter:u) (func:Closure'0.c06mapprecond_increment_closure2 u) (return'  (ret:Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32))= {[@expl:precondition] [%#span64] inv'4 func}
-    {[@expl:precondition] [%#span63] inv'2 iter}
-    {[@expl:precondition] [%#span62] preservation'0 iter func}
-    {[@expl:precondition] [%#span61] reinitialize'0 ()}
-    {[@expl:precondition] [%#span60] forall i2 : u . forall e : uint32 . inv'2 i2
+  let rec map'0 (iter:u) (func:Closure'0.c06mapprecond_increment_closure2 u) (return'  (ret:Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32))= {[@expl:precondition] [%#span50] inv'4 func}
+    {[@expl:precondition] [%#span49] inv'2 iter}
+    {[@expl:precondition] [%#span48] preservation'0 iter func}
+    {[@expl:precondition] [%#span47] reinitialize'0 ()}
+    {[@expl:precondition] [%#span46] forall i2 : u . forall e : uint32 . inv'2 i2
      -> inv'3 e
      -> produces'1 iter (singleton'0 e) i2  -> precondition'0 func (e, new'0 (empty'0 : Seq'0.t_seq uint32))}
     any
-    [ return' (result:Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32)-> {[%#span66] inv'0 result}
-      {[%#span65] result = Map'0.C_Map iter func (new'0 (empty'0 : Seq'0.t_seq uint32))}
+    [ return' (result:Map'0.t_map u uint32 (Closure'0.c06mapprecond_increment_closure2 u) uint32)-> {[%#span52] inv'0 result}
+      {[%#span51] result = Map'0.C_Map iter func (new'0 (empty'0 : Seq'0.t_seq uint32))}
       (! return' {result}) ]
     
   
@@ -4527,49 +3919,29 @@ module C06MapPrecond_Counter_Closure2
   
   let%span s06_map_precond2 = "../06_map_precond.rs" 206 18 206 39
   
-  let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "" 0 0 0 0
   
-  let%span span9 = "" 0 0 0 0
+  let%span span6 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span10 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  use prelude.prelude.Int
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq uint32) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq uint32 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.Int16
   
@@ -4591,7 +3963,7 @@ module C06MapPrecond_Counter_Closure2
    =
      ^ field_0'0 _2 =  ^ field_0'0 self
   
-  constant max'0 : usize = [%#span9] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
   
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) : Seq'0.t_seq uint32
   
@@ -4600,7 +3972,7 @@ module C06MapPrecond_Counter_Closure2
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed (Closure'0.c06mapprecond_counter_closure2 i)) =
-    [%#span10]  ^ self =  * self
+    [%#span6]  ^ self =  * self
   
   let rec c06mapprecond_counter_closure2 (_1:borrowed (Closure'0.c06mapprecond_counter_closure2 i)) (x:uint32) (_prod:Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) (return'  (ret:uint32))= {[%#s06_map_precond1] UIntSize.to_int ( * field_0'0 ( * _1))
     = len'0 (deref'0 _prod)
@@ -4649,95 +4021,75 @@ module C06MapPrecond_Counter
   
   let%span span4 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../common.rs" 18 15 18 32
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span16 = "../common.rs" 19 15 19 32
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span17 = "../common.rs" 21 22 21 23
+  let%span span9 = "../common.rs" 18 15 18 32
   
-  let%span span18 = "../common.rs" 21 31 21 33
+  let%span span10 = "../common.rs" 19 15 19 32
   
-  let%span span19 = "../common.rs" 21 52 21 53
+  let%span span11 = "../common.rs" 21 22 21 23
   
-  let%span span20 = "../common.rs" 21 61 21 63
+  let%span span12 = "../common.rs" 21 52 21 53
   
-  let%span span21 = "../common.rs" 21 82 21 83
+  let%span span13 = "../common.rs" 21 82 21 83
   
-  let%span span22 = "../common.rs" 20 14 20 42
+  let%span span14 = "../common.rs" 20 14 20 42
   
-  let%span span23 = "../common.rs" 15 21 15 25
+  let%span span15 = "../common.rs" 15 21 15 25
   
-  let%span span24 = "../common.rs" 14 14 14 45
+  let%span span16 = "../common.rs" 14 14 14 45
   
-  let%span span25 = "" 0 0 0 0
+  let%span span17 = "" 0 0 0 0
   
-  let%span span26 = "../06_map_precond.rs" 205 19 205 61
+  let%span span18 = "../06_map_precond.rs" 205 19 205 61
   
-  let%span span27 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span19 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span28 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span20 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span33 = "../06_map_precond.rs" 84 8 88 9
-  
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span24 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span35 = "../06_map_precond.rs" 106 8 113 9
+  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span36 = "../06_map_precond.rs" 93 24 93 28
+  let%span span26 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span37 = "../06_map_precond.rs" 93 33 93 37
+  let%span span27 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span38 = "../06_map_precond.rs" 93 42 93 50
+  let%span span28 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span39 = "../06_map_precond.rs" 92 4 92 83
+  let%span span29 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span40 = "../06_map_precond.rs" 94 8 101 9
+  let%span span30 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span41 = "../06_map_precond.rs" 118 8 123 9
+  let%span span31 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span42 = "../06_map_precond.rs" 159 12 161 73
+  let%span span32 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span43 = "../06_map_precond.rs" 166 0 166 131
+  let%span span33 = "../06_map_precond.rs" 166 0 166 131
   
-  let%span span44 = "../06_map_precond.rs" 167 11 167 41
+  let%span span34 = "../06_map_precond.rs" 167 11 167 41
   
-  let%span span45 = "../06_map_precond.rs" 168 11 168 51
+  let%span span35 = "../06_map_precond.rs" 168 11 168 51
   
-  let%span span46 = "../06_map_precond.rs" 171 4 171 8
+  let%span span36 = "../06_map_precond.rs" 171 4 171 8
   
-  let%span span47 = "../06_map_precond.rs" 172 4 172 8
+  let%span span37 = "../06_map_precond.rs" 172 4 172 8
   
-  let%span span48 = "../06_map_precond.rs" 169 10 169 75
+  let%span span38 = "../06_map_precond.rs" 169 10 169 75
   
-  let%span span49 = "../06_map_precond.rs" 173 5 173 17
+  let%span span39 = "../06_map_precond.rs" 173 5 173 17
   
   use prelude.prelude.UIntSize
   
@@ -4783,20 +4135,15 @@ module C06MapPrecond_Counter
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span5] inv'5 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span5] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   predicate invariant'2 (self : i)
   
@@ -4804,38 +4151,31 @@ module C06MapPrecond_Counter
   
   axiom inv'2 : forall x : i . inv'2 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span10] inv'5 self)
-   -> ([%#span11] inv'5 other)
-   -> ([%#span14] inv'5 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'0 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq uint32) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq uint32) (b : i) (bc : Seq'0.t_seq uint32) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq uint32, b : i, bc : Seq'0.t_seq uint32, c : i . ([%#span15] produces'0 a ab b)
-   -> ([%#span16] produces'0 b bc c)
-   -> ([%#span17] inv'2 a)
-   -> ([%#span18] inv'5 ab)
-   -> ([%#span19] inv'2 b)
-   -> ([%#span20] inv'5 bc)  -> ([%#span21] inv'2 c)  -> ([%#span22] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq uint32, b : i, bc : Seq'0.t_seq uint32, c : i . ([%#span9] produces'0 a ab b)
+   -> ([%#span10] produces'0 b bc c)
+   -> ([%#span11] inv'2 a)
+   -> ([%#span12] inv'2 b)  -> ([%#span13] inv'2 c)  -> ([%#span14] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span23] inv'2 self)
-   -> ([%#span24] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span15] inv'2 self)
+   -> ([%#span16] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   predicate invariant'1 (self : borrowed i)
   
@@ -4843,7 +4183,7 @@ module C06MapPrecond_Counter
   
   axiom inv'1 : forall x : borrowed i . inv'1 x = true
   
-  constant max'0 : usize = [%#span25] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span17] (18446744073709551615 : usize)
   
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)) : Seq'0.t_seq uint32
   
@@ -4857,25 +4197,22 @@ module C06MapPrecond_Counter
   predicate precondition'0 [#"../06_map_precond.rs" 206 8 206 41] (self : Closure'0.c06mapprecond_counter_closure2 i) (args : (uint32, Snapshot'0.t_snapshot (Seq'0.t_seq uint32)))
     
    =
-    [%#span26] let (x, _prod) = args in UIntSize.to_int ( * field_0'0 self) = len'0 (deref'0 _prod)
+    [%#span18] let (x, _prod) = args in UIntSize.to_int ( * field_0'0 self) = len'0 (deref'0 _prod)
     /\  * field_0'0 self < (max'0 : usize)
   
   function new'0 (x : Seq'0.t_seq uint32) : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq uint32 . ([%#span27] inv'5 x)  -> ([%#span28] deref'0 (new'0 x) = x)
-  
-  use seq.Seq
+  axiom new'0_spec : forall x : Seq'0.t_seq uint32 . ([%#span19] inv'5 x)  -> ([%#span20] deref'0 (new'0 x) = x)
   
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span29] inv'3 v)
-   -> ([%#span32] inv'5 (singleton'0 v))
-  && ([%#span31] index_logic'0 (singleton'0 v) 0 = v) && ([%#span30] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span21] inv'3 v)
+   -> ([%#span23] index_logic'0 (singleton'0 v) 0 = v) && ([%#span22] len'0 (singleton'0 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : Closure'0.c06mapprecond_counter_closure2 i) (produced : Seq'0.t_seq uint32)
     
    =
-    [%#span33] forall i : i . forall e : uint32 . inv'2 i
+    [%#span24] forall i : i . forall e : uint32 . inv'2 i
      -> inv'3 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   predicate unnest'0 [#"../06_map_precond.rs" 206 8 206 41] (self : Closure'0.c06mapprecond_counter_closure2 i) (_2 : Closure'0.c06mapprecond_counter_closure2 i)
@@ -4890,17 +4227,16 @@ module C06MapPrecond_Counter
     /\ unnest'0 ( * self) ( ^ self)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq uint32) (v : uint32) : Seq'0.t_seq uint32 =
-    [%#span34] concat'0 self (singleton'0 v)
+    [%#span25] concat'0 self (singleton'0 v)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : Closure'0.c06mapprecond_counter_closure2 i)
     
    =
-    [%#span35] forall i : i . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_counter_closure2 i) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
+    [%#span26] forall i : i . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_counter_closure2 i) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
      -> inv'3 b
      -> inv'6 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'5 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
@@ -4909,22 +4245,20 @@ module C06MapPrecond_Counter
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : Closure'0.c06mapprecond_counter_closure2 i) (produced : Seq'0.t_seq uint32)
     
    =
-    [%#span40] forall i : i . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_counter_closure2 i) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
+    [%#span30] forall i : i . forall b : uint32 . forall f : borrowed (Closure'0.c06mapprecond_counter_closure2 i) . forall e2 : uint32 . forall e1 : uint32 . forall s : Seq'0.t_seq uint32 . inv'2 i
      -> inv'3 b
      -> inv'6 f
      -> inv'3 e2
      -> inv'3 e1
-     -> inv'5 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'0 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'0 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'0 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : Closure'0.c06mapprecond_counter_closure2 i, produced : Seq'0.t_seq uint32 . ([%#span36] inv'2 iter)
-   -> ([%#span37] inv'4 func)
-   -> ([%#span38] inv'5 produced)
-   -> ([%#span39] produced = (empty'0 : Seq'0.t_seq uint32)
+  axiom preservation_inv'0_spec : forall iter : i, func : Closure'0.c06mapprecond_counter_closure2 i, produced : Seq'0.t_seq uint32 . ([%#span27] inv'2 iter)
+   -> ([%#span28] inv'4 func)
+   -> ([%#span29] produced = (empty'0 : Seq'0.t_seq uint32)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -4932,7 +4266,7 @@ module C06MapPrecond_Counter
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span41] forall func : Closure'0.c06mapprecond_counter_closure2 i . forall iter : borrowed i . inv'4 func
+    [%#span31] forall func : Closure'0.c06mapprecond_counter_closure2 i . forall iter : borrowed i . inv'4 func
      -> inv'1 iter
      -> completed'0 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq uint32) /\ preservation'0 ( ^ iter) func
@@ -4942,7 +4276,7 @@ module C06MapPrecond_Counter
   predicate invariant'0 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i uint32 (Closure'0.c06mapprecond_counter_closure2 i) uint32)
     
    =
-    [%#span42] reinitialize'0 ()
+    [%#span32] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -4958,16 +4292,16 @@ module C06MapPrecond_Counter
   
   predicate resolve'0 (self : Map'0.t_map i uint32 (Closure'0.c06mapprecond_counter_closure2 i) uint32)
   
-  let rec map'0 (iter:i) (func:Closure'0.c06mapprecond_counter_closure2 i) (return'  (ret:Map'0.t_map i uint32 (Closure'0.c06mapprecond_counter_closure2 i) uint32))= {[@expl:precondition] [%#span47] inv'4 func}
-    {[@expl:precondition] [%#span46] inv'2 iter}
-    {[@expl:precondition] [%#span45] preservation'0 iter func}
-    {[@expl:precondition] [%#span44] reinitialize'0 ()}
-    {[@expl:precondition] [%#span43] forall i2 : i . forall e : uint32 . inv'2 i2
+  let rec map'0 (iter:i) (func:Closure'0.c06mapprecond_counter_closure2 i) (return'  (ret:Map'0.t_map i uint32 (Closure'0.c06mapprecond_counter_closure2 i) uint32))= {[@expl:precondition] [%#span37] inv'4 func}
+    {[@expl:precondition] [%#span36] inv'2 iter}
+    {[@expl:precondition] [%#span35] preservation'0 iter func}
+    {[@expl:precondition] [%#span34] reinitialize'0 ()}
+    {[@expl:precondition] [%#span33] forall i2 : i . forall e : uint32 . inv'2 i2
      -> inv'3 e
      -> produces'0 iter (singleton'0 e) i2  -> precondition'0 func (e, new'0 (empty'0 : Seq'0.t_seq uint32))}
     any
-    [ return' (result:Map'0.t_map i uint32 (Closure'0.c06mapprecond_counter_closure2 i) uint32)-> {[%#span49] inv'0 result}
-      {[%#span48] result = Map'0.C_Map iter func (new'0 (empty'0 : Seq'0.t_seq uint32))}
+    [ return' (result:Map'0.t_map i uint32 (Closure'0.c06mapprecond_counter_closure2 i) uint32)-> {[%#span39] inv'0 result}
+      {[%#span38] result = Map'0.C_Map iter func (new'0 (empty'0 : Seq'0.t_seq uint32))}
       (! return' {result}) ]
     
   
@@ -5018,133 +4352,103 @@ module C06MapPrecond_Impl0
   
   let%span span4 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span9 = "../06_map_precond.rs" 84 8 88 9
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span11 = "../06_map_precond.rs" 84 8 88 9
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span13 = "../06_map_precond.rs" 106 8 113 9
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span14 = "../06_map_precond.rs" 93 24 93 28
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span15 = "../06_map_precond.rs" 93 33 93 37
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span16 = "../06_map_precond.rs" 92 4 92 83
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span17 = "../06_map_precond.rs" 94 8 101 9
   
-  let%span span18 = "../06_map_precond.rs" 106 8 113 9
+  let%span span18 = "../06_map_precond.rs" 118 8 123 9
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span19 = "../06_map_precond.rs" 159 12 161 73
   
-  let%span span20 = "../06_map_precond.rs" 93 24 93 28
-  
-  let%span span21 = "../06_map_precond.rs" 93 33 93 37
-  
-  let%span span22 = "../06_map_precond.rs" 93 42 93 50
-  
-  let%span span23 = "../06_map_precond.rs" 92 4 92 83
-  
-  let%span span24 = "../06_map_precond.rs" 94 8 101 9
-  
-  let%span span25 = "../06_map_precond.rs" 118 8 123 9
-  
-  let%span span26 = "../06_map_precond.rs" 159 12 161 73
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span23 = "../06_map_precond.rs" 44 8 56 9
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span24 = "../06_map_precond.rs" 142 20 142 24
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span25 = "../06_map_precond.rs" 142 26 142 33
   
-  let%span span32 = "../06_map_precond.rs" 44 8 56 9
+  let%span span26 = "../06_map_precond.rs" 142 38 142 42
   
-  let%span span33 = "../06_map_precond.rs" 142 20 142 24
+  let%span span27 = "../06_map_precond.rs" 141 14 141 68
   
-  let%span span34 = "../06_map_precond.rs" 142 26 142 33
+  let%span span28 = "../06_map_precond.rs" 143 8 149 9
   
-  let%span span35 = "../06_map_precond.rs" 142 38 142 42
-  
-  let%span span36 = "../06_map_precond.rs" 141 14 141 68
-  
-  let%span span37 = "../06_map_precond.rs" 143 8 149 9
-  
-  let%span span38 = "../06_map_precond.rs" 22 8 25 9
+  let%span span29 = "../06_map_precond.rs" 22 8 25 9
   
   use prelude.prelude.Borrow
   
-  predicate invariant'11 (self : borrowed i)
-  
-  predicate inv'11 (_x : borrowed i)
-  
-  axiom inv'11 : forall x : borrowed i . inv'11 x = true
-  
-  predicate invariant'10 (self : f)
-  
-  predicate inv'10 (_x : f)
+  predicate invariant'9 (self : borrowed i)
   
-  axiom inv'10 : forall x : f . inv'10 x = true
+  predicate inv'9 (_x : borrowed i)
   
-  predicate invariant'9 (self : i)
+  axiom inv'9 : forall x : borrowed i . inv'9 x = true
   
-  predicate inv'9 (_x : i)
+  predicate invariant'8 (self : f)
   
-  axiom inv'9 : forall x : i . inv'9 x = true
+  predicate inv'8 (_x : f)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'8 : forall x : f . inv'8 x = true
   
-  predicate invariant'8 (self : Seq'0.t_seq (borrowed f))
+  predicate invariant'7 (self : i)
   
-  predicate inv'8 (_x : Seq'0.t_seq (borrowed f))
+  predicate inv'7 (_x : i)
   
-  axiom inv'8 : forall x : Seq'0.t_seq (borrowed f) . inv'8 x = true
+  axiom inv'7 : forall x : i . inv'7 x = true
   
   type item'0
   
-  predicate invariant'7 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'7 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq item'0 . inv'7 x = true
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'6 (self : item'0)
+  predicate invariant'6 (self : Seq'0.t_seq item'0)
   
-  predicate inv'6 (_x : item'0)
+  predicate inv'6 (_x : Seq'0.t_seq item'0)
   
-  axiom inv'6 : forall x : item'0 . inv'6 x = true
+  axiom inv'6 : forall x : Seq'0.t_seq item'0 . inv'6 x = true
   
-  predicate invariant'5 (self : borrowed f)
+  predicate invariant'5 (self : item'0)
   
-  predicate inv'5 (_x : borrowed f)
+  predicate inv'5 (_x : item'0)
   
-  axiom inv'5 : forall x : borrowed f . inv'5 x = true
+  axiom inv'5 : forall x : item'0 . inv'5 x = true
   
-  predicate invariant'4 (self : b)
+  predicate invariant'4 (self : borrowed f)
   
-  predicate inv'4 (_x : b)
+  predicate inv'4 (_x : borrowed f)
   
-  axiom inv'4 : forall x : b . inv'4 x = true
+  axiom inv'4 : forall x : borrowed f . inv'4 x = true
   
-  predicate invariant'3 (self : Seq'0.t_seq b)
+  predicate invariant'3 (self : b)
   
-  predicate inv'3 (_x : Seq'0.t_seq b)
+  predicate inv'3 (_x : b)
   
-  axiom inv'3 : forall x : Seq'0.t_seq b . inv'3 x = true
+  axiom inv'3 : forall x : b . inv'3 x = true
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
@@ -5154,90 +4458,75 @@ module C06MapPrecond_Impl0
   
   function new'0 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span3] inv'7 x)  -> ([%#span4] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Seq'0.t_seq item'0 . ([%#span3] inv'6 x)  -> ([%#span4] deref'0 (new'0 x) = x)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'2 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span5] inv'7 self)  -> ([%#span6] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span5] len'1 self >= 0
   
   function singleton'1 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'1_spec : forall v : item'0 . ([%#span7] inv'6 v)
-   -> ([%#span10] inv'7 (singleton'1 v))
-  && ([%#span9] index_logic'2 (singleton'1 v) 0 = v) && ([%#span8] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : item'0 . ([%#span6] inv'5 v)
+   -> ([%#span8] index_logic'2 (singleton'1 v) 0 = v) && ([%#span7] len'1 (singleton'1 v) = 1)
   
   predicate next_precondition'0 [#"../06_map_precond.rs" 83 4 83 74] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span11] forall i : i . forall e : item'0 . inv'9 i
-     -> inv'6 e  -> produces'1 iter (singleton'1 e) i  -> precondition'0 func (e, new'0 produced)
+    [%#span9] forall i : i . forall e : item'0 . inv'7 i
+     -> inv'5 e  -> produces'1 iter (singleton'1 e) i  -> precondition'0 func (e, new'0 produced)
   
   predicate postcondition_mut'0 (self : borrowed f) (_2 : (item'0, Snapshot'0.t_snapshot (Seq'0.t_seq item'0))) (_3 : b)
   
-  use seq.Seq
-  
   function concat'1 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span12] inv'7 self)
-   -> ([%#span13] inv'7 other)
-   -> ([%#span16] inv'7 (concat'1 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span11] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'2 (concat'1 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span14] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span10] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span17] concat'1 self (singleton'1 v)
+    [%#span12] concat'1 self (singleton'1 v)
   
   predicate unnest'0 (self : f) (_2 : f)
   
   predicate preservation'0 [#"../06_map_precond.rs" 105 4 105 45] (iter : i) (func : f) =
-    [%#span18] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'9 i
-     -> inv'4 b
-     -> inv'5 f
-     -> inv'6 e2
-     -> inv'6 e1
-     -> inv'7 s
+    [%#span13] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'7 i
+     -> inv'3 b
+     -> inv'4 f
+     -> inv'5 e2
+     -> inv'5 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
      -> postcondition_mut'0 f (e1, new'0 s) b  -> precondition'0 ( ^ f) (e2, new'0 (push'0 s e1))
   
-  constant empty'2 : Seq'0.t_seq item'0 = [%#span19] ()
+  constant empty'2 : Seq'0.t_seq item'0
   
   predicate preservation_inv'0 [#"../06_map_precond.rs" 93 4 93 73] (iter : i) (func : f) (produced : Seq'0.t_seq item'0)
     
    =
-    [%#span24] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'9 i
-     -> inv'4 b
-     -> inv'5 f
-     -> inv'6 e2
-     -> inv'6 e1
-     -> inv'7 s
+    [%#span17] forall i : i . forall b : b . forall f : borrowed f . forall e2 : item'0 . forall e1 : item'0 . forall s : Seq'0.t_seq item'0 . inv'7 i
+     -> inv'3 b
+     -> inv'4 f
+     -> inv'5 e2
+     -> inv'5 e1
      -> unnest'0 func ( * f)
      -> produces'1 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 (concat'1 produced s))
      -> postcondition_mut'0 f (e1, new'0 (concat'1 produced s)) b
      -> precondition'0 ( ^ f) (e2, new'0 (push'0 (concat'1 produced s) e1))
   
-  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span20] inv'9 iter)
-   -> ([%#span21] inv'10 func)
-   -> ([%#span22] inv'7 produced)
-   -> ([%#span23] produced = (empty'2 : Seq'0.t_seq item'0)
+  axiom preservation_inv'0_spec : forall iter : i, func : f, produced : Seq'0.t_seq item'0 . ([%#span14] inv'7 iter)
+   -> ([%#span15] inv'8 func)
+   -> ([%#span16] produced = (empty'2 : Seq'0.t_seq item'0)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   use C06MapPrecond_Map_Type as C06MapPrecond_Map_Type
@@ -5245,15 +4534,15 @@ module C06MapPrecond_Impl0
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate reinitialize'0 [#"../06_map_precond.rs" 117 4 117 29] (_1 : ()) =
-    [%#span25] forall func : f . forall iter : borrowed i . inv'10 func
-     -> inv'11 iter
+    [%#span18] forall func : f . forall iter : borrowed i . inv'8 func
+     -> inv'9 iter
      -> completed'1 iter
      -> next_precondition'0 ( ^ iter) func (empty'2 : Seq'0.t_seq item'0) /\ preservation'0 ( ^ iter) func
   
   use C06MapPrecond_Map_Type as Map'0
   
   predicate invariant'2 [#"../06_map_precond.rs" 157 4 157 30] (self : Map'0.t_map i b f item'0) =
-    [%#span26] reinitialize'0 ()
+    [%#span19] reinitialize'0 ()
     /\ preservation_inv'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
     /\ next_precondition'0 (C06MapPrecond_Map_Type.map_iter self) (C06MapPrecond_Map_Type.map_func self) (deref'0 (C06MapPrecond_Map_Type.map_produced self))
   
@@ -5279,67 +4568,49 @@ module C06MapPrecond_Impl0
   
   axiom inv'0 : forall x : borrowed (Map'0.t_map i b f item'0) . inv'0 x = (inv'2 ( * x) /\ inv'2 ( ^ x))
   
-  constant empty'0 : Seq'0.t_seq b = [%#span19] ()
-  
-  constant empty'0 : Seq'0.t_seq b = [%#span19] ()
-  
-  use seq.Seq
-  
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq b
   
-  function index_logic'0 (self : Seq'0.t_seq b) (x : int) : b
+  constant empty'0 : Seq'0.t_seq b
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq b) (_2 : int) : b
   
   function len'0 (self : Seq'0.t_seq b) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq b . ([%#span5] inv'3 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq b . [%#span5] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq b) (other : Seq'0.t_seq b) : Seq'0.t_seq b
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span12] inv'3 self)
-   -> ([%#span13] inv'3 other)
-   -> ([%#span16] inv'3 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq b, other : Seq'0.t_seq b . ([%#span11] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use prelude.seq_ext.SeqExt
+  && ([%#span10] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function subsequence'0 (self : Seq'0.t_seq item'0) (n : int) (m : int) : Seq'0.t_seq item'0
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span27] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq item'0, n : int, m : int . ([%#span20] 0 <= n
   /\ n <= m /\ m <= len'1 self)
-   -> ([%#span28] inv'7 self)
-   -> ([%#span31] inv'7 (subsequence'0 self n m))
-  && ([%#span30] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
+   -> ([%#span22] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
    -> index_logic'2 (subsequence'0 self n m) i = index_logic'2 self (n + i))
-  && ([%#span29] len'1 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span21] len'1 (subsequence'0 self n m) = m - n)
   
-  function index_logic'1 (self : Seq'0.t_seq (borrowed f)) (x : int) : borrowed f
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq (borrowed f)) (_2 : int) : borrowed f
   
   function len'2 (self : Seq'0.t_seq (borrowed f)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . ([%#span5] inv'8 self)  -> ([%#span6] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed f) . [%#span5] len'2 self >= 0
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
   predicate produces'0 [@inline:trivial] [#"../06_map_precond.rs" 43 4 43 67] (self : Map'0.t_map i b f item'0) (visited : Seq'0.t_seq b) (succ : Map'0.t_map i b f item'0)
     
    =
-    [%#span32] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'7 s
-    /\ len'1 s = len'0 visited
+    [%#span23] unnest'0 (C06MapPrecond_Map_Type.map_func self) (C06MapPrecond_Map_Type.map_func succ)
+    /\ (exists s : Seq'0.t_seq item'0 . len'1 s = len'0 visited
     /\ produces'1 (C06MapPrecond_Map_Type.map_iter self) s (C06MapPrecond_Map_Type.map_iter succ)
     /\ inner'0 (C06MapPrecond_Map_Type.map_produced succ)
     = concat'1 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed f) . inv'8 fs
-    /\ len'2 fs = len'0 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed f) . len'2 fs = len'0 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'1 fs (i - 1) =  * index_logic'1 fs i)
     /\ (if len'0 visited = 0 then
       C06MapPrecond_Map_Type.map_func self = C06MapPrecond_Map_Type.map_func succ
@@ -5352,34 +4623,31 @@ module C06MapPrecond_Impl0
     /\ precondition'0 ( * index_logic'1 fs i) (index_logic'2 s i, new'0 (concat'1 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) (subsequence'0 s 0 i)))
     /\ postcondition_mut'0 (index_logic'1 fs i) (index_logic'2 s i, new'0 (concat'1 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) (subsequence'0 s 0 i))) (index_logic'0 visited i))))
   
-  use seq.Seq
-  
   function singleton'0 (v : b) : Seq'0.t_seq b
   
-  axiom singleton'0_spec : forall v : b . ([%#span7] inv'4 v)
-   -> ([%#span10] inv'3 (singleton'0 v))
-  && ([%#span9] index_logic'0 (singleton'0 v) 0 = v) && ([%#span8] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : b . ([%#span6] inv'3 v)
+   -> ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
   
   predicate produces_one'0 [#"../06_map_precond.rs" 142 4 142 57] (self : Map'0.t_map i b f item'0) (visited : b) (succ : Map'0.t_map i b f item'0)
     
    =
-    [%#span37] exists f : borrowed f . inv'5 f
+    [%#span28] exists f : borrowed f . inv'4 f
     /\  * f = C06MapPrecond_Map_Type.map_func self
     /\  ^ f = C06MapPrecond_Map_Type.map_func succ
-    /\ (exists e : item'0 . inv'6 e
+    /\ (exists e : item'0 . inv'5 e
     /\ produces'1 (C06MapPrecond_Map_Type.map_iter self) (singleton'1 e) (C06MapPrecond_Map_Type.map_iter succ)
     /\ inner'0 (C06MapPrecond_Map_Type.map_produced succ)
     = push'0 (deref'0 (C06MapPrecond_Map_Type.map_produced self)) e
     /\ precondition'0 ( * f) (e, C06MapPrecond_Map_Type.map_produced self)
     /\ postcondition_mut'0 f (e, C06MapPrecond_Map_Type.map_produced self) visited)
   
-  axiom produces_one'0_spec : forall self : Map'0.t_map i b f item'0, visited : b, succ : Map'0.t_map i b f item'0 . ([%#span33] inv'2 self)
-   -> ([%#span34] inv'4 visited)
-   -> ([%#span35] inv'2 succ)
-   -> ([%#span36] produces_one'0 self visited succ = produces'0 self (singleton'0 visited) succ)
+  axiom produces_one'0_spec : forall self : Map'0.t_map i b f item'0, visited : b, succ : Map'0.t_map i b f item'0 . ([%#span24] inv'2 self)
+   -> ([%#span25] inv'3 visited)
+   -> ([%#span26] inv'2 succ)
+   -> ([%#span27] produces_one'0 self visited succ = produces'0 self (singleton'0 visited) succ)
   
   predicate completed'0 [#"../06_map_precond.rs" 21 4 21 35] (self : borrowed (Map'0.t_map i b f item'0)) =
-    [%#span38] deref'0 (C06MapPrecond_Map_Type.map_produced ( ^ self)) = (empty'2 : Seq'0.t_seq item'0)
+    [%#span29] deref'0 (C06MapPrecond_Map_Type.map_produced ( ^ self)) = (empty'2 : Seq'0.t_seq item'0)
     /\ completed'1 (Borrow.borrow_logic (C06MapPrecond_Map_Type.map_iter ( * self)) (C06MapPrecond_Map_Type.map_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ C06MapPrecond_Map_Type.map_func ( * self) = C06MapPrecond_Map_Type.map_func ( ^ self)
   
@@ -5397,11 +4665,9 @@ module C06MapPrecond_Impl0
     end)
   
   goal produces_trans_refn : [%#s06_map_precond1] forall a : Map'0.t_map i b f item'0 . forall ab : Seq'0.t_seq b . forall b : Map'0.t_map i b f item'0 . forall bc : Seq'0.t_seq b . forall c : Map'0.t_map i b f item'0 . inv'2 c
-  /\ inv'3 bc /\ inv'2 b /\ inv'3 ab /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'2 b /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'2 c
-  /\ inv'3 bc
   /\ inv'2 b
-  /\ inv'3 ab
   /\ inv'2 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
diff --git a/creusot/tests/should_succeed/iterators/07_fuse.coma b/creusot/tests/should_succeed/iterators/07_fuse.coma
index 7d2b23e203..b925201ddc 100644
--- a/creusot/tests/should_succeed/iterators/07_fuse.coma
+++ b/creusot/tests/should_succeed/iterators/07_fuse.coma
@@ -34,22 +34,7 @@ module C07Fuse_Fuse_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C07Fuse_Impl0_Next
   type i
@@ -62,76 +47,50 @@ module C07Fuse_Impl0_Next
   
   let%span s07_fuse3 = "../07_fuse.rs" 39 26 39 44
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span14 = "../common.rs" 18 15 18 32
-  
-  let%span span15 = "../common.rs" 19 15 19 32
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span16 = "../common.rs" 21 22 21 23
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span17 = "../common.rs" 21 31 21 33
+  let%span span8 = "../common.rs" 18 15 18 32
   
-  let%span span18 = "../common.rs" 21 52 21 53
+  let%span span9 = "../common.rs" 19 15 19 32
   
-  let%span span19 = "../common.rs" 21 61 21 63
+  let%span span10 = "../common.rs" 21 22 21 23
   
-  let%span span20 = "../common.rs" 21 82 21 83
+  let%span span11 = "../common.rs" 21 52 21 53
   
-  let%span span21 = "../common.rs" 20 14 20 42
+  let%span span12 = "../common.rs" 21 82 21 83
   
-  let%span span22 = "../common.rs" 15 21 15 25
+  let%span span13 = "../common.rs" 20 14 20 42
   
-  let%span span23 = "../common.rs" 14 14 14 45
+  let%span span14 = "../common.rs" 15 21 15 25
   
-  let%span span24 = "../07_fuse.rs" 26 8 32 9
+  let%span span15 = "../common.rs" 14 14 14 45
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span16 = "../07_fuse.rs" 26 8 32 9
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span29 = "../07_fuse.rs" 18 12 19 32
+  let%span span20 = "../07_fuse.rs" 18 12 19 32
   
-  let%span span30 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span21 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span31 = "../common.rs" 27 17 27 21
+  let%span span22 = "../common.rs" 27 17 27 21
   
-  let%span span32 = "../common.rs" 23 14 26 5
+  let%span span23 = "../common.rs" 23 14 26 5
   
-  let%span span33 = "../common.rs" 27 26 27 44
+  let%span span24 = "../common.rs" 27 26 27 44
   
   type item'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'7 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'7 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq item'0 . inv'7 x = true
-  
   predicate invariant'6 (self : item'0)
   
   predicate inv'6 (_x : item'0)
@@ -140,20 +99,17 @@ module C07Fuse_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span4] inv'7 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span4] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use Core_Option_Option_Type as Option'0
   
@@ -171,21 +127,16 @@ module C07Fuse_Impl0_Next
   
   axiom inv'4 : forall x : borrowed i . inv'4 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span9] inv'7 self)
-   -> ([%#span10] inv'7 other)
-   -> ([%#span13] inv'7 (concat'0 self other))
-  && ([%#span12] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span7] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span11] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span6] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'3 (_x : i)
   
@@ -194,17 +145,15 @@ module C07Fuse_Impl0_Next
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span14] produces'1 a ab b)
-   -> ([%#span15] produces'1 b bc c)
-   -> ([%#span16] inv'3 a)
-   -> ([%#span17] inv'7 ab)
-   -> ([%#span18] inv'3 b)
-   -> ([%#span19] inv'7 bc)  -> ([%#span20] inv'3 c)  -> ([%#span21] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span8] produces'1 a ab b)
+   -> ([%#span9] produces'1 b bc c)
+   -> ([%#span10] inv'3 a)
+   -> ([%#span11] inv'3 b)  -> ([%#span12] inv'3 c)  -> ([%#span13] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span22] inv'3 self)
-   -> ([%#span23] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span14] inv'3 self)
+   -> ([%#span15] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'3 (self : i)
   
@@ -235,7 +184,7 @@ module C07Fuse_Impl0_Next
   predicate produces'0 [#"../07_fuse.rs" 25 4 25 65] (self : Fuse'0.t_fuse i) (prod : Seq'0.t_seq item'0) (other : Fuse'0.t_fuse i)
     
    =
-    [%#span24] match C07Fuse_Fuse_Type.fuse_iter self with
+    [%#span16] match C07Fuse_Fuse_Type.fuse_iter self with
       | Option'0.C_None -> prod = (empty'0 : Seq'0.t_seq item'0)
       /\ C07Fuse_Fuse_Type.fuse_iter other = C07Fuse_Fuse_Type.fuse_iter self
       | Option'0.C_Some i -> match C07Fuse_Fuse_Type.fuse_iter other with
@@ -244,18 +193,15 @@ module C07Fuse_Impl0_Next
         end
       end
   
-  use seq.Seq
-  
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span25] inv'6 v)
-   -> ([%#span28] inv'7 (singleton'0 v))
-  && ([%#span27] index_logic'0 (singleton'0 v) 0 = v) && ([%#span26] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span17] inv'6 v)
+   -> ([%#span19] index_logic'0 (singleton'0 v) 0 = v) && ([%#span18] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate completed'0 [#"../07_fuse.rs" 16 4 16 35] (self : borrowed (Fuse'0.t_fuse i)) =
-    [%#span29] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
+    [%#span20] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
     \/ (exists it : borrowed i . inv'4 it
     /\ completed'1 it /\ C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_Some ( * it)))
     /\ C07Fuse_Fuse_Type.fuse_iter ( ^ self) = Option'0.C_None
@@ -267,12 +213,12 @@ module C07Fuse_Impl0_Next
   predicate resolve'3 (self : Option'0.t_option item'0)
   
   predicate resolve'2 (self : borrowed i) =
-    [%#span30]  ^ self =  * self
+    [%#span21]  ^ self =  * self
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span31] inv'4 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span22] inv'4 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span33] inv'5 result}
-      {[%#span32] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span24] inv'5 result}
+      {[%#span23] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -280,10 +226,10 @@ module C07Fuse_Impl0_Next
     
   
   predicate resolve'1 (self : borrowed (Fuse'0.t_fuse i)) =
-    [%#span30]  ^ self =  * self
+    [%#span21]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed (Option'0.t_option i)) =
-    [%#span30]  ^ self =  * self
+    [%#span21]  ^ self =  * self
   
   let rec next (self:borrowed (Fuse'0.t_fuse i)) (return'  (ret:Option'0.t_option item'0))= {[%#s07_fuse1] inv'2 self}
     (! bb0
@@ -394,113 +340,79 @@ module C07Fuse_Impl0_ProducesRefl_Impl
   
   let%span s07_fuse1 = "../07_fuse.rs" 54 14 54 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span5 = "../common.rs" 18 15 18 32
   
-  let%span span9 = "../common.rs" 18 15 18 32
+  let%span span6 = "../common.rs" 19 15 19 32
   
-  let%span span10 = "../common.rs" 19 15 19 32
+  let%span span7 = "../common.rs" 21 22 21 23
   
-  let%span span11 = "../common.rs" 21 22 21 23
+  let%span span8 = "../common.rs" 21 52 21 53
   
-  let%span span12 = "../common.rs" 21 31 21 33
+  let%span span9 = "../common.rs" 21 82 21 83
   
-  let%span span13 = "../common.rs" 21 52 21 53
+  let%span span10 = "../common.rs" 20 14 20 42
   
-  let%span span14 = "../common.rs" 21 61 21 63
+  let%span span11 = "../common.rs" 15 21 15 25
   
-  let%span span15 = "../common.rs" 21 82 21 83
+  let%span span12 = "../common.rs" 14 14 14 45
   
-  let%span span16 = "../common.rs" 20 14 20 42
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span14 = "../07_fuse.rs" 26 8 32 9
   
-  let%span span18 = "../common.rs" 15 21 15 25
+  predicate invariant'1 (self : i)
   
-  let%span span19 = "../common.rs" 14 14 14 45
+  predicate inv'1 (_x : i)
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span22 = "../07_fuse.rs" 26 8 32 9
-  
-  predicate invariant'2 (self : i)
-  
-  predicate inv'2 (_x : i)
-  
-  axiom inv'2 : forall x : i . inv'2 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] inv'1 self)
-   -> ([%#span5] inv'1 other)
-   -> ([%#span8] inv'1 (concat'0 self other))
-  && ([%#span7] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span6] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span3] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'1 a ab b)
-   -> ([%#span10] produces'1 b bc c)
-   -> ([%#span11] inv'2 a)
-   -> ([%#span12] inv'1 ab)
-   -> ([%#span13] inv'2 b)
-   -> ([%#span14] inv'1 bc)  -> ([%#span15] inv'2 c)  -> ([%#span16] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span5] produces'1 a ab b)
+   -> ([%#span6] produces'1 b bc c)
+   -> ([%#span7] inv'1 a)
+   -> ([%#span8] inv'1 b)  -> ([%#span9] inv'1 c)  -> ([%#span10] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span18] inv'2 self)
-   -> ([%#span19] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span11] inv'1 self)
+   -> ([%#span12] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span21] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C07Fuse_Fuse_Type as Fuse'0
   
@@ -517,7 +429,7 @@ module C07Fuse_Impl0_ProducesRefl_Impl
   predicate produces'0 [#"../07_fuse.rs" 25 4 25 65] (self : Fuse'0.t_fuse i) (prod : Seq'0.t_seq item'0) (other : Fuse'0.t_fuse i)
     
    =
-    [%#span22] match C07Fuse_Fuse_Type.fuse_iter self with
+    [%#span14] match C07Fuse_Fuse_Type.fuse_iter self with
       | Option'0.C_None -> prod = (empty'0 : Seq'0.t_seq item'0)
       /\ C07Fuse_Fuse_Type.fuse_iter other = C07Fuse_Fuse_Type.fuse_iter self
       | Option'0.C_Some i -> match C07Fuse_Fuse_Type.fuse_iter other with
@@ -542,123 +454,85 @@ module C07Fuse_Impl0_ProducesTrans_Impl
   
   let%span s07_fuse2 = "../07_fuse.rs" 62 22 62 23
   
-  let%span s07_fuse3 = "../07_fuse.rs" 62 31 62 33
-  
-  let%span s07_fuse4 = "../07_fuse.rs" 62 52 62 53
-  
-  let%span s07_fuse5 = "../07_fuse.rs" 62 61 62 63
-  
-  let%span s07_fuse6 = "../07_fuse.rs" 62 82 62 83
-  
-  let%span s07_fuse7 = "../07_fuse.rs" 61 14 61 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span s07_fuse3 = "../07_fuse.rs" 62 52 62 53
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s07_fuse4 = "../07_fuse.rs" 62 82 62 83
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span s07_fuse5 = "../07_fuse.rs" 61 14 61 42
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../common.rs" 18 15 18 32
-  
-  let%span span16 = "../common.rs" 19 15 19 32
-  
-  let%span span17 = "../common.rs" 21 22 21 23
-  
-  let%span span18 = "../common.rs" 21 31 21 33
-  
-  let%span span19 = "../common.rs" 21 52 21 53
+  let%span span9 = "../common.rs" 18 15 18 32
   
-  let%span span20 = "../common.rs" 21 61 21 63
+  let%span span10 = "../common.rs" 19 15 19 32
   
-  let%span span21 = "../common.rs" 21 82 21 83
+  let%span span11 = "../common.rs" 21 22 21 23
   
-  let%span span22 = "../common.rs" 20 14 20 42
+  let%span span12 = "../common.rs" 21 52 21 53
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span13 = "../common.rs" 21 82 21 83
   
-  let%span span24 = "../common.rs" 15 21 15 25
+  let%span span14 = "../common.rs" 20 14 20 42
   
-  let%span span25 = "../common.rs" 14 14 14 45
+  let%span span15 = "../common.rs" 15 21 15 25
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span16 = "../common.rs" 14 14 14 45
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span28 = "../07_fuse.rs" 26 8 32 9
+  let%span span18 = "../07_fuse.rs" 26 8 32 9
   
-  predicate invariant'2 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'2 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'2 : forall x : i . inv'2 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] inv'1 self)
-   -> ([%#span11] inv'1 other)
-   -> ([%#span14] inv'1 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span15] produces'1 a ab b)
-   -> ([%#span16] produces'1 b bc c)
-   -> ([%#span17] inv'2 a)
-   -> ([%#span18] inv'1 ab)
-   -> ([%#span19] inv'2 b)
-   -> ([%#span20] inv'1 bc)  -> ([%#span21] inv'2 c)  -> ([%#span22] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'1 a ab b)
+   -> ([%#span10] produces'1 b bc c)
+   -> ([%#span11] inv'1 a)
+   -> ([%#span12] inv'1 b)  -> ([%#span13] inv'1 c)  -> ([%#span14] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span23] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span24] inv'2 self)
-   -> ([%#span25] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span15] inv'1 self)
+   -> ([%#span16] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span27] ()
-  
-  axiom empty_len'0_spec : forall _1 : () . [%#span26] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C07Fuse_Fuse_Type as Fuse'0
   
@@ -675,7 +549,7 @@ module C07Fuse_Impl0_ProducesTrans_Impl
   predicate produces'0 [#"../07_fuse.rs" 25 4 25 65] (self : Fuse'0.t_fuse i) (prod : Seq'0.t_seq item'0) (other : Fuse'0.t_fuse i)
     
    =
-    [%#span28] match C07Fuse_Fuse_Type.fuse_iter self with
+    [%#span18] match C07Fuse_Fuse_Type.fuse_iter self with
       | Option'0.C_None -> prod = (empty'0 : Seq'0.t_seq item'0)
       /\ C07Fuse_Fuse_Type.fuse_iter other = C07Fuse_Fuse_Type.fuse_iter self
       | Option'0.C_Some i -> match C07Fuse_Fuse_Type.fuse_iter other with
@@ -697,13 +571,11 @@ module C07Fuse_Impl0_ProducesTrans_Impl
   function produces_trans [#"../07_fuse.rs" 62 4 62 90] (a : Fuse'0.t_fuse i) (ab : Seq'0.t_seq item'0) (b : Fuse'0.t_fuse i) (bc : Seq'0.t_seq item'0) (c : Fuse'0.t_fuse i) : ()
     
   
-  goal vc_produces_trans : ([%#s07_fuse6] inv'0 c)
-   -> ([%#s07_fuse5] inv'1 bc)
-   -> ([%#s07_fuse4] inv'0 b)
-   -> ([%#s07_fuse3] inv'1 ab)
+  goal vc_produces_trans : ([%#s07_fuse4] inv'0 c)
+   -> ([%#s07_fuse3] inv'0 b)
    -> ([%#s07_fuse2] inv'0 a)
    -> ([%#s07_fuse1] produces'0 b bc c)
-   -> ([%#s07_fuse0] produces'0 a ab b)  -> ([%#s07_fuse7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s07_fuse0] produces'0 a ab b)  -> ([%#s07_fuse5] produces'0 a (concat'0 ab bc) c)
 end
 module C07Fuse_Impl1_IsFused_Impl
   type i
@@ -714,161 +586,121 @@ module C07Fuse_Impl1_IsFused_Impl
   
   let%span s07_fuse2 = "../07_fuse.rs" 81 21 81 25
   
-  let%span s07_fuse3 = "../07_fuse.rs" 81 27 81 32
-  
-  let%span s07_fuse4 = "../07_fuse.rs" 81 51 81 55
+  let%span s07_fuse3 = "../07_fuse.rs" 81 51 81 55
   
-  let%span s07_fuse5 = "../07_fuse.rs" 80 14 80 50
+  let%span s07_fuse4 = "../07_fuse.rs" 80 14 80 50
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span13 = "../common.rs" 18 15 18 32
-  
-  let%span span14 = "../common.rs" 19 15 19 32
-  
-  let%span span15 = "../common.rs" 21 22 21 23
-  
-  let%span span16 = "../common.rs" 21 31 21 33
-  
-  let%span span17 = "../common.rs" 21 52 21 53
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span18 = "../common.rs" 21 61 21 63
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span19 = "../common.rs" 21 82 21 83
+  let%span span8 = "../common.rs" 18 15 18 32
   
-  let%span span20 = "../common.rs" 20 14 20 42
+  let%span span9 = "../common.rs" 19 15 19 32
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span10 = "../common.rs" 21 22 21 23
   
-  let%span span22 = "../common.rs" 15 21 15 25
+  let%span span11 = "../common.rs" 21 52 21 53
   
-  let%span span23 = "../common.rs" 14 14 14 45
+  let%span span12 = "../common.rs" 21 82 21 83
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span13 = "../common.rs" 20 14 20 42
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span14 = "../common.rs" 15 21 15 25
   
-  let%span span26 = "../07_fuse.rs" 26 8 32 9
+  let%span span15 = "../common.rs" 14 14 14 45
   
-  let%span span27 = "../07_fuse.rs" 59 15 59 32
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span28 = "../07_fuse.rs" 60 15 60 32
+  let%span span17 = "../07_fuse.rs" 26 8 32 9
   
-  let%span span29 = "../07_fuse.rs" 62 22 62 23
+  let%span span18 = "../07_fuse.rs" 59 15 59 32
   
-  let%span span30 = "../07_fuse.rs" 62 31 62 33
+  let%span span19 = "../07_fuse.rs" 60 15 60 32
   
-  let%span span31 = "../07_fuse.rs" 62 52 62 53
+  let%span span20 = "../07_fuse.rs" 62 22 62 23
   
-  let%span span32 = "../07_fuse.rs" 62 61 62 63
+  let%span span21 = "../07_fuse.rs" 62 52 62 53
   
-  let%span span33 = "../07_fuse.rs" 62 82 62 83
+  let%span span22 = "../07_fuse.rs" 62 82 62 83
   
-  let%span span34 = "../07_fuse.rs" 61 14 61 42
+  let%span span23 = "../07_fuse.rs" 61 14 61 42
   
-  let%span span35 = "../07_fuse.rs" 57 4 57 10
+  let%span span24 = "../07_fuse.rs" 57 4 57 10
   
-  let%span span36 = "../07_fuse.rs" 55 21 55 25
+  let%span span25 = "../07_fuse.rs" 55 21 55 25
   
-  let%span span37 = "../07_fuse.rs" 54 14 54 45
+  let%span span26 = "../07_fuse.rs" 54 14 54 45
   
-  let%span span38 = "../07_fuse.rs" 52 4 52 10
+  let%span span27 = "../07_fuse.rs" 52 4 52 10
   
-  let%span span39 = "../07_fuse.rs" 18 12 19 32
+  let%span span28 = "../07_fuse.rs" 18 12 19 32
   
-  predicate invariant'4 (self : i)
+  predicate invariant'3 (self : i)
   
-  predicate inv'4 (_x : i)
+  predicate inv'3 (_x : i)
   
-  axiom inv'4 : forall x : i . inv'4 x = true
+  axiom inv'3 : forall x : i . inv'3 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'3 (self : borrowed i)
+  predicate invariant'2 (self : borrowed i)
   
-  predicate inv'3 (_x : borrowed i)
+  predicate inv'2 (_x : borrowed i)
   
-  axiom inv'3 : forall x : borrowed i . inv'3 x = true
+  axiom inv'2 : forall x : borrowed i . inv'2 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span6] inv'1 self)  -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span5] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span8] inv'1 self)
-   -> ([%#span9] inv'1 other)
-   -> ([%#span12] inv'1 (concat'0 self other))
-  && ([%#span11] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span7] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span10] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span6] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'1 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'1_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span13] produces'1 a ab b)
-   -> ([%#span14] produces'1 b bc c)
-   -> ([%#span15] inv'4 a)
-   -> ([%#span16] inv'1 ab)
-   -> ([%#span17] inv'4 b)
-   -> ([%#span18] inv'1 bc)  -> ([%#span19] inv'4 c)  -> ([%#span20] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span8] produces'1 a ab b)
+   -> ([%#span9] produces'1 b bc c)
+   -> ([%#span10] inv'3 a)
+   -> ([%#span11] inv'3 b)  -> ([%#span12] inv'3 c)  -> ([%#span13] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span21] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'1 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'1_spec : forall self : i . ([%#span22] inv'4 self)
-   -> ([%#span23] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'1_spec : forall self : i . ([%#span14] inv'3 self)
+   -> ([%#span15] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span25] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span24] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C07Fuse_Fuse_Type as Fuse'0
   
-  predicate invariant'2 (self : Fuse'0.t_fuse i)
-  
-  predicate inv'2 (_x : Fuse'0.t_fuse i)
+  predicate invariant'1 (self : Fuse'0.t_fuse i)
   
-  axiom inv'2 : forall x : Fuse'0.t_fuse i . inv'2 x = true
+  predicate inv'1 (_x : Fuse'0.t_fuse i)
   
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
+  axiom inv'1 : forall x : Fuse'0.t_fuse i . inv'1 x = true
   
   predicate invariant'0 (self : borrowed (Fuse'0.t_fuse i))
   
@@ -883,7 +715,7 @@ module C07Fuse_Impl1_IsFused_Impl
   predicate produces'0 [#"../07_fuse.rs" 25 4 25 65] (self : Fuse'0.t_fuse i) (prod : Seq'0.t_seq item'0) (other : Fuse'0.t_fuse i)
     
    =
-    [%#span26] match C07Fuse_Fuse_Type.fuse_iter self with
+    [%#span17] match C07Fuse_Fuse_Type.fuse_iter self with
       | Option'0.C_None -> prod = (empty'0 : Seq'0.t_seq item'0)
       /\ C07Fuse_Fuse_Type.fuse_iter other = C07Fuse_Fuse_Type.fuse_iter self
       | Option'0.C_Some i -> match C07Fuse_Fuse_Type.fuse_iter other with
@@ -895,26 +727,24 @@ module C07Fuse_Impl1_IsFused_Impl
   function produces_trans'0 [#"../07_fuse.rs" 62 4 62 90] (a : Fuse'0.t_fuse i) (ab : Seq'0.t_seq item'0) (b : Fuse'0.t_fuse i) (bc : Seq'0.t_seq item'0) (c : Fuse'0.t_fuse i) : ()
     
    =
-    [%#span35] ()
+    [%#span24] ()
   
-  axiom produces_trans'0_spec : forall a : Fuse'0.t_fuse i, ab : Seq'0.t_seq item'0, b : Fuse'0.t_fuse i, bc : Seq'0.t_seq item'0, c : Fuse'0.t_fuse i . ([%#span27] produces'0 a ab b)
-   -> ([%#span28] produces'0 b bc c)
-   -> ([%#span29] inv'2 a)
-   -> ([%#span30] inv'1 ab)
-   -> ([%#span31] inv'2 b)
-   -> ([%#span32] inv'1 bc)  -> ([%#span33] inv'2 c)  -> ([%#span34] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Fuse'0.t_fuse i, ab : Seq'0.t_seq item'0, b : Fuse'0.t_fuse i, bc : Seq'0.t_seq item'0, c : Fuse'0.t_fuse i . ([%#span18] produces'0 a ab b)
+   -> ([%#span19] produces'0 b bc c)
+   -> ([%#span20] inv'1 a)
+   -> ([%#span21] inv'1 b)  -> ([%#span22] inv'1 c)  -> ([%#span23] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../07_fuse.rs" 55 4 55 26] (self : Fuse'0.t_fuse i) : () =
-    [%#span38] ()
+    [%#span27] ()
   
-  axiom produces_refl'0_spec : forall self : Fuse'0.t_fuse i . ([%#span36] inv'2 self)
-   -> ([%#span37] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : Fuse'0.t_fuse i . ([%#span25] inv'1 self)
+   -> ([%#span26] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate completed'0 [#"../07_fuse.rs" 16 4 16 35] (self : borrowed (Fuse'0.t_fuse i)) =
-    [%#span39] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
-    \/ (exists it : borrowed i . inv'3 it
+    [%#span28] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
+    \/ (exists it : borrowed i . inv'2 it
     /\ completed'1 it /\ C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_Some ( * it)))
     /\ C07Fuse_Fuse_Type.fuse_iter ( ^ self) = Option'0.C_None
   
@@ -927,11 +757,10 @@ module C07Fuse_Impl1_IsFused_Impl
   function is_fused [#"../07_fuse.rs" 81 4 81 62] (self : borrowed (Fuse'0.t_fuse i)) (steps : Seq'0.t_seq item'0) (next : Fuse'0.t_fuse i) : ()
     
   
-  goal vc_is_fused : ([%#s07_fuse4] inv'2 next)
-   -> ([%#s07_fuse3] inv'1 steps)
+  goal vc_is_fused : ([%#s07_fuse3] inv'1 next)
    -> ([%#s07_fuse2] inv'0 self)
    -> ([%#s07_fuse1] produces'0 ( ^ self) steps next)
-   -> ([%#s07_fuse0] completed'0 self)  -> ([%#s07_fuse5] steps = (empty'0 : Seq'0.t_seq item'0) /\  ^ self = next)
+   -> ([%#s07_fuse0] completed'0 self)  -> ([%#s07_fuse4] steps = (empty'0 : Seq'0.t_seq item'0) /\  ^ self = next)
 end
 module C07Fuse_Impl0
   type i
@@ -942,73 +771,53 @@ module C07Fuse_Impl0
   
   let%span s07_fuse2 = "../07_fuse.rs" 55 4 55 26
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span7 = "../07_fuse.rs" 18 12 19 32
   
-  let%span span10 = "../07_fuse.rs" 18 12 19 32
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span16 = "../07_fuse.rs" 26 8 32 9
+  let%span span10 = "../07_fuse.rs" 26 8 32 9
   
   type item'0
   
-  predicate invariant'5 (self : item'0)
+  predicate invariant'4 (self : item'0)
   
-  predicate inv'5 (_x : item'0)
+  predicate inv'4 (_x : item'0)
   
-  axiom inv'5 : forall x : item'0 . inv'5 x = true
+  axiom inv'4 : forall x : item'0 . inv'4 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'4 (self : borrowed i)
+  predicate invariant'3 (self : borrowed i)
   
-  predicate inv'4 (_x : borrowed i)
+  predicate inv'3 (_x : borrowed i)
   
-  axiom inv'4 : forall x : borrowed i . inv'4 x = true
+  axiom inv'3 : forall x : borrowed i . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'3 (self : Option'0.t_option item'0)
+  predicate invariant'2 (self : Option'0.t_option item'0)
   
-  predicate inv'3 (_x : Option'0.t_option item'0)
+  predicate inv'2 (_x : Option'0.t_option item'0)
   
-  axiom inv'3 : forall x : Option'0.t_option item'0 . inv'3 x = true
+  axiom inv'2 : forall x : Option'0.t_option item'0 . inv'2 x = true
   
   use C07Fuse_Fuse_Type as Fuse'0
   
-  predicate invariant'2 (self : borrowed (Fuse'0.t_fuse i))
-  
-  predicate inv'2 (_x : borrowed (Fuse'0.t_fuse i))
-  
-  axiom inv'2 : forall x : borrowed (Fuse'0.t_fuse i) . inv'2 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
+  predicate invariant'1 (self : borrowed (Fuse'0.t_fuse i))
   
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
+  predicate inv'1 (_x : borrowed (Fuse'0.t_fuse i))
   
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
+  axiom inv'1 : forall x : borrowed (Fuse'0.t_fuse i) . inv'1 x = true
   
   predicate invariant'0 (self : Fuse'0.t_fuse i)
   
@@ -1016,60 +825,50 @@ module C07Fuse_Impl0
   
   axiom inv'0 : forall x : Fuse'0.t_fuse i . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span3] ()
-  
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span3] ()
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq item'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  use prelude.prelude.Int
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span4] inv'1 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span3] len'0 self >= 0
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span6] inv'5 v)
-   -> ([%#span9] inv'1 (singleton'0 v))
-  && ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span4] inv'4 v)
+   -> ([%#span6] index_logic'0 (singleton'0 v) 0 = v) && ([%#span5] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   use C07Fuse_Fuse_Type as C07Fuse_Fuse_Type
   
   predicate completed'0 [#"../07_fuse.rs" 16 4 16 35] (self : borrowed (Fuse'0.t_fuse i)) =
-    [%#span10] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
-    \/ (exists it : borrowed i . inv'4 it
+    [%#span7] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
+    \/ (exists it : borrowed i . inv'3 it
     /\ completed'1 it /\ C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_Some ( * it)))
     /\ C07Fuse_Fuse_Type.fuse_iter ( ^ self) = Option'0.C_None
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span11] inv'1 self)
-   -> ([%#span12] inv'1 other)
-   -> ([%#span15] inv'1 (concat'0 self other))
-  && ([%#span14] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span13] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   predicate produces'0 [#"../07_fuse.rs" 25 4 25 65] (self : Fuse'0.t_fuse i) (prod : Seq'0.t_seq item'0) (other : Fuse'0.t_fuse i)
     
    =
-    [%#span16] match C07Fuse_Fuse_Type.fuse_iter self with
+    [%#span10] match C07Fuse_Fuse_Type.fuse_iter self with
       | Option'0.C_None -> prod = (empty'0 : Seq'0.t_seq item'0)
       /\ C07Fuse_Fuse_Type.fuse_iter other = C07Fuse_Fuse_Type.fuse_iter self
       | Option'0.C_Some i -> match C07Fuse_Fuse_Type.fuse_iter other with
@@ -1079,23 +878,21 @@ module C07Fuse_Impl0
       end
   
   goal produces_trans_refn : [%#s07_fuse0] forall a : Fuse'0.t_fuse i . forall ab : Seq'0.t_seq item'0 . forall b : Fuse'0.t_fuse i . forall bc : Seq'0.t_seq item'0 . forall c : Fuse'0.t_fuse i . inv'0 c
-  /\ inv'1 bc /\ inv'0 b /\ inv'1 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'0 c
-  /\ inv'1 bc
   /\ inv'0 b
-  /\ inv'1 ab
   /\ inv'0 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
   
-  goal next_refn : [%#s07_fuse1] forall self : borrowed (Fuse'0.t_fuse i) . inv'2 self
-   -> inv'2 self
-  /\ (forall result : Option'0.t_option item'0 . inv'3 result
+  goal next_refn : [%#s07_fuse1] forall self : borrowed (Fuse'0.t_fuse i) . inv'1 self
+   -> inv'1 self
+  /\ (forall result : Option'0.t_option item'0 . inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
     end
-   -> inv'3 result
+   -> inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
@@ -1111,37 +908,25 @@ module C07Fuse_Impl1
   
   let%span s07_fuse0 = "../07_fuse.rs" 81 4 81 62
   
-  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span1 = "../07_fuse.rs" 18 12 19 32
   
-  let%span span2 = "../07_fuse.rs" 18 12 19 32
-  
-  let%span span3 = "../07_fuse.rs" 26 8 32 9
+  let%span span2 = "../07_fuse.rs" 26 8 32 9
   
   use prelude.prelude.Borrow
   
-  predicate invariant'3 (self : borrowed i)
+  predicate invariant'2 (self : borrowed i)
   
-  predicate inv'3 (_x : borrowed i)
+  predicate inv'2 (_x : borrowed i)
   
-  axiom inv'3 : forall x : borrowed i . inv'3 x = true
+  axiom inv'2 : forall x : borrowed i . inv'2 x = true
   
   use C07Fuse_Fuse_Type as Fuse'0
   
-  predicate invariant'2 (self : borrowed (Fuse'0.t_fuse i))
-  
-  predicate inv'2 (_x : borrowed (Fuse'0.t_fuse i))
+  predicate invariant'1 (self : borrowed (Fuse'0.t_fuse i))
   
-  axiom inv'2 : forall x : borrowed (Fuse'0.t_fuse i) . inv'2 x = true
+  predicate inv'1 (_x : borrowed (Fuse'0.t_fuse i))
   
-  type item'0
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
+  axiom inv'1 : forall x : borrowed (Fuse'0.t_fuse i) . inv'1 x = true
   
   predicate invariant'0 (self : Fuse'0.t_fuse i)
   
@@ -1149,9 +934,13 @@ module C07Fuse_Impl1
   
   axiom inv'0 : forall x : Fuse'0.t_fuse i . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span1] ()
+  type item'0
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span1] ()
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  
+  constant empty'0 : Seq'0.t_seq item'0
+  
+  constant empty'0 : Seq'0.t_seq item'0
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
@@ -1160,8 +949,8 @@ module C07Fuse_Impl1
   use C07Fuse_Fuse_Type as C07Fuse_Fuse_Type
   
   predicate completed'0 [#"../07_fuse.rs" 16 4 16 35] (self : borrowed (Fuse'0.t_fuse i)) =
-    [%#span2] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
-    \/ (exists it : borrowed i . inv'3 it
+    [%#span1] (C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_None
+    \/ (exists it : borrowed i . inv'2 it
     /\ completed'1 it /\ C07Fuse_Fuse_Type.fuse_iter ( * self) = Option'0.C_Some ( * it)))
     /\ C07Fuse_Fuse_Type.fuse_iter ( ^ self) = Option'0.C_None
   
@@ -1170,7 +959,7 @@ module C07Fuse_Impl1
   predicate produces'0 [#"../07_fuse.rs" 25 4 25 65] (self : Fuse'0.t_fuse i) (prod : Seq'0.t_seq item'0) (other : Fuse'0.t_fuse i)
     
    =
-    [%#span3] match C07Fuse_Fuse_Type.fuse_iter self with
+    [%#span2] match C07Fuse_Fuse_Type.fuse_iter self with
       | Option'0.C_None -> prod = (empty'0 : Seq'0.t_seq item'0)
       /\ C07Fuse_Fuse_Type.fuse_iter other = C07Fuse_Fuse_Type.fuse_iter self
       | Option'0.C_Some i -> match C07Fuse_Fuse_Type.fuse_iter other with
@@ -1180,10 +969,9 @@ module C07Fuse_Impl1
       end
   
   goal is_fused_refn : [%#s07_fuse0] forall self : borrowed (Fuse'0.t_fuse i) . forall steps : Seq'0.t_seq item'0 . forall next : Fuse'0.t_fuse i . inv'0 next
-  /\ inv'1 steps /\ inv'2 self /\ produces'0 ( ^ self) steps next /\ completed'0 self
+  /\ inv'1 self /\ produces'0 ( ^ self) steps next /\ completed'0 self
    -> inv'0 next
-  /\ inv'1 steps
-  /\ inv'2 self
+  /\ inv'1 self
   /\ produces'0 ( ^ self) steps next
   /\ completed'0 self
   /\ (forall result : () . steps = (empty'0 : Seq'0.t_seq item'0) /\  ^ self = next
diff --git a/creusot/tests/should_succeed/iterators/08_collect_extend.coma b/creusot/tests/should_succeed/iterators/08_collect_extend.coma
index c7e1eafab9..1e79d64a3c 100644
--- a/creusot/tests/should_succeed/iterators/08_collect_extend.coma
+++ b/creusot/tests/should_succeed/iterators/08_collect_extend.coma
@@ -3,22 +3,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -162,105 +147,81 @@ module C08CollectExtend_Extend
   
   let%span span9 = "" 0 0 0 0
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span16 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span17 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span18 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span19 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span20 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
+  let%span span23 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/iter.rs" 41 31 41 33
+  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
+  let%span span25 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/iter.rs" 41 61 41 63
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
+  let%span span30 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
+  let%span span31 = "" 0 0 0 0
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span32 = "" 0 0 0 0
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span34 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span34 = "" 0 0 0 0
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span36 = "" 0 0 0 0
   
-  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span39 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span40 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span40 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span41 = "" 0 0 0 0
+  let%span span41 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span42 = "" 0 0 0 0
+  let%span span42 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span44 = "" 0 0 0 0
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span45 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
   let%span span46 = "" 0 0 0 0
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
-  
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
-  
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
-  
-  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
-  
-  let%span span51 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span52 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
-  
-  let%span span53 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span54 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span55 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span58 = "" 0 0 0 0
-  
-  let%span span59 = "" 0 0 0 0
+  let%span span47 = "" 0 0 0 0
   
   predicate invariant'6 (self : t)
   
@@ -296,24 +257,19 @@ module C08CollectExtend_Extend
   
   constant max'0 : usize = [%#span9] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span10] inv'5 self)  -> ([%#span11] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span10] len'0 self >= 0
   
   predicate inv'3 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span12] inv'3 self)
-   -> ([%#span14] inv'5 (shallow_model'2 self))
-  && ([%#span13] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span11] inv'3 self)
+   -> ([%#span12] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'3 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span15] inv'5 (shallow_model'2 self)
+    [%#span13] inv'5 (shallow_model'2 self)
   
   axiom inv'3 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'3 x = true
   
@@ -331,21 +287,15 @@ module C08CollectExtend_Extend
   
   axiom inv'1 : forall x : borrowed i . inv'1 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span16] inv'5 self)
-   -> ([%#span17] inv'5 other)
-   -> ([%#span20] inv'5 (concat'0 self other))
-  && ([%#span19] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span15] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span18] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : i)
   
@@ -353,28 +303,25 @@ module C08CollectExtend_Extend
   
   function produces_trans'0 (a : i) (ab : Seq'0.t_seq t) (b : i) (bc : Seq'0.t_seq t) (c : i) : ()
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span21] produces'0 a ab b)
-   -> ([%#span22] produces'0 b bc c)
-   -> ([%#span23] inv'0 a)
-   -> ([%#span24] inv'5 ab)
-   -> ([%#span25] inv'0 b)
-   -> ([%#span26] inv'5 bc)  -> ([%#span27] inv'0 c)  -> ([%#span28] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span16] produces'0 a ab b)
+   -> ([%#span17] produces'0 b bc c)
+   -> ([%#span18] inv'0 a)
+   -> ([%#span19] inv'0 b)  -> ([%#span20] inv'0 c)  -> ([%#span21] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq t = [%#span29] ()
+  constant empty'0 : Seq'0.t_seq t
   
   function produces_refl'0 (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span30] inv'0 self)
-   -> ([%#span31] produces'0 self (empty'0 : Seq'0.t_seq t) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span22] inv'0 self)
+   -> ([%#span23] produces'0 self (empty'0 : Seq'0.t_seq t) self)
   
   predicate invariant'0 (self : i)
   
   axiom inv'0 : forall x : i . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span33] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span32] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span24] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate completed'0 (self : borrowed i)
   
@@ -383,67 +330,60 @@ module C08CollectExtend_Extend
   use prelude.prelude.Intrinsic
   
   predicate resolve'6 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span34]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
   predicate resolve'5 (self : i)
   
-  use seq.Seq
-  
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span35] inv'6 v)
-   -> ([%#span38] inv'5 (singleton'0 v))
-  && ([%#span37] index_logic'0 (singleton'0 v) 0 = v) && ([%#span36] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span26] inv'6 v)
+   -> ([%#span28] index_logic'0 (singleton'0 v) 0 = v) && ([%#span27] len'0 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq t) (v : t) : Seq'0.t_seq t =
-    [%#span39] concat'0 self (singleton'0 v)
+    [%#span29] concat'0 self (singleton'0 v)
   
   function shallow_model'0 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span40] shallow_model'2 ( * self)
+    [%#span30] shallow_model'2 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (value:t) (return'  (ret:()))= {[@expl:precondition] [%#span42] inv'6 value}
-    {[@expl:precondition] [%#span41] inv'4 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (value:t) (return'  (ret:()))= {[@expl:precondition] [%#span32] inv'6 value}
+    {[@expl:precondition] [%#span31] inv'4 self}
     any
-    [ return' (result:())-> {[%#span43] shallow_model'2 ( ^ self) = push'1 (shallow_model'0 self) value}
+    [ return' (result:())-> {[%#span33] shallow_model'2 ( ^ self) = push'1 (shallow_model'0 self) value}
       (! return' {result}) ]
     
   
   predicate resolve'4 (self : Option'0.t_option t)
   
   predicate resolve'3 (self : borrowed i) =
-    [%#span34]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span44] inv'1 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span34] inv'1 self}
     any
-    [ return' (result:Option'0.t_option t)-> {[%#span46] inv'2 result}
-      {[%#span45] match result with
+    [ return' (result:Option'0.t_option t)-> {[%#span36] inv'2 result}
+      {[%#span35] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   predicate ext_eq'0 (self : Seq'0.t_seq t) (oth : Seq'0.t_seq t)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span47] inv'5 self)
-   -> ([%#span48] inv'5 oth)
-   -> ([%#span50] len'0 self = len'0 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq t, oth : Seq'0.t_seq t . ([%#span38] len'0 self = len'0 oth
   /\ (forall i : int . 0 <= i /\ i < len'0 self  -> index_logic'0 self i = index_logic'0 oth i)  -> ext_eq'0 self oth)
-  && ([%#span49] ext_eq'0 self oth  -> self = oth)
+  && ([%#span37] ext_eq'0 self oth  -> self = oth)
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq t)) : Seq'0.t_seq t
   
   function shallow_model'3 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span51] shallow_model'0 self
+    [%#span39] shallow_model'0 self
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))) : borrowed (Vec'0.t_vec t (Global'0.t_global))
     
   
   function shallow_model'1 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))) : Seq'0.t_seq t
    =
-    [%#span52] shallow_model'3 (deref'0 self)
+    [%#span40] shallow_model'3 (deref'0 self)
   
   function inner'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq t)) : Seq'0.t_seq t
   
@@ -455,24 +395,24 @@ module C08CollectExtend_Extend
   
   function new'2 (x : Seq'0.t_seq t) : Snapshot'0.t_snapshot (Seq'0.t_seq t)
   
-  axiom new'2_spec : forall x : Seq'0.t_seq t . ([%#span53] inv'5 x)  -> ([%#span54] deref'1 (new'2 x) = x)
+  axiom new'2_spec : forall x : Seq'0.t_seq t . ([%#span41] inv'5 x)  -> ([%#span42] deref'1 (new'2 x) = x)
   
   predicate resolve'1 (self : Snapshot'0.t_snapshot i)
   
   function new'1 (x : i) : Snapshot'0.t_snapshot i
   
-  axiom new'1_spec : forall x : i . ([%#span53] inv'0 x)  -> ([%#span54] deref'2 (new'1 x) = x)
+  axiom new'1_spec : forall x : i . ([%#span41] inv'0 x)  -> ([%#span42] deref'2 (new'1 x) = x)
   
   predicate into_iter_post'0 (self : i) (res : i) =
-    [%#span55] self = res
+    [%#span43] self = res
   
   predicate into_iter_pre'0 (self : i) =
-    [%#span56] true
+    [%#span44] true
   
-  let rec into_iter'0 (self:i) (return'  (ret:i))= {[@expl:precondition] [%#span58] inv'0 self}
-    {[@expl:precondition] [%#span57] into_iter_pre'0 self}
+  let rec into_iter'0 (self:i) (return'  (ret:i))= {[@expl:precondition] [%#span46] inv'0 self}
+    {[@expl:precondition] [%#span45] into_iter_pre'0 self}
     any
-    [ return' (result:i)-> {[%#span59] inv'0 result} {[%#span57] into_iter_post'0 self result} (! return' {result}) ]
+    [ return' (result:i)-> {[%#span47] inv'0 result} {[%#span45] into_iter_post'0 self result} (! return' {result}) ]
     
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global))))
@@ -480,8 +420,8 @@ module C08CollectExtend_Extend
   function new'0 (x : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global)))
     
   
-  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span53] inv'4 x)
-   -> ([%#span54] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . ([%#span41] inv'4 x)
+   -> ([%#span42] deref'0 (new'0 x) = x)
   
   let rec extend (vec:borrowed (Vec'0.t_vec t (Global'0.t_global))) (iter:i) (return'  (ret:()))= {[%#s08_collect_extend7] inv'0 iter}
     {[%#s08_collect_extend6] inv'4 vec}
@@ -597,8 +537,7 @@ module C08CollectExtend_Extend
     | & _26 : borrowed (Vec'0.t_vec t (Global'0.t_global)) = any_l ()
     | & old_8_0 : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec t (Global'0.t_global))) = any_l () ]
     
-    [ return' (result:())-> {[@expl:postcondition] [%#s08_collect_extend8] exists prod : Seq'0.t_seq t . exists done' : borrowed i . inv'5 prod
-      /\ inv'1 done'
+    [ return' (result:())-> {[@expl:postcondition] [%#s08_collect_extend8] exists prod : Seq'0.t_seq t . exists done' : borrowed i . inv'1 done'
       /\ completed'0 done'
       /\ produces'0 iter prod ( * done') /\ shallow_model'2 ( ^ vec) = concat'0 (shallow_model'0 vec) prod}
       (! return' {result}) ]
@@ -625,109 +564,85 @@ module C08CollectExtend_Collect
   
   let%span span8 = "" 0 0 0 0
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span15 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span16 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span17 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span18 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span19 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
+  let%span span20 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/iter.rs" 41 31 41 33
+  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
+  let%span span24 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/iter.rs" 41 61 41 63
+  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
+  let%span span30 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span31 = "" 0 0 0 0
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span32 = "" 0 0 0 0
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span34 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span35 = "" 0 0 0 0
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span36 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span37 = "" 0 0 0 0
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span39 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span40 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span40 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span41 = "" 0 0 0 0
+  let%span span41 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span42 = "" 0 0 0 0
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span44 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
   let%span span45 = "" 0 0 0 0
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
-  
-  let%span span47 = "" 0 0 0 0
-  
-  let%span span48 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
-  
-  let%span span49 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
-  
-  let%span span50 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
-  
-  let%span span51 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
-  
-  let%span span52 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span53 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span54 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span55 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span57 = "" 0 0 0 0
-  
-  let%span span58 = "" 0 0 0 0
+  let%span span46 = "" 0 0 0 0
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
+  let%span span47 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
-  let%span span60 = "" 0 0 0 0
+  let%span span48 = "" 0 0 0 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -765,24 +680,19 @@ module C08CollectExtend_Collect
   
   constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span9] inv'4 self)  -> ([%#span10] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span9] len'0 self >= 0
   
   predicate inv'3 (_x : Vec'0.t_vec item'0 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec item'0 (Global'0.t_global)) : Seq'0.t_seq item'0
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec item'0 (Global'0.t_global) . ([%#span11] inv'3 self)
-   -> ([%#span13] inv'4 (shallow_model'0 self))
-  && ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec item'0 (Global'0.t_global) . ([%#span10] inv'3 self)
+   -> ([%#span11] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'3 (self : Vec'0.t_vec item'0 (Global'0.t_global)) =
-    [%#span14] inv'4 (shallow_model'0 self)
+    [%#span12] inv'4 (shallow_model'0 self)
   
   axiom inv'3 : forall x : Vec'0.t_vec item'0 (Global'0.t_global) . inv'3 x = true
   
@@ -800,21 +710,16 @@ module C08CollectExtend_Collect
   
   axiom inv'1 : forall x : borrowed i . inv'1 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span15] inv'4 self)
-   -> ([%#span16] inv'4 other)
-   -> ([%#span19] inv'4 (concat'0 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span14] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span17] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span13] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : i)
   
@@ -822,28 +727,25 @@ module C08CollectExtend_Collect
   
   function produces_trans'0 (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span20] produces'0 a ab b)
-   -> ([%#span21] produces'0 b bc c)
-   -> ([%#span22] inv'0 a)
-   -> ([%#span23] inv'4 ab)
-   -> ([%#span24] inv'0 b)
-   -> ([%#span25] inv'4 bc)  -> ([%#span26] inv'0 c)  -> ([%#span27] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span15] produces'0 a ab b)
+   -> ([%#span16] produces'0 b bc c)
+   -> ([%#span17] inv'0 a)
+   -> ([%#span18] inv'0 b)  -> ([%#span19] inv'0 c)  -> ([%#span20] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span28] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span29] inv'0 self)
-   -> ([%#span30] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span21] inv'0 self)
+   -> ([%#span22] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'0 (self : i)
   
   axiom inv'0 : forall x : i . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span32] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span31] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate completed'0 (self : borrowed i)
   
@@ -854,58 +756,51 @@ module C08CollectExtend_Collect
   predicate resolve'6 (self : item'0)
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec item'0 (Global'0.t_global)) (ix : int) : item'0 =
-    [%#span33] index_logic'0 (shallow_model'0 self) ix
+    [%#span24] index_logic'0 (shallow_model'0 self) ix
   
   predicate resolve'5 (self : Vec'0.t_vec item'0 (Global'0.t_global)) =
-    [%#span34] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'6 (index_logic'1 self i)
+    [%#span25] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'6 (index_logic'1 self i)
   
   predicate resolve'4 (self : i)
   
-  use seq.Seq
-  
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span35] inv'5 v)
-   -> ([%#span38] inv'4 (singleton'0 v))
-  && ([%#span37] index_logic'0 (singleton'0 v) 0 = v) && ([%#span36] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span26] inv'5 v)
+   -> ([%#span28] index_logic'0 (singleton'0 v) 0 = v) && ([%#span27] len'0 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq item'0) (v : item'0) : Seq'0.t_seq item'0 =
-    [%#span39] concat'0 self (singleton'0 v)
+    [%#span29] concat'0 self (singleton'0 v)
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec item'0 (Global'0.t_global))) : Seq'0.t_seq item'0 =
-    [%#span40] shallow_model'0 ( * self)
+    [%#span30] shallow_model'0 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec item'0 (Global'0.t_global))) (value:item'0) (return'  (ret:()))= {[@expl:precondition] [%#span42] inv'5 value}
-    {[@expl:precondition] [%#span41] inv'6 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec item'0 (Global'0.t_global))) (value:item'0) (return'  (ret:()))= {[@expl:precondition] [%#span32] inv'5 value}
+    {[@expl:precondition] [%#span31] inv'6 self}
     any
-    [ return' (result:())-> {[%#span43] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
+    [ return' (result:())-> {[%#span33] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
       (! return' {result}) ]
     
   
   predicate resolve'3 (self : Option'0.t_option item'0)
   
   predicate resolve'2 (self : borrowed i) =
-    [%#span44]  ^ self =  * self
+    [%#span34]  ^ self =  * self
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span45] inv'1 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span35] inv'1 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span47] inv'2 result}
-      {[%#span46] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span37] inv'2 result}
+      {[%#span36] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   predicate ext_eq'0 (self : Seq'0.t_seq item'0) (oth : Seq'0.t_seq item'0)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq item'0, oth : Seq'0.t_seq item'0 . ([%#span48] inv'4 self)
-   -> ([%#span49] inv'4 oth)
-   -> ([%#span51] len'0 self = len'0 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq item'0, oth : Seq'0.t_seq item'0 . ([%#span39] len'0 self = len'0 oth
   /\ (forall i : int . 0 <= i /\ i < len'0 self  -> index_logic'0 self i = index_logic'0 oth i)  -> ext_eq'0 self oth)
-  && ([%#span50] ext_eq'0 self oth  -> self = oth)
+  && ([%#span38] ext_eq'0 self oth  -> self = oth)
   
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)) : Seq'0.t_seq item'0
   
@@ -919,29 +814,29 @@ module C08CollectExtend_Collect
   
   function new'2 (x : Seq'0.t_seq item'0) : Snapshot'0.t_snapshot (Seq'0.t_seq item'0)
   
-  axiom new'2_spec : forall x : Seq'0.t_seq item'0 . ([%#span52] inv'4 x)  -> ([%#span53] deref'0 (new'2 x) = x)
+  axiom new'2_spec : forall x : Seq'0.t_seq item'0 . ([%#span40] inv'4 x)  -> ([%#span41] deref'0 (new'2 x) = x)
   
   predicate resolve'0 (self : Snapshot'0.t_snapshot i)
   
   function new'1 (x : i) : Snapshot'0.t_snapshot i
   
-  axiom new'1_spec : forall x : i . ([%#span52] inv'0 x)  -> ([%#span53] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : i . ([%#span40] inv'0 x)  -> ([%#span41] deref'1 (new'1 x) = x)
   
   predicate into_iter_post'0 (self : i) (res : i) =
-    [%#span54] self = res
+    [%#span42] self = res
   
   predicate into_iter_pre'0 (self : i) =
-    [%#span55] true
+    [%#span43] true
   
-  let rec into_iter'0 (self:i) (return'  (ret:i))= {[@expl:precondition] [%#span57] inv'0 self}
-    {[@expl:precondition] [%#span56] into_iter_pre'0 self}
+  let rec into_iter'0 (self:i) (return'  (ret:i))= {[@expl:precondition] [%#span45] inv'0 self}
+    {[@expl:precondition] [%#span44] into_iter_pre'0 self}
     any
-    [ return' (result:i)-> {[%#span58] inv'0 result} {[%#span56] into_iter_post'0 self result} (! return' {result}) ]
+    [ return' (result:i)-> {[%#span46] inv'0 result} {[%#span44] into_iter_post'0 self result} (! return' {result}) ]
     
   
   let rec new'0 (_1:()) (return'  (ret:Vec'0.t_vec item'0 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec item'0 (Global'0.t_global))-> {[%#span60] inv'3 result}
-      {[%#span59] len'0 (shallow_model'0 result) = 0}
+    [ return' (result:Vec'0.t_vec item'0 (Global'0.t_global))-> {[%#span48] inv'3 result}
+      {[%#span47] len'0 (shallow_model'0 result) = 0}
       (! return' {result}) ]
     
   
@@ -1063,8 +958,8 @@ module C08CollectExtend_Collect
     | & _24 : borrowed (Vec'0.t_vec item'0 (Global'0.t_global)) = any_l () ]
     
     [ return' (result:Vec'0.t_vec item'0 (Global'0.t_global))-> {[@expl:postcondition] [%#s08_collect_extend7] inv'3 result}
-      {[@expl:postcondition] [%#s08_collect_extend6] exists prod : Seq'0.t_seq item'0 . exists done' : borrowed i . inv'4 prod
-      /\ inv'1 done' /\ completed'0 done' /\ produces'0 iter prod ( * done') /\ shallow_model'0 result = prod}
+      {[@expl:postcondition] [%#s08_collect_extend6] exists prod : Seq'0.t_seq item'0 . exists done' : borrowed i . inv'1 done'
+      /\ completed'0 done' /\ produces'0 iter prod ( * done') /\ shallow_model'0 result = prod}
       (! return' {result}) ]
     
 end
@@ -1114,143 +1009,117 @@ module C08CollectExtend_ExtendIndex
   
   let%span s08_collect_extend2 = "../08_collect_extend.rs" 57 4 57 55
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
+  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 268 31 268 33
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 268 52 268 54
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
+  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
+  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
+  let%span span18 = "" 0 0 0 0
   
-  let%span span24 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span25 = "" 0 0 0 0
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 87 4 87 38
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 89 81
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span25 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span26 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 18 91 22
+  let%span span27 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 91 24 91 27
+  let%span span28 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 88 4 88 38
+  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 89 4 90 81
+  let%span span30 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span36 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span31 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span37 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
+  let%span span32 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
   
-  let%span span38 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span33 = "../08_collect_extend.rs" 25 40 25 43
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span34 = "../08_collect_extend.rs" 25 58 25 62
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span35 = "../08_collect_extend.rs" 21 0 24 2
   
-  let%span span41 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span36 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
   
-  let%span span42 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span37 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
+  let%span span38 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span44 = "../08_collect_extend.rs" 25 40 25 43
+  let%span span39 = "" 0 0 0 0
   
-  let%span span45 = "../08_collect_extend.rs" 25 58 25 62
+  let%span span40 = "" 0 0 0 0
   
-  let%span span46 = "../08_collect_extend.rs" 21 0 24 2
+  let%span span41 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
-  
-  let%span span48 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
-  
-  let%span span49 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span50 = "" 0 0 0 0
-  
-  let%span span51 = "" 0 0 0 0
-  
-  let%span span52 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span53 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span42 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use Alloc_Alloc_Global_Type as Global'0
+  predicate invariant'4 (self : Seq'0.t_seq uint32) =
+    [%#span3] true
   
-  use Alloc_Vec_IntoIter_IntoIter_Type as IntoIter'0
+  predicate inv'4 (_x : Seq'0.t_seq uint32)
   
-  use seq.Seq
+  axiom inv'4 : forall x : Seq'0.t_seq uint32 . inv'4 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use Alloc_Alloc_Global_Type as Global'0
   
-  use seq.Seq
+  use Alloc_Vec_IntoIter_IntoIter_Type as IntoIter'0
   
   use prelude.prelude.Int
   
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
-  
-  use seq.Seq
-  
-  predicate inv'3 (_x : Seq'0.t_seq uint32)
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span4] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span5] inv'3 self)
-   -> ([%#span6] inv'3 other)
-   -> ([%#span9] inv'3 (concat'0 self other))
-  && ([%#span8] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span6] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span5] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'1 (_x : IntoIter'0.t_intoiter uint32 (Global'0.t_global))
   
@@ -1259,53 +1128,46 @@ module C08CollectExtend_ExtendIndex
   predicate produces'0 (self : IntoIter'0.t_intoiter uint32 (Global'0.t_global)) (visited : Seq'0.t_seq uint32) (rhs : IntoIter'0.t_intoiter uint32 (Global'0.t_global))
     
    =
-    [%#span10] shallow_model'4 self = concat'0 visited (shallow_model'4 rhs)
+    [%#span7] shallow_model'4 self = concat'0 visited (shallow_model'4 rhs)
   
   function produces_trans'0 (a : IntoIter'0.t_intoiter uint32 (Global'0.t_global)) (ab : Seq'0.t_seq uint32) (b : IntoIter'0.t_intoiter uint32 (Global'0.t_global)) (bc : Seq'0.t_seq uint32) (c : IntoIter'0.t_intoiter uint32 (Global'0.t_global)) : ()
     
    =
-    [%#span19] ()
+    [%#span14] ()
   
-  axiom produces_trans'0_spec : forall a : IntoIter'0.t_intoiter uint32 (Global'0.t_global), ab : Seq'0.t_seq uint32, b : IntoIter'0.t_intoiter uint32 (Global'0.t_global), bc : Seq'0.t_seq uint32, c : IntoIter'0.t_intoiter uint32 (Global'0.t_global) . ([%#span11] produces'0 a ab b)
-   -> ([%#span12] produces'0 b bc c)
-   -> ([%#span13] inv'1 a)
-   -> ([%#span14] inv'3 ab)
-   -> ([%#span15] inv'1 b)
-   -> ([%#span16] inv'3 bc)  -> ([%#span17] inv'1 c)  -> ([%#span18] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : IntoIter'0.t_intoiter uint32 (Global'0.t_global), ab : Seq'0.t_seq uint32, b : IntoIter'0.t_intoiter uint32 (Global'0.t_global), bc : Seq'0.t_seq uint32, c : IntoIter'0.t_intoiter uint32 (Global'0.t_global) . ([%#span8] produces'0 a ab b)
+   -> ([%#span9] produces'0 b bc c)
+   -> ([%#span10] inv'1 a)
+   -> ([%#span11] inv'1 b)  -> ([%#span12] inv'1 c)  -> ([%#span13] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span20] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   function produces_refl'0 (self : IntoIter'0.t_intoiter uint32 (Global'0.t_global)) : () =
-    [%#span23] ()
+    [%#span17] ()
   
-  axiom produces_refl'0_spec : forall self : IntoIter'0.t_intoiter uint32 (Global'0.t_global) . ([%#span21] inv'1 self)
-   -> ([%#span22] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'0_spec : forall self : IntoIter'0.t_intoiter uint32 (Global'0.t_global) . ([%#span15] inv'1 self)
+   -> ([%#span16] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   use prelude.prelude.Borrow
   
-  predicate invariant'4 (self : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global))) =
-    [%#span24] true
+  predicate invariant'3 (self : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global))) =
+    [%#span3] true
   
-  predicate inv'4 (_x : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global)))
+  predicate inv'3 (_x : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global)))
   
-  axiom inv'4 : forall x : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global)) . inv'4 x = true
-  
-  predicate invariant'3 (self : Seq'0.t_seq uint32) =
-    [%#span24] true
-  
-  axiom inv'3 : forall x : Seq'0.t_seq uint32 . inv'3 x = true
+  axiom inv'3 : forall x : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global)) . inv'3 x = true
   
   use Alloc_Vec_Vec_Type as Vec'0
   
   predicate invariant'2 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) =
-    [%#span24] true
+    [%#span3] true
   
   predicate inv'2 (_x : borrowed (Vec'0.t_vec uint32 (Global'0.t_global)))
   
   axiom inv'2 : forall x : borrowed (Vec'0.t_vec uint32 (Global'0.t_global)) . inv'2 x = true
   
   predicate invariant'1 (self : IntoIter'0.t_intoiter uint32 (Global'0.t_global)) =
-    [%#span24] true
+    [%#span3] true
   
   axiom inv'1 : forall x : IntoIter'0.t_intoiter uint32 (Global'0.t_global) . inv'1 x = true
   
@@ -1313,79 +1175,72 @@ module C08CollectExtend_ExtendIndex
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span25] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span18] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span26] inv'0 self)
-   -> ([%#span28] inv'3 (shallow_model'0 self))
-  && ([%#span27] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span19] inv'0 self)
+   -> ([%#span20] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span29] inv'3 (shallow_model'0 self)
+    [%#span21] inv'4 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span31] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span30] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span22] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   predicate ext_eq'0 (self : Seq'0.t_seq uint32) (oth : Seq'0.t_seq uint32)
   
-  axiom ext_eq'0_spec : forall self : Seq'0.t_seq uint32, oth : Seq'0.t_seq uint32 . ([%#span32] inv'3 self)
-   -> ([%#span33] inv'3 oth)
-   -> ([%#span35] len'0 self = len'0 oth
+  axiom ext_eq'0_spec : forall self : Seq'0.t_seq uint32, oth : Seq'0.t_seq uint32 . ([%#span24] len'0 self = len'0 oth
   /\ (forall i : int . 0 <= i /\ i < len'0 self  -> index_logic'1 self i = index_logic'1 oth i)  -> ext_eq'0 self oth)
-  && ([%#span34] ext_eq'0 self oth  -> self = oth)
+  && ([%#span23] ext_eq'0 self oth  -> self = oth)
   
   function shallow_model'3 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32 =
-    [%#span36] shallow_model'0 self
+    [%#span25] shallow_model'0 self
   
   function deref'0 (self : Snapshot'0.t_snapshot (Vec'0.t_vec uint32 (Global'0.t_global))) : Vec'0.t_vec uint32 (Global'0.t_global)
     
   
   function shallow_model'1 (self : Snapshot'0.t_snapshot (Vec'0.t_vec uint32 (Global'0.t_global))) : Seq'0.t_seq uint32
    =
-    [%#span37] shallow_model'3 (deref'0 self)
+    [%#span26] shallow_model'3 (deref'0 self)
   
   predicate resolve'2 (self : uint32) =
-    [%#span38] true
+    [%#span27] true
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span39] index_logic'1 (shallow_model'0 self) ix
+    [%#span28] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span40] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span29] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   predicate resolve'0 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) =
-    [%#span41]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   function shallow_model'2 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) : Seq'0.t_seq uint32 =
-    [%#span42] shallow_model'0 ( * self)
+    [%#span31] shallow_model'0 ( * self)
   
   function shallow_model'5 (self : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global))) : Seq'0.t_seq uint32 =
-    [%#span42] shallow_model'4 ( * self)
+    [%#span31] shallow_model'4 ( * self)
   
   predicate resolve'3 (self : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global))) =
-    [%#span41]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global))) =
-    [%#span43] resolve'3 self /\ shallow_model'5 self = (empty'0 : Seq'0.t_seq uint32)
+    [%#span32] resolve'3 self /\ shallow_model'5 self = (empty'0 : Seq'0.t_seq uint32)
   
-  let rec extend'0 (vec:borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) (iter:IntoIter'0.t_intoiter uint32 (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span45] inv'1 iter}
-    {[@expl:precondition] [%#span44] inv'2 vec}
+  let rec extend'0 (vec:borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) (iter:IntoIter'0.t_intoiter uint32 (Global'0.t_global)) (return'  (ret:()))= {[@expl:precondition] [%#span34] inv'1 iter}
+    {[@expl:precondition] [%#span33] inv'2 vec}
     any
-    [ return' (result:())-> {[%#span46] exists prod : Seq'0.t_seq uint32 . exists done' : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global)) . inv'3 prod
-      /\ inv'4 done'
+    [ return' (result:())-> {[%#span35] exists prod : Seq'0.t_seq uint32 . exists done' : borrowed (IntoIter'0.t_intoiter uint32 (Global'0.t_global)) . inv'3 done'
       /\ completed'0 done'
       /\ produces'0 iter prod ( * done') /\ shallow_model'0 ( ^ vec) = concat'0 (shallow_model'2 vec) prod}
       (! return' {result}) ]
@@ -1394,24 +1249,24 @@ module C08CollectExtend_ExtendIndex
   predicate into_iter_post'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) (res : IntoIter'0.t_intoiter uint32 (Global'0.t_global))
     
    =
-    [%#span47] shallow_model'0 self = shallow_model'4 res
+    [%#span36] shallow_model'0 self = shallow_model'4 res
   
   predicate into_iter_pre'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span48] true
+    [%#span37] true
   
-  let rec into_iter'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:IntoIter'0.t_intoiter uint32 (Global'0.t_global)))= {[@expl:precondition] [%#span50] inv'0 self}
-    {[@expl:precondition] [%#span49] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:IntoIter'0.t_intoiter uint32 (Global'0.t_global)))= {[@expl:precondition] [%#span39] inv'0 self}
+    {[@expl:precondition] [%#span38] into_iter_pre'0 self}
     any
-    [ return' (result:IntoIter'0.t_intoiter uint32 (Global'0.t_global))-> {[%#span51] inv'1 result}
-      {[%#span49] into_iter_post'0 self result}
+    [ return' (result:IntoIter'0.t_intoiter uint32 (Global'0.t_global))-> {[%#span40] inv'1 result}
+      {[%#span38] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
   function new'0 (x : Vec'0.t_vec uint32 (Global'0.t_global)) : Snapshot'0.t_snapshot (Vec'0.t_vec uint32 (Global'0.t_global))
     
   
-  axiom new'0_spec : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span52] inv'0 x)
-   -> ([%#span53] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span41] inv'0 x)
+   -> ([%#span42] deref'0 (new'0 x) = x)
   
   let rec extend_index (v1:Vec'0.t_vec uint32 (Global'0.t_global)) (v2:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:()))= (! bb0
     [ bb0 = s0 [ s0 =  [ &oldv1 <- [%#s08_collect_extend0] new'0 v1 ] s1 | s1 = bb1 ] 
@@ -1459,75 +1314,62 @@ module C08CollectExtend_CollectExample
   
   let%span s08_collect_extend2 = "../08_collect_extend.rs" 61 48 61 52
   
-  let%span span3 = "" 0 0 0 0
+  let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span4 = "" 0 0 0 0
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span10 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span11 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span12 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span13 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span14 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span15 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
+  let%span span16 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
-  
-  let%span span18 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
-  
-  let%span span19 = "../../../../../creusot-contracts/src/std/iter.rs" 41 31 41 33
-  
-  let%span span20 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
-  
-  let%span span21 = "../../../../../creusot-contracts/src/std/iter.rs" 41 61 41 63
-  
-  let%span span22 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
-  
-  let%span span23 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
+  let%span span17 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span18 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
+  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
+  let%span span20 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span21 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span23 = "../08_collect_extend.rs" 42 28 42 32
   
-  let%span span30 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span24 = "../08_collect_extend.rs" 38 0 41 2
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
-  
-  let%span span32 = "../08_collect_extend.rs" 42 28 42 32
-  
-  let%span span33 = "../08_collect_extend.rs" 38 0 41 2
-  
-  let%span span34 = "../08_collect_extend.rs" 42 40 42 52
+  let%span span25 = "../08_collect_extend.rs" 42 40 42 52
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq uint32)
+  predicate invariant'3 (self : Seq'0.t_seq uint32) =
+    [%#span3] true
+  
+  predicate inv'3 (_x : Seq'0.t_seq uint32)
+  
+  axiom inv'3 : forall x : Seq'0.t_seq uint32 . inv'3 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1539,57 +1381,42 @@ module C08CollectExtend_CollectExample
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span3] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span4] inv'1 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span5] len'0 self >= 0
   
-  predicate inv'3 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
+  predicate inv'2 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span6] inv'3 self)
-   -> ([%#span8] inv'1 (shallow_model'0 self))
-  && ([%#span7] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span6] inv'2 self)
+   -> ([%#span7] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'3 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span9] inv'1 (shallow_model'0 self)
+  predicate invariant'2 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
+    [%#span8] inv'3 (shallow_model'0 self)
   
-  axiom inv'3 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'3 x = true
+  axiom inv'2 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'2 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'2 (self : borrowed i)
-  
-  predicate inv'2 (_x : borrowed i)
-  
-  axiom inv'2 : forall x : borrowed i . inv'2 x = true
-  
-  predicate invariant'1 (self : Seq'0.t_seq uint32) =
-    [%#span10] true
-  
-  axiom inv'1 : forall x : Seq'0.t_seq uint32 . inv'1 x = true
+  predicate invariant'1 (self : borrowed i)
   
-  use seq.Seq
+  predicate inv'1 (_x : borrowed i)
   
-  use seq.Seq
+  axiom inv'1 : forall x : borrowed i . inv'1 x = true
   
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span11] inv'1 self)
-   -> ([%#span12] inv'1 other)
-   -> ([%#span15] inv'1 (concat'0 self other))
-  && ([%#span14] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span10] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span13] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : i)
   
@@ -1597,49 +1424,46 @@ module C08CollectExtend_CollectExample
   
   function produces_trans'0 (a : i) (ab : Seq'0.t_seq uint32) (b : i) (bc : Seq'0.t_seq uint32) (c : i) : ()
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq uint32, b : i, bc : Seq'0.t_seq uint32, c : i . ([%#span16] produces'0 a ab b)
-   -> ([%#span17] produces'0 b bc c)
-   -> ([%#span18] inv'0 a)
-   -> ([%#span19] inv'1 ab)
-   -> ([%#span20] inv'0 b)
-   -> ([%#span21] inv'1 bc)  -> ([%#span22] inv'0 c)  -> ([%#span23] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq uint32, b : i, bc : Seq'0.t_seq uint32, c : i . ([%#span11] produces'0 a ab b)
+   -> ([%#span12] produces'0 b bc c)
+   -> ([%#span13] inv'0 a)
+   -> ([%#span14] inv'0 b)  -> ([%#span15] inv'0 c)  -> ([%#span16] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span24] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   function produces_refl'0 (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span25] inv'0 self)
-   -> ([%#span26] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span17] inv'0 self)
+   -> ([%#span18] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   predicate invariant'0 (self : i)
   
   axiom inv'0 : forall x : i . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span28] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span27] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span19] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.Intrinsic
   
   use prelude.prelude.UInt32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span29] index_logic'1 (shallow_model'0 self) ix
+    [%#span20] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'1 (self : uint32) =
-    [%#span30] true
+    [%#span21] true
   
   predicate resolve'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span31] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
+    [%#span22] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
   
   predicate completed'0 (self : borrowed i)
   
-  let rec collect'0 (iter:i) (return'  (ret:Vec'0.t_vec uint32 (Global'0.t_global)))= {[@expl:precondition] [%#span32] inv'0 iter}
+  let rec collect'0 (iter:i) (return'  (ret:Vec'0.t_vec uint32 (Global'0.t_global)))= {[@expl:precondition] [%#span23] inv'0 iter}
     any
-    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span34] inv'3 result}
-      {[%#span33] exists prod : Seq'0.t_seq uint32 . exists done' : borrowed i . inv'1 prod
-      /\ inv'2 done' /\ completed'0 done' /\ produces'0 iter prod ( * done') /\ shallow_model'0 result = prod}
+    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span25] inv'2 result}
+      {[%#span24] exists prod : Seq'0.t_seq uint32 . exists done' : borrowed i . inv'1 done'
+      /\ completed'0 done' /\ produces'0 iter prod ( * done') /\ shallow_model'0 result = prod}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/iterators/09_empty.coma b/creusot/tests/should_succeed/iterators/09_empty.coma
index d99a3d53a7..2287b7148d 100644
--- a/creusot/tests/should_succeed/iterators/09_empty.coma
+++ b/creusot/tests/should_succeed/iterators/09_empty.coma
@@ -23,71 +23,39 @@ module C09Empty_Empty_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C09Empty_Impl0_ProducesRefl_Impl
   type t
   
   let%span s09_empty0 = "../09_empty.rs" 27 14 27 45
   
-  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span1 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span6 = "../09_empty.rs" 22 20 22 54
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'0 (self : Seq'0.t_seq t)
-  
-  predicate inv'0 (_x : Seq'0.t_seq t)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq t . inv'0 x = true
+  let%span span3 = "../09_empty.rs" 22 20 22 54
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span1] inv'0 self)  -> ([%#span2] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span1] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span3] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span5] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span2] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C09Empty_Empty_Type as Empty'0
   
   predicate produces'0 [#"../09_empty.rs" 21 4 21 64] (self : Empty'0.t_empty t) (visited : Seq'0.t_seq t) (o : Empty'0.t_empty t)
     
    =
-    [%#span6] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
+    [%#span3] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
   
   constant self  : Empty'0.t_empty t
   
@@ -102,81 +70,48 @@ module C09Empty_Impl0_ProducesTrans_Impl
   
   let%span s09_empty1 = "../09_empty.rs" 33 15 33 32
   
-  let%span s09_empty2 = "../09_empty.rs" 35 31 35 33
+  let%span s09_empty2 = "../09_empty.rs" 34 14 34 42
   
-  let%span s09_empty3 = "../09_empty.rs" 35 61 35 63
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span s09_empty4 = "../09_empty.rs" 34 14 34 42
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../09_empty.rs" 22 20 22 54
+  let%span span7 = "../09_empty.rs" 22 20 22 54
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'0 (_x : Seq'0.t_seq t)
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span5] inv'0 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq t) = 0
-  
-  predicate invariant'0 (self : Seq'0.t_seq t)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq t . inv'0 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C09Empty_Empty_Type as Empty'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span10] inv'0 self)
-   -> ([%#span11] inv'0 other)
-   -> ([%#span14] inv'0 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span6] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span5] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'0 [#"../09_empty.rs" 21 4 21 64] (self : Empty'0.t_empty t) (visited : Seq'0.t_seq t) (o : Empty'0.t_empty t)
     
    =
-    [%#span15] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
+    [%#span7] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
   
   constant a  : Empty'0.t_empty t
   
@@ -191,10 +126,8 @@ module C09Empty_Impl0_ProducesTrans_Impl
   function produces_trans [#"../09_empty.rs" 35 4 35 90] (a : Empty'0.t_empty t) (ab : Seq'0.t_seq t) (b : Empty'0.t_empty t) (bc : Seq'0.t_seq t) (c : Empty'0.t_empty t) : ()
     
   
-  goal vc_produces_trans : ([%#s09_empty3] inv'0 bc)
-   -> ([%#s09_empty2] inv'0 ab)
-   -> ([%#s09_empty1] produces'0 b bc c)
-   -> ([%#s09_empty0] produces'0 a ab b)  -> ([%#s09_empty4] produces'0 a (concat'0 ab bc) c)
+  goal vc_produces_trans : ([%#s09_empty1] produces'0 b bc c)
+   -> ([%#s09_empty0] produces'0 a ab b)  -> ([%#s09_empty2] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -219,37 +152,21 @@ module C09Empty_Impl0_Next
   
   let%span s09_empty1 = "../09_empty.rs" 41 26 41 35
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../09_empty.rs" 22 20 22 54
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../09_empty.rs" 22 20 22 54
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span8 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span12 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span13 = "../09_empty.rs" 16 20 16 34
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'2 (self : Seq'0.t_seq t)
-  
-  predicate inv'2 (_x : Seq'0.t_seq t)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq t . inv'2 x = true
+  let%span span9 = "../09_empty.rs" 16 20 16 34
   
   predicate invariant'1 (self : t)
   
@@ -267,47 +184,39 @@ module C09Empty_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'2 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C09Empty_Empty_Type as Empty'0
   
   predicate produces'0 [#"../09_empty.rs" 21 4 21 64] (self : Empty'0.t_empty t) (visited : Seq'0.t_seq t) (o : Empty'0.t_empty t)
     
    =
-    [%#span7] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
-  
-  use seq.Seq
-  
-  use seq.Seq
+    [%#span4] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
   
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span8] inv'1 v)
-   -> ([%#span11] inv'2 (singleton'0 v))
-  && ([%#span10] index_logic'0 (singleton'0 v) 0 = v) && ([%#span9] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span5] inv'1 v)
+   -> ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
   
   use prelude.prelude.Borrow
   
   predicate resolve'0 (self : borrowed (Empty'0.t_empty t)) =
-    [%#span12]  ^ self =  * self
+    [%#span8]  ^ self =  * self
   
   predicate completed'0 [#"../09_empty.rs" 15 4 15 35] (self : borrowed (Empty'0.t_empty t)) =
-    [%#span13] resolve'0 self
+    [%#span9] resolve'0 self
   
   use prelude.prelude.Intrinsic
   
@@ -331,49 +240,29 @@ module C09Empty_Impl0
   
   let%span s09_empty2 = "../09_empty.rs" 35 4 35 90
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span9 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span10 = "../09_empty.rs" 16 20 16 34
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span11 = "../09_empty.rs" 22 20 22 54
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  predicate invariant'3 (self : t)
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  predicate inv'3 (_x : t)
   
-  let%span span14 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span15 = "../09_empty.rs" 16 20 16 34
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span17 = "../09_empty.rs" 22 20 22 54
-  
-  predicate invariant'4 (self : t)
-  
-  predicate inv'4 (_x : t)
-  
-  axiom inv'4 : forall x : t . inv'4 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'3 (self : Seq'0.t_seq t)
-  
-  predicate inv'3 (_x : Seq'0.t_seq t)
-  
-  axiom inv'3 : forall x : Seq'0.t_seq t . inv'3 x = true
+  axiom inv'3 : forall x : t . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
@@ -399,54 +288,43 @@ module C09Empty_Impl0
   
   axiom inv'0 : forall x : Empty'0.t_empty t . inv'0 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span5] inv'3 self)
-   -> ([%#span6] inv'3 other)
-   -> ([%#span9] inv'3 (concat'0 self other))
-  && ([%#span8] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span5] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span4] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span10] inv'4 v)
-   -> ([%#span13] inv'3 (singleton'0 v))
-  && ([%#span12] index_logic'0 (singleton'0 v) 0 = v) && ([%#span11] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span6] inv'3 v)
+   -> ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Empty'0.t_empty t)) =
-    [%#span14]  ^ self =  * self
+    [%#span9]  ^ self =  * self
   
   predicate completed'0 [#"../09_empty.rs" 15 4 15 35] (self : borrowed (Empty'0.t_empty t)) =
-    [%#span15] resolve'0 self
+    [%#span10] resolve'0 self
   
-  constant empty'0 : Seq'0.t_seq t = [%#span16] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  constant empty'0 : Seq'0.t_seq t = [%#span16] ()
+  constant empty'0 : Seq'0.t_seq t
   
   predicate produces'0 [#"../09_empty.rs" 21 4 21 64] (self : Empty'0.t_empty t) (visited : Seq'0.t_seq t) (o : Empty'0.t_empty t)
     
    =
-    [%#span17] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
+    [%#span11] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
   
   goal produces_refl_refn : [%#s09_empty0] forall self : Empty'0.t_empty t . inv'0 self
    -> (forall result : () . produces'0 self (empty'0 : Seq'0.t_seq t) self
@@ -465,9 +343,7 @@ module C09Empty_Impl0
     end)
   
   goal produces_trans_refn : [%#s09_empty2] forall a : Empty'0.t_empty t . forall ab : Seq'0.t_seq t . forall b : Empty'0.t_empty t . forall bc : Seq'0.t_seq t . forall c : Empty'0.t_empty t . inv'0 c
-  /\ inv'3 bc /\ inv'0 b /\ inv'3 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
-   -> inv'3 bc
-  /\ inv'3 ab
-  /\ produces'0 b bc c
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+   -> produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
 end
diff --git a/creusot/tests/should_succeed/iterators/10_once.coma b/creusot/tests/should_succeed/iterators/10_once.coma
index 38645564f7..97399b9e4a 100644
--- a/creusot/tests/should_succeed/iterators/10_once.coma
+++ b/creusot/tests/should_succeed/iterators/10_once.coma
@@ -29,22 +29,7 @@ module C10Once_Once_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C10Once_Impl0_ProducesRefl_Impl
   type t
@@ -53,56 +38,37 @@ module C10Once_Impl0_ProducesRefl_Impl
   
   let%span s10_once1 = "../10_once.rs" 30 14 30 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span11 = "../10_once.rs" 22 8 25 9
+  let%span span7 = "../10_once.rs" 22 8 25 9
   
-  predicate invariant'2 (self : t)
+  predicate invariant'1 (self : t)
   
-  predicate inv'2 (_x : t)
+  predicate inv'1 (_x : t)
   
-  axiom inv'2 : forall x : t . inv'2 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
-  
-  predicate inv'1 (_x : Seq'0.t_seq t)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
+  axiom inv'1 : forall x : t . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C10Once_Once_Type as Once'0
   
@@ -112,25 +78,20 @@ module C10Once_Impl0_ProducesRefl_Impl
   
   axiom inv'0 : forall x : Once'0.t_once t . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span7] inv'2 v)
-   -> ([%#span10] inv'1 (singleton'0 v))
-  && ([%#span9] index_logic'0 (singleton'0 v) 0 = v) && ([%#span8] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span4] inv'1 v)
+   -> ([%#span6] index_logic'0 (singleton'0 v) 0 = v) && ([%#span5] len'0 (singleton'0 v) = 1)
   
   use Core_Option_Option_Type as Option'0
   
   predicate produces'0 [#"../10_once.rs" 21 4 21 64] (self : Once'0.t_once t) (visited : Seq'0.t_seq t) (o : Once'0.t_once t)
     
    =
-    [%#span11] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
-    \/ (exists e : t . inv'2 e
+    [%#span7] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
+    \/ (exists e : t . inv'1 e
     /\ self = Once'0.C_Once (Option'0.C_Some e) /\ visited = singleton'0 e /\ o = Once'0.C_Once (Option'0.C_None))
   
   constant self  : Once'0.t_once t
@@ -148,76 +109,47 @@ module C10Once_Impl0_ProducesTrans_Impl
   
   let%span s10_once2 = "../10_once.rs" 38 22 38 23
   
-  let%span s10_once3 = "../10_once.rs" 38 31 38 33
+  let%span s10_once3 = "../10_once.rs" 38 52 38 53
   
-  let%span s10_once4 = "../10_once.rs" 38 52 38 53
+  let%span s10_once4 = "../10_once.rs" 38 82 38 83
   
-  let%span s10_once5 = "../10_once.rs" 38 61 38 63
+  let%span s10_once5 = "../10_once.rs" 37 14 37 42
   
-  let%span s10_once6 = "../10_once.rs" 38 82 38 83
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span s10_once7 = "../10_once.rs" 37 14 37 42
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span13 = "../10_once.rs" 22 8 25 9
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  predicate invariant'1 (self : t)
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  predicate inv'1 (_x : t)
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span22 = "../10_once.rs" 22 8 25 9
-  
-  predicate invariant'2 (self : t)
-  
-  predicate inv'2 (_x : t)
-  
-  axiom inv'2 : forall x : t . inv'2 x = true
+  axiom inv'1 : forall x : t . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq t)
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq t = [%#span10] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span6] len'0 self >= 0
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  constant empty'0 : Seq'0.t_seq t
   
-  predicate invariant'1 (self : Seq'0.t_seq t)
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C10Once_Once_Type as Once'0
   
@@ -227,37 +159,28 @@ module C10Once_Impl0_ProducesTrans_Impl
   
   axiom inv'0 : forall x : Once'0.t_once t . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span18] inv'2 v)
-   -> ([%#span21] inv'1 (singleton'0 v))
-  && ([%#span20] index_logic'0 (singleton'0 v) 0 = v) && ([%#span19] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span10] inv'1 v)
+   -> ([%#span12] index_logic'0 (singleton'0 v) 0 = v) && ([%#span11] len'0 (singleton'0 v) = 1)
   
   use Core_Option_Option_Type as Option'0
   
   predicate produces'0 [#"../10_once.rs" 21 4 21 64] (self : Once'0.t_once t) (visited : Seq'0.t_seq t) (o : Once'0.t_once t)
     
    =
-    [%#span22] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
-    \/ (exists e : t . inv'2 e
+    [%#span13] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
+    \/ (exists e : t . inv'1 e
     /\ self = Once'0.C_Once (Option'0.C_Some e) /\ visited = singleton'0 e /\ o = Once'0.C_Once (Option'0.C_None))
   
   constant a  : Once'0.t_once t
@@ -273,13 +196,11 @@ module C10Once_Impl0_ProducesTrans_Impl
   function produces_trans [#"../10_once.rs" 38 4 38 90] (a : Once'0.t_once t) (ab : Seq'0.t_seq t) (b : Once'0.t_once t) (bc : Seq'0.t_seq t) (c : Once'0.t_once t) : ()
     
   
-  goal vc_produces_trans : ([%#s10_once6] inv'0 c)
-   -> ([%#s10_once5] inv'1 bc)
-   -> ([%#s10_once4] inv'0 b)
-   -> ([%#s10_once3] inv'1 ab)
+  goal vc_produces_trans : ([%#s10_once4] inv'0 c)
+   -> ([%#s10_once3] inv'0 b)
    -> ([%#s10_once2] inv'0 a)
    -> ([%#s10_once1] produces'0 b bc c)
-   -> ([%#s10_once0] produces'0 a ab b)  -> ([%#s10_once7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s10_once0] produces'0 a ab b)  -> ([%#s10_once5] produces'0 a (concat'0 ab bc) c)
 end
 module C10Once_Impl0_Next
   type t
@@ -290,43 +211,27 @@ module C10Once_Impl0_Next
   
   let%span s10_once2 = "../10_once.rs" 44 26 44 35
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span12 = "../10_once.rs" 22 8 25 9
+  let%span span8 = "../10_once.rs" 22 8 25 9
   
-  let%span span13 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span14 = "../10_once.rs" 16 20 16 57
-  
-  let%span span15 = "" 0 0 0 0
-  
-  let%span span16 = "../../../../../creusot-contracts/src/std/option.rs" 29 0 140 1
-  
-  let%span span17 = "" 0 0 0 0
+  let%span span9 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  let%span span10 = "../10_once.rs" 16 20 16 57
   
-  predicate invariant'4 (self : Seq'0.t_seq t)
+  let%span span11 = "" 0 0 0 0
   
-  predicate inv'4 (_x : Seq'0.t_seq t)
+  let%span span12 = "../../../../../creusot-contracts/src/std/option.rs" 29 0 140 1
   
-  axiom inv'4 : forall x : Seq'0.t_seq t . inv'4 x = true
+  let%span span13 = "" 0 0 0 0
   
   predicate invariant'3 (self : t)
   
@@ -346,20 +251,17 @@ module C10Once_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'4 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C10Once_Once_Type as Once'0
   
@@ -375,37 +277,32 @@ module C10Once_Impl0_Next
   
   axiom inv'0 : forall x : Option'0.t_option t . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span8] inv'3 v)
-   -> ([%#span11] inv'4 (singleton'0 v))
-  && ([%#span10] index_logic'0 (singleton'0 v) 0 = v) && ([%#span9] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span5] inv'3 v)
+   -> ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
   
   predicate produces'0 [#"../10_once.rs" 21 4 21 64] (self : Once'0.t_once t) (visited : Seq'0.t_seq t) (o : Once'0.t_once t)
     
    =
-    [%#span12] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
+    [%#span8] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
     \/ (exists e : t . inv'3 e
     /\ self = Once'0.C_Once (Option'0.C_Some e) /\ visited = singleton'0 e /\ o = Once'0.C_Once (Option'0.C_None))
   
   predicate resolve'0 (self : borrowed (Once'0.t_once t)) =
-    [%#span13]  ^ self =  * self
+    [%#span9]  ^ self =  * self
   
   predicate completed'0 [#"../10_once.rs" 15 4 15 35] (self : borrowed (Once'0.t_once t)) =
-    [%#span14]  * self = Once'0.C_Once (Option'0.C_None) /\ resolve'0 self
+    [%#span10]  * self = Once'0.C_Once (Option'0.C_None) /\ resolve'0 self
   
   use prelude.prelude.Intrinsic
   
-  let rec take'0 (self:borrowed (Option'0.t_option t)) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span15] inv'2 self}
+  let rec take'0 (self:borrowed (Option'0.t_option t)) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span11] inv'2 self}
     any
-    [ return' (result:Option'0.t_option t)-> {[%#span17] inv'0 result}
-      {[%#span16] result =  * self /\  ^ self = Option'0.C_None}
+    [ return' (result:Option'0.t_option t)-> {[%#span13] inv'0 result}
+      {[%#span12] result =  * self /\  ^ self = Option'0.C_None}
       (! return' {result}) ]
     
   
@@ -448,67 +345,47 @@ module C10Once_Impl0
   
   let%span s10_once2 = "../10_once.rs" 44 4 44 35
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span9 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span10 = "../10_once.rs" 16 20 16 57
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span7 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span8 = "../10_once.rs" 16 20 16 57
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span17 = "../10_once.rs" 22 8 25 9
+  let%span span11 = "../10_once.rs" 22 8 25 9
   
-  predicate invariant'4 (self : t)
+  predicate invariant'3 (self : t)
   
-  predicate inv'4 (_x : t)
+  predicate inv'3 (_x : t)
   
-  axiom inv'4 : forall x : t . inv'4 x = true
+  axiom inv'3 : forall x : t . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'3 (self : Option'0.t_option t)
+  predicate invariant'2 (self : Option'0.t_option t)
   
-  predicate inv'3 (_x : Option'0.t_option t)
+  predicate inv'2 (_x : Option'0.t_option t)
   
-  axiom inv'3 : forall x : Option'0.t_option t . inv'3 x = true
+  axiom inv'2 : forall x : Option'0.t_option t . inv'2 x = true
   
   use C10Once_Once_Type as Once'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'2 (self : borrowed (Once'0.t_once t))
-  
-  predicate inv'2 (_x : borrowed (Once'0.t_once t))
-  
-  axiom inv'2 : forall x : borrowed (Once'0.t_once t) . inv'2 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
+  predicate invariant'1 (self : borrowed (Once'0.t_once t))
   
-  predicate inv'1 (_x : Seq'0.t_seq t)
+  predicate inv'1 (_x : borrowed (Once'0.t_once t))
   
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
+  axiom inv'1 : forall x : borrowed (Once'0.t_once t) . inv'1 x = true
   
   predicate invariant'0 (self : Once'0.t_once t)
   
@@ -518,61 +395,48 @@ module C10Once_Impl0
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'1 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span5] inv'4 v)
-   -> ([%#span8] inv'1 (singleton'0 v))
-  && ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span4] inv'3 v)
+   -> ([%#span6] index_logic'0 (singleton'0 v) 0 = v) && ([%#span5] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Once'0.t_once t)) =
-    [%#span9]  ^ self =  * self
+    [%#span7]  ^ self =  * self
   
   predicate completed'0 [#"../10_once.rs" 15 4 15 35] (self : borrowed (Once'0.t_once t)) =
-    [%#span10]  * self = Once'0.C_Once (Option'0.C_None) /\ resolve'0 self
-  
-  constant empty'0 : Seq'0.t_seq t = [%#span11] ()
+    [%#span8]  * self = Once'0.C_Once (Option'0.C_None) /\ resolve'0 self
   
-  constant empty'0 : Seq'0.t_seq t = [%#span11] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span12] inv'1 self)
-   -> ([%#span13] inv'1 other)
-   -> ([%#span16] inv'1 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span10] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'0 [#"../10_once.rs" 21 4 21 64] (self : Once'0.t_once t) (visited : Seq'0.t_seq t) (o : Once'0.t_once t)
     
    =
-    [%#span17] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
-    \/ (exists e : t . inv'4 e
+    [%#span11] visited = (empty'0 : Seq'0.t_seq t) /\ self = o
+    \/ (exists e : t . inv'3 e
     /\ self = Once'0.C_Once (Option'0.C_Some e) /\ visited = singleton'0 e /\ o = Once'0.C_Once (Option'0.C_None))
   
   goal produces_trans_refn : [%#s10_once0] forall a : Once'0.t_once t . forall ab : Seq'0.t_seq t . forall b : Once'0.t_once t . forall bc : Seq'0.t_seq t . forall c : Once'0.t_once t . inv'0 c
-  /\ inv'1 bc /\ inv'0 b /\ inv'1 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'0 c
-  /\ inv'1 bc
   /\ inv'0 b
-  /\ inv'1 ab
   /\ inv'0 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
@@ -582,14 +446,14 @@ module C10Once_Impl0
   /\ (forall result : () . produces'0 self (empty'0 : Seq'0.t_seq t) self
    -> produces'0 self (empty'1 : Seq'0.t_seq t) self)
   
-  goal next_refn : [%#s10_once2] forall self : borrowed (Once'0.t_once t) . inv'2 self
-   -> inv'2 self
-  /\ (forall result : Option'0.t_option t . inv'3 result
+  goal next_refn : [%#s10_once2] forall self : borrowed (Once'0.t_once t) . inv'1 self
+   -> inv'1 self
+  /\ (forall result : Option'0.t_option t . inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
     end
-   -> inv'3 result
+   -> inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
diff --git a/creusot/tests/should_succeed/iterators/11_repeat.coma b/creusot/tests/should_succeed/iterators/11_repeat.coma
index 67e1861d93..2a621f7607 100644
--- a/creusot/tests/should_succeed/iterators/11_repeat.coma
+++ b/creusot/tests/should_succeed/iterators/11_repeat.coma
@@ -16,22 +16,7 @@ module C11Repeat_Repeat_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C11Repeat_Impl0_ProducesRefl_Impl
   type a
@@ -40,42 +25,25 @@ module C11Repeat_Impl0_ProducesRefl_Impl
   
   let%span s11_repeat1 = "../11_repeat.rs" 32 14 32 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../11_repeat.rs" 24 8 27 9
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq a)
-  
-  predicate inv'1 (_x : Seq'0.t_seq a)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq a . inv'1 x = true
+  let%span span4 = "../11_repeat.rs" 24 8 27 9
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq a) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq a . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq a . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq a = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq a
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq a) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq a) = 0
   
   use C11Repeat_Repeat_Type as Repeat'0
   
@@ -87,14 +55,12 @@ module C11Repeat_Impl0_ProducesRefl_Impl
   
   use C11Repeat_Repeat_Type as C11Repeat_Repeat_Type
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq a) (x : int) : a
+  function index_logic'0 (self : Seq'0.t_seq a) (_2 : int) : a
   
   predicate produces'0 [#"../11_repeat.rs" 23 4 23 64] (self : Repeat'0.t_repeat a) (visited : Seq'0.t_seq a) (o : Repeat'0.t_repeat a)
     
    =
-    [%#span7] self = o
+    [%#span4] self = o
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> index_logic'0 visited i = C11Repeat_Repeat_Type.repeat_element self)
   
@@ -114,62 +80,35 @@ module C11Repeat_Impl0_ProducesTrans_Impl
   
   let%span s11_repeat2 = "../11_repeat.rs" 40 22 40 23
   
-  let%span s11_repeat3 = "../11_repeat.rs" 40 31 40 33
-  
-  let%span s11_repeat4 = "../11_repeat.rs" 40 52 40 53
-  
-  let%span s11_repeat5 = "../11_repeat.rs" 40 61 40 63
-  
-  let%span s11_repeat6 = "../11_repeat.rs" 40 82 40 83
-  
-  let%span s11_repeat7 = "../11_repeat.rs" 39 14 39 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s11_repeat3 = "../11_repeat.rs" 40 52 40 53
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span s11_repeat4 = "../11_repeat.rs" 40 82 40 83
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span s11_repeat5 = "../11_repeat.rs" 39 14 39 42
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span18 = "../11_repeat.rs" 24 8 27 9
+  let%span span10 = "../11_repeat.rs" 24 8 27 9
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq a)
-  
   function len'0 (self : Seq'0.t_seq a) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq a . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq a = [%#span10] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq a . [%#span6] len'0 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'0 : Seq'0.t_seq a
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq a) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq a)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq a . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq a) = 0
   
   use C11Repeat_Repeat_Type as Repeat'0
   
@@ -179,28 +118,22 @@ module C11Repeat_Impl0_ProducesTrans_Impl
   
   axiom inv'0 : forall x : Repeat'0.t_repeat a . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq a) (x : int) : a
+  function index_logic'0 (self : Seq'0.t_seq a) (_2 : int) : a
   
   function concat'0 (self : Seq'0.t_seq a) (other : Seq'0.t_seq a) : Seq'0.t_seq a
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq a, other : Seq'0.t_seq a . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq a, other : Seq'0.t_seq a . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   use C11Repeat_Repeat_Type as C11Repeat_Repeat_Type
   
   predicate produces'0 [#"../11_repeat.rs" 23 4 23 64] (self : Repeat'0.t_repeat a) (visited : Seq'0.t_seq a) (o : Repeat'0.t_repeat a)
     
    =
-    [%#span18] self = o
+    [%#span10] self = o
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> index_logic'0 visited i = C11Repeat_Repeat_Type.repeat_element self)
   
@@ -217,13 +150,11 @@ module C11Repeat_Impl0_ProducesTrans_Impl
   function produces_trans [#"../11_repeat.rs" 40 4 40 90] (a : Repeat'0.t_repeat a) (ab : Seq'0.t_seq a) (b : Repeat'0.t_repeat a) (bc : Seq'0.t_seq a) (c : Repeat'0.t_repeat a) : ()
     
   
-  goal vc_produces_trans : ([%#s11_repeat6] inv'0 c)
-   -> ([%#s11_repeat5] inv'1 bc)
-   -> ([%#s11_repeat4] inv'0 b)
-   -> ([%#s11_repeat3] inv'1 ab)
+  goal vc_produces_trans : ([%#s11_repeat4] inv'0 c)
+   -> ([%#s11_repeat3] inv'0 b)
    -> ([%#s11_repeat2] inv'0 a)
    -> ([%#s11_repeat1] produces'0 b bc c)
-   -> ([%#s11_repeat0] produces'0 a ab b)  -> ([%#s11_repeat7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s11_repeat0] produces'0 a ab b)  -> ([%#s11_repeat5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -250,43 +181,27 @@ module C11Repeat_Impl0_Next
   
   let%span s11_repeat2 = "../11_repeat.rs" 46 26 46 35
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../11_repeat.rs" 24 8 27 9
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span5 = "../11_repeat.rs" 24 8 27 9
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span13 = "../11_repeat.rs" 18 20 18 25
+  let%span span9 = "../11_repeat.rs" 18 20 18 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span10 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span15 = "" 0 0 0 0
-  
-  let%span span16 = "../../../../../creusot-contracts/src/std/clone.rs" 7 0 20 1
-  
-  let%span span17 = "" 0 0 0 0
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  let%span span11 = "" 0 0 0 0
   
-  predicate invariant'4 (self : Seq'0.t_seq a)
+  let%span span12 = "../../../../../creusot-contracts/src/std/clone.rs" 7 0 20 1
   
-  predicate inv'4 (_x : Seq'0.t_seq a)
-  
-  axiom inv'4 : forall x : Seq'0.t_seq a . inv'4 x = true
+  let%span span13 = "" 0 0 0 0
   
   predicate invariant'3 (self : a)
   
@@ -310,20 +225,17 @@ module C11Repeat_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq a) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq a . ([%#span3] inv'4 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq a . [%#span3] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq a = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq a
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq a) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq a) = 0
   
   use C11Repeat_Repeat_Type as Repeat'0
   
@@ -337,35 +249,30 @@ module C11Repeat_Impl0_Next
   
   use C11Repeat_Repeat_Type as C11Repeat_Repeat_Type
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq a) (x : int) : a
+  function index_logic'0 (self : Seq'0.t_seq a) (_2 : int) : a
   
   predicate produces'0 [#"../11_repeat.rs" 23 4 23 64] (self : Repeat'0.t_repeat a) (visited : Seq'0.t_seq a) (o : Repeat'0.t_repeat a)
     
    =
-    [%#span8] self = o
+    [%#span5] self = o
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> index_logic'0 visited i = C11Repeat_Repeat_Type.repeat_element self)
   
-  use seq.Seq
-  
   function singleton'0 (v : a) : Seq'0.t_seq a
   
-  axiom singleton'0_spec : forall v : a . ([%#span9] inv'3 v)
-   -> ([%#span12] inv'4 (singleton'0 v))
-  && ([%#span11] index_logic'0 (singleton'0 v) 0 = v) && ([%#span10] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : a . ([%#span6] inv'3 v)
+   -> ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
   
   predicate completed'0 [#"../11_repeat.rs" 17 4 17 35] (self : borrowed (Repeat'0.t_repeat a)) =
-    [%#span13] false
+    [%#span9] false
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed (Repeat'0.t_repeat a)) =
-    [%#span14]  ^ self =  * self
+    [%#span10]  ^ self =  * self
   
-  let rec clone'0 (self:a) (return'  (ret:a))= {[@expl:precondition] [%#span15] inv'2 self}
-    any [ return' (result:a)-> {[%#span17] inv'3 result} {[%#span16] result = self} (! return' {result}) ] 
+  let rec clone'0 (self:a) (return'  (ret:a))= {[@expl:precondition] [%#span11] inv'2 self}
+    any [ return' (result:a)-> {[%#span13] inv'3 result} {[%#span12] result = self} (! return' {result}) ] 
   
   let rec next (self:borrowed (Repeat'0.t_repeat a)) (return'  (ret:Option'0.t_option a))= {[%#s11_repeat0] inv'0 self}
     (! bb0
@@ -399,47 +306,27 @@ module C11Repeat_Impl0
   
   let%span s11_repeat2 = "../11_repeat.rs" 40 4 40 90
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span6 = "../11_repeat.rs" 24 8 27 9
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span11 = "../11_repeat.rs" 24 8 27 9
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span10 = "../11_repeat.rs" 18 20 18 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span16 = "../11_repeat.rs" 18 20 18 25
-  
-  predicate invariant'4 (self : a)
-  
-  predicate inv'4 (_x : a)
-  
-  axiom inv'4 : forall x : a . inv'4 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'3 (self : Seq'0.t_seq a)
+  predicate invariant'3 (self : a)
   
-  predicate inv'3 (_x : Seq'0.t_seq a)
+  predicate inv'3 (_x : a)
   
-  axiom inv'3 : forall x : Seq'0.t_seq a . inv'3 x = true
+  axiom inv'3 : forall x : a . inv'3 x = true
   
   use C11Repeat_Repeat_Type as Repeat'0
   
@@ -465,55 +352,44 @@ module C11Repeat_Impl0
   
   axiom inv'0 : forall x : borrowed (Repeat'0.t_repeat a) . inv'0 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq a) (x : int) : a
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq a) (_2 : int) : a
   
   function len'0 (self : Seq'0.t_seq a) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq a . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq a . [%#span3] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq a) (other : Seq'0.t_seq a) : Seq'0.t_seq a
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq a, other : Seq'0.t_seq a . ([%#span5] inv'3 self)
-   -> ([%#span6] inv'3 other)
-   -> ([%#span9] inv'3 (concat'0 self other))
-  && ([%#span8] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq a, other : Seq'0.t_seq a . ([%#span5] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span4] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  constant empty'0 : Seq'0.t_seq a = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq a
   
-  constant empty'0 : Seq'0.t_seq a = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq a
   
   use C11Repeat_Repeat_Type as C11Repeat_Repeat_Type
   
   predicate produces'0 [#"../11_repeat.rs" 23 4 23 64] (self : Repeat'0.t_repeat a) (visited : Seq'0.t_seq a) (o : Repeat'0.t_repeat a)
     
    =
-    [%#span11] self = o
+    [%#span6] self = o
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> index_logic'0 visited i = C11Repeat_Repeat_Type.repeat_element self)
   
-  use seq.Seq
-  
   function singleton'0 (v : a) : Seq'0.t_seq a
   
-  axiom singleton'0_spec : forall v : a . ([%#span12] inv'4 v)
-   -> ([%#span15] inv'3 (singleton'0 v))
-  && ([%#span14] index_logic'0 (singleton'0 v) 0 = v) && ([%#span13] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : a . ([%#span7] inv'3 v)
+   -> ([%#span9] index_logic'0 (singleton'0 v) 0 = v) && ([%#span8] len'0 (singleton'0 v) = 1)
   
   predicate completed'0 [#"../11_repeat.rs" 17 4 17 35] (self : borrowed (Repeat'0.t_repeat a)) =
-    [%#span16] false
+    [%#span10] false
   
   goal next_refn : [%#s11_repeat0] forall self : borrowed (Repeat'0.t_repeat a) . inv'0 self
    -> inv'0 self
@@ -534,11 +410,9 @@ module C11Repeat_Impl0
    -> produces'0 self (empty'1 : Seq'0.t_seq a) self)
   
   goal produces_trans_refn : [%#s11_repeat2] forall a : Repeat'0.t_repeat a . forall ab : Seq'0.t_seq a . forall b : Repeat'0.t_repeat a . forall bc : Seq'0.t_seq a . forall c : Repeat'0.t_repeat a . inv'2 c
-  /\ inv'3 bc /\ inv'2 b /\ inv'3 ab /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'2 b /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'2 c
-  /\ inv'3 bc
   /\ inv'2 b
-  /\ inv'3 ab
   /\ inv'2 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
diff --git a/creusot/tests/should_succeed/iterators/12_zip.coma b/creusot/tests/should_succeed/iterators/12_zip.coma
index f62da705fb..55f8ab74ff 100644
--- a/creusot/tests/should_succeed/iterators/12_zip.coma
+++ b/creusot/tests/should_succeed/iterators/12_zip.coma
@@ -20,22 +20,7 @@ module C12Zip_Zip_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C12Zip_Impl0_ProducesRefl_Impl
   type a
@@ -46,192 +31,133 @@ module C12Zip_Impl0_ProducesRefl_Impl
   
   let%span s12_zip1 = "../12_zip.rs" 40 14 40 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span6 = "../common.rs" 18 15 18 32
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span7 = "../common.rs" 19 15 19 32
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span8 = "../common.rs" 21 22 21 23
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span9 = "../common.rs" 21 52 21 53
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span10 = "../common.rs" 21 82 21 83
   
-  let%span span12 = "../common.rs" 18 15 18 32
+  let%span span11 = "../common.rs" 20 14 20 42
   
-  let%span span13 = "../common.rs" 19 15 19 32
+  let%span span12 = "../common.rs" 15 21 15 25
   
-  let%span span14 = "../common.rs" 21 22 21 23
+  let%span span13 = "../common.rs" 14 14 14 45
   
-  let%span span15 = "../common.rs" 21 31 21 33
+  let%span span14 = "../12_zip.rs" 29 8 35 9
   
-  let%span span16 = "../common.rs" 21 52 21 53
+  predicate invariant'2 (self : b)
   
-  let%span span17 = "../common.rs" 21 61 21 63
+  predicate inv'2 (_x : b)
   
-  let%span span18 = "../common.rs" 21 82 21 83
+  axiom inv'2 : forall x : b . inv'2 x = true
   
-  let%span span19 = "../common.rs" 20 14 20 42
+  predicate invariant'1 (self : a)
   
-  let%span span20 = "../common.rs" 15 21 15 25
+  predicate inv'1 (_x : a)
   
-  let%span span21 = "../common.rs" 14 14 14 45
-  
-  let%span span22 = "../12_zip.rs" 29 8 35 9
-  
-  predicate invariant'5 (self : b)
-  
-  predicate inv'5 (_x : b)
-  
-  axiom inv'5 : forall x : b . inv'5 x = true
-  
-  predicate invariant'4 (self : a)
-  
-  predicate inv'4 (_x : a)
-  
-  axiom inv'4 : forall x : a . inv'4 x = true
+  axiom inv'1 : forall x : a . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   type item'1
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq item'1)
-  
   function len'1 (self : Seq'0.t_seq item'1) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'1 . ([%#span2] inv'2 self)  -> ([%#span3] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq item'1 . [%#span2] len'1 self >= 0
   
-  constant empty'2 : Seq'0.t_seq item'1 = [%#span4] ()
+  constant empty'2 : Seq'0.t_seq item'1
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span5] len'1 (empty'2 : Seq'0.t_seq item'1) = 0
-  
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span3] len'1 (empty'2 : Seq'0.t_seq item'1) = 0
   
   type item'0
   
-  predicate inv'3 (_x : Seq'0.t_seq item'0)
-  
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'3 self)  -> ([%#span3] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span4] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span6] ()
-  
-  axiom empty_len'1_spec : forall _1 : () . [%#span5] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
-  
-  predicate invariant'3 (self : Seq'0.t_seq item'0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
-  axiom inv'3 : forall x : Seq'0.t_seq item'0 . inv'3 x = true
+  constant empty'1 : Seq'0.t_seq item'0
   
-  predicate invariant'2 (self : Seq'0.t_seq item'1)
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom inv'2 : forall x : Seq'0.t_seq item'1 . inv'2 x = true
+  axiom empty_len'1_spec : forall _1 : () . [%#span3] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
-  predicate invariant'1 (self : Seq'0.t_seq (item'0, item'1))
-  
-  predicate inv'1 (_x : Seq'0.t_seq (item'0, item'1))
-  
-  axiom inv'1 : forall x : Seq'0.t_seq (item'0, item'1) . inv'1 x = true
-  
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq item'1) (x : int) : item'1
+  function index_logic'2 (self : Seq'0.t_seq item'1) (_2 : int) : item'1
   
   function concat'1 (self : Seq'0.t_seq item'1) (other : Seq'0.t_seq item'1) : Seq'0.t_seq item'1
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'1, other : Seq'0.t_seq item'1 . ([%#span7] inv'2 self)
-   -> ([%#span8] inv'2 other)
-   -> ([%#span11] inv'2 (concat'1 self other))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'1, other : Seq'0.t_seq item'1 . ([%#span5] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'2 (concat'1 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span9] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span4] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   predicate produces'2 [#"../common.rs" 8 4 8 65] (self : b) (visited : Seq'0.t_seq item'1) (o : b)
   
   function produces_trans'1 [#"../common.rs" 21 4 21 91] (a : b) (ab : Seq'0.t_seq item'1) (b : b) (bc : Seq'0.t_seq item'1) (c : b) : ()
     
   
-  axiom produces_trans'1_spec : forall a : b, ab : Seq'0.t_seq item'1, b : b, bc : Seq'0.t_seq item'1, c : b . ([%#span12] produces'2 a ab b)
-   -> ([%#span13] produces'2 b bc c)
-   -> ([%#span14] inv'5 a)
-   -> ([%#span15] inv'2 ab)
-   -> ([%#span16] inv'5 b)
-   -> ([%#span17] inv'2 bc)  -> ([%#span18] inv'5 c)  -> ([%#span19] produces'2 a (concat'1 ab bc) c)
+  axiom produces_trans'1_spec : forall a : b, ab : Seq'0.t_seq item'1, b : b, bc : Seq'0.t_seq item'1, c : b . ([%#span6] produces'2 a ab b)
+   -> ([%#span7] produces'2 b bc c)
+   -> ([%#span8] inv'2 a)
+   -> ([%#span9] inv'2 b)  -> ([%#span10] inv'2 c)  -> ([%#span11] produces'2 a (concat'1 ab bc) c)
   
   function produces_refl'1 [#"../common.rs" 15 4 15 27] (self : b) : ()
   
-  axiom produces_refl'1_spec : forall self : b . ([%#span20] inv'5 self)
-   -> ([%#span21] produces'2 self (empty'2 : Seq'0.t_seq item'1) self)
-  
-  use seq.Seq
+  axiom produces_refl'1_spec : forall self : b . ([%#span12] inv'2 self)
+   -> ([%#span13] produces'2 self (empty'2 : Seq'0.t_seq item'1) self)
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span7] inv'3 self)
-   -> ([%#span8] inv'3 other)
-   -> ([%#span11] inv'3 (concat'0 self other))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span5] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span4] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : a) (visited : Seq'0.t_seq item'0) (o : a)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : a) (ab : Seq'0.t_seq item'0) (b : a) (bc : Seq'0.t_seq item'0) (c : a) : ()
     
   
-  axiom produces_trans'0_spec : forall a : a, ab : Seq'0.t_seq item'0, b : a, bc : Seq'0.t_seq item'0, c : a . ([%#span12] produces'1 a ab b)
-   -> ([%#span13] produces'1 b bc c)
-   -> ([%#span14] inv'4 a)
-   -> ([%#span15] inv'3 ab)
-   -> ([%#span16] inv'4 b)
-   -> ([%#span17] inv'3 bc)  -> ([%#span18] inv'4 c)  -> ([%#span19] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : a, ab : Seq'0.t_seq item'0, b : a, bc : Seq'0.t_seq item'0, c : a . ([%#span6] produces'1 a ab b)
+   -> ([%#span7] produces'1 b bc c)
+   -> ([%#span8] inv'1 a)
+   -> ([%#span9] inv'1 b)  -> ([%#span10] inv'1 c)  -> ([%#span11] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : a) : ()
   
-  axiom produces_refl'0_spec : forall self : a . ([%#span20] inv'4 self)
-   -> ([%#span21] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
-  
-  use seq.Seq
+  axiom produces_refl'0_spec : forall self : a . ([%#span12] inv'1 self)
+   -> ([%#span13] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   function len'2 (self : Seq'0.t_seq (item'0, item'1)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (item'0, item'1) . ([%#span2] inv'1 self)  -> ([%#span3] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (item'0, item'1) . [%#span2] len'2 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (item'0, item'1) = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq (item'0, item'1)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'2 (empty'0 : Seq'0.t_seq (item'0, item'1)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'2 (empty'0 : Seq'0.t_seq (item'0, item'1)) = 0
   
   use C12Zip_Zip_Type as Zip'0
   
@@ -243,16 +169,12 @@ module C12Zip_Impl0_ProducesRefl_Impl
   
   use C12Zip_Zip_Type as C12Zip_Zip_Type
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (x : int) : (item'0, item'1)
+  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (_2 : int) : (item'0, item'1)
   
   predicate produces'0 [#"../12_zip.rs" 28 4 28 65] (self : Zip'0.t_zip a b) (visited : Seq'0.t_seq (item'0, item'1)) (tl : Zip'0.t_zip a b)
     
    =
-    [%#span22] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . inv'2 p2
-    /\ inv'3 p1
-    /\ len'0 p1 = len'1 p2
+    [%#span14] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . len'0 p1 = len'1 p2
     /\ len'1 p2 = len'2 visited
     /\ (forall i : int . 0 <= i /\ i < len'2 visited
      -> index_logic'0 visited i = (index_logic'1 p1 i, index_logic'2 p2 i))
@@ -277,202 +199,139 @@ module C12Zip_Impl0_ProducesTrans_Impl
   
   let%span s12_zip2 = "../12_zip.rs" 48 22 48 23
   
-  let%span s12_zip3 = "../12_zip.rs" 48 31 48 33
-  
-  let%span s12_zip4 = "../12_zip.rs" 48 52 48 53
-  
-  let%span s12_zip5 = "../12_zip.rs" 48 61 48 63
-  
-  let%span s12_zip6 = "../12_zip.rs" 48 82 48 83
-  
-  let%span s12_zip7 = "../12_zip.rs" 47 14 47 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span s12_zip3 = "../12_zip.rs" 48 52 48 53
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span s12_zip4 = "../12_zip.rs" 48 82 48 83
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span s12_zip5 = "../12_zip.rs" 47 14 47 42
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span18 = "../common.rs" 18 15 18 32
+  let%span span10 = "../common.rs" 18 15 18 32
   
-  let%span span19 = "../common.rs" 19 15 19 32
+  let%span span11 = "../common.rs" 19 15 19 32
   
-  let%span span20 = "../common.rs" 21 22 21 23
+  let%span span12 = "../common.rs" 21 22 21 23
   
-  let%span span21 = "../common.rs" 21 31 21 33
+  let%span span13 = "../common.rs" 21 52 21 53
   
-  let%span span22 = "../common.rs" 21 52 21 53
+  let%span span14 = "../common.rs" 21 82 21 83
   
-  let%span span23 = "../common.rs" 21 61 21 63
+  let%span span15 = "../common.rs" 20 14 20 42
   
-  let%span span24 = "../common.rs" 21 82 21 83
+  let%span span16 = "../common.rs" 15 21 15 25
   
-  let%span span25 = "../common.rs" 20 14 20 42
+  let%span span17 = "../common.rs" 14 14 14 45
   
-  let%span span26 = "../common.rs" 15 21 15 25
+  let%span span18 = "../12_zip.rs" 29 8 35 9
   
-  let%span span27 = "../common.rs" 14 14 14 45
+  predicate invariant'2 (self : b)
   
-  let%span span28 = "../12_zip.rs" 29 8 35 9
+  predicate inv'2 (_x : b)
   
-  predicate invariant'5 (self : b)
+  axiom inv'2 : forall x : b . inv'2 x = true
   
-  predicate inv'5 (_x : b)
+  predicate invariant'1 (self : a)
   
-  axiom inv'5 : forall x : b . inv'5 x = true
+  predicate inv'1 (_x : a)
   
-  predicate invariant'4 (self : a)
-  
-  predicate inv'4 (_x : a)
-  
-  axiom inv'4 : forall x : a . inv'4 x = true
+  axiom inv'1 : forall x : a . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   type item'1
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq item'1)
-  
   function len'1 (self : Seq'0.t_seq item'1) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'1 . ([%#span8] inv'2 self)  -> ([%#span9] len'1 self >= 0)
-  
-  constant empty'2 : Seq'0.t_seq item'1 = [%#span10] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq item'1 . [%#span6] len'1 self >= 0
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'2 : Seq'0.t_seq item'1
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span11] len'1 (empty'2 : Seq'0.t_seq item'1) = 0
+  function empty_len'2 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span7] len'1 (empty'2 : Seq'0.t_seq item'1) = 0
   
   type item'0
   
-  predicate inv'3 (_x : Seq'0.t_seq item'0)
-  
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'3 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span10] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'1 : Seq'0.t_seq item'0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  predicate invariant'3 (self : Seq'0.t_seq item'0)
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'0 (empty'1 : Seq'0.t_seq item'0) = 0
   
-  axiom inv'3 : forall x : Seq'0.t_seq item'0 . inv'3 x = true
-  
-  predicate invariant'2 (self : Seq'0.t_seq item'1)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq item'1 . inv'2 x = true
-  
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq item'1) (x : int) : item'1
+  function index_logic'2 (self : Seq'0.t_seq item'1) (_2 : int) : item'1
   
   function concat'2 (self : Seq'0.t_seq item'1) (other : Seq'0.t_seq item'1) : Seq'0.t_seq item'1
   
-  axiom concat'2_spec : forall self : Seq'0.t_seq item'1, other : Seq'0.t_seq item'1 . ([%#span13] inv'2 self)
-   -> ([%#span14] inv'2 other)
-   -> ([%#span17] inv'2 (concat'2 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'1 (concat'2 self other)
+  axiom concat'2_spec : forall self : Seq'0.t_seq item'1, other : Seq'0.t_seq item'1 . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'2 self other)
    -> index_logic'2 (concat'2 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span15] len'1 (concat'2 self other) = len'1 self + len'1 other)
+  && ([%#span8] len'1 (concat'2 self other) = len'1 self + len'1 other)
   
   predicate produces'2 [#"../common.rs" 8 4 8 65] (self : b) (visited : Seq'0.t_seq item'1) (o : b)
   
   function produces_trans'1 [#"../common.rs" 21 4 21 91] (a : b) (ab : Seq'0.t_seq item'1) (b : b) (bc : Seq'0.t_seq item'1) (c : b) : ()
     
   
-  axiom produces_trans'1_spec : forall a : b, ab : Seq'0.t_seq item'1, b : b, bc : Seq'0.t_seq item'1, c : b . ([%#span18] produces'2 a ab b)
-   -> ([%#span19] produces'2 b bc c)
-   -> ([%#span20] inv'5 a)
-   -> ([%#span21] inv'2 ab)
-   -> ([%#span22] inv'5 b)
-   -> ([%#span23] inv'2 bc)  -> ([%#span24] inv'5 c)  -> ([%#span25] produces'2 a (concat'2 ab bc) c)
+  axiom produces_trans'1_spec : forall a : b, ab : Seq'0.t_seq item'1, b : b, bc : Seq'0.t_seq item'1, c : b . ([%#span10] produces'2 a ab b)
+   -> ([%#span11] produces'2 b bc c)
+   -> ([%#span12] inv'2 a)
+   -> ([%#span13] inv'2 b)  -> ([%#span14] inv'2 c)  -> ([%#span15] produces'2 a (concat'2 ab bc) c)
   
   function produces_refl'1 [#"../common.rs" 15 4 15 27] (self : b) : ()
   
-  axiom produces_refl'1_spec : forall self : b . ([%#span26] inv'5 self)
-   -> ([%#span27] produces'2 self (empty'2 : Seq'0.t_seq item'1) self)
-  
-  use seq.Seq
+  axiom produces_refl'1_spec : forall self : b . ([%#span16] inv'2 self)
+   -> ([%#span17] produces'2 self (empty'2 : Seq'0.t_seq item'1) self)
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'1 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span13] inv'3 self)
-   -> ([%#span14] inv'3 other)
-   -> ([%#span17] inv'3 (concat'1 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'1 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'1 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : a) (visited : Seq'0.t_seq item'0) (o : a)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : a) (ab : Seq'0.t_seq item'0) (b : a) (bc : Seq'0.t_seq item'0) (c : a) : ()
     
   
-  axiom produces_trans'0_spec : forall a : a, ab : Seq'0.t_seq item'0, b : a, bc : Seq'0.t_seq item'0, c : a . ([%#span18] produces'1 a ab b)
-   -> ([%#span19] produces'1 b bc c)
-   -> ([%#span20] inv'4 a)
-   -> ([%#span21] inv'3 ab)
-   -> ([%#span22] inv'4 b)
-   -> ([%#span23] inv'3 bc)  -> ([%#span24] inv'4 c)  -> ([%#span25] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'0_spec : forall a : a, ab : Seq'0.t_seq item'0, b : a, bc : Seq'0.t_seq item'0, c : a . ([%#span10] produces'1 a ab b)
+   -> ([%#span11] produces'1 b bc c)
+   -> ([%#span12] inv'1 a)
+   -> ([%#span13] inv'1 b)  -> ([%#span14] inv'1 c)  -> ([%#span15] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : a) : ()
   
-  axiom produces_refl'0_spec : forall self : a . ([%#span26] inv'4 self)
-   -> ([%#span27] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq (item'0, item'1))
+  axiom produces_refl'0_spec : forall self : a . ([%#span16] inv'1 self)
+   -> ([%#span17] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   function len'2 (self : Seq'0.t_seq (item'0, item'1)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (item'0, item'1) . ([%#span8] inv'1 self)  -> ([%#span9] len'2 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq (item'0, item'1) = [%#span10] ()
+  axiom len'2_spec : forall self : Seq'0.t_seq (item'0, item'1) . [%#span6] len'2 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'0 : Seq'0.t_seq (item'0, item'1)
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'2 (empty'0 : Seq'0.t_seq (item'0, item'1)) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq (item'0, item'1))
-  
-  axiom inv'1 : forall x : Seq'0.t_seq (item'0, item'1) . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'2 (empty'0 : Seq'0.t_seq (item'0, item'1)) = 0
   
   use C12Zip_Zip_Type as Zip'0
   
@@ -482,31 +341,24 @@ module C12Zip_Impl0_ProducesTrans_Impl
   
   axiom inv'0 : forall x : Zip'0.t_zip a b . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (x : int) : (item'0, item'1)
+  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (_2 : int) : (item'0, item'1)
   
   function concat'0 (self : Seq'0.t_seq (item'0, item'1)) (other : Seq'0.t_seq (item'0, item'1)) : Seq'0.t_seq (item'0, item'1)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (item'0, item'1), other : Seq'0.t_seq (item'0, item'1) . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'2 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (item'0, item'1), other : Seq'0.t_seq (item'0, item'1) . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'2 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'2 self then index_logic'0 self i else index_logic'0 other (i - len'2 self)))
-  && ([%#span15] len'2 (concat'0 self other) = len'2 self + len'2 other)
+  && ([%#span8] len'2 (concat'0 self other) = len'2 self + len'2 other)
   
   use C12Zip_Zip_Type as C12Zip_Zip_Type
   
   predicate produces'0 [#"../12_zip.rs" 28 4 28 65] (self : Zip'0.t_zip a b) (visited : Seq'0.t_seq (item'0, item'1)) (tl : Zip'0.t_zip a b)
     
    =
-    [%#span28] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . inv'2 p2
-    /\ inv'3 p1
-    /\ len'0 p1 = len'1 p2
+    [%#span18] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . len'0 p1 = len'1 p2
     /\ len'1 p2 = len'2 visited
     /\ (forall i : int . 0 <= i /\ i < len'2 visited
      -> index_logic'0 visited i = (index_logic'1 p1 i, index_logic'2 p2 i))
@@ -526,13 +378,11 @@ module C12Zip_Impl0_ProducesTrans_Impl
   function produces_trans [#"../12_zip.rs" 48 4 48 90] (a : Zip'0.t_zip a b) (ab : Seq'0.t_seq (item'0, item'1)) (b : Zip'0.t_zip a b) (bc : Seq'0.t_seq (item'0, item'1)) (c : Zip'0.t_zip a b) : ()
     
   
-  goal vc_produces_trans : ([%#s12_zip6] inv'0 c)
-   -> ([%#s12_zip5] inv'1 bc)
-   -> ([%#s12_zip4] inv'0 b)
-   -> ([%#s12_zip3] inv'1 ab)
+  goal vc_produces_trans : ([%#s12_zip4] inv'0 c)
+   -> ([%#s12_zip3] inv'0 b)
    -> ([%#s12_zip2] inv'0 a)
    -> ([%#s12_zip1] produces'0 b bc c)
-   -> ([%#s12_zip0] produces'0 a ab b)  -> ([%#s12_zip7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s12_zip0] produces'0 a ab b)  -> ([%#s12_zip5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -565,96 +415,58 @@ module C12Zip_Impl0_Next
   
   let%span s12_zip4 = "../12_zip.rs" 54 26 54 44
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../common.rs" 18 15 18 32
-  
-  let%span span16 = "../common.rs" 19 15 19 32
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span17 = "../common.rs" 21 22 21 23
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span18 = "../common.rs" 21 31 21 33
+  let%span span9 = "../common.rs" 18 15 18 32
   
-  let%span span19 = "../common.rs" 21 52 21 53
+  let%span span10 = "../common.rs" 19 15 19 32
   
-  let%span span20 = "../common.rs" 21 61 21 63
+  let%span span11 = "../common.rs" 21 22 21 23
   
-  let%span span21 = "../common.rs" 21 82 21 83
+  let%span span12 = "../common.rs" 21 52 21 53
   
-  let%span span22 = "../common.rs" 20 14 20 42
+  let%span span13 = "../common.rs" 21 82 21 83
   
-  let%span span23 = "../common.rs" 15 21 15 25
+  let%span span14 = "../common.rs" 20 14 20 42
   
-  let%span span24 = "../common.rs" 14 14 14 45
+  let%span span15 = "../common.rs" 15 21 15 25
   
-  let%span span25 = "../12_zip.rs" 29 8 35 9
+  let%span span16 = "../common.rs" 14 14 14 45
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span17 = "../12_zip.rs" 29 8 35 9
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span30 = "../12_zip.rs" 20 13 22 67
+  let%span span21 = "../12_zip.rs" 20 13 22 67
   
-  let%span span31 = "../common.rs" 27 17 27 21
+  let%span span22 = "../common.rs" 27 17 27 21
   
-  let%span span32 = "../common.rs" 23 14 26 5
+  let%span span23 = "../common.rs" 23 14 26 5
   
-  let%span span33 = "../common.rs" 27 26 27 44
+  let%span span24 = "../common.rs" 27 26 27 44
   
-  let%span span34 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span25 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
   type item'1
   
-  predicate invariant'13 (self : item'1)
+  predicate invariant'10 (self : item'1)
   
-  predicate inv'13 (_x : item'1)
+  predicate inv'10 (_x : item'1)
   
-  axiom inv'13 : forall x : item'1 . inv'13 x = true
+  axiom inv'10 : forall x : item'1 . inv'10 x = true
   
   type item'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'12 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'12 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'12 : forall x : Seq'0.t_seq item'0 . inv'12 x = true
-  
-  predicate invariant'11 (self : Seq'0.t_seq item'1)
-  
-  predicate inv'11 (_x : Seq'0.t_seq item'1)
-  
-  axiom inv'11 : forall x : Seq'0.t_seq item'1 . inv'11 x = true
-  
-  predicate invariant'10 (self : Seq'0.t_seq (item'0, item'1))
-  
-  predicate inv'10 (_x : Seq'0.t_seq (item'0, item'1))
-  
-  axiom inv'10 : forall x : Seq'0.t_seq (item'0, item'1) . inv'10 x = true
-  
   predicate invariant'9 (self : (item'0, item'1))
   
   predicate inv'9 (_x : (item'0, item'1))
@@ -663,20 +475,17 @@ module C12Zip_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'2 (self : Seq'0.t_seq item'1) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq item'1 . ([%#span5] inv'11 self)  -> ([%#span6] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq item'1 . [%#span5] len'2 self >= 0
   
-  constant empty'1 : Seq'0.t_seq item'1 = [%#span7] ()
+  constant empty'1 : Seq'0.t_seq item'1
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span8] len'2 (empty'1 : Seq'0.t_seq item'1) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span6] len'2 (empty'1 : Seq'0.t_seq item'1) = 0
   
   use prelude.prelude.Borrow
   
@@ -686,18 +495,15 @@ module C12Zip_Impl0_Next
   
   axiom inv'8 : forall x : borrowed b . inv'8 x = true
   
-  use seq.Seq
-  
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span5] inv'12 self)  -> ([%#span6] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span5] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span8] len'1 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'7 (self : borrowed a)
   
@@ -713,19 +519,15 @@ module C12Zip_Impl0_Next
   
   axiom inv'6 : forall x : Option'0.t_option (item'0, item'1) . inv'6 x = true
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq (item'0, item'1)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (item'0, item'1) . ([%#span5] inv'10 self)
-   -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (item'0, item'1) . [%#span5] len'0 self >= 0
   
-  constant empty'2 : Seq'0.t_seq (item'0, item'1) = [%#span7] ()
+  constant empty'2 : Seq'0.t_seq (item'0, item'1)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'2 : Seq'0.t_seq (item'0, item'1)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'2 : Seq'0.t_seq (item'0, item'1)) = 0
   
   predicate invariant'5 (self : Option'0.t_option item'1)
   
@@ -739,21 +541,16 @@ module C12Zip_Impl0_Next
   
   axiom inv'4 : forall x : item'0 . inv'4 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq item'1) (x : int) : item'1
+  function index_logic'2 (self : Seq'0.t_seq item'1) (_2 : int) : item'1
   
   function concat'1 (self : Seq'0.t_seq item'1) (other : Seq'0.t_seq item'1) : Seq'0.t_seq item'1
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'1, other : Seq'0.t_seq item'1 . ([%#span10] inv'11 self)
-   -> ([%#span11] inv'11 other)
-   -> ([%#span14] inv'11 (concat'1 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'2 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'1, other : Seq'0.t_seq item'1 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'2 (concat'1 self other)
    -> index_logic'2 (concat'1 self other) i
   = (if i < len'2 self then index_logic'2 self i else index_logic'2 other (i - len'2 self)))
-  && ([%#span12] len'2 (concat'1 self other) = len'2 self + len'2 other)
+  && ([%#span7] len'2 (concat'1 self other) = len'2 self + len'2 other)
   
   predicate inv'3 (_x : b)
   
@@ -762,17 +559,15 @@ module C12Zip_Impl0_Next
   function produces_trans'1 [#"../common.rs" 21 4 21 91] (a : b) (ab : Seq'0.t_seq item'1) (b : b) (bc : Seq'0.t_seq item'1) (c : b) : ()
     
   
-  axiom produces_trans'1_spec : forall a : b, ab : Seq'0.t_seq item'1, b : b, bc : Seq'0.t_seq item'1, c : b . ([%#span15] produces'2 a ab b)
-   -> ([%#span16] produces'2 b bc c)
-   -> ([%#span17] inv'3 a)
-   -> ([%#span18] inv'11 ab)
-   -> ([%#span19] inv'3 b)
-   -> ([%#span20] inv'11 bc)  -> ([%#span21] inv'3 c)  -> ([%#span22] produces'2 a (concat'1 ab bc) c)
+  axiom produces_trans'1_spec : forall a : b, ab : Seq'0.t_seq item'1, b : b, bc : Seq'0.t_seq item'1, c : b . ([%#span9] produces'2 a ab b)
+   -> ([%#span10] produces'2 b bc c)
+   -> ([%#span11] inv'3 a)
+   -> ([%#span12] inv'3 b)  -> ([%#span13] inv'3 c)  -> ([%#span14] produces'2 a (concat'1 ab bc) c)
   
   function produces_refl'1 [#"../common.rs" 15 4 15 27] (self : b) : ()
   
-  axiom produces_refl'1_spec : forall self : b . ([%#span23] inv'3 self)
-   -> ([%#span24] produces'2 self (empty'1 : Seq'0.t_seq item'1) self)
+  axiom produces_refl'1_spec : forall self : b . ([%#span15] inv'3 self)
+   -> ([%#span16] produces'2 self (empty'1 : Seq'0.t_seq item'1) self)
   
   predicate invariant'3 (self : b)
   
@@ -792,21 +587,16 @@ module C12Zip_Impl0_Next
   
   axiom inv'1 : forall x : borrowed (Zip'0.t_zip a b) . inv'1 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] inv'12 self)
-   -> ([%#span11] inv'12 other)
-   -> ([%#span14] inv'12 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span12] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span7] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : a)
   
@@ -815,17 +605,15 @@ module C12Zip_Impl0_Next
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : a) (ab : Seq'0.t_seq item'0) (b : a) (bc : Seq'0.t_seq item'0) (c : a) : ()
     
   
-  axiom produces_trans'0_spec : forall a : a, ab : Seq'0.t_seq item'0, b : a, bc : Seq'0.t_seq item'0, c : a . ([%#span15] produces'1 a ab b)
-   -> ([%#span16] produces'1 b bc c)
-   -> ([%#span17] inv'0 a)
-   -> ([%#span18] inv'12 ab)
-   -> ([%#span19] inv'0 b)
-   -> ([%#span20] inv'12 bc)  -> ([%#span21] inv'0 c)  -> ([%#span22] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : a, ab : Seq'0.t_seq item'0, b : a, bc : Seq'0.t_seq item'0, c : a . ([%#span9] produces'1 a ab b)
+   -> ([%#span10] produces'1 b bc c)
+   -> ([%#span11] inv'0 a)
+   -> ([%#span12] inv'0 b)  -> ([%#span13] inv'0 c)  -> ([%#span14] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : a) : ()
   
-  axiom produces_refl'0_spec : forall self : a . ([%#span23] inv'0 self)
-   -> ([%#span24] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : a . ([%#span15] inv'0 self)
+   -> ([%#span16] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'0 (self : a)
   
@@ -833,46 +621,36 @@ module C12Zip_Impl0_Next
   
   use C12Zip_Zip_Type as C12Zip_Zip_Type
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (x : int) : (item'0, item'1)
+  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (_2 : int) : (item'0, item'1)
   
   predicate produces'0 [#"../12_zip.rs" 28 4 28 65] (self : Zip'0.t_zip a b) (visited : Seq'0.t_seq (item'0, item'1)) (tl : Zip'0.t_zip a b)
     
    =
-    [%#span25] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . inv'11 p2
-    /\ inv'12 p1
-    /\ len'1 p1 = len'2 p2
+    [%#span17] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . len'1 p1 = len'2 p2
     /\ len'2 p2 = len'0 visited
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> index_logic'0 visited i = (index_logic'1 p1 i, index_logic'2 p2 i))
     /\ produces'1 (C12Zip_Zip_Type.zip_a self) p1 (C12Zip_Zip_Type.zip_a tl)
     /\ produces'2 (C12Zip_Zip_Type.zip_b self) p2 (C12Zip_Zip_Type.zip_b tl)
   
-  use seq.Seq
-  
   function singleton'0 (v : (item'0, item'1)) : Seq'0.t_seq (item'0, item'1)
   
-  axiom singleton'0_spec : forall v : (item'0, item'1) . ([%#span26] inv'9 v)
-   -> ([%#span29] inv'10 (singleton'0 v))
-  && ([%#span28] index_logic'0 (singleton'0 v) 0 = v) && ([%#span27] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (item'0, item'1) . ([%#span18] inv'9 v)
+   -> ([%#span20] index_logic'0 (singleton'0 v) 0 = v) && ([%#span19] len'0 (singleton'0 v) = 1)
   
   predicate completed'2 [#"../common.rs" 11 4 11 36] (self : borrowed b)
   
   predicate resolve'2 (self : item'0)
   
-  use seq.Seq
-  
   function singleton'1 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'1_spec : forall v : item'0 . ([%#span26] inv'4 v)
-   -> ([%#span29] inv'12 (singleton'1 v))
-  && ([%#span28] index_logic'1 (singleton'1 v) 0 = v) && ([%#span27] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : item'0 . ([%#span18] inv'4 v)
+   -> ([%#span20] index_logic'1 (singleton'1 v) 0 = v) && ([%#span19] len'1 (singleton'1 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed a)
   
   predicate completed'0 [#"../12_zip.rs" 18 4 18 35] (self : borrowed (Zip'0.t_zip a b)) =
-    [%#span30] completed'1 (Borrow.borrow_logic (C12Zip_Zip_Type.zip_a ( * self)) (C12Zip_Zip_Type.zip_a ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span21] completed'1 (Borrow.borrow_logic (C12Zip_Zip_Type.zip_a ( * self)) (C12Zip_Zip_Type.zip_a ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ C12Zip_Zip_Type.zip_b ( * self) = C12Zip_Zip_Type.zip_b ( ^ self)
     \/ (exists x : item'0 . inv'4 x
     /\ produces'1 (C12Zip_Zip_Type.zip_a ( * self)) (singleton'1 x) (C12Zip_Zip_Type.zip_a ( ^ self))
@@ -883,18 +661,15 @@ module C12Zip_Impl0_Next
   
   predicate resolve'3 (self : Option'0.t_option item'1)
   
-  use seq.Seq
-  
   function singleton'2 (v : item'1) : Seq'0.t_seq item'1
   
-  axiom singleton'2_spec : forall v : item'1 . ([%#span26] inv'13 v)
-   -> ([%#span29] inv'11 (singleton'2 v))
-  && ([%#span28] index_logic'2 (singleton'2 v) 0 = v) && ([%#span27] len'2 (singleton'2 v) = 1)
+  axiom singleton'2_spec : forall v : item'1 . ([%#span18] inv'10 v)
+   -> ([%#span20] index_logic'2 (singleton'2 v) 0 = v) && ([%#span19] len'2 (singleton'2 v) = 1)
   
-  let rec next'1 (self:borrowed b) (return'  (ret:Option'0.t_option item'1))= {[@expl:precondition] [%#span31] inv'8 self}
+  let rec next'1 (self:borrowed b) (return'  (ret:Option'0.t_option item'1))= {[@expl:precondition] [%#span22] inv'8 self}
     any
-    [ return' (result:Option'0.t_option item'1)-> {[%#span33] inv'5 result}
-      {[%#span32] match result with
+    [ return' (result:Option'0.t_option item'1)-> {[%#span24] inv'5 result}
+      {[%#span23] match result with
         | Option'0.C_None -> completed'2 self
         | Option'0.C_Some v -> produces'2 ( * self) (singleton'2 v) ( ^ self)
         end}
@@ -904,12 +679,12 @@ module C12Zip_Impl0_Next
   predicate resolve'1 (self : Option'0.t_option item'0)
   
   predicate resolve'0 (self : borrowed (Zip'0.t_zip a b)) =
-    [%#span34]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
-  let rec next'0 (self:borrowed a) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span31] inv'7 self}
+  let rec next'0 (self:borrowed a) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span22] inv'7 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span33] inv'2 result}
-      {[%#span32] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span24] inv'2 result}
+      {[%#span23] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'1 v) ( ^ self)
         end}
@@ -1057,69 +832,37 @@ module C12Zip_Impl0
   
   let%span s12_zip2 = "../12_zip.rs" 48 4 48 90
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../12_zip.rs" 29 8 35 9
+  let%span span6 = "../12_zip.rs" 29 8 35 9
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span16 = "../12_zip.rs" 20 13 22 67
-  
-  type item'0
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'7 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'7 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq item'0 . inv'7 x = true
+  let%span span10 = "../12_zip.rs" 20 13 22 67
   
   type item'1
   
-  predicate invariant'6 (self : Seq'0.t_seq item'1)
-  
-  predicate inv'6 (_x : Seq'0.t_seq item'1)
-  
-  axiom inv'6 : forall x : Seq'0.t_seq item'1 . inv'6 x = true
-  
-  predicate invariant'5 (self : (item'0, item'1))
-  
-  predicate inv'5 (_x : (item'0, item'1))
-  
-  axiom inv'5 : forall x : (item'0, item'1) . inv'5 x = true
+  type item'0
   
-  predicate invariant'4 (self : item'0)
+  predicate invariant'4 (self : (item'0, item'1))
   
-  predicate inv'4 (_x : item'0)
+  predicate inv'4 (_x : (item'0, item'1))
   
-  axiom inv'4 : forall x : item'0 . inv'4 x = true
+  axiom inv'4 : forall x : (item'0, item'1) . inv'4 x = true
   
-  predicate invariant'3 (self : Seq'0.t_seq (item'0, item'1))
+  predicate invariant'3 (self : item'0)
   
-  predicate inv'3 (_x : Seq'0.t_seq (item'0, item'1))
+  predicate inv'3 (_x : item'0)
   
-  axiom inv'3 : forall x : Seq'0.t_seq (item'0, item'1) . inv'3 x = true
+  axiom inv'3 : forall x : item'0 . inv'3 x = true
   
   use C12Zip_Zip_Type as Zip'0
   
@@ -1145,36 +888,29 @@ module C12Zip_Impl0
   
   axiom inv'0 : forall x : borrowed (Zip'0.t_zip a b) . inv'0 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (x : int) : (item'0, item'1)
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq (item'0, item'1)) (_2 : int) : (item'0, item'1)
   
   function len'0 (self : Seq'0.t_seq (item'0, item'1)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (item'0, item'1) . ([%#span3] inv'3 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (item'0, item'1) . [%#span3] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq (item'0, item'1)) (other : Seq'0.t_seq (item'0, item'1)) : Seq'0.t_seq (item'0, item'1)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (item'0, item'1), other : Seq'0.t_seq (item'0, item'1) . ([%#span5] inv'3 self)
-   -> ([%#span6] inv'3 other)
-   -> ([%#span9] inv'3 (concat'0 self other))
-  && ([%#span8] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (item'0, item'1), other : Seq'0.t_seq (item'0, item'1) . ([%#span5] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span4] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  constant empty'0 : Seq'0.t_seq (item'0, item'1) = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq (item'0, item'1)
   
-  constant empty'0 : Seq'0.t_seq (item'0, item'1) = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq (item'0, item'1)
   
   predicate produces'2 [#"../common.rs" 8 4 8 65] (self : b) (visited : Seq'0.t_seq item'1) (o : b)
   
@@ -1182,64 +918,48 @@ module C12Zip_Impl0
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : a) (visited : Seq'0.t_seq item'0) (o : a)
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq item'1) (x : int) : item'1
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'2 (self : Seq'0.t_seq item'1) (_2 : int) : item'1
   
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'2 (self : Seq'0.t_seq item'1) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq item'1 . ([%#span3] inv'6 self)  -> ([%#span4] len'2 self >= 0)
-  
-  use seq.Seq
+  axiom len'2_spec : forall self : Seq'0.t_seq item'1 . [%#span3] len'2 self >= 0
   
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span3] inv'7 self)  -> ([%#span4] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span3] len'1 self >= 0
   
   predicate produces'0 [#"../12_zip.rs" 28 4 28 65] (self : Zip'0.t_zip a b) (visited : Seq'0.t_seq (item'0, item'1)) (tl : Zip'0.t_zip a b)
     
    =
-    [%#span11] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . inv'6 p2
-    /\ inv'7 p1
-    /\ len'1 p1 = len'2 p2
+    [%#span6] exists p2 : Seq'0.t_seq item'1 . exists p1 : Seq'0.t_seq item'0 . len'1 p1 = len'2 p2
     /\ len'2 p2 = len'0 visited
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
      -> index_logic'0 visited i = (index_logic'1 p1 i, index_logic'2 p2 i))
     /\ produces'1 (C12Zip_Zip_Type.zip_a self) p1 (C12Zip_Zip_Type.zip_a tl)
     /\ produces'2 (C12Zip_Zip_Type.zip_b self) p2 (C12Zip_Zip_Type.zip_b tl)
   
-  use seq.Seq
-  
   function singleton'0 (v : (item'0, item'1)) : Seq'0.t_seq (item'0, item'1)
   
-  axiom singleton'0_spec : forall v : (item'0, item'1) . ([%#span12] inv'5 v)
-   -> ([%#span15] inv'3 (singleton'0 v))
-  && ([%#span14] index_logic'0 (singleton'0 v) 0 = v) && ([%#span13] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (item'0, item'1) . ([%#span7] inv'4 v)
+   -> ([%#span9] index_logic'0 (singleton'0 v) 0 = v) && ([%#span8] len'0 (singleton'0 v) = 1)
   
   predicate completed'2 [#"../common.rs" 11 4 11 36] (self : borrowed b)
   
   predicate resolve'0 (self : item'0)
   
-  use seq.Seq
-  
   function singleton'1 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'1_spec : forall v : item'0 . ([%#span12] inv'4 v)
-   -> ([%#span15] inv'7 (singleton'1 v))
-  && ([%#span14] index_logic'1 (singleton'1 v) 0 = v) && ([%#span13] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : item'0 . ([%#span7] inv'3 v)
+   -> ([%#span9] index_logic'1 (singleton'1 v) 0 = v) && ([%#span8] len'1 (singleton'1 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed a)
   
   predicate completed'0 [#"../12_zip.rs" 18 4 18 35] (self : borrowed (Zip'0.t_zip a b)) =
-    [%#span16] completed'1 (Borrow.borrow_logic (C12Zip_Zip_Type.zip_a ( * self)) (C12Zip_Zip_Type.zip_a ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span10] completed'1 (Borrow.borrow_logic (C12Zip_Zip_Type.zip_a ( * self)) (C12Zip_Zip_Type.zip_a ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ C12Zip_Zip_Type.zip_b ( * self) = C12Zip_Zip_Type.zip_b ( ^ self)
-    \/ (exists x : item'0 . inv'4 x
+    \/ (exists x : item'0 . inv'3 x
     /\ produces'1 (C12Zip_Zip_Type.zip_a ( * self)) (singleton'1 x) (C12Zip_Zip_Type.zip_a ( ^ self))
     /\ resolve'0 x
     /\ completed'2 (Borrow.borrow_logic (C12Zip_Zip_Type.zip_b ( * self)) (C12Zip_Zip_Type.zip_b ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 2)))
@@ -1263,11 +983,9 @@ module C12Zip_Impl0
    -> produces'0 self (empty'1 : Seq'0.t_seq (item'0, item'1)) self)
   
   goal produces_trans_refn : [%#s12_zip2] forall a : Zip'0.t_zip a b . forall ab : Seq'0.t_seq (item'0, item'1) . forall b : Zip'0.t_zip a b . forall bc : Seq'0.t_seq (item'0, item'1) . forall c : Zip'0.t_zip a b . inv'2 c
-  /\ inv'3 bc /\ inv'2 b /\ inv'3 ab /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'2 b /\ inv'2 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'2 c
-  /\ inv'3 bc
   /\ inv'2 b
-  /\ inv'3 ab
   /\ inv'2 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
diff --git a/creusot/tests/should_succeed/iterators/13_cloned.coma b/creusot/tests/should_succeed/iterators/13_cloned.coma
index 72baf86de4..bf42494ff6 100644
--- a/creusot/tests/should_succeed/iterators/13_cloned.coma
+++ b/creusot/tests/should_succeed/iterators/13_cloned.coma
@@ -15,22 +15,7 @@ module C13Cloned_Cloned_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C13Cloned_Impl0_ProducesRefl_Impl
   type i
@@ -41,130 +26,86 @@ module C13Cloned_Impl0_ProducesRefl_Impl
   
   let%span s13_cloned1 = "../13_cloned.rs" 38 14 38 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span12 = "../common.rs" 18 15 18 32
+  let%span span6 = "../common.rs" 18 15 18 32
   
-  let%span span13 = "../common.rs" 19 15 19 32
+  let%span span7 = "../common.rs" 19 15 19 32
   
-  let%span span14 = "../common.rs" 21 22 21 23
+  let%span span8 = "../common.rs" 21 22 21 23
   
-  let%span span15 = "../common.rs" 21 31 21 33
+  let%span span9 = "../common.rs" 21 52 21 53
   
-  let%span span16 = "../common.rs" 21 52 21 53
+  let%span span10 = "../common.rs" 21 82 21 83
   
-  let%span span17 = "../common.rs" 21 61 21 63
+  let%span span11 = "../common.rs" 20 14 20 42
   
-  let%span span18 = "../common.rs" 21 82 21 83
+  let%span span12 = "../common.rs" 15 21 15 25
   
-  let%span span19 = "../common.rs" 20 14 20 42
+  let%span span13 = "../common.rs" 14 14 14 45
   
-  let%span span20 = "../common.rs" 15 21 15 25
+  let%span span14 = "../13_cloned.rs" 29 8 33 9
   
-  let%span span21 = "../common.rs" 14 14 14 45
+  predicate invariant'1 (self : i)
   
-  let%span span22 = "../13_cloned.rs" 29 8 33 9
+  predicate inv'1 (_x : i)
   
-  predicate invariant'3 (self : i)
-  
-  predicate inv'3 (_x : i)
-  
-  axiom inv'3 : forall x : i . inv'3 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq t)
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'2 self)  -> ([%#span3] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span4] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span6] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span2] len'1 self >= 0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span5] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  constant empty'1 : Seq'0.t_seq t
   
-  use seq.Seq
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span3] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span7] inv'2 self)
-   -> ([%#span8] inv'2 other)
-   -> ([%#span11] inv'2 (concat'0 self other))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span5] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span9] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span4] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq t) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq t) (b : i) (bc : Seq'0.t_seq t) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span12] produces'1 a ab b)
-   -> ([%#span13] produces'1 b bc c)
-   -> ([%#span14] inv'3 a)
-   -> ([%#span15] inv'2 ab)
-   -> ([%#span16] inv'3 b)
-   -> ([%#span17] inv'2 bc)  -> ([%#span18] inv'3 c)  -> ([%#span19] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span6] produces'1 a ab b)
+   -> ([%#span7] produces'1 b bc c)
+   -> ([%#span8] inv'1 a)
+   -> ([%#span9] inv'1 b)  -> ([%#span10] inv'1 c)  -> ([%#span11] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span20] inv'3 self)
-   -> ([%#span21] produces'1 self (empty'1 : Seq'0.t_seq t) self)
-  
-  predicate invariant'2 (self : Seq'0.t_seq t)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq t . inv'2 x = true
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
-  
-  predicate inv'1 (_x : Seq'0.t_seq t)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
-  
-  use seq.Seq
+  axiom produces_refl'0_spec : forall self : i . ([%#span12] inv'1 self)
+   -> ([%#span13] produces'1 self (empty'1 : Seq'0.t_seq t) self)
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C13Cloned_Cloned_Type as Cloned'0
   
@@ -174,9 +115,7 @@ module C13Cloned_Impl0_ProducesRefl_Impl
   
   axiom inv'0 : forall x : Cloned'0.t_cloned i . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   use C13Cloned_Cloned_Type as C13Cloned_Cloned_Type
   
@@ -185,8 +124,7 @@ module C13Cloned_Impl0_ProducesRefl_Impl
   predicate produces'0 [#"../13_cloned.rs" 28 4 28 64] (self : Cloned'0.t_cloned i) (visited : Seq'0.t_seq t) (o : Cloned'0.t_cloned i)
     
    =
-    [%#span22] exists s : Seq'0.t_seq t . inv'2 s
-    /\ produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
+    [%#span14] exists s : Seq'0.t_seq t . produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
@@ -208,140 +146,92 @@ module C13Cloned_Impl0_ProducesTrans_Impl
   
   let%span s13_cloned2 = "../13_cloned.rs" 46 22 46 23
   
-  let%span s13_cloned3 = "../13_cloned.rs" 46 31 46 33
-  
-  let%span s13_cloned4 = "../13_cloned.rs" 46 52 46 53
-  
-  let%span s13_cloned5 = "../13_cloned.rs" 46 61 46 63
-  
-  let%span s13_cloned6 = "../13_cloned.rs" 46 82 46 83
-  
-  let%span s13_cloned7 = "../13_cloned.rs" 45 14 45 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s13_cloned3 = "../13_cloned.rs" 46 52 46 53
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span s13_cloned4 = "../13_cloned.rs" 46 82 46 83
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span s13_cloned5 = "../13_cloned.rs" 45 14 45 42
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span10 = "../common.rs" 18 15 18 32
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span11 = "../common.rs" 19 15 19 32
   
-  let%span span18 = "../common.rs" 18 15 18 32
+  let%span span12 = "../common.rs" 21 22 21 23
   
-  let%span span19 = "../common.rs" 19 15 19 32
+  let%span span13 = "../common.rs" 21 52 21 53
   
-  let%span span20 = "../common.rs" 21 22 21 23
+  let%span span14 = "../common.rs" 21 82 21 83
   
-  let%span span21 = "../common.rs" 21 31 21 33
+  let%span span15 = "../common.rs" 20 14 20 42
   
-  let%span span22 = "../common.rs" 21 52 21 53
+  let%span span16 = "../common.rs" 15 21 15 25
   
-  let%span span23 = "../common.rs" 21 61 21 63
+  let%span span17 = "../common.rs" 14 14 14 45
   
-  let%span span24 = "../common.rs" 21 82 21 83
+  let%span span18 = "../13_cloned.rs" 29 8 33 9
   
-  let%span span25 = "../common.rs" 20 14 20 42
+  predicate invariant'1 (self : i)
   
-  let%span span26 = "../common.rs" 15 21 15 25
+  predicate inv'1 (_x : i)
   
-  let%span span27 = "../common.rs" 14 14 14 45
-  
-  let%span span28 = "../13_cloned.rs" 29 8 33 9
-  
-  predicate invariant'3 (self : i)
-  
-  predicate inv'3 (_x : i)
-  
-  axiom inv'3 : forall x : i . inv'3 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq t)
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span8] inv'2 self)  -> ([%#span9] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span10] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span6] len'1 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'1 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span13] inv'2 self)
-   -> ([%#span14] inv'2 other)
-   -> ([%#span17] inv'2 (concat'1 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span15] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span8] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq t) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq t) (b : i) (bc : Seq'0.t_seq t) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span18] produces'1 a ab b)
-   -> ([%#span19] produces'1 b bc c)
-   -> ([%#span20] inv'3 a)
-   -> ([%#span21] inv'2 ab)
-   -> ([%#span22] inv'3 b)
-   -> ([%#span23] inv'2 bc)  -> ([%#span24] inv'3 c)  -> ([%#span25] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span10] produces'1 a ab b)
+   -> ([%#span11] produces'1 b bc c)
+   -> ([%#span12] inv'1 a)
+   -> ([%#span13] inv'1 b)  -> ([%#span14] inv'1 c)  -> ([%#span15] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span26] inv'3 self)
-   -> ([%#span27] produces'1 self (empty'1 : Seq'0.t_seq t) self)
-  
-  predicate invariant'2 (self : Seq'0.t_seq t)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq t . inv'2 x = true
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq t)
+  axiom produces_refl'0_spec : forall self : i . ([%#span16] inv'1 self)
+   -> ([%#span17] produces'1 self (empty'1 : Seq'0.t_seq t) self)
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span6] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq t) = 0
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C13Cloned_Cloned_Type as Cloned'0
   
@@ -351,21 +241,15 @@ module C13Cloned_Impl0_ProducesTrans_Impl
   
   axiom inv'0 : forall x : Cloned'0.t_cloned i . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   use C13Cloned_Cloned_Type as C13Cloned_Cloned_Type
   
@@ -374,8 +258,7 @@ module C13Cloned_Impl0_ProducesTrans_Impl
   predicate produces'0 [#"../13_cloned.rs" 28 4 28 64] (self : Cloned'0.t_cloned i) (visited : Seq'0.t_seq t) (o : Cloned'0.t_cloned i)
     
    =
-    [%#span28] exists s : Seq'0.t_seq t . inv'2 s
-    /\ produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
+    [%#span18] exists s : Seq'0.t_seq t . produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
@@ -392,13 +275,11 @@ module C13Cloned_Impl0_ProducesTrans_Impl
   function produces_trans [#"../13_cloned.rs" 46 4 46 90] (a : Cloned'0.t_cloned i) (ab : Seq'0.t_seq t) (b : Cloned'0.t_cloned i) (bc : Seq'0.t_seq t) (c : Cloned'0.t_cloned i) : ()
     
   
-  goal vc_produces_trans : ([%#s13_cloned6] inv'0 c)
-   -> ([%#s13_cloned5] inv'1 bc)
-   -> ([%#s13_cloned4] inv'0 b)
-   -> ([%#s13_cloned3] inv'1 ab)
+  goal vc_produces_trans : ([%#s13_cloned4] inv'0 c)
+   -> ([%#s13_cloned3] inv'0 b)
    -> ([%#s13_cloned2] inv'0 a)
    -> ([%#s13_cloned1] produces'0 b bc c)
-   -> ([%#s13_cloned0] produces'0 a ab b)  -> ([%#s13_cloned7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s13_cloned0] produces'0 a ab b)  -> ([%#s13_cloned5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -427,87 +308,55 @@ module C13Cloned_Impl0_Next
   
   let%span s13_cloned2 = "../13_cloned.rs" 52 26 52 35
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span7 = "../common.rs" 18 15 18 32
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span8 = "../common.rs" 19 15 19 32
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span9 = "../common.rs" 21 22 21 23
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span10 = "../common.rs" 21 52 21 53
   
-  let%span span13 = "../common.rs" 18 15 18 32
+  let%span span11 = "../common.rs" 21 82 21 83
   
-  let%span span14 = "../common.rs" 19 15 19 32
+  let%span span12 = "../common.rs" 20 14 20 42
   
-  let%span span15 = "../common.rs" 21 22 21 23
+  let%span span13 = "../common.rs" 15 21 15 25
   
-  let%span span16 = "../common.rs" 21 31 21 33
+  let%span span14 = "../common.rs" 14 14 14 45
   
-  let%span span17 = "../common.rs" 21 52 21 53
+  let%span span15 = "../13_cloned.rs" 29 8 33 9
   
-  let%span span18 = "../common.rs" 21 61 21 63
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span19 = "../common.rs" 21 82 21 83
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span20 = "../common.rs" 20 14 20 42
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span21 = "../common.rs" 15 21 15 25
+  let%span span19 = "../13_cloned.rs" 23 8 23 43
   
-  let%span span22 = "../common.rs" 14 14 14 45
+  let%span span20 = "" 0 0 0 0
   
-  let%span span23 = "../13_cloned.rs" 29 8 33 9
+  let%span span21 = "../../../../../creusot-contracts/src/std/option.rs" 104 16 104 59
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span22 = "../../../../../creusot-contracts/src/std/option.rs" 29 0 140 1
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span23 = "" 0 0 0 0
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span24 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span25 = "../common.rs" 27 17 27 21
   
-  let%span span28 = "../13_cloned.rs" 23 8 23 43
+  let%span span26 = "../common.rs" 23 14 26 5
   
-  let%span span29 = "" 0 0 0 0
-  
-  let%span span30 = "../../../../../creusot-contracts/src/std/option.rs" 104 16 104 59
-  
-  let%span span31 = "../../../../../creusot-contracts/src/std/option.rs" 29 0 140 1
-  
-  let%span span32 = "" 0 0 0 0
-  
-  let%span span33 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span34 = "../common.rs" 27 17 27 21
-  
-  let%span span35 = "../common.rs" 23 14 26 5
-  
-  let%span span36 = "../common.rs" 27 26 27 44
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'8 (self : Seq'0.t_seq t)
-  
-  predicate inv'8 (_x : Seq'0.t_seq t)
-  
-  axiom inv'8 : forall x : Seq'0.t_seq t . inv'8 x = true
-  
-  predicate invariant'7 (self : Seq'0.t_seq t)
-  
-  predicate inv'7 (_x : Seq'0.t_seq t)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq t . inv'7 x = true
+  let%span span27 = "../common.rs" 27 26 27 44
   
   predicate invariant'6 (self : t)
   
@@ -531,20 +380,17 @@ module C13Cloned_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'8 self)  -> ([%#span4] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span3] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span4] len'1 (empty'0 : Seq'0.t_seq t) = 0
   
   use prelude.prelude.Borrow
   
@@ -560,18 +406,15 @@ module C13Cloned_Impl0_Next
   
   axiom inv'2 : forall x : Option'0.t_option t . inv'2 x = true
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'7 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
-  constant empty'1 : Seq'0.t_seq t = [%#span5] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'1 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'1 : Seq'0.t_seq t) = 0
   
   use C13Cloned_Cloned_Type as Cloned'0
   
@@ -581,21 +424,15 @@ module C13Cloned_Impl0_Next
   
   axiom inv'1 : forall x : borrowed (Cloned'0.t_cloned i) . inv'1 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span8] inv'8 self)
-   -> ([%#span9] inv'8 other)
-   -> ([%#span12] inv'8 (concat'0 self other))
-  && ([%#span11] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span6] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span10] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span5] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : i)
   
@@ -604,75 +441,64 @@ module C13Cloned_Impl0_Next
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq t) (b : i) (bc : Seq'0.t_seq t) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span13] produces'1 a ab b)
-   -> ([%#span14] produces'1 b bc c)
-   -> ([%#span15] inv'0 a)
-   -> ([%#span16] inv'8 ab)
-   -> ([%#span17] inv'0 b)
-   -> ([%#span18] inv'8 bc)  -> ([%#span19] inv'0 c)  -> ([%#span20] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span7] produces'1 a ab b)
+   -> ([%#span8] produces'1 b bc c)
+   -> ([%#span9] inv'0 a)
+   -> ([%#span10] inv'0 b)  -> ([%#span11] inv'0 c)  -> ([%#span12] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span21] inv'0 self)
-   -> ([%#span22] produces'1 self (empty'0 : Seq'0.t_seq t) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span13] inv'0 self)
+   -> ([%#span14] produces'1 self (empty'0 : Seq'0.t_seq t) self)
   
   predicate invariant'0 (self : i)
   
   axiom inv'0 : forall x : i . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   use C13Cloned_Cloned_Type as C13Cloned_Cloned_Type
   
   predicate produces'0 [#"../13_cloned.rs" 28 4 28 64] (self : Cloned'0.t_cloned i) (visited : Seq'0.t_seq t) (o : Cloned'0.t_cloned i)
     
    =
-    [%#span23] exists s : Seq'0.t_seq t . inv'8 s
-    /\ produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
+    [%#span15] exists s : Seq'0.t_seq t . produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
-  use seq.Seq
-  
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span24] inv'6 v)
-   -> ([%#span27] inv'7 (singleton'0 v))
-  && ([%#span26] index_logic'0 (singleton'0 v) 0 = v) && ([%#span25] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span16] inv'6 v)
+   -> ([%#span18] index_logic'0 (singleton'0 v) 0 = v) && ([%#span17] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate completed'0 [#"../13_cloned.rs" 22 4 22 35] (self : borrowed (Cloned'0.t_cloned i)) =
-    [%#span28] completed'1 (Borrow.borrow_logic (C13Cloned_Cloned_Type.cloned_iter ( * self)) (C13Cloned_Cloned_Type.cloned_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span19] completed'1 (Borrow.borrow_logic (C13Cloned_Cloned_Type.cloned_iter ( * self)) (C13Cloned_Cloned_Type.cloned_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
   use prelude.prelude.Intrinsic
   
-  let rec cloned'0 (self:Option'0.t_option t) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span29] inv'4 self}
+  let rec cloned'0 (self:Option'0.t_option t) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span20] inv'4 self}
     any
-    [ return' (result:Option'0.t_option t)-> {[%#span32] inv'2 result}
-      {[%#span31] self = Option'0.C_None
+    [ return' (result:Option'0.t_option t)-> {[%#span23] inv'2 result}
+      {[%#span22] self = Option'0.C_None
       \/ (exists t : t . inv'5 t /\ self = Option'0.C_Some t /\ result = Option'0.C_Some t)}
-      {[%#span30] self = Option'0.C_None  -> result = Option'0.C_None}
+      {[%#span21] self = Option'0.C_None  -> result = Option'0.C_None}
       (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (Cloned'0.t_cloned i)) =
-    [%#span33]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span24]  ^ self =  * self
   
   function singleton'1 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'1_spec : forall v : t . ([%#span24] inv'5 v)
-   -> ([%#span27] inv'8 (singleton'1 v))
-  && ([%#span26] index_logic'1 (singleton'1 v) 0 = v) && ([%#span25] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : t . ([%#span16] inv'5 v)
+   -> ([%#span18] index_logic'1 (singleton'1 v) 0 = v) && ([%#span17] len'1 (singleton'1 v) = 1)
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span34] inv'3 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span25] inv'3 self}
     any
-    [ return' (result:Option'0.t_option t)-> {[%#span36] inv'4 result}
-      {[%#span35] match result with
+    [ return' (result:Option'0.t_option t)-> {[%#span27] inv'4 result}
+      {[%#span26] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'1 v) ( ^ self)
         end}
@@ -725,71 +551,45 @@ module C13Cloned_Impl0
   
   let%span s13_cloned2 = "../13_cloned.rs" 52 4 52 35
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span7 = "../13_cloned.rs" 23 8 23 43
   
-  let%span span9 = "../13_cloned.rs" 23 8 23 43
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span10 = "../13_cloned.rs" 29 8 33 9
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  predicate invariant'3 (self : t)
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  predicate inv'3 (_x : t)
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span16 = "../13_cloned.rs" 29 8 33 9
-  
-  predicate invariant'5 (self : t)
-  
-  predicate inv'5 (_x : t)
-  
-  axiom inv'5 : forall x : t . inv'5 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'4 (self : Seq'0.t_seq t)
-  
-  predicate inv'4 (_x : Seq'0.t_seq t)
-  
-  axiom inv'4 : forall x : Seq'0.t_seq t . inv'4 x = true
+  axiom inv'3 : forall x : t . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'3 (self : Option'0.t_option t)
+  predicate invariant'2 (self : Option'0.t_option t)
   
-  predicate inv'3 (_x : Option'0.t_option t)
+  predicate inv'2 (_x : Option'0.t_option t)
   
-  axiom inv'3 : forall x : Option'0.t_option t . inv'3 x = true
+  axiom inv'2 : forall x : Option'0.t_option t . inv'2 x = true
   
   use C13Cloned_Cloned_Type as Cloned'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'2 (self : borrowed (Cloned'0.t_cloned i))
-  
-  predicate inv'2 (_x : borrowed (Cloned'0.t_cloned i))
-  
-  axiom inv'2 : forall x : borrowed (Cloned'0.t_cloned i) . inv'2 x = true
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
+  predicate invariant'1 (self : borrowed (Cloned'0.t_cloned i))
   
-  predicate inv'1 (_x : Seq'0.t_seq t)
+  predicate inv'1 (_x : borrowed (Cloned'0.t_cloned i))
   
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
+  axiom inv'1 : forall x : borrowed (Cloned'0.t_cloned i) . inv'1 x = true
   
   predicate invariant'0 (self : Cloned'0.t_cloned i)
   
@@ -799,75 +599,57 @@ module C13Cloned_Impl0
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'1 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span5] inv'5 v)
-   -> ([%#span8] inv'1 (singleton'0 v))
-  && ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span4] inv'3 v)
+   -> ([%#span6] index_logic'0 (singleton'0 v) 0 = v) && ([%#span5] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   use C13Cloned_Cloned_Type as C13Cloned_Cloned_Type
   
   predicate completed'0 [#"../13_cloned.rs" 22 4 22 35] (self : borrowed (Cloned'0.t_cloned i)) =
-    [%#span9] completed'1 (Borrow.borrow_logic (C13Cloned_Cloned_Type.cloned_iter ( * self)) (C13Cloned_Cloned_Type.cloned_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span7] completed'1 (Borrow.borrow_logic (C13Cloned_Cloned_Type.cloned_iter ( * self)) (C13Cloned_Cloned_Type.cloned_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
-  constant empty'0 : Seq'0.t_seq t = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  constant empty'0 : Seq'0.t_seq t = [%#span10] ()
-  
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span11] inv'1 self)
-   -> ([%#span12] inv'1 other)
-   -> ([%#span15] inv'1 (concat'0 self other))
-  && ([%#span14] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span13] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'4 self)  -> ([%#span4] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span3] len'1 self >= 0
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq t) (o : i)
   
   predicate produces'0 [#"../13_cloned.rs" 28 4 28 64] (self : Cloned'0.t_cloned i) (visited : Seq'0.t_seq t) (o : Cloned'0.t_cloned i)
     
    =
-    [%#span16] exists s : Seq'0.t_seq t . inv'4 s
-    /\ produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
+    [%#span10] exists s : Seq'0.t_seq t . produces'1 (C13Cloned_Cloned_Type.cloned_iter self) s (C13Cloned_Cloned_Type.cloned_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
   goal produces_trans_refn : [%#s13_cloned0] forall a : Cloned'0.t_cloned i . forall ab : Seq'0.t_seq t . forall b : Cloned'0.t_cloned i . forall bc : Seq'0.t_seq t . forall c : Cloned'0.t_cloned i . inv'0 c
-  /\ inv'1 bc /\ inv'0 b /\ inv'1 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'0 c
-  /\ inv'1 bc
   /\ inv'0 b
-  /\ inv'1 ab
   /\ inv'0 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
@@ -877,14 +659,14 @@ module C13Cloned_Impl0
   /\ (forall result : () . produces'0 self (empty'0 : Seq'0.t_seq t) self
    -> produces'0 self (empty'1 : Seq'0.t_seq t) self)
   
-  goal next_refn : [%#s13_cloned2] forall self : borrowed (Cloned'0.t_cloned i) . inv'2 self
-   -> inv'2 self
-  /\ (forall result : Option'0.t_option t . inv'3 result
+  goal next_refn : [%#s13_cloned2] forall self : borrowed (Cloned'0.t_cloned i) . inv'1 self
+   -> inv'1 self
+  /\ (forall result : Option'0.t_option t . inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
     end
-   -> inv'3 result
+   -> inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
diff --git a/creusot/tests/should_succeed/iterators/14_copied.coma b/creusot/tests/should_succeed/iterators/14_copied.coma
index 558a436de7..f43b791afb 100644
--- a/creusot/tests/should_succeed/iterators/14_copied.coma
+++ b/creusot/tests/should_succeed/iterators/14_copied.coma
@@ -15,22 +15,7 @@ module C14Copied_Copied_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C14Copied_Impl0_ProducesRefl_Impl
   type i
@@ -41,130 +26,86 @@ module C14Copied_Impl0_ProducesRefl_Impl
   
   let%span s14_copied1 = "../14_copied.rs" 38 14 38 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span12 = "../common.rs" 18 15 18 32
+  let%span span6 = "../common.rs" 18 15 18 32
   
-  let%span span13 = "../common.rs" 19 15 19 32
+  let%span span7 = "../common.rs" 19 15 19 32
   
-  let%span span14 = "../common.rs" 21 22 21 23
+  let%span span8 = "../common.rs" 21 22 21 23
   
-  let%span span15 = "../common.rs" 21 31 21 33
+  let%span span9 = "../common.rs" 21 52 21 53
   
-  let%span span16 = "../common.rs" 21 52 21 53
+  let%span span10 = "../common.rs" 21 82 21 83
   
-  let%span span17 = "../common.rs" 21 61 21 63
+  let%span span11 = "../common.rs" 20 14 20 42
   
-  let%span span18 = "../common.rs" 21 82 21 83
+  let%span span12 = "../common.rs" 15 21 15 25
   
-  let%span span19 = "../common.rs" 20 14 20 42
+  let%span span13 = "../common.rs" 14 14 14 45
   
-  let%span span20 = "../common.rs" 15 21 15 25
+  let%span span14 = "../14_copied.rs" 29 8 33 9
   
-  let%span span21 = "../common.rs" 14 14 14 45
+  predicate invariant'1 (self : i)
   
-  let%span span22 = "../14_copied.rs" 29 8 33 9
+  predicate inv'1 (_x : i)
   
-  predicate invariant'3 (self : i)
-  
-  predicate inv'3 (_x : i)
-  
-  axiom inv'3 : forall x : i . inv'3 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq t)
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'2 self)  -> ([%#span3] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span4] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span6] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span2] len'1 self >= 0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span5] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  constant empty'1 : Seq'0.t_seq t
   
-  use seq.Seq
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span3] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span7] inv'2 self)
-   -> ([%#span8] inv'2 other)
-   -> ([%#span11] inv'2 (concat'0 self other))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span5] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span9] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span4] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq t) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq t) (b : i) (bc : Seq'0.t_seq t) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span12] produces'1 a ab b)
-   -> ([%#span13] produces'1 b bc c)
-   -> ([%#span14] inv'3 a)
-   -> ([%#span15] inv'2 ab)
-   -> ([%#span16] inv'3 b)
-   -> ([%#span17] inv'2 bc)  -> ([%#span18] inv'3 c)  -> ([%#span19] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span6] produces'1 a ab b)
+   -> ([%#span7] produces'1 b bc c)
+   -> ([%#span8] inv'1 a)
+   -> ([%#span9] inv'1 b)  -> ([%#span10] inv'1 c)  -> ([%#span11] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span20] inv'3 self)
-   -> ([%#span21] produces'1 self (empty'1 : Seq'0.t_seq t) self)
-  
-  predicate invariant'2 (self : Seq'0.t_seq t)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq t . inv'2 x = true
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
-  
-  predicate inv'1 (_x : Seq'0.t_seq t)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
-  
-  use seq.Seq
+  axiom produces_refl'0_spec : forall self : i . ([%#span12] inv'1 self)
+   -> ([%#span13] produces'1 self (empty'1 : Seq'0.t_seq t) self)
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C14Copied_Copied_Type as Copied'0
   
@@ -174,9 +115,7 @@ module C14Copied_Impl0_ProducesRefl_Impl
   
   axiom inv'0 : forall x : Copied'0.t_copied i . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   use C14Copied_Copied_Type as C14Copied_Copied_Type
   
@@ -185,8 +124,7 @@ module C14Copied_Impl0_ProducesRefl_Impl
   predicate produces'0 [#"../14_copied.rs" 28 4 28 64] (self : Copied'0.t_copied i) (visited : Seq'0.t_seq t) (o : Copied'0.t_copied i)
     
    =
-    [%#span22] exists s : Seq'0.t_seq t . inv'2 s
-    /\ produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
+    [%#span14] exists s : Seq'0.t_seq t . produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
@@ -208,140 +146,92 @@ module C14Copied_Impl0_ProducesTrans_Impl
   
   let%span s14_copied2 = "../14_copied.rs" 46 22 46 23
   
-  let%span s14_copied3 = "../14_copied.rs" 46 31 46 33
-  
-  let%span s14_copied4 = "../14_copied.rs" 46 52 46 53
-  
-  let%span s14_copied5 = "../14_copied.rs" 46 61 46 63
-  
-  let%span s14_copied6 = "../14_copied.rs" 46 82 46 83
-  
-  let%span s14_copied7 = "../14_copied.rs" 45 14 45 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s14_copied3 = "../14_copied.rs" 46 52 46 53
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span s14_copied4 = "../14_copied.rs" 46 82 46 83
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span s14_copied5 = "../14_copied.rs" 45 14 45 42
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span10 = "../common.rs" 18 15 18 32
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span11 = "../common.rs" 19 15 19 32
   
-  let%span span18 = "../common.rs" 18 15 18 32
+  let%span span12 = "../common.rs" 21 22 21 23
   
-  let%span span19 = "../common.rs" 19 15 19 32
+  let%span span13 = "../common.rs" 21 52 21 53
   
-  let%span span20 = "../common.rs" 21 22 21 23
+  let%span span14 = "../common.rs" 21 82 21 83
   
-  let%span span21 = "../common.rs" 21 31 21 33
+  let%span span15 = "../common.rs" 20 14 20 42
   
-  let%span span22 = "../common.rs" 21 52 21 53
+  let%span span16 = "../common.rs" 15 21 15 25
   
-  let%span span23 = "../common.rs" 21 61 21 63
+  let%span span17 = "../common.rs" 14 14 14 45
   
-  let%span span24 = "../common.rs" 21 82 21 83
+  let%span span18 = "../14_copied.rs" 29 8 33 9
   
-  let%span span25 = "../common.rs" 20 14 20 42
+  predicate invariant'1 (self : i)
   
-  let%span span26 = "../common.rs" 15 21 15 25
+  predicate inv'1 (_x : i)
   
-  let%span span27 = "../common.rs" 14 14 14 45
-  
-  let%span span28 = "../14_copied.rs" 29 8 33 9
-  
-  predicate invariant'3 (self : i)
-  
-  predicate inv'3 (_x : i)
-  
-  axiom inv'3 : forall x : i . inv'3 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq t)
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span8] inv'2 self)  -> ([%#span9] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span6] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq t = [%#span10] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'1 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span13] inv'2 self)
-   -> ([%#span14] inv'2 other)
-   -> ([%#span17] inv'2 (concat'1 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span15] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span8] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq t) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq t) (b : i) (bc : Seq'0.t_seq t) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span18] produces'1 a ab b)
-   -> ([%#span19] produces'1 b bc c)
-   -> ([%#span20] inv'3 a)
-   -> ([%#span21] inv'2 ab)
-   -> ([%#span22] inv'3 b)
-   -> ([%#span23] inv'2 bc)  -> ([%#span24] inv'3 c)  -> ([%#span25] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span10] produces'1 a ab b)
+   -> ([%#span11] produces'1 b bc c)
+   -> ([%#span12] inv'1 a)
+   -> ([%#span13] inv'1 b)  -> ([%#span14] inv'1 c)  -> ([%#span15] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span26] inv'3 self)
-   -> ([%#span27] produces'1 self (empty'1 : Seq'0.t_seq t) self)
-  
-  predicate invariant'2 (self : Seq'0.t_seq t)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq t . inv'2 x = true
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq t)
+  axiom produces_refl'0_spec : forall self : i . ([%#span16] inv'1 self)
+   -> ([%#span17] produces'1 self (empty'1 : Seq'0.t_seq t) self)
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq t = [%#span10] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span6] len'0 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq t)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use C14Copied_Copied_Type as Copied'0
   
@@ -351,21 +241,15 @@ module C14Copied_Impl0_ProducesTrans_Impl
   
   axiom inv'0 : forall x : Copied'0.t_copied i . inv'0 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   use C14Copied_Copied_Type as C14Copied_Copied_Type
   
@@ -374,8 +258,7 @@ module C14Copied_Impl0_ProducesTrans_Impl
   predicate produces'0 [#"../14_copied.rs" 28 4 28 64] (self : Copied'0.t_copied i) (visited : Seq'0.t_seq t) (o : Copied'0.t_copied i)
     
    =
-    [%#span28] exists s : Seq'0.t_seq t . inv'2 s
-    /\ produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
+    [%#span18] exists s : Seq'0.t_seq t . produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
@@ -392,13 +275,11 @@ module C14Copied_Impl0_ProducesTrans_Impl
   function produces_trans [#"../14_copied.rs" 46 4 46 90] (a : Copied'0.t_copied i) (ab : Seq'0.t_seq t) (b : Copied'0.t_copied i) (bc : Seq'0.t_seq t) (c : Copied'0.t_copied i) : ()
     
   
-  goal vc_produces_trans : ([%#s14_copied6] inv'0 c)
-   -> ([%#s14_copied5] inv'1 bc)
-   -> ([%#s14_copied4] inv'0 b)
-   -> ([%#s14_copied3] inv'1 ab)
+  goal vc_produces_trans : ([%#s14_copied4] inv'0 c)
+   -> ([%#s14_copied3] inv'0 b)
    -> ([%#s14_copied2] inv'0 a)
    -> ([%#s14_copied1] produces'0 b bc c)
-   -> ([%#s14_copied0] produces'0 a ab b)  -> ([%#s14_copied7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s14_copied0] produces'0 a ab b)  -> ([%#s14_copied5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -427,87 +308,55 @@ module C14Copied_Impl0_Next
   
   let%span s14_copied2 = "../14_copied.rs" 52 26 52 35
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "../common.rs" 18 15 18 32
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../common.rs" 19 15 19 32
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span9 = "../common.rs" 21 22 21 23
   
-  let%span span13 = "../common.rs" 18 15 18 32
+  let%span span10 = "../common.rs" 21 52 21 53
   
-  let%span span14 = "../common.rs" 19 15 19 32
+  let%span span11 = "../common.rs" 21 82 21 83
   
-  let%span span15 = "../common.rs" 21 22 21 23
+  let%span span12 = "../common.rs" 20 14 20 42
   
-  let%span span16 = "../common.rs" 21 31 21 33
+  let%span span13 = "../common.rs" 15 21 15 25
   
-  let%span span17 = "../common.rs" 21 52 21 53
+  let%span span14 = "../common.rs" 14 14 14 45
   
-  let%span span18 = "../common.rs" 21 61 21 63
+  let%span span15 = "../14_copied.rs" 29 8 33 9
   
-  let%span span19 = "../common.rs" 21 82 21 83
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span20 = "../common.rs" 20 14 20 42
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span21 = "../common.rs" 15 21 15 25
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span22 = "../common.rs" 14 14 14 45
+  let%span span19 = "../14_copied.rs" 23 8 23 43
   
-  let%span span23 = "../14_copied.rs" 29 8 33 9
+  let%span span20 = "" 0 0 0 0
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span21 = "../../../../../creusot-contracts/src/std/option.rs" 98 16 98 59
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span22 = "../../../../../creusot-contracts/src/std/option.rs" 29 0 140 1
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span23 = "" 0 0 0 0
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span24 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span28 = "../14_copied.rs" 23 8 23 43
+  let%span span25 = "../common.rs" 27 17 27 21
   
-  let%span span29 = "" 0 0 0 0
+  let%span span26 = "../common.rs" 23 14 26 5
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/option.rs" 98 16 98 59
-  
-  let%span span31 = "../../../../../creusot-contracts/src/std/option.rs" 29 0 140 1
-  
-  let%span span32 = "" 0 0 0 0
-  
-  let%span span33 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span34 = "../common.rs" 27 17 27 21
-  
-  let%span span35 = "../common.rs" 23 14 26 5
-  
-  let%span span36 = "../common.rs" 27 26 27 44
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'8 (self : Seq'0.t_seq t)
-  
-  predicate inv'8 (_x : Seq'0.t_seq t)
-  
-  axiom inv'8 : forall x : Seq'0.t_seq t . inv'8 x = true
-  
-  predicate invariant'7 (self : Seq'0.t_seq t)
-  
-  predicate inv'7 (_x : Seq'0.t_seq t)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq t . inv'7 x = true
+  let%span span27 = "../common.rs" 27 26 27 44
   
   predicate invariant'6 (self : t)
   
@@ -531,20 +380,17 @@ module C14Copied_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'8 self)  -> ([%#span4] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span3] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span4] len'1 (empty'0 : Seq'0.t_seq t) = 0
   
   use prelude.prelude.Borrow
   
@@ -560,18 +406,15 @@ module C14Copied_Impl0_Next
   
   axiom inv'2 : forall x : Option'0.t_option t . inv'2 x = true
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span3] inv'7 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
-  constant empty'1 : Seq'0.t_seq t = [%#span5] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'1 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'1 : Seq'0.t_seq t) = 0
   
   use C14Copied_Copied_Type as Copied'0
   
@@ -581,21 +424,15 @@ module C14Copied_Impl0_Next
   
   axiom inv'1 : forall x : borrowed (Copied'0.t_copied i) . inv'1 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span8] inv'8 self)
-   -> ([%#span9] inv'8 other)
-   -> ([%#span12] inv'8 (concat'0 self other))
-  && ([%#span11] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span6] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span10] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span5] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : i)
   
@@ -604,75 +441,64 @@ module C14Copied_Impl0_Next
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq t) (b : i) (bc : Seq'0.t_seq t) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span13] produces'1 a ab b)
-   -> ([%#span14] produces'1 b bc c)
-   -> ([%#span15] inv'0 a)
-   -> ([%#span16] inv'8 ab)
-   -> ([%#span17] inv'0 b)
-   -> ([%#span18] inv'8 bc)  -> ([%#span19] inv'0 c)  -> ([%#span20] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq t, b : i, bc : Seq'0.t_seq t, c : i . ([%#span7] produces'1 a ab b)
+   -> ([%#span8] produces'1 b bc c)
+   -> ([%#span9] inv'0 a)
+   -> ([%#span10] inv'0 b)  -> ([%#span11] inv'0 c)  -> ([%#span12] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span21] inv'0 self)
-   -> ([%#span22] produces'1 self (empty'0 : Seq'0.t_seq t) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span13] inv'0 self)
+   -> ([%#span14] produces'1 self (empty'0 : Seq'0.t_seq t) self)
   
   predicate invariant'0 (self : i)
   
   axiom inv'0 : forall x : i . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   use C14Copied_Copied_Type as C14Copied_Copied_Type
   
   predicate produces'0 [#"../14_copied.rs" 28 4 28 64] (self : Copied'0.t_copied i) (visited : Seq'0.t_seq t) (o : Copied'0.t_copied i)
     
    =
-    [%#span23] exists s : Seq'0.t_seq t . inv'8 s
-    /\ produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
+    [%#span15] exists s : Seq'0.t_seq t . produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
-  use seq.Seq
-  
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span24] inv'6 v)
-   -> ([%#span27] inv'7 (singleton'0 v))
-  && ([%#span26] index_logic'0 (singleton'0 v) 0 = v) && ([%#span25] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span16] inv'6 v)
+   -> ([%#span18] index_logic'0 (singleton'0 v) 0 = v) && ([%#span17] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate completed'0 [#"../14_copied.rs" 22 4 22 35] (self : borrowed (Copied'0.t_copied i)) =
-    [%#span28] completed'1 (Borrow.borrow_logic (C14Copied_Copied_Type.copied_iter ( * self)) (C14Copied_Copied_Type.copied_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span19] completed'1 (Borrow.borrow_logic (C14Copied_Copied_Type.copied_iter ( * self)) (C14Copied_Copied_Type.copied_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
   use prelude.prelude.Intrinsic
   
-  let rec copied'0 (self:Option'0.t_option t) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span29] inv'4 self}
+  let rec copied'0 (self:Option'0.t_option t) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span20] inv'4 self}
     any
-    [ return' (result:Option'0.t_option t)-> {[%#span32] inv'2 result}
-      {[%#span31] self = Option'0.C_None
+    [ return' (result:Option'0.t_option t)-> {[%#span23] inv'2 result}
+      {[%#span22] self = Option'0.C_None
       \/ (exists t : t . inv'5 t /\ self = Option'0.C_Some t /\ result = Option'0.C_Some t)}
-      {[%#span30] self = Option'0.C_None  -> result = Option'0.C_None}
+      {[%#span21] self = Option'0.C_None  -> result = Option'0.C_None}
       (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (Copied'0.t_copied i)) =
-    [%#span33]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span24]  ^ self =  * self
   
   function singleton'1 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'1_spec : forall v : t . ([%#span24] inv'5 v)
-   -> ([%#span27] inv'8 (singleton'1 v))
-  && ([%#span26] index_logic'1 (singleton'1 v) 0 = v) && ([%#span25] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : t . ([%#span16] inv'5 v)
+   -> ([%#span18] index_logic'1 (singleton'1 v) 0 = v) && ([%#span17] len'1 (singleton'1 v) = 1)
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span34] inv'3 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option t))= {[@expl:precondition] [%#span25] inv'3 self}
     any
-    [ return' (result:Option'0.t_option t)-> {[%#span36] inv'4 result}
-      {[%#span35] match result with
+    [ return' (result:Option'0.t_option t)-> {[%#span27] inv'4 result}
+      {[%#span26] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'1 v) ( ^ self)
         end}
@@ -725,71 +551,45 @@ module C14Copied_Impl0
   
   let%span s14_copied2 = "../14_copied.rs" 39 4 39 26
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span10 = "../14_copied.rs" 23 8 23 43
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span7 = "../14_copied.rs" 23 8 23 43
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span10 = "../14_copied.rs" 29 8 33 9
   
-  let%span span16 = "../14_copied.rs" 29 8 33 9
+  predicate invariant'3 (self : t)
   
-  predicate invariant'5 (self : t)
-  
-  predicate inv'5 (_x : t)
-  
-  axiom inv'5 : forall x : t . inv'5 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'3 (_x : t)
   
-  predicate invariant'4 (self : Seq'0.t_seq t)
-  
-  predicate inv'4 (_x : Seq'0.t_seq t)
-  
-  axiom inv'4 : forall x : Seq'0.t_seq t . inv'4 x = true
+  axiom inv'3 : forall x : t . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'3 (self : Option'0.t_option t)
+  predicate invariant'2 (self : Option'0.t_option t)
   
-  predicate inv'3 (_x : Option'0.t_option t)
+  predicate inv'2 (_x : Option'0.t_option t)
   
-  axiom inv'3 : forall x : Option'0.t_option t . inv'3 x = true
+  axiom inv'2 : forall x : Option'0.t_option t . inv'2 x = true
   
   use C14Copied_Copied_Type as Copied'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'2 (self : borrowed (Copied'0.t_copied i))
-  
-  predicate inv'2 (_x : borrowed (Copied'0.t_copied i))
-  
-  axiom inv'2 : forall x : borrowed (Copied'0.t_copied i) . inv'2 x = true
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
+  predicate invariant'1 (self : borrowed (Copied'0.t_copied i))
   
-  predicate inv'1 (_x : Seq'0.t_seq t)
+  predicate inv'1 (_x : borrowed (Copied'0.t_copied i))
   
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
+  axiom inv'1 : forall x : borrowed (Copied'0.t_copied i) . inv'1 x = true
   
   predicate invariant'0 (self : Copied'0.t_copied i)
   
@@ -797,89 +597,71 @@ module C14Copied_Impl0
   
   axiom inv'0 : forall x : Copied'0.t_copied i . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq t = [%#span3] ()
-  
-  constant empty'0 : Seq'0.t_seq t = [%#span3] ()
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq t
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant empty'0 : Seq'0.t_seq t
   
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  use prelude.prelude.Int
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span4] inv'1 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span3] len'0 self >= 0
   
   function singleton'0 (v : t) : Seq'0.t_seq t
   
-  axiom singleton'0_spec : forall v : t . ([%#span6] inv'5 v)
-   -> ([%#span9] inv'1 (singleton'0 v))
-  && ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : t . ([%#span4] inv'3 v)
+   -> ([%#span6] index_logic'0 (singleton'0 v) 0 = v) && ([%#span5] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   use C14Copied_Copied_Type as C14Copied_Copied_Type
   
   predicate completed'0 [#"../14_copied.rs" 22 4 22 35] (self : borrowed (Copied'0.t_copied i)) =
-    [%#span10] completed'1 (Borrow.borrow_logic (C14Copied_Copied_Type.copied_iter ( * self)) (C14Copied_Copied_Type.copied_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
-  
-  use seq.Seq
+    [%#span7] completed'1 (Borrow.borrow_logic (C14Copied_Copied_Type.copied_iter ( * self)) (C14Copied_Copied_Type.copied_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
   function concat'0 (self : Seq'0.t_seq t) (other : Seq'0.t_seq t) : Seq'0.t_seq t
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span11] inv'1 self)
-   -> ([%#span12] inv'1 other)
-   -> ([%#span15] inv'1 (concat'0 self other))
-  && ([%#span14] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq t, other : Seq'0.t_seq t . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span13] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span4] inv'4 self)  -> ([%#span5] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span3] len'1 self >= 0
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq t) (o : i)
   
   predicate produces'0 [#"../14_copied.rs" 28 4 28 64] (self : Copied'0.t_copied i) (visited : Seq'0.t_seq t) (o : Copied'0.t_copied i)
     
    =
-    [%#span16] exists s : Seq'0.t_seq t . inv'4 s
-    /\ produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
+    [%#span10] exists s : Seq'0.t_seq t . produces'1 (C14Copied_Copied_Type.copied_iter self) s (C14Copied_Copied_Type.copied_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s  -> index_logic'0 visited i = index_logic'1 s i)
   
   goal produces_trans_refn : [%#s14_copied0] forall a : Copied'0.t_copied i . forall ab : Seq'0.t_seq t . forall b : Copied'0.t_copied i . forall bc : Seq'0.t_seq t . forall c : Copied'0.t_copied i . inv'0 c
-  /\ inv'1 bc /\ inv'0 b /\ inv'1 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'0 c
-  /\ inv'1 bc
   /\ inv'0 b
-  /\ inv'1 ab
   /\ inv'0 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
   
-  goal next_refn : [%#s14_copied1] forall self : borrowed (Copied'0.t_copied i) . inv'2 self
-   -> inv'2 self
-  /\ (forall result : Option'0.t_option t . inv'3 result
+  goal next_refn : [%#s14_copied1] forall self : borrowed (Copied'0.t_copied i) . inv'1 self
+   -> inv'1 self
+  /\ (forall result : Option'0.t_option t . inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
     end
-   -> inv'3 result
+   -> inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
diff --git a/creusot/tests/should_succeed/iterators/15_enumerate.coma b/creusot/tests/should_succeed/iterators/15_enumerate.coma
index a12d45e813..99f8872d19 100644
--- a/creusot/tests/should_succeed/iterators/15_enumerate.coma
+++ b/creusot/tests/should_succeed/iterators/15_enumerate.coma
@@ -25,22 +25,7 @@ module C15Enumerate_Enumerate_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C15Enumerate_Impl0_ProducesRefl_Impl
   type i
@@ -49,150 +34,107 @@ module C15Enumerate_Impl0_ProducesRefl_Impl
   
   let%span s15_enumerate1 = "../15_enumerate.rs" 39 14 39 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span12 = "../common.rs" 18 15 18 32
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span13 = "../common.rs" 19 15 19 32
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span14 = "../common.rs" 21 22 21 23
+  let%span span6 = "../common.rs" 18 15 18 32
   
-  let%span span15 = "../common.rs" 21 31 21 33
+  let%span span7 = "../common.rs" 19 15 19 32
   
-  let%span span16 = "../common.rs" 21 52 21 53
+  let%span span8 = "../common.rs" 21 22 21 23
   
-  let%span span17 = "../common.rs" 21 61 21 63
+  let%span span9 = "../common.rs" 21 52 21 53
   
-  let%span span18 = "../common.rs" 21 82 21 83
+  let%span span10 = "../common.rs" 21 82 21 83
   
-  let%span span19 = "../common.rs" 20 14 20 42
+  let%span span11 = "../common.rs" 20 14 20 42
   
-  let%span span20 = "../common.rs" 15 21 15 25
+  let%span span12 = "../common.rs" 15 21 15 25
   
-  let%span span21 = "../common.rs" 14 14 14 45
+  let%span span13 = "../common.rs" 14 14 14 45
   
-  let%span span22 = "" 0 0 0 0
+  let%span span14 = "" 0 0 0 0
   
-  let%span span23 = "../15_enumerate.rs" 73 12 74 79
+  let%span span15 = "../15_enumerate.rs" 73 12 74 79
   
-  let%span span24 = "../15_enumerate.rs" 29 8 34 9
+  let%span span16 = "../15_enumerate.rs" 29 8 34 9
   
   use prelude.prelude.Borrow
   
-  predicate invariant'4 (self : borrowed i)
+  predicate invariant'2 (self : borrowed i)
   
-  predicate inv'4 (_x : borrowed i)
+  predicate inv'2 (_x : borrowed i)
   
-  axiom inv'4 : forall x : borrowed i . inv'4 x = true
+  axiom inv'2 : forall x : borrowed i . inv'2 x = true
   
-  predicate invariant'3 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'3 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'3 : forall x : i . inv'3 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   type item'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
-  
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'2 self)  -> ([%#span3] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span4] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span6] ()
-  
-  axiom empty_len'1_spec : forall _1 : () . [%#span5] len'1 (empty'1 : Seq'0.t_seq item'0) = 0
-  
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
-  
-  use prelude.prelude.UIntSize
-  
-  predicate invariant'1 (self : Seq'0.t_seq (usize, item'0))
-  
-  predicate inv'1 (_x : Seq'0.t_seq (usize, item'0))
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'1 self >= 0
   
-  axiom inv'1 : forall x : Seq'0.t_seq (usize, item'0) . inv'1 x = true
+  constant empty'1 : Seq'0.t_seq item'0
   
-  use seq.Seq
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span3] len'1 (empty'1 : Seq'0.t_seq item'0) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span7] inv'2 self)
-   -> ([%#span8] inv'2 other)
-   -> ([%#span11] inv'2 (concat'0 self other))
-  && ([%#span10] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span5] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span9] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span4] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span12] produces'1 a ab b)
-   -> ([%#span13] produces'1 b bc c)
-   -> ([%#span14] inv'3 a)
-   -> ([%#span15] inv'2 ab)
-   -> ([%#span16] inv'3 b)
-   -> ([%#span17] inv'2 bc)  -> ([%#span18] inv'3 c)  -> ([%#span19] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span6] produces'1 a ab b)
+   -> ([%#span7] produces'1 b bc c)
+   -> ([%#span8] inv'1 a)
+   -> ([%#span9] inv'1 b)  -> ([%#span10] inv'1 c)  -> ([%#span11] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span20] inv'3 self)
-   -> ([%#span21] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span12] inv'1 self)
+   -> ([%#span13] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
-  use seq.Seq
+  use prelude.prelude.UIntSize
   
   function len'0 (self : Seq'0.t_seq (usize, item'0)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (usize, item'0) = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq (usize, item'0)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq (usize, item'0)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq (usize, item'0)) = 0
   
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
-  constant max'0 : usize = [%#span22] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span14] (18446744073709551615 : usize)
   
   use prelude.prelude.UIntSize
   
@@ -201,11 +143,10 @@ module C15Enumerate_Impl0_ProducesRefl_Impl
   use C15Enumerate_Enumerate_Type as Enumerate'0
   
   predicate invariant'0 [#"../15_enumerate.rs" 71 4 71 30] (self : Enumerate'0.t_enumerate i) =
-    [%#span23] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'3 i
-     -> inv'2 s
+    [%#span15] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'1 i
      -> produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s i
      -> UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self) + len'1 s < UIntSize.to_int max'0)
-    /\ (forall i : borrowed i . inv'4 i  -> completed'0 i  -> produces'1 ( * i) (empty'1 : Seq'0.t_seq item'0) ( ^ i))
+    /\ (forall i : borrowed i . inv'2 i  -> completed'0 i  -> produces'1 ( * i) (empty'1 : Seq'0.t_seq item'0) ( ^ i))
   
   predicate inv'0 (_x : Enumerate'0.t_enumerate i)
   
@@ -215,18 +156,15 @@ module C15Enumerate_Impl0_ProducesRefl_Impl
     | Enumerate'0.C_Enumerate iter count -> true
     end)
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (x : int) : (usize, item'0)
+  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (_2 : int) : (usize, item'0)
   
   predicate produces'0 [#"../15_enumerate.rs" 28 4 28 64] (self : Enumerate'0.t_enumerate i) (visited : Seq'0.t_seq (usize, item'0)) (o : Enumerate'0.t_enumerate i)
     
    =
-    [%#span24] len'0 visited
+    [%#span16] len'0 visited
     = UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count o)
     - UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'2 s
-    /\ produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
+    /\ (exists s : Seq'0.t_seq item'0 . produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s
      -> UIntSize.to_int (let (a, _) = index_logic'0 visited i in a)
@@ -249,160 +187,113 @@ module C15Enumerate_Impl0_ProducesTrans_Impl
   
   let%span s15_enumerate2 = "../15_enumerate.rs" 47 22 47 23
   
-  let%span s15_enumerate3 = "../15_enumerate.rs" 47 31 47 33
-  
-  let%span s15_enumerate4 = "../15_enumerate.rs" 47 52 47 53
-  
-  let%span s15_enumerate5 = "../15_enumerate.rs" 47 61 47 63
-  
-  let%span s15_enumerate6 = "../15_enumerate.rs" 47 82 47 83
-  
-  let%span s15_enumerate7 = "../15_enumerate.rs" 46 14 46 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s15_enumerate3 = "../15_enumerate.rs" 47 52 47 53
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span s15_enumerate4 = "../15_enumerate.rs" 47 82 47 83
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span s15_enumerate5 = "../15_enumerate.rs" 46 14 46 42
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span10 = "../common.rs" 18 15 18 32
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span11 = "../common.rs" 19 15 19 32
   
-  let%span span18 = "../common.rs" 18 15 18 32
+  let%span span12 = "../common.rs" 21 22 21 23
   
-  let%span span19 = "../common.rs" 19 15 19 32
+  let%span span13 = "../common.rs" 21 52 21 53
   
-  let%span span20 = "../common.rs" 21 22 21 23
+  let%span span14 = "../common.rs" 21 82 21 83
   
-  let%span span21 = "../common.rs" 21 31 21 33
+  let%span span15 = "../common.rs" 20 14 20 42
   
-  let%span span22 = "../common.rs" 21 52 21 53
+  let%span span16 = "../common.rs" 15 21 15 25
   
-  let%span span23 = "../common.rs" 21 61 21 63
+  let%span span17 = "../common.rs" 14 14 14 45
   
-  let%span span24 = "../common.rs" 21 82 21 83
+  let%span span18 = "" 0 0 0 0
   
-  let%span span25 = "../common.rs" 20 14 20 42
+  let%span span19 = "../15_enumerate.rs" 73 12 74 79
   
-  let%span span26 = "../common.rs" 15 21 15 25
-  
-  let%span span27 = "../common.rs" 14 14 14 45
-  
-  let%span span28 = "" 0 0 0 0
-  
-  let%span span29 = "../15_enumerate.rs" 73 12 74 79
-  
-  let%span span30 = "../15_enumerate.rs" 29 8 34 9
+  let%span span20 = "../15_enumerate.rs" 29 8 34 9
   
   use prelude.prelude.Borrow
   
-  predicate invariant'4 (self : borrowed i)
+  predicate invariant'2 (self : borrowed i)
   
-  predicate inv'4 (_x : borrowed i)
+  predicate inv'2 (_x : borrowed i)
   
-  axiom inv'4 : forall x : borrowed i . inv'4 x = true
+  axiom inv'2 : forall x : borrowed i . inv'2 x = true
   
-  predicate invariant'3 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'3 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'3 : forall x : i . inv'3 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   type item'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
-  
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'2 self)  -> ([%#span9] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq item'0 = [%#span10] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'1 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'1 : Seq'0.t_seq item'0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq item'0) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
+  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'1 (empty'1 : Seq'0.t_seq item'0) = 0
   
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
-  
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'1 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span13] inv'2 self)
-   -> ([%#span14] inv'2 other)
-   -> ([%#span17] inv'2 (concat'1 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'1 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'1 self other)
    -> index_logic'1 (concat'1 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span15] len'1 (concat'1 self other) = len'1 self + len'1 other)
+  && ([%#span8] len'1 (concat'1 self other) = len'1 self + len'1 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span18] produces'1 a ab b)
-   -> ([%#span19] produces'1 b bc c)
-   -> ([%#span20] inv'3 a)
-   -> ([%#span21] inv'2 ab)
-   -> ([%#span22] inv'3 b)
-   -> ([%#span23] inv'2 bc)  -> ([%#span24] inv'3 c)  -> ([%#span25] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span10] produces'1 a ab b)
+   -> ([%#span11] produces'1 b bc c)
+   -> ([%#span12] inv'1 a)
+   -> ([%#span13] inv'1 b)  -> ([%#span14] inv'1 c)  -> ([%#span15] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span26] inv'3 self)
-   -> ([%#span27] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
-  
-  use seq.Seq
+  axiom produces_refl'0_spec : forall self : i . ([%#span16] inv'1 self)
+   -> ([%#span17] produces'1 self (empty'1 : Seq'0.t_seq item'0) self)
   
   use prelude.prelude.UIntSize
   
-  predicate inv'1 (_x : Seq'0.t_seq (usize, item'0))
-  
   function len'0 (self : Seq'0.t_seq (usize, item'0)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq (usize, item'0) = [%#span10] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . [%#span6] len'0 self >= 0
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq (usize, item'0)) = 0
+  constant empty'0 : Seq'0.t_seq (usize, item'0)
   
-  predicate invariant'1 (self : Seq'0.t_seq (usize, item'0))
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom inv'1 : forall x : Seq'0.t_seq (usize, item'0) . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq (usize, item'0)) = 0
   
   predicate completed'0 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
-  constant max'0 : usize = [%#span28] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span18] (18446744073709551615 : usize)
   
   use prelude.prelude.UIntSize
   
@@ -411,11 +302,10 @@ module C15Enumerate_Impl0_ProducesTrans_Impl
   use C15Enumerate_Enumerate_Type as Enumerate'0
   
   predicate invariant'0 [#"../15_enumerate.rs" 71 4 71 30] (self : Enumerate'0.t_enumerate i) =
-    [%#span29] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'3 i
-     -> inv'2 s
+    [%#span19] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'1 i
      -> produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s i
      -> UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self) + len'1 s < UIntSize.to_int max'0)
-    /\ (forall i : borrowed i . inv'4 i  -> completed'0 i  -> produces'1 ( * i) (empty'1 : Seq'0.t_seq item'0) ( ^ i))
+    /\ (forall i : borrowed i . inv'2 i  -> completed'0 i  -> produces'1 ( * i) (empty'1 : Seq'0.t_seq item'0) ( ^ i))
   
   predicate inv'0 (_x : Enumerate'0.t_enumerate i)
   
@@ -425,31 +315,25 @@ module C15Enumerate_Impl0_ProducesTrans_Impl
     | Enumerate'0.C_Enumerate iter count -> true
     end)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (x : int) : (usize, item'0)
+  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (_2 : int) : (usize, item'0)
   
   function concat'0 (self : Seq'0.t_seq (usize, item'0)) (other : Seq'0.t_seq (usize, item'0)) : Seq'0.t_seq (usize, item'0)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, item'0), other : Seq'0.t_seq (usize, item'0) . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, item'0), other : Seq'0.t_seq (usize, item'0) . ([%#span9] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'0 [#"../15_enumerate.rs" 28 4 28 64] (self : Enumerate'0.t_enumerate i) (visited : Seq'0.t_seq (usize, item'0)) (o : Enumerate'0.t_enumerate i)
     
    =
-    [%#span30] len'0 visited
+    [%#span20] len'0 visited
     = UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count o)
     - UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'2 s
-    /\ produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
+    /\ (exists s : Seq'0.t_seq item'0 . produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s
      -> UIntSize.to_int (let (a, _) = index_logic'0 visited i in a)
@@ -469,13 +353,11 @@ module C15Enumerate_Impl0_ProducesTrans_Impl
   function produces_trans [#"../15_enumerate.rs" 47 4 47 90] (a : Enumerate'0.t_enumerate i) (ab : Seq'0.t_seq (usize, item'0)) (b : Enumerate'0.t_enumerate i) (bc : Seq'0.t_seq (usize, item'0)) (c : Enumerate'0.t_enumerate i) : ()
     
   
-  goal vc_produces_trans : ([%#s15_enumerate6] inv'0 c)
-   -> ([%#s15_enumerate5] inv'1 bc)
-   -> ([%#s15_enumerate4] inv'0 b)
-   -> ([%#s15_enumerate3] inv'1 ab)
+  goal vc_produces_trans : ([%#s15_enumerate4] inv'0 c)
+   -> ([%#s15_enumerate3] inv'0 b)
    -> ([%#s15_enumerate2] inv'0 a)
    -> ([%#s15_enumerate1] produces'0 b bc c)
-   -> ([%#s15_enumerate0] produces'0 a ab b)  -> ([%#s15_enumerate7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s15_enumerate0] produces'0 a ab b)  -> ([%#s15_enumerate5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -506,69 +388,51 @@ module C15Enumerate_Impl0_Next
   
   let%span s15_enumerate4 = "../15_enumerate.rs" 53 26 53 44
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span6 = "" 0 0 0 0
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span9 = "../15_enumerate.rs" 73 12 74 79
+  let%span span5 = "" 0 0 0 0
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span7 = "../15_enumerate.rs" 73 12 74 79
   
-  let%span span17 = "../common.rs" 18 15 18 32
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span18 = "../common.rs" 19 15 19 32
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span19 = "../common.rs" 21 22 21 23
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span20 = "../common.rs" 21 31 21 33
+  let%span span11 = "../common.rs" 18 15 18 32
   
-  let%span span21 = "../common.rs" 21 52 21 53
+  let%span span12 = "../common.rs" 19 15 19 32
   
-  let%span span22 = "../common.rs" 21 61 21 63
+  let%span span13 = "../common.rs" 21 22 21 23
   
-  let%span span23 = "../common.rs" 21 82 21 83
+  let%span span14 = "../common.rs" 21 52 21 53
   
-  let%span span24 = "../common.rs" 20 14 20 42
+  let%span span15 = "../common.rs" 21 82 21 83
   
-  let%span span25 = "../common.rs" 15 21 15 25
+  let%span span16 = "../common.rs" 20 14 20 42
   
-  let%span span26 = "../common.rs" 14 14 14 45
+  let%span span17 = "../common.rs" 15 21 15 25
   
-  let%span span27 = "../15_enumerate.rs" 29 8 34 9
+  let%span span18 = "../common.rs" 14 14 14 45
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span19 = "../15_enumerate.rs" 29 8 34 9
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span32 = "../15_enumerate.rs" 23 8 23 43
+  let%span span23 = "../15_enumerate.rs" 23 8 23 43
   
-  let%span span33 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span24 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span34 = "../common.rs" 27 17 27 21
+  let%span span25 = "../common.rs" 27 17 27 21
   
-  let%span span35 = "../common.rs" 23 14 26 5
+  let%span span26 = "../common.rs" 23 14 26 5
   
-  let%span span36 = "../common.rs" 27 26 27 44
+  let%span span27 = "../common.rs" 27 26 27 44
   
   predicate inv'0 (_x : i)
   
@@ -578,9 +442,7 @@ module C15Enumerate_Impl0_Next
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'7 (_x : Seq'0.t_seq item'0)
-  
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   use prelude.prelude.Borrow
   
@@ -590,15 +452,11 @@ module C15Enumerate_Impl0_Next
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span6] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span7] inv'7 self)  -> ([%#span8] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'1 self >= 0
   
   use prelude.prelude.UIntSize
   
@@ -608,36 +466,25 @@ module C15Enumerate_Impl0_Next
   
   use C15Enumerate_Enumerate_Type as Enumerate'0
   
-  predicate invariant'9 [#"../15_enumerate.rs" 71 4 71 30] (self : Enumerate'0.t_enumerate i) =
-    [%#span9] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'0 i
-     -> inv'7 s
+  predicate invariant'7 [#"../15_enumerate.rs" 71 4 71 30] (self : Enumerate'0.t_enumerate i) =
+    [%#span7] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'0 i
      -> produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s i
      -> UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self) + len'1 s < UIntSize.to_int max'0)
     /\ (forall i : borrowed i . inv'4 i  -> completed'1 i  -> produces'1 ( * i) (empty'0 : Seq'0.t_seq item'0) ( ^ i))
   
-  predicate inv'9 (_x : Enumerate'0.t_enumerate i)
+  predicate inv'7 (_x : Enumerate'0.t_enumerate i)
   
-  axiom inv'9 : forall x : Enumerate'0.t_enumerate i . inv'9 x
-  = (invariant'9 x
+  axiom inv'7 : forall x : Enumerate'0.t_enumerate i . inv'7 x
+  = (invariant'7 x
   /\ match x with
     | Enumerate'0.C_Enumerate iter count -> true
     end)
   
-  predicate invariant'8 (self : item'0)
-  
-  predicate inv'8 (_x : item'0)
-  
-  axiom inv'8 : forall x : item'0 . inv'8 x = true
-  
-  predicate invariant'7 (self : Seq'0.t_seq item'0)
+  predicate invariant'6 (self : item'0)
   
-  axiom inv'7 : forall x : Seq'0.t_seq item'0 . inv'7 x = true
+  predicate inv'6 (_x : item'0)
   
-  predicate invariant'6 (self : Seq'0.t_seq (usize, item'0))
-  
-  predicate inv'6 (_x : Seq'0.t_seq (usize, item'0))
-  
-  axiom inv'6 : forall x : Seq'0.t_seq (usize, item'0) . inv'6 x = true
+  axiom inv'6 : forall x : item'0 . inv'6 x = true
   
   predicate invariant'5 (self : (usize, item'0))
   
@@ -645,10 +492,9 @@ module C15Enumerate_Impl0_Next
   
   axiom inv'5 : forall x : (usize, item'0) . inv'5 x = true
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span11] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span10] len'1 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span8] len'1 (empty'0 : Seq'0.t_seq item'0) = 0
   
   predicate invariant'4 (self : borrowed i)
   
@@ -662,18 +508,15 @@ module C15Enumerate_Impl0_Next
   
   axiom inv'3 : forall x : Option'0.t_option (usize, item'0) . inv'3 x = true
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq (usize, item'0)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . ([%#span7] inv'6 self)  -> ([%#span8] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . [%#span6] len'0 self >= 0
   
-  constant empty'1 : Seq'0.t_seq (usize, item'0) = [%#span5] ()
+  constant empty'1 : Seq'0.t_seq (usize, item'0)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span11] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'1 : Seq'0.t_seq (usize, item'0)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'1 : Seq'0.t_seq (usize, item'0)) = 0
   
   predicate invariant'2 (self : Option'0.t_option item'0)
   
@@ -685,91 +528,75 @@ module C15Enumerate_Impl0_Next
   
   predicate inv'1 (_x : borrowed (Enumerate'0.t_enumerate i))
   
-  axiom inv'1 : forall x : borrowed (Enumerate'0.t_enumerate i) . inv'1 x = (inv'9 ( * x) /\ inv'9 ( ^ x))
-  
-  use seq.Seq
+  axiom inv'1 : forall x : borrowed (Enumerate'0.t_enumerate i) . inv'1 x = (inv'7 ( * x) /\ inv'7 ( ^ x))
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span12] inv'7 self)
-   -> ([%#span13] inv'7 other)
-   -> ([%#span16] inv'7 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span14] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span9] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span17] produces'1 a ab b)
-   -> ([%#span18] produces'1 b bc c)
-   -> ([%#span19] inv'0 a)
-   -> ([%#span20] inv'7 ab)
-   -> ([%#span21] inv'0 b)
-   -> ([%#span22] inv'7 bc)  -> ([%#span23] inv'0 c)  -> ([%#span24] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span11] produces'1 a ab b)
+   -> ([%#span12] produces'1 b bc c)
+   -> ([%#span13] inv'0 a)
+   -> ([%#span14] inv'0 b)  -> ([%#span15] inv'0 c)  -> ([%#span16] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span25] inv'0 self)
-   -> ([%#span26] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span17] inv'0 self)
+   -> ([%#span18] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'0 (self : i)
   
   axiom inv'0 : forall x : i . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (x : int) : (usize, item'0)
+  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (_2 : int) : (usize, item'0)
   
   predicate produces'0 [#"../15_enumerate.rs" 28 4 28 64] (self : Enumerate'0.t_enumerate i) (visited : Seq'0.t_seq (usize, item'0)) (o : Enumerate'0.t_enumerate i)
     
    =
-    [%#span27] len'0 visited
+    [%#span19] len'0 visited
     = UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count o)
     - UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'7 s
-    /\ produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
+    /\ (exists s : Seq'0.t_seq item'0 . produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s
      -> UIntSize.to_int (let (a, _) = index_logic'0 visited i in a)
     = UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self) + i
     /\ (let (_, a) = index_logic'0 visited i in a) = index_logic'1 s i))
   
-  use seq.Seq
-  
   function singleton'0 (v : (usize, item'0)) : Seq'0.t_seq (usize, item'0)
   
-  axiom singleton'0_spec : forall v : (usize, item'0) . ([%#span28] inv'5 v)
-   -> ([%#span31] inv'6 (singleton'0 v))
-  && ([%#span30] index_logic'0 (singleton'0 v) 0 = v) && ([%#span29] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (usize, item'0) . ([%#span20] inv'5 v)
+   -> ([%#span22] index_logic'0 (singleton'0 v) 0 = v) && ([%#span21] len'0 (singleton'0 v) = 1)
   
   predicate completed'0 [#"../15_enumerate.rs" 22 4 22 35] (self : borrowed (Enumerate'0.t_enumerate i)) =
-    [%#span32] completed'1 (Borrow.borrow_logic (C15Enumerate_Enumerate_Type.enumerate_iter ( * self)) (C15Enumerate_Enumerate_Type.enumerate_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
+    [%#span23] completed'1 (Borrow.borrow_logic (C15Enumerate_Enumerate_Type.enumerate_iter ( * self)) (C15Enumerate_Enumerate_Type.enumerate_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : Option'0.t_option item'0)
   
   predicate resolve'0 (self : borrowed (Enumerate'0.t_enumerate i)) =
-    [%#span33]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span24]  ^ self =  * self
   
   function singleton'1 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'1_spec : forall v : item'0 . ([%#span28] inv'8 v)
-   -> ([%#span31] inv'7 (singleton'1 v))
-  && ([%#span30] index_logic'1 (singleton'1 v) 0 = v) && ([%#span29] len'1 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : item'0 . ([%#span20] inv'6 v)
+   -> ([%#span22] index_logic'1 (singleton'1 v) 0 = v) && ([%#span21] len'1 (singleton'1 v) = 1)
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span34] inv'4 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span25] inv'4 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span36] inv'2 result}
-      {[%#span35] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span27] inv'2 result}
+      {[%#span26] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'1 v) ( ^ self)
         end}
@@ -871,49 +698,33 @@ module C15Enumerate_Enumerate
   
   let%span s15_enumerate4 = "../15_enumerate.rs" 81 42 81 54
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span6 = "" 0 0 0 0
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span9 = "../15_enumerate.rs" 73 12 74 79
+  let%span span5 = "" 0 0 0 0
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span7 = "../15_enumerate.rs" 73 12 74 79
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../common.rs" 18 15 18 32
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span18 = "../common.rs" 19 15 19 32
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span19 = "../common.rs" 21 22 21 23
+  let%span span11 = "../common.rs" 18 15 18 32
   
-  let%span span20 = "../common.rs" 21 31 21 33
+  let%span span12 = "../common.rs" 19 15 19 32
   
-  let%span span21 = "../common.rs" 21 52 21 53
+  let%span span13 = "../common.rs" 21 22 21 23
   
-  let%span span22 = "../common.rs" 21 61 21 63
+  let%span span14 = "../common.rs" 21 52 21 53
   
-  let%span span23 = "../common.rs" 21 82 21 83
+  let%span span15 = "../common.rs" 21 82 21 83
   
-  let%span span24 = "../common.rs" 20 14 20 42
+  let%span span16 = "../common.rs" 20 14 20 42
   
-  let%span span25 = "../common.rs" 15 21 15 25
+  let%span span17 = "../common.rs" 15 21 15 25
   
-  let%span span26 = "../common.rs" 14 14 14 45
+  let%span span18 = "../common.rs" 14 14 14 45
   
   predicate inv'1 (_x : i)
   
@@ -923,9 +734,7 @@ module C15Enumerate_Enumerate
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq item'0)
-  
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   use prelude.prelude.Borrow
   
@@ -935,15 +744,11 @@ module C15Enumerate_Enumerate
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span6] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span7] inv'2 self)  -> ([%#span8] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
   use prelude.prelude.UIntSize
   
@@ -953,64 +758,51 @@ module C15Enumerate_Enumerate
   
   use C15Enumerate_Enumerate_Type as Enumerate'0
   
-  predicate invariant'3 [#"../15_enumerate.rs" 71 4 71 30] (self : Enumerate'0.t_enumerate i) =
-    [%#span9] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'1 i
-     -> inv'2 s
+  predicate invariant'2 [#"../15_enumerate.rs" 71 4 71 30] (self : Enumerate'0.t_enumerate i) =
+    [%#span7] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'1 i
      -> produces'0 (C15Enumerate_Enumerate_Type.enumerate_iter self) s i
      -> UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self) + len'0 s < UIntSize.to_int max'0)
     /\ (forall i : borrowed i . inv'0 i  -> completed'0 i  -> produces'0 ( * i) (empty'0 : Seq'0.t_seq item'0) ( ^ i))
   
-  predicate inv'3 (_x : Enumerate'0.t_enumerate i)
+  predicate inv'2 (_x : Enumerate'0.t_enumerate i)
   
-  axiom inv'3 : forall x : Enumerate'0.t_enumerate i . inv'3 x
-  = (invariant'3 x
+  axiom inv'2 : forall x : Enumerate'0.t_enumerate i . inv'2 x
+  = (invariant'2 x
   /\ match x with
     | Enumerate'0.C_Enumerate iter count -> true
     end)
   
-  predicate invariant'2 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'2 : forall x : Seq'0.t_seq item'0 . inv'2 x = true
-  
   predicate invariant'1 (self : i)
   
   axiom inv'1 : forall x : i . inv'1 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span11] ()
-  
-  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
-  
-  use seq.Seq
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span12] inv'2 self)
-   -> ([%#span13] inv'2 other)
-   -> ([%#span16] inv'2 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span17] produces'0 a ab b)
-   -> ([%#span18] produces'0 b bc c)
-   -> ([%#span19] inv'1 a)
-   -> ([%#span20] inv'2 ab)
-   -> ([%#span21] inv'1 b)
-   -> ([%#span22] inv'2 bc)  -> ([%#span23] inv'1 c)  -> ([%#span24] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span11] produces'0 a ab b)
+   -> ([%#span12] produces'0 b bc c)
+   -> ([%#span13] inv'1 a)
+   -> ([%#span14] inv'1 b)  -> ([%#span15] inv'1 c)  -> ([%#span16] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span25] inv'1 self)
-   -> ([%#span26] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span17] inv'1 self)
+   -> ([%#span18] produces'0 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'0 (self : borrowed i)
   
@@ -1020,7 +812,7 @@ module C15Enumerate_Enumerate
   
   let rec enumerate (iter:i) (return'  (ret:Enumerate'0.t_enumerate i))= {[%#s15_enumerate3] inv'1 iter}
     {[%#s15_enumerate2] forall i : i . forall s : Seq'0.t_seq item'0 . inv'1 i
-     -> inv'2 s  -> produces'0 iter s i  -> len'0 s < UIntSize.to_int max'0}
+     -> produces'0 iter s i  -> len'0 s < UIntSize.to_int max'0}
     {[%#s15_enumerate1] forall i : borrowed i . inv'0 i
      -> completed'0 i  -> produces'0 ( * i) (empty'0 : Seq'0.t_seq item'0) ( ^ i)}
     (! bb0
@@ -1033,7 +825,7 @@ module C15Enumerate_Enumerate
     | bb2 = bb3
     | bb3 = return' {_0} ]
     ) [ & _0 : Enumerate'0.t_enumerate i = any_l () | & iter : i = iter ] 
-    [ return' (result:Enumerate'0.t_enumerate i)-> {[@expl:postcondition] [%#s15_enumerate4] inv'3 result}
+    [ return' (result:Enumerate'0.t_enumerate i)-> {[@expl:postcondition] [%#s15_enumerate4] inv'2 result}
       (! return' {result}) ]
     
 end
@@ -1046,109 +838,81 @@ module C15Enumerate_Impl0
   
   let%span s15_enumerate2 = "../15_enumerate.rs" 53 4 53 44
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span4 = "" 0 0 0 0
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span7 = "../15_enumerate.rs" 73 12 74 79
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span3 = "" 0 0 0 0
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span5 = "../15_enumerate.rs" 73 12 74 79
   
-  let%span span12 = "../15_enumerate.rs" 23 8 23 43
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span9 = "../15_enumerate.rs" 23 8 23 43
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span18 = "../15_enumerate.rs" 29 8 34 9
+  let%span span12 = "../15_enumerate.rs" 29 8 34 9
   
   use prelude.prelude.Borrow
   
-  predicate invariant'7 (self : borrowed i)
+  predicate invariant'5 (self : borrowed i)
   
-  predicate inv'7 (_x : borrowed i)
+  predicate inv'5 (_x : borrowed i)
   
-  axiom inv'7 : forall x : borrowed i . inv'7 x = true
+  axiom inv'5 : forall x : borrowed i . inv'5 x = true
   
-  predicate invariant'6 (self : i)
+  predicate invariant'4 (self : i)
   
-  predicate inv'6 (_x : i)
+  predicate inv'4 (_x : i)
   
-  axiom inv'6 : forall x : i . inv'6 x = true
+  axiom inv'4 : forall x : i . inv'4 x = true
   
   type item'0
   
   use prelude.prelude.UIntSize
   
-  predicate invariant'5 (self : (usize, item'0))
+  predicate invariant'3 (self : (usize, item'0))
   
-  predicate inv'5 (_x : (usize, item'0))
-  
-  axiom inv'5 : forall x : (usize, item'0) . inv'5 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'3 (_x : (usize, item'0))
   
-  predicate invariant'4 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'4 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'4 : forall x : Seq'0.t_seq item'0 . inv'4 x = true
+  axiom inv'3 : forall x : (usize, item'0) . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'3 (self : Option'0.t_option (usize, item'0))
+  predicate invariant'2 (self : Option'0.t_option (usize, item'0))
   
-  predicate inv'3 (_x : Option'0.t_option (usize, item'0))
+  predicate inv'2 (_x : Option'0.t_option (usize, item'0))
   
-  axiom inv'3 : forall x : Option'0.t_option (usize, item'0) . inv'3 x = true
+  axiom inv'2 : forall x : Option'0.t_option (usize, item'0) . inv'2 x = true
   
   use C15Enumerate_Enumerate_Type as Enumerate'0
   
-  predicate invariant'2 (self : borrowed (Enumerate'0.t_enumerate i))
+  predicate invariant'1 (self : borrowed (Enumerate'0.t_enumerate i))
   
   predicate inv'0 (_x : Enumerate'0.t_enumerate i)
   
-  predicate inv'2 (_x : borrowed (Enumerate'0.t_enumerate i))
-  
-  axiom inv'2 : forall x : borrowed (Enumerate'0.t_enumerate i) . inv'2 x = (inv'0 ( * x) /\ inv'0 ( ^ x))
-  
-  predicate invariant'1 (self : Seq'0.t_seq (usize, item'0))
+  predicate inv'1 (_x : borrowed (Enumerate'0.t_enumerate i))
   
-  predicate inv'1 (_x : Seq'0.t_seq (usize, item'0))
+  axiom inv'1 : forall x : borrowed (Enumerate'0.t_enumerate i) . inv'1 x = (inv'0 ( * x) /\ inv'0 ( ^ x))
   
-  axiom inv'1 : forall x : Seq'0.t_seq (usize, item'0) . inv'1 x = true
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  constant empty'2 : Seq'0.t_seq item'0 = [%#span3] ()
+  constant empty'2 : Seq'0.t_seq item'0
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span3] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . ([%#span5] inv'4 self)  -> ([%#span6] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq item'0 . [%#span4] len'1 self >= 0
   
   use prelude.prelude.UIntSize
   
@@ -1157,11 +921,10 @@ module C15Enumerate_Impl0
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   predicate invariant'0 [#"../15_enumerate.rs" 71 4 71 30] (self : Enumerate'0.t_enumerate i) =
-    [%#span7] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'6 i
-     -> inv'4 s
+    [%#span5] (forall i : i . forall s : Seq'0.t_seq item'0 . inv'4 i
      -> produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s i
      -> UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self) + len'1 s < UIntSize.to_int max'0)
-    /\ (forall i : borrowed i . inv'7 i  -> completed'1 i  -> produces'1 ( * i) (empty'2 : Seq'0.t_seq item'0) ( ^ i))
+    /\ (forall i : borrowed i . inv'5 i  -> completed'1 i  -> produces'1 ( * i) (empty'2 : Seq'0.t_seq item'0) ( ^ i))
   
   axiom inv'0 : forall x : Enumerate'0.t_enumerate i . inv'0 x
   = (invariant'0 x
@@ -1169,61 +932,48 @@ module C15Enumerate_Impl0
     | Enumerate'0.C_Enumerate iter count -> true
     end)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (x : int) : (usize, item'0)
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq (usize, item'0)) (_2 : int) : (usize, item'0)
   
   function len'0 (self : Seq'0.t_seq (usize, item'0)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . ([%#span5] inv'1 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (usize, item'0) . [%#span4] len'0 self >= 0
   
   function singleton'0 (v : (usize, item'0)) : Seq'0.t_seq (usize, item'0)
   
-  axiom singleton'0_spec : forall v : (usize, item'0) . ([%#span8] inv'5 v)
-   -> ([%#span11] inv'1 (singleton'0 v))
-  && ([%#span10] index_logic'0 (singleton'0 v) 0 = v) && ([%#span9] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (usize, item'0) . ([%#span6] inv'3 v)
+   -> ([%#span8] index_logic'0 (singleton'0 v) 0 = v) && ([%#span7] len'0 (singleton'0 v) = 1)
   
   predicate completed'0 [#"../15_enumerate.rs" 22 4 22 35] (self : borrowed (Enumerate'0.t_enumerate i)) =
-    [%#span12] completed'1 (Borrow.borrow_logic (C15Enumerate_Enumerate_Type.enumerate_iter ( * self)) (C15Enumerate_Enumerate_Type.enumerate_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
-  
-  use seq.Seq
+    [%#span9] completed'1 (Borrow.borrow_logic (C15Enumerate_Enumerate_Type.enumerate_iter ( * self)) (C15Enumerate_Enumerate_Type.enumerate_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
   function concat'0 (self : Seq'0.t_seq (usize, item'0)) (other : Seq'0.t_seq (usize, item'0)) : Seq'0.t_seq (usize, item'0)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, item'0), other : Seq'0.t_seq (usize, item'0) . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, item'0), other : Seq'0.t_seq (usize, item'0) . ([%#span11] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  constant empty'0 : Seq'0.t_seq (usize, item'0) = [%#span3] ()
+  && ([%#span10] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq (usize, item'0)
   
-  function index_logic'1 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'1 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   predicate produces'0 [#"../15_enumerate.rs" 28 4 28 64] (self : Enumerate'0.t_enumerate i) (visited : Seq'0.t_seq (usize, item'0)) (o : Enumerate'0.t_enumerate i)
     
    =
-    [%#span18] len'0 visited
+    [%#span12] len'0 visited
     = UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count o)
     - UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self)
-    /\ (exists s : Seq'0.t_seq item'0 . inv'4 s
-    /\ produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
+    /\ (exists s : Seq'0.t_seq item'0 . produces'1 (C15Enumerate_Enumerate_Type.enumerate_iter self) s (C15Enumerate_Enumerate_Type.enumerate_iter o)
     /\ len'0 visited = len'1 s
     /\ (forall i : int . 0 <= i /\ i < len'1 s
      -> UIntSize.to_int (let (a, _) = index_logic'0 visited i in a)
     = UIntSize.to_int (C15Enumerate_Enumerate_Type.enumerate_count self) + i
     /\ (let (_, a) = index_logic'0 visited i in a) = index_logic'1 s i))
   
-  constant empty'0 : Seq'0.t_seq (usize, item'0) = [%#span3] ()
+  constant empty'0 : Seq'0.t_seq (usize, item'0)
   
   goal produces_refl_refn : [%#s15_enumerate0] forall self : Enumerate'0.t_enumerate i . inv'0 self
    -> inv'0 self
@@ -1231,23 +981,21 @@ module C15Enumerate_Impl0
    -> produces'0 self (empty'1 : Seq'0.t_seq (usize, item'0)) self)
   
   goal produces_trans_refn : [%#s15_enumerate1] forall a : Enumerate'0.t_enumerate i . forall ab : Seq'0.t_seq (usize, item'0) . forall b : Enumerate'0.t_enumerate i . forall bc : Seq'0.t_seq (usize, item'0) . forall c : Enumerate'0.t_enumerate i . inv'0 c
-  /\ inv'1 bc /\ inv'0 b /\ inv'1 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'0 c
-  /\ inv'1 bc
   /\ inv'0 b
-  /\ inv'1 ab
   /\ inv'0 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
   
-  goal next_refn : [%#s15_enumerate2] forall self : borrowed (Enumerate'0.t_enumerate i) . inv'2 self
-   -> inv'2 self
-  /\ (forall result : Option'0.t_option (usize, item'0) . inv'3 result
+  goal next_refn : [%#s15_enumerate2] forall self : borrowed (Enumerate'0.t_enumerate i) . inv'1 self
+   -> inv'1 self
+  /\ (forall result : Option'0.t_option (usize, item'0) . inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
     end
-   -> inv'3 result
+   -> inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
diff --git a/creusot/tests/should_succeed/iterators/16_take.coma b/creusot/tests/should_succeed/iterators/16_take.coma
index fa4059147d..2087eb31fe 100644
--- a/creusot/tests/should_succeed/iterators/16_take.coma
+++ b/creusot/tests/should_succeed/iterators/16_take.coma
@@ -25,22 +25,7 @@ module C16Take_Take_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C16Take_Impl0_ProducesRefl_Impl
   type i
@@ -49,113 +34,79 @@ module C16Take_Impl0_ProducesRefl_Impl
   
   let%span s16_take1 = "../16_take.rs" 39 14 39 45
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span9 = "../common.rs" 18 15 18 32
-  
-  let%span span10 = "../common.rs" 19 15 19 32
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../common.rs" 21 22 21 23
+  let%span span5 = "../common.rs" 18 15 18 32
   
-  let%span span12 = "../common.rs" 21 31 21 33
+  let%span span6 = "../common.rs" 19 15 19 32
   
-  let%span span13 = "../common.rs" 21 52 21 53
+  let%span span7 = "../common.rs" 21 22 21 23
   
-  let%span span14 = "../common.rs" 21 61 21 63
+  let%span span8 = "../common.rs" 21 52 21 53
   
-  let%span span15 = "../common.rs" 21 82 21 83
+  let%span span9 = "../common.rs" 21 82 21 83
   
-  let%span span16 = "../common.rs" 20 14 20 42
+  let%span span10 = "../common.rs" 20 14 20 42
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span11 = "../common.rs" 15 21 15 25
   
-  let%span span18 = "../common.rs" 15 21 15 25
+  let%span span12 = "../common.rs" 14 14 14 45
   
-  let%span span19 = "../common.rs" 14 14 14 45
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span14 = "../16_take.rs" 32 8 34 9
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  predicate invariant'1 (self : i)
   
-  let%span span22 = "../16_take.rs" 32 8 34 9
+  predicate inv'1 (_x : i)
   
-  predicate invariant'2 (self : i)
-  
-  predicate inv'2 (_x : i)
-  
-  axiom inv'2 : forall x : i . inv'2 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span2] inv'1 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span2] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] inv'1 self)
-   -> ([%#span5] inv'1 other)
-   -> ([%#span8] inv'1 (concat'0 self other))
-  && ([%#span7] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span4] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span6] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span3] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'1 a ab b)
-   -> ([%#span10] produces'1 b bc c)
-   -> ([%#span11] inv'2 a)
-   -> ([%#span12] inv'1 ab)
-   -> ([%#span13] inv'2 b)
-   -> ([%#span14] inv'1 bc)  -> ([%#span15] inv'2 c)  -> ([%#span16] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span5] produces'1 a ab b)
+   -> ([%#span6] produces'1 b bc c)
+   -> ([%#span7] inv'1 a)
+   -> ([%#span8] inv'1 b)  -> ([%#span9] inv'1 c)  -> ([%#span10] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span18] inv'2 self)
-   -> ([%#span19] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span11] inv'1 self)
+   -> ([%#span12] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span21] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C16Take_Take_Type as Take'0
   
@@ -172,7 +123,7 @@ module C16Take_Impl0_ProducesRefl_Impl
   predicate produces'0 [#"../16_take.rs" 31 4 31 64] (self : Take'0.t_take i) (visited : Seq'0.t_seq item'0) (o : Take'0.t_take i)
     
    =
-    [%#span22] UIntSize.to_int (C16Take_Take_Type.take_n self)
+    [%#span14] UIntSize.to_int (C16Take_Take_Type.take_n self)
     = UIntSize.to_int (C16Take_Take_Type.take_n o) + len'0 visited
     /\ produces'1 (C16Take_Take_Type.take_iter self) visited (C16Take_Take_Type.take_iter o)
   
@@ -192,123 +143,85 @@ module C16Take_Impl0_ProducesTrans_Impl
   
   let%span s16_take2 = "../16_take.rs" 47 22 47 23
   
-  let%span s16_take3 = "../16_take.rs" 47 31 47 33
-  
-  let%span s16_take4 = "../16_take.rs" 47 52 47 53
-  
-  let%span s16_take5 = "../16_take.rs" 47 61 47 63
-  
-  let%span s16_take6 = "../16_take.rs" 47 82 47 83
-  
-  let%span s16_take7 = "../16_take.rs" 46 14 46 42
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span s16_take3 = "../16_take.rs" 47 52 47 53
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span s16_take4 = "../16_take.rs" 47 82 47 83
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span s16_take5 = "../16_take.rs" 46 14 46 42
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../common.rs" 18 15 18 32
-  
-  let%span span16 = "../common.rs" 19 15 19 32
-  
-  let%span span17 = "../common.rs" 21 22 21 23
-  
-  let%span span18 = "../common.rs" 21 31 21 33
-  
-  let%span span19 = "../common.rs" 21 52 21 53
+  let%span span9 = "../common.rs" 18 15 18 32
   
-  let%span span20 = "../common.rs" 21 61 21 63
+  let%span span10 = "../common.rs" 19 15 19 32
   
-  let%span span21 = "../common.rs" 21 82 21 83
+  let%span span11 = "../common.rs" 21 22 21 23
   
-  let%span span22 = "../common.rs" 20 14 20 42
+  let%span span12 = "../common.rs" 21 52 21 53
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span13 = "../common.rs" 21 82 21 83
   
-  let%span span24 = "../common.rs" 15 21 15 25
+  let%span span14 = "../common.rs" 20 14 20 42
   
-  let%span span25 = "../common.rs" 14 14 14 45
+  let%span span15 = "../common.rs" 15 21 15 25
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span16 = "../common.rs" 14 14 14 45
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span28 = "../16_take.rs" 32 8 34 9
+  let%span span18 = "../16_take.rs" 32 8 34 9
   
-  predicate invariant'2 (self : i)
+  predicate invariant'1 (self : i)
   
-  predicate inv'2 (_x : i)
+  predicate inv'1 (_x : i)
   
-  axiom inv'2 : forall x : i . inv'2 x = true
+  axiom inv'1 : forall x : i . inv'1 x = true
   
   type item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
-  
-  use seq.Seq
-  
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span8] inv'1 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span6] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] inv'1 self)
-   -> ([%#span11] inv'1 other)
-   -> ([%#span14] inv'1 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span15] produces'1 a ab b)
-   -> ([%#span16] produces'1 b bc c)
-   -> ([%#span17] inv'2 a)
-   -> ([%#span18] inv'1 ab)
-   -> ([%#span19] inv'2 b)
-   -> ([%#span20] inv'1 bc)  -> ([%#span21] inv'2 c)  -> ([%#span22] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'1 a ab b)
+   -> ([%#span10] produces'1 b bc c)
+   -> ([%#span11] inv'1 a)
+   -> ([%#span12] inv'1 b)  -> ([%#span13] inv'1 c)  -> ([%#span14] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span23] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span24] inv'2 self)
-   -> ([%#span25] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span27] ()
+  axiom produces_refl'0_spec : forall self : i . ([%#span15] inv'1 self)
+   -> ([%#span16] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span26] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
+  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C16Take_Take_Type as Take'0
   
@@ -325,7 +238,7 @@ module C16Take_Impl0_ProducesTrans_Impl
   predicate produces'0 [#"../16_take.rs" 31 4 31 64] (self : Take'0.t_take i) (visited : Seq'0.t_seq item'0) (o : Take'0.t_take i)
     
    =
-    [%#span28] UIntSize.to_int (C16Take_Take_Type.take_n self)
+    [%#span18] UIntSize.to_int (C16Take_Take_Type.take_n self)
     = UIntSize.to_int (C16Take_Take_Type.take_n o) + len'0 visited
     /\ produces'1 (C16Take_Take_Type.take_iter self) visited (C16Take_Take_Type.take_iter o)
   
@@ -342,13 +255,11 @@ module C16Take_Impl0_ProducesTrans_Impl
   function produces_trans [#"../16_take.rs" 47 4 47 90] (a : Take'0.t_take i) (ab : Seq'0.t_seq item'0) (b : Take'0.t_take i) (bc : Seq'0.t_seq item'0) (c : Take'0.t_take i) : ()
     
   
-  goal vc_produces_trans : ([%#s16_take6] inv'0 c)
-   -> ([%#s16_take5] inv'1 bc)
-   -> ([%#s16_take4] inv'0 b)
-   -> ([%#s16_take3] inv'1 ab)
+  goal vc_produces_trans : ([%#s16_take4] inv'0 c)
+   -> ([%#s16_take3] inv'0 b)
    -> ([%#s16_take2] inv'0 a)
    -> ([%#s16_take1] produces'0 b bc c)
-   -> ([%#s16_take0] produces'0 a ab b)  -> ([%#s16_take7] produces'0 a (concat'0 ab bc) c)
+   -> ([%#s16_take0] produces'0 a ab b)  -> ([%#s16_take5] produces'0 a (concat'0 ab bc) c)
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -379,76 +290,50 @@ module C16Take_Impl0_Next
   
   let%span s16_take4 = "../16_take.rs" 53 26 53 41
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span15 = "../common.rs" 18 15 18 32
-  
-  let%span span16 = "../common.rs" 19 15 19 32
-  
-  let%span span17 = "../common.rs" 21 22 21 23
-  
-  let%span span18 = "../common.rs" 21 31 21 33
+  let%span span9 = "../common.rs" 18 15 18 32
   
-  let%span span19 = "../common.rs" 21 52 21 53
+  let%span span10 = "../common.rs" 19 15 19 32
   
-  let%span span20 = "../common.rs" 21 61 21 63
+  let%span span11 = "../common.rs" 21 22 21 23
   
-  let%span span21 = "../common.rs" 21 82 21 83
+  let%span span12 = "../common.rs" 21 52 21 53
   
-  let%span span22 = "../common.rs" 20 14 20 42
+  let%span span13 = "../common.rs" 21 82 21 83
   
-  let%span span23 = "../common.rs" 15 21 15 25
+  let%span span14 = "../common.rs" 20 14 20 42
   
-  let%span span24 = "../common.rs" 14 14 14 45
+  let%span span15 = "../common.rs" 15 21 15 25
   
-  let%span span25 = "../16_take.rs" 32 8 34 9
+  let%span span16 = "../common.rs" 14 14 14 45
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span17 = "../16_take.rs" 32 8 34 9
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span30 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span21 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span31 = "../16_take.rs" 23 8 26 9
+  let%span span22 = "../16_take.rs" 23 8 26 9
   
-  let%span span32 = "../common.rs" 27 17 27 21
+  let%span span23 = "../common.rs" 27 17 27 21
   
-  let%span span33 = "../common.rs" 23 14 26 5
+  let%span span24 = "../common.rs" 23 14 26 5
   
-  let%span span34 = "../common.rs" 27 26 27 44
+  let%span span25 = "../common.rs" 27 26 27 44
   
   type item'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'5 (self : Seq'0.t_seq item'0)
-  
-  predicate inv'5 (_x : Seq'0.t_seq item'0)
-  
-  axiom inv'5 : forall x : Seq'0.t_seq item'0 . inv'5 x = true
-  
   predicate invariant'4 (self : item'0)
   
   predicate inv'4 (_x : item'0)
@@ -473,20 +358,17 @@ module C16Take_Impl0_Next
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span5] inv'5 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span5] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq item'0) = 0
   
   use C16Take_Take_Type as Take'0
   
@@ -496,21 +378,16 @@ module C16Take_Impl0_Next
   
   axiom inv'1 : forall x : borrowed (Take'0.t_take i) . inv'1 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] inv'5 self)
-   -> ([%#span11] inv'5 other)
-   -> ([%#span14] inv'5 (concat'0 self other))
-  && ([%#span13] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span8] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span7] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : i)
   
@@ -519,17 +396,15 @@ module C16Take_Impl0_Next
   function produces_trans'0 [#"../common.rs" 21 4 21 91] (a : i) (ab : Seq'0.t_seq item'0) (b : i) (bc : Seq'0.t_seq item'0) (c : i) : ()
     
   
-  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span15] produces'1 a ab b)
-   -> ([%#span16] produces'1 b bc c)
-   -> ([%#span17] inv'0 a)
-   -> ([%#span18] inv'5 ab)
-   -> ([%#span19] inv'0 b)
-   -> ([%#span20] inv'5 bc)  -> ([%#span21] inv'0 c)  -> ([%#span22] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : i, ab : Seq'0.t_seq item'0, b : i, bc : Seq'0.t_seq item'0, c : i . ([%#span9] produces'1 a ab b)
+   -> ([%#span10] produces'1 b bc c)
+   -> ([%#span11] inv'0 a)
+   -> ([%#span12] inv'0 b)  -> ([%#span13] inv'0 c)  -> ([%#span14] produces'1 a (concat'0 ab bc) c)
   
   function produces_refl'0 [#"../common.rs" 15 4 15 27] (self : i) : ()
   
-  axiom produces_refl'0_spec : forall self : i . ([%#span23] inv'0 self)
-   -> ([%#span24] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
+  axiom produces_refl'0_spec : forall self : i . ([%#span15] inv'0 self)
+   -> ([%#span16] produces'1 self (empty'0 : Seq'0.t_seq item'0) self)
   
   predicate invariant'0 (self : i)
   
@@ -542,35 +417,32 @@ module C16Take_Impl0_Next
   predicate produces'0 [#"../16_take.rs" 31 4 31 64] (self : Take'0.t_take i) (visited : Seq'0.t_seq item'0) (o : Take'0.t_take i)
     
    =
-    [%#span25] UIntSize.to_int (C16Take_Take_Type.take_n self)
+    [%#span17] UIntSize.to_int (C16Take_Take_Type.take_n self)
     = UIntSize.to_int (C16Take_Take_Type.take_n o) + len'0 visited
     /\ produces'1 (C16Take_Take_Type.take_iter self) visited (C16Take_Take_Type.take_iter o)
   
-  use seq.Seq
-  
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span26] inv'4 v)
-   -> ([%#span29] inv'5 (singleton'0 v))
-  && ([%#span28] index_logic'0 (singleton'0 v) 0 = v) && ([%#span27] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span18] inv'4 v)
+   -> ([%#span20] index_logic'0 (singleton'0 v) 0 = v) && ([%#span19] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   predicate resolve'0 (self : borrowed (Take'0.t_take i)) =
-    [%#span30]  ^ self =  * self
+    [%#span21]  ^ self =  * self
   
   predicate completed'0 [#"../16_take.rs" 22 4 22 35] (self : borrowed (Take'0.t_take i)) =
-    [%#span31] UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) = 0 /\ resolve'0 self
+    [%#span22] UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) = 0 /\ resolve'0 self
     \/ UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) > 0
     /\ UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) = UIntSize.to_int (C16Take_Take_Type.take_n ( ^ self)) + 1
     /\ completed'1 (Borrow.borrow_logic (C16Take_Take_Type.take_iter ( * self)) (C16Take_Take_Type.take_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
   use prelude.prelude.Intrinsic
   
-  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span32] inv'3 self}
+  let rec next'0 (self:borrowed i) (return'  (ret:Option'0.t_option item'0))= {[@expl:precondition] [%#span23] inv'3 self}
     any
-    [ return' (result:Option'0.t_option item'0)-> {[%#span34] inv'2 result}
-      {[%#span33] match result with
+    [ return' (result:Option'0.t_option item'0)-> {[%#span25] inv'2 result}
+      {[%#span24] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -640,69 +512,49 @@ module C16Take_Impl0
   
   let%span s16_take2 = "../16_take.rs" 53 4 53 41
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span9 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span7 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span10 = "../16_take.rs" 23 8 26 9
+  let%span span8 = "../16_take.rs" 23 8 26 9
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span17 = "../16_take.rs" 32 8 34 9
+  let%span span11 = "../16_take.rs" 32 8 34 9
   
   type item'0
   
-  predicate invariant'4 (self : item'0)
+  predicate invariant'3 (self : item'0)
   
-  predicate inv'4 (_x : item'0)
+  predicate inv'3 (_x : item'0)
   
-  axiom inv'4 : forall x : item'0 . inv'4 x = true
+  axiom inv'3 : forall x : item'0 . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'3 (self : Option'0.t_option item'0)
+  predicate invariant'2 (self : Option'0.t_option item'0)
   
-  predicate inv'3 (_x : Option'0.t_option item'0)
+  predicate inv'2 (_x : Option'0.t_option item'0)
   
-  axiom inv'3 : forall x : Option'0.t_option item'0 . inv'3 x = true
+  axiom inv'2 : forall x : Option'0.t_option item'0 . inv'2 x = true
   
   use C16Take_Take_Type as Take'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'2 (self : borrowed (Take'0.t_take i))
-  
-  predicate inv'2 (_x : borrowed (Take'0.t_take i))
-  
-  axiom inv'2 : forall x : borrowed (Take'0.t_take i) . inv'2 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq item'0)
+  predicate invariant'1 (self : borrowed (Take'0.t_take i))
   
-  predicate inv'1 (_x : Seq'0.t_seq item'0)
+  predicate inv'1 (_x : borrowed (Take'0.t_take i))
   
-  axiom inv'1 : forall x : Seq'0.t_seq item'0 . inv'1 x = true
+  axiom inv'1 : forall x : borrowed (Take'0.t_take i) . inv'1 x = true
   
   predicate invariant'0 (self : Take'0.t_take i)
   
@@ -712,72 +564,60 @@ module C16Take_Impl0
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  function index_logic'0 (self : Seq'0.t_seq item'0) (x : int) : item'0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq item'0) (_2 : int) : item'0
   
   function len'0 (self : Seq'0.t_seq item'0) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . ([%#span3] inv'1 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq item'0 . [%#span3] len'0 self >= 0
   
   function singleton'0 (v : item'0) : Seq'0.t_seq item'0
   
-  axiom singleton'0_spec : forall v : item'0 . ([%#span5] inv'4 v)
-   -> ([%#span8] inv'1 (singleton'0 v))
-  && ([%#span7] index_logic'0 (singleton'0 v) 0 = v) && ([%#span6] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : item'0 . ([%#span4] inv'3 v)
+   -> ([%#span6] index_logic'0 (singleton'0 v) 0 = v) && ([%#span5] len'0 (singleton'0 v) = 1)
   
   predicate completed'1 [#"../common.rs" 11 4 11 36] (self : borrowed i)
   
   use C16Take_Take_Type as C16Take_Take_Type
   
   predicate resolve'0 (self : borrowed (Take'0.t_take i)) =
-    [%#span9]  ^ self =  * self
+    [%#span7]  ^ self =  * self
   
   use prelude.prelude.UIntSize
   
   predicate completed'0 [#"../16_take.rs" 22 4 22 35] (self : borrowed (Take'0.t_take i)) =
-    [%#span10] UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) = 0 /\ resolve'0 self
+    [%#span8] UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) = 0 /\ resolve'0 self
     \/ UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) > 0
     /\ UIntSize.to_int (C16Take_Take_Type.take_n ( * self)) = UIntSize.to_int (C16Take_Take_Type.take_n ( ^ self)) + 1
     /\ completed'1 (Borrow.borrow_logic (C16Take_Take_Type.take_iter ( * self)) (C16Take_Take_Type.take_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
   
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span11] ()
-  
-  constant empty'0 : Seq'0.t_seq item'0 = [%#span11] ()
+  constant empty'0 : Seq'0.t_seq item'0
   
-  use seq.Seq
+  constant empty'0 : Seq'0.t_seq item'0
   
   function concat'0 (self : Seq'0.t_seq item'0) (other : Seq'0.t_seq item'0) : Seq'0.t_seq item'0
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span12] inv'1 self)
-   -> ([%#span13] inv'1 other)
-   -> ([%#span16] inv'1 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq item'0, other : Seq'0.t_seq item'0 . ([%#span10] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span9] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate produces'1 [#"../common.rs" 8 4 8 65] (self : i) (visited : Seq'0.t_seq item'0) (o : i)
   
   predicate produces'0 [#"../16_take.rs" 31 4 31 64] (self : Take'0.t_take i) (visited : Seq'0.t_seq item'0) (o : Take'0.t_take i)
     
    =
-    [%#span17] UIntSize.to_int (C16Take_Take_Type.take_n self)
+    [%#span11] UIntSize.to_int (C16Take_Take_Type.take_n self)
     = UIntSize.to_int (C16Take_Take_Type.take_n o) + len'0 visited
     /\ produces'1 (C16Take_Take_Type.take_iter self) visited (C16Take_Take_Type.take_iter o)
   
   goal produces_trans_refn : [%#s16_take0] forall a : Take'0.t_take i . forall ab : Seq'0.t_seq item'0 . forall b : Take'0.t_take i . forall bc : Seq'0.t_seq item'0 . forall c : Take'0.t_take i . inv'0 c
-  /\ inv'1 bc /\ inv'0 b /\ inv'1 ab /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
+  /\ inv'0 b /\ inv'0 a /\ produces'0 b bc c /\ produces'0 a ab b
    -> inv'0 c
-  /\ inv'1 bc
   /\ inv'0 b
-  /\ inv'1 ab
   /\ inv'0 a
   /\ produces'0 b bc c
   /\ produces'0 a ab b /\ (forall result : () . produces'0 a (concat'0 ab bc) c  -> produces'0 a (concat'0 ab bc) c)
@@ -787,14 +627,14 @@ module C16Take_Impl0
   /\ (forall result : () . produces'0 self (empty'0 : Seq'0.t_seq item'0) self
    -> produces'0 self (empty'1 : Seq'0.t_seq item'0) self)
   
-  goal next_refn : [%#s16_take2] forall self : borrowed (Take'0.t_take i) . inv'2 self
-   -> inv'2 self
-  /\ (forall result : Option'0.t_option item'0 . inv'3 result
+  goal next_refn : [%#s16_take2] forall self : borrowed (Take'0.t_take i) . inv'1 self
+   -> inv'1 self
+  /\ (forall result : Option'0.t_option item'0 . inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
     end
-   -> inv'3 result
+   -> inv'2 result
   /\ match result with
     | Option'0.C_None -> completed'0 self
     | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
diff --git a/creusot/tests/should_succeed/knapsack.coma b/creusot/tests/should_succeed/knapsack.coma
index 12b9442499..88e6c97ab1 100644
--- a/creusot/tests/should_succeed/knapsack.coma
+++ b/creusot/tests/should_succeed/knapsack.coma
@@ -30,22 +30,7 @@ module Knapsack_Max
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Knapsack_Item_Type
   use prelude.prelude.UIntSize
@@ -80,49 +65,29 @@ module Knapsack_M_Impl
   
   let%span sknapsack1 = "../knapsack.rs" 32 11 32 17
   
-  let%span sknapsack2 = "../knapsack.rs" 34 11 34 16
-  
-  let%span sknapsack3 = "../knapsack.rs" 33 10 33 21
-  
-  let%span sknapsack4 = "../knapsack.rs" 30 10 30 11
-  
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span sknapsack2 = "../knapsack.rs" 33 10 33 21
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span sknapsack3 = "../knapsack.rs" 30 10 30 11
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  use prelude.prelude.Int
   
   use Knapsack_Item_Type as Item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq (Item'0.t_item name))
-  
-  predicate inv'0 (_x : Seq'0.t_seq (Item'0.t_item name))
-  
-  axiom inv'0 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#span5] inv'0 self)
-   -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#span4] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (Item'0.t_item name) = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq (Item'0.t_item name)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   use int.MinMax
   
@@ -132,9 +97,7 @@ module Knapsack_M_Impl
   
   use prelude.prelude.UIntSize
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   constant items  : Seq'0.t_seq (Item'0.t_item name)
   
@@ -144,28 +107,24 @@ module Knapsack_M_Impl
   
   function m [#"../knapsack.rs" 34 0 34 57] (items : Seq'0.t_seq (Item'0.t_item name)) (i : int) (w : int) : int
   
-  goal vc_m : ([%#sknapsack2] inv'0 items)
-   -> ([%#sknapsack1] 0 <= w)
+  goal vc_m : ([%#sknapsack1] 0 <= w)
    -> ([%#sknapsack0] 0 <= i /\ i <= len'0 items)
    -> match i = 0 with
-    | True -> [%#sknapsack3] 0 >= 0
+    | True -> [%#sknapsack2] 0 >= 0
     | False -> match UIntSize.to_int (Knapsack_Item_Type.item_weight (index_logic'0 items (i - 1))) > w with
-      | True -> ((([%#sknapsack2] inv'0 items)
-      && ([%#sknapsack1] 0 <= w) && ([%#sknapsack0] 0 <= i - 1 /\ i - 1 <= len'0 items))
-      /\ 0 <= ([%#sknapsack4] i) /\ ([%#sknapsack4] i - 1) < ([%#sknapsack4] i))
-      /\ (([%#sknapsack3] m items (i - 1) w >= 0)  -> ([%#sknapsack3] m items (i - 1) w >= 0))
-      | False -> ((([%#sknapsack2] inv'0 items)
-      && ([%#sknapsack1] 0 <= w) && ([%#sknapsack0] 0 <= i - 1 /\ i - 1 <= len'0 items))
-      /\ 0 <= ([%#sknapsack4] i) /\ ([%#sknapsack4] i - 1) < ([%#sknapsack4] i))
-      /\ (([%#sknapsack3] m items (i - 1) w >= 0)
-       -> ((([%#sknapsack2] inv'0 items)
-      && ([%#sknapsack1] 0 <= w - UIntSize.to_int (Knapsack_Item_Type.item_weight (index_logic'0 items (i - 1))))
+      | True -> ((([%#sknapsack1] 0 <= w) && ([%#sknapsack0] 0 <= i - 1 /\ i - 1 <= len'0 items))
+      /\ 0 <= ([%#sknapsack3] i) /\ ([%#sknapsack3] i - 1) < ([%#sknapsack3] i))
+      /\ (([%#sknapsack2] m items (i - 1) w >= 0)  -> ([%#sknapsack2] m items (i - 1) w >= 0))
+      | False -> ((([%#sknapsack1] 0 <= w) && ([%#sknapsack0] 0 <= i - 1 /\ i - 1 <= len'0 items))
+      /\ 0 <= ([%#sknapsack3] i) /\ ([%#sknapsack3] i - 1) < ([%#sknapsack3] i))
+      /\ (([%#sknapsack2] m items (i - 1) w >= 0)
+       -> ((([%#sknapsack1] 0 <= w - UIntSize.to_int (Knapsack_Item_Type.item_weight (index_logic'0 items (i - 1))))
       && ([%#sknapsack0] 0 <= i - 1 /\ i - 1 <= len'0 items))
-      /\ 0 <= ([%#sknapsack4] i) /\ ([%#sknapsack4] i - 1) < ([%#sknapsack4] i))
-      /\ (([%#sknapsack3] m items (i - 1) (w
+      /\ 0 <= ([%#sknapsack3] i) /\ ([%#sknapsack3] i - 1) < ([%#sknapsack3] i))
+      /\ (([%#sknapsack2] m items (i - 1) (w
       - UIntSize.to_int (Knapsack_Item_Type.item_weight (index_logic'0 items (i - 1))))
       >= 0)
-       -> ([%#sknapsack3] MinMax.max (m items (i - 1) w) (m items (i - 1) (w
+       -> ([%#sknapsack2] MinMax.max (m items (i - 1) w) (m items (i - 1) (w
       - UIntSize.to_int (Knapsack_Item_Type.item_weight (index_logic'0 items (i - 1))))
       + UIntSize.to_int (Knapsack_Item_Type.item_value (index_logic'0 items (i - 1))))
       >= 0)))
@@ -320,266 +279,235 @@ module Knapsack_Knapsack01Dyn
   
   let%span sknapsack21 = "../knapsack.rs" 48 75 48 91
   
-  let%span span22 = "" 0 0 0 0
+  let%span span22 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span23 = "" 0 0 0 0
   
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span29 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span30 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span31 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span32 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span34 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span35 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span35 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span38 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span39 = "" 0 0 0 0
   
-  let%span span40 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span40 = "" 0 0 0 0
   
-  let%span span41 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span41 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span42 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span42 = "../../../../creusot-contracts/src/std/vec.rs" 73 26 73 44
   
-  let%span span43 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span43 = "" 0 0 0 0
   
-  let%span span44 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span44 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span45 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span46 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span46 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span47 = "" 0 0 0 0
+  let%span span47 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span48 = "" 0 0 0 0
+  let%span span48 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span49 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span49 = "" 0 0 0 0
   
-  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 73 26 73 44
+  let%span span50 = "" 0 0 0 0
   
-  let%span span51 = "" 0 0 0 0
+  let%span span51 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span52 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span52 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span53 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span54 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span54 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span55 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span55 = "" 0 0 0 0
   
-  let%span span56 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span56 = "../knapsack.rs" 13 11 13 15
   
-  let%span span57 = "" 0 0 0 0
+  let%span span57 = "../knapsack.rs" 14 10 14 31
   
-  let%span span58 = "" 0 0 0 0
+  let%span span58 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span59 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span59 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span60 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span60 = "" 0 0 0 0
   
-  let%span span61 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span61 = "" 0 0 0 0
   
-  let%span span62 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span62 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
   let%span span63 = "" 0 0 0 0
   
-  let%span span64 = "../knapsack.rs" 13 11 13 15
+  let%span span64 = "../knapsack.rs" 31 11 31 37
   
-  let%span span65 = "../knapsack.rs" 14 10 14 31
+  let%span span65 = "../knapsack.rs" 32 11 32 17
   
-  let%span span66 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span66 = "../knapsack.rs" 33 10 33 21
   
-  let%span span67 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span67 = "../knapsack.rs" 30 10 30 11
   
-  let%span span68 = "" 0 0 0 0
+  let%span span68 = "../knapsack.rs" 35 4 42 5
   
   let%span span69 = "" 0 0 0 0
   
-  let%span span70 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
-  
-  let%span span71 = "" 0 0 0 0
+  let%span span70 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span72 = "../knapsack.rs" 31 11 31 37
+  let%span span71 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
-  let%span span73 = "../knapsack.rs" 32 11 32 17
+  let%span span72 = "" 0 0 0 0
   
-  let%span span74 = "../knapsack.rs" 34 11 34 16
+  let%span span73 = "" 0 0 0 0
   
-  let%span span75 = "../knapsack.rs" 33 10 33 21
+  let%span span74 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span76 = "../knapsack.rs" 30 10 30 11
+  use Knapsack_Item_Type as Item'0
   
-  let%span span77 = "../knapsack.rs" 35 4 42 5
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span78 = "" 0 0 0 0
+  predicate invariant'17 (self : Seq'0.t_seq (Item'0.t_item name))
   
-  let%span span79 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
+  predicate inv'17 (_x : Seq'0.t_seq (Item'0.t_item name))
   
-  let%span span80 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
+  axiom inv'17 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'17 x = true
   
-  let%span span81 = "" 0 0 0 0
+  use Alloc_Alloc_Global_Type as Global'0
   
-  let%span span82 = "" 0 0 0 0
+  use prelude.prelude.UIntSize
   
-  let%span span83 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  use Alloc_Vec_Vec_Type as Vec'0
   
-  use Knapsack_Item_Type as Item'0
+  predicate invariant'16 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span22] true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'16 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   
-  predicate invariant'17 (self : Seq'0.t_seq (Item'0.t_item name))
+  axiom inv'16 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'16 x = true
   
-  predicate inv'17 (_x : Seq'0.t_seq (Item'0.t_item name))
+  predicate invariant'15 (self : Seq'0.t_seq usize) =
+    [%#span22] true
   
-  axiom inv'17 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'17 x = true
+  predicate inv'15 (_x : Seq'0.t_seq usize)
   
-  predicate inv'6 (_x : Seq'0.t_seq (Item'0.t_item name))
+  axiom inv'15 : forall x : Seq'0.t_seq usize . inv'15 x = true
   
-  use Alloc_Alloc_Global_Type as Global'0
+  predicate invariant'14 (self : Seq'0.t_seq (Item'0.t_item name))
   
-  use Alloc_Vec_Vec_Type as Vec'0
+  predicate inv'14 (_x : Seq'0.t_seq (Item'0.t_item name))
   
-  use prelude.prelude.UIntSize
+  axiom inv'14 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'14 x = true
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.Int
   
-  constant max'1 : usize = [%#span22] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'1 : usize = [%#span23] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#span23] inv'6 self)
-   -> ([%#span24] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#span24] len'1 self >= 0
   
-  predicate inv'16 (_x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
+  predicate inv'13 (_x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) : Seq'0.t_seq (Item'0.t_item name)
     
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . ([%#span25] inv'16 self)
-   -> ([%#span27] inv'6 (shallow_model'3 self))
-  && ([%#span26] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'1 : usize))
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . ([%#span25] inv'13 self)
+   -> ([%#span26] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'1 : usize))
   
-  predicate invariant'16 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) =
-    [%#span28] inv'6 (shallow_model'3 self)
+  predicate invariant'13 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) =
+    [%#span27] inv'17 (shallow_model'3 self)
   
-  axiom inv'16 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'16 x = true
+  axiom inv'13 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'13 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'15 (self : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
+  predicate invariant'12 (self : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
   
-  predicate inv'15 (_x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
+  predicate inv'12 (_x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
   
-  axiom inv'15 : forall x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) . inv'15 x = true
-  
-  use seq.Seq
+  axiom inv'12 : forall x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) . inv'12 x = true
   
   function len'4 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'4_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#span23] inv'17 self)
-   -> ([%#span24] len'4 self >= 0)
+  axiom len'4_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#span24] len'4 self >= 0
   
-  constant empty'3 : Seq'0.t_seq (Item'0.t_item name) = [%#span29] ()
+  constant empty'3 : Seq'0.t_seq (Item'0.t_item name)
   
-  function empty_len'3 (_1 : ()) : () =
-    [%#span31] ()
+  function empty_len'3 (_1 : ()) : ()
   
-  axiom empty_len'3_spec : forall _1 : () . [%#span30] len'4 (empty'3 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  axiom empty_len'3_spec : forall _1 : () . [%#span28] len'4 (empty'3 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
-  predicate invariant'14 (self : borrowed usize) =
-    [%#span32] true
+  predicate invariant'11 (self : borrowed usize) =
+    [%#span22] true
   
-  predicate inv'14 (_x : borrowed usize)
+  predicate inv'11 (_x : borrowed usize)
   
-  axiom inv'14 : forall x : borrowed usize . inv'14 x = true
+  axiom inv'11 : forall x : borrowed usize . inv'11 x = true
   
-  predicate invariant'13 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span32] true
+  predicate invariant'10 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span22] true
   
-  predicate inv'13 (_x : borrowed (Vec'0.t_vec usize (Global'0.t_global)))
+  predicate inv'10 (_x : borrowed (Vec'0.t_vec usize (Global'0.t_global)))
   
-  axiom inv'13 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'13 x = true
+  axiom inv'10 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'10 x = true
   
-  predicate invariant'12 (self : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) =
-    [%#span32] true
+  predicate invariant'9 (self : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) =
+    [%#span22] true
   
-  predicate inv'12 (_x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))
+  predicate inv'9 (_x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))
   
-  axiom inv'12 : forall x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) . inv'12 x
+  axiom inv'9 : forall x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) . inv'9 x
   = true
   
-  predicate invariant'11 (self : usize) =
-    [%#span32] true
-  
-  predicate inv'11 (_x : usize)
-  
-  axiom inv'11 : forall x : usize . inv'11 x = true
+  predicate invariant'8 (self : usize) =
+    [%#span22] true
   
-  predicate invariant'10 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span32] true
+  predicate inv'8 (_x : usize)
   
-  predicate inv'10 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  axiom inv'8 : forall x : usize . inv'8 x = true
   
-  axiom inv'10 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'10 x = true
+  predicate invariant'7 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span22] true
   
-  predicate invariant'9 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span32] true
+  predicate inv'7 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
-  predicate inv'9 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
+  axiom inv'7 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'7 x = true
   
-  axiom inv'9 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'9 x = true
+  predicate invariant'6 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
+    [%#span22] true
   
-  predicate invariant'8 (self : Seq'0.t_seq usize) =
-    [%#span32] true
+  predicate inv'6 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
-  predicate inv'8 (_x : Seq'0.t_seq usize)
-  
-  axiom inv'8 : forall x : Seq'0.t_seq usize . inv'8 x = true
-  
-  predicate invariant'7 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span32] true
-  
-  predicate inv'7 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
-  
-  axiom inv'7 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'7 x = true
-  
-  predicate invariant'6 (self : Seq'0.t_seq (Item'0.t_item name))
-  
-  axiom inv'6 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'6 x = true
-  
-  use seq.Seq
+  axiom inv'6 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'6 x = true
   
   function len'2 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span23] inv'7 self)
-   -> ([%#span24] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . [%#span24] len'2 self >= 0
   
   predicate inv'5 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
@@ -587,35 +515,31 @@ module Knapsack_Knapsack01Dyn
     
   
   axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span25] inv'5 self)
-   -> ([%#span27] inv'7 (shallow_model'1 self))
-  && ([%#span26] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'1 : usize))
+   -> ([%#span26] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'1 : usize))
   
   predicate invariant'5 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span28] inv'7 (shallow_model'1 self)
+    [%#span27] inv'16 (shallow_model'1 self)
   
   axiom inv'5 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'5 x = true
   
-  use seq.Seq
-  
   function len'3 (self : Seq'0.t_seq usize) : int
   
-  axiom len'3_spec : forall self : Seq'0.t_seq usize . ([%#span23] inv'8 self)  -> ([%#span24] len'3 self >= 0)
+  axiom len'3_spec : forall self : Seq'0.t_seq usize . [%#span24] len'3 self >= 0
   
   predicate inv'4 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
   axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span25] inv'4 self)
-   -> ([%#span27] inv'8 (shallow_model'2 self))
-  && ([%#span26] len'3 (shallow_model'2 self) <= UIntSize.to_int (max'1 : usize))
+   -> ([%#span26] len'3 (shallow_model'2 self) <= UIntSize.to_int (max'1 : usize))
   
   predicate invariant'4 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span28] inv'8 (shallow_model'2 self)
+    [%#span27] inv'15 (shallow_model'2 self)
   
   axiom inv'4 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'4 x = true
   
   predicate invariant'3 (self : usize) =
-    [%#span32] true
+    [%#span22] true
   
   predicate inv'3 (_x : usize)
   
@@ -633,11 +557,10 @@ module Knapsack_Knapsack01Dyn
     
   
   axiom shallow_model'8_spec : forall self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . ([%#span25] inv'1 self)
-   -> ([%#span27] inv'17 (shallow_model'8 self))
-  && ([%#span26] len'4 (shallow_model'8 self) <= UIntSize.to_int (max'1 : usize))
+   -> ([%#span26] len'4 (shallow_model'8 self) <= UIntSize.to_int (max'1 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) =
-    [%#span28] inv'17 (shallow_model'8 self)
+    [%#span27] inv'14 (shallow_model'8 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'1 x = true
   
@@ -647,212 +570,195 @@ module Knapsack_Knapsack01Dyn
   
   axiom inv'0 : forall x : Item'0.t_item name . inv'0 x = true
   
-  constant empty'2 : Seq'0.t_seq usize = [%#span29] ()
+  constant empty'2 : Seq'0.t_seq usize
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span31] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span30] len'3 (empty'2 : Seq'0.t_seq usize) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span28] len'3 (empty'2 : Seq'0.t_seq usize) = 0
   
-  constant empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) = [%#span29] ()
+  constant empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span31] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span30] len'2 (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom empty_len'1_spec : forall _1 : () . [%#span28] len'2 (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   = 0
   
-  constant empty'0 : Seq'0.t_seq (Item'0.t_item name) = [%#span29] ()
+  constant empty'0 : Seq'0.t_seq (Item'0.t_item name)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span31] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span30] len'1 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span28] len'1 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   use Knapsack_Item_Type as Knapsack_Item_Type
   
-  use seq.Seq
-  
-  function index_logic'5 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'5 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (ix : int) : Item'0.t_item name
     
    =
-    [%#span33] index_logic'5 (shallow_model'3 self) ix
+    [%#span29] index_logic'5 (shallow_model'3 self) ix
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'4 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
   
   predicate resolve'6 (self : usize) =
-    [%#span34] true
+    [%#span30] true
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'3 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span33] index_logic'1 (shallow_model'2 self) ix
+    [%#span29] index_logic'1 (shallow_model'2 self) ix
   
   predicate resolve'5 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span35] forall i : int . 0 <= i /\ i < len'3 (shallow_model'2 self)  -> resolve'6 (index_logic'3 self i)
-  
-  use seq.Seq
+    [%#span31] forall i : int . 0 <= i /\ i < len'3 (shallow_model'2 self)  -> resolve'6 (index_logic'3 self i)
   
-  function index_logic'4 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (x : int) : Vec'0.t_vec usize (Global'0.t_global)
+  function index_logic'4 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (_2 : int) : Vec'0.t_vec usize (Global'0.t_global)
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (ix : int) : Vec'0.t_vec usize (Global'0.t_global)
     
    =
-    [%#span33] index_logic'4 (shallow_model'1 self) ix
+    [%#span29] index_logic'4 (shallow_model'1 self) ix
   
   predicate resolve'3 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span35] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)  -> resolve'5 (index_logic'0 self i)
+    [%#span31] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)  -> resolve'5 (index_logic'0 self i)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'6 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'6 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   function concat'0 (self : Seq'0.t_seq (Item'0.t_item name)) (other : Seq'0.t_seq (Item'0.t_item name)) : Seq'0.t_seq (Item'0.t_item name)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name), other : Seq'0.t_seq (Item'0.t_item name) . ([%#span36] inv'17 self)
-   -> ([%#span37] inv'17 other)
-   -> ([%#span40] inv'17 (concat'0 self other))
-  && ([%#span39] forall i : int . 0 <= i /\ i < len'4 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name), other : Seq'0.t_seq (Item'0.t_item name) . ([%#span33] forall i : int . 0
+  <= i
+  /\ i < len'4 (concat'0 self other)
    -> index_logic'6 (concat'0 self other) i
   = (if i < len'4 self then index_logic'6 self i else index_logic'6 other (i - len'4 self)))
-  && ([%#span38] len'4 (concat'0 self other) = len'4 self + len'4 other)
-  
-  use seq.Seq
+  && ([%#span32] len'4 (concat'0 self other) = len'4 self + len'4 other)
   
   function singleton'0 (v : Item'0.t_item name) : Seq'0.t_seq (Item'0.t_item name)
   
-  axiom singleton'0_spec : forall v : Item'0.t_item name . ([%#span41] inv'0 v)
-   -> ([%#span44] inv'17 (singleton'0 v))
-  && ([%#span43] index_logic'6 (singleton'0 v) 0 = v) && ([%#span42] len'4 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : Item'0.t_item name . ([%#span34] inv'0 v)
+   -> ([%#span36] index_logic'6 (singleton'0 v) 0 = v) && ([%#span35] len'4 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq (Item'0.t_item name)) (v : Item'0.t_item name) : Seq'0.t_seq (Item'0.t_item name)
     
    =
-    [%#span45] concat'0 self (singleton'0 v)
+    [%#span37] concat'0 self (singleton'0 v)
   
   function shallow_model'9 (self : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))) : Seq'0.t_seq (Item'0.t_item name)
     
    =
-    [%#span46] shallow_model'8 ( * self)
+    [%#span38] shallow_model'8 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))) (value:Item'0.t_item name) (return'  (ret:()))= {[@expl:precondition] [%#span48] inv'0 value}
-    {[@expl:precondition] [%#span47] inv'15 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))) (value:Item'0.t_item name) (return'  (ret:()))= {[@expl:precondition] [%#span40] inv'0 value}
+    {[@expl:precondition] [%#span39] inv'12 self}
     any
-    [ return' (result:())-> {[%#span49] shallow_model'8 ( ^ self) = push'1 (shallow_model'9 self) value}
+    [ return' (result:())-> {[%#span41] shallow_model'8 ( ^ self) = push'1 (shallow_model'9 self) value}
       (! return' {result}) ]
     
   
   let rec with_capacity'0 (capacity:usize) (return'  (ret:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))-> {[%#span51] inv'1 result}
-      {[%#span50] len'4 (shallow_model'8 result) = 0}
+    [ return' (result:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))-> {[%#span43] inv'1 result}
+      {[%#span42] len'4 (shallow_model'8 result) = 0}
       (! return' {result}) ]
     
   
   predicate resolve'2 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span52]  ^ self =  * self
+    [%#span44]  ^ self =  * self
   
   predicate resolve'1 (self : borrowed usize) =
-    [%#span52]  ^ self =  * self
+    [%#span44]  ^ self =  * self
   
   use prelude.prelude.Slice
   
   predicate resolve_elswhere'1 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq usize) (fin : Seq'0.t_seq usize) =
-    [%#span53] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'3 old'
+    [%#span45] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'3 old'
      -> index_logic'1 old' i = index_logic'1 fin i
   
   predicate has_value'2 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span54] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span46] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'2 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span55] UIntSize.to_int self < len'3 seq
+    [%#span47] UIntSize.to_int self < len'3 seq
   
   function shallow_model'7 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span46] shallow_model'2 ( * self)
+    [%#span38] shallow_model'2 ( * self)
   
-  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span58] inv'3 index}
-    {[@expl:precondition] [%#span57] inv'13 self}
-    {[@expl:precondition] [%#span56] in_bounds'2 index (shallow_model'7 self)}
+  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span50] inv'3 index}
+    {[@expl:precondition] [%#span49] inv'10 self}
+    {[@expl:precondition] [%#span48] in_bounds'2 index (shallow_model'7 self)}
     any
-    [ return' (result:borrowed usize)-> {[%#span63] inv'14 result}
-      {[%#span62] len'3 (shallow_model'2 ( ^ self)) = len'3 (shallow_model'7 self)}
-      {[%#span61] resolve_elswhere'1 index (shallow_model'7 self) (shallow_model'2 ( ^ self))}
-      {[%#span60] has_value'2 index (shallow_model'2 ( ^ self)) ( ^ result)}
-      {[%#span59] has_value'2 index (shallow_model'7 self) ( * result)}
+    [ return' (result:borrowed usize)-> {[%#span55] inv'11 result}
+      {[%#span54] len'3 (shallow_model'2 ( ^ self)) = len'3 (shallow_model'7 self)}
+      {[%#span53] resolve_elswhere'1 index (shallow_model'7 self) (shallow_model'2 ( ^ self))}
+      {[%#span52] has_value'2 index (shallow_model'2 ( ^ self)) ( ^ result)}
+      {[%#span51] has_value'2 index (shallow_model'7 self) ( * result)}
       (! return' {result}) ]
     
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (fin : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
     
    =
-    [%#span53] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'2 old'
+    [%#span45] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'2 old'
      -> index_logic'4 old' i = index_logic'4 fin i
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (out : Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span54] index_logic'4 seq (UIntSize.to_int self) = out
+    [%#span46] index_logic'4 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span55] UIntSize.to_int self < len'2 seq
+    [%#span47] UIntSize.to_int self < len'2 seq
   
   function shallow_model'6 (self : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span46] shallow_model'1 ( * self)
+    [%#span38] shallow_model'1 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (Vec'0.t_vec usize (Global'0.t_global))))= {[@expl:precondition] [%#span58] inv'3 index}
-    {[@expl:precondition] [%#span57] inv'12 self}
-    {[@expl:precondition] [%#span56] in_bounds'1 index (shallow_model'6 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (Vec'0.t_vec usize (Global'0.t_global))))= {[@expl:precondition] [%#span50] inv'3 index}
+    {[@expl:precondition] [%#span49] inv'9 self}
+    {[@expl:precondition] [%#span48] in_bounds'1 index (shallow_model'6 self)}
     any
-    [ return' (result:borrowed (Vec'0.t_vec usize (Global'0.t_global)))-> {[%#span63] inv'13 result}
-      {[%#span62] len'2 (shallow_model'1 ( ^ self)) = len'2 (shallow_model'6 self)}
-      {[%#span61] resolve_elswhere'0 index (shallow_model'6 self) (shallow_model'1 ( ^ self))}
-      {[%#span60] has_value'1 index (shallow_model'1 ( ^ self)) ( ^ result)}
-      {[%#span59] has_value'1 index (shallow_model'6 self) ( * result)}
+    [ return' (result:borrowed (Vec'0.t_vec usize (Global'0.t_global)))-> {[%#span55] inv'10 result}
+      {[%#span54] len'2 (shallow_model'1 ( ^ self)) = len'2 (shallow_model'6 self)}
+      {[%#span53] resolve_elswhere'0 index (shallow_model'6 self) (shallow_model'1 ( ^ self))}
+      {[%#span52] has_value'1 index (shallow_model'1 ( ^ self)) ( ^ result)}
+      {[%#span51] has_value'1 index (shallow_model'6 self) ( * result)}
       (! return' {result}) ]
     
   
   use int.MinMax
   
-  let rec max'0 (a:usize) (b:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span64] true}
+  let rec max'0 (a:usize) (b:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span56] true}
     any
-    [ return' (result:usize)-> {[%#span65] UIntSize.to_int result = MinMax.max (UIntSize.to_int a) (UIntSize.to_int b)}
+    [ return' (result:usize)-> {[%#span57] UIntSize.to_int result = MinMax.max (UIntSize.to_int a) (UIntSize.to_int b)}
       (! return' {result}) ]
     
   
   function shallow_model'5 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize =
-    [%#span66] shallow_model'2 self
+    [%#span58] shallow_model'2 self
   
-  let rec index'2 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span69] inv'3 index}
-    {[@expl:precondition] [%#span68] inv'10 self}
-    {[@expl:precondition] [%#span67] in_bounds'2 index (shallow_model'5 self)}
+  let rec index'2 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span61] inv'3 index}
+    {[@expl:precondition] [%#span60] inv'7 self}
+    {[@expl:precondition] [%#span59] in_bounds'2 index (shallow_model'5 self)}
     any
-    [ return' (result:usize)-> {[%#span71] inv'11 result}
-      {[%#span70] has_value'2 index (shallow_model'5 self) result}
+    [ return' (result:usize)-> {[%#span63] inv'8 result}
+      {[%#span62] has_value'2 index (shallow_model'5 self) result}
       (! return' {result}) ]
     
   
   function shallow_model'4 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span66] shallow_model'1 self
+    [%#span58] shallow_model'1 self
   
-  let rec index'1 (self:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (index:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span69] inv'3 index}
-    {[@expl:precondition] [%#span68] inv'9 self}
-    {[@expl:precondition] [%#span67] in_bounds'1 index (shallow_model'4 self)}
+  let rec index'1 (self:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (index:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span61] inv'3 index}
+    {[@expl:precondition] [%#span60] inv'6 self}
+    {[@expl:precondition] [%#span59] in_bounds'1 index (shallow_model'4 self)}
     any
-    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span71] inv'10 result}
-      {[%#span70] has_value'1 index (shallow_model'4 self) result}
+    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span63] inv'7 result}
+      {[%#span62] has_value'1 index (shallow_model'4 self) result}
       (! return' {result}) ]
     
   
@@ -861,29 +767,29 @@ module Knapsack_Knapsack01Dyn
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Item'0.t_item name)) (out : Item'0.t_item name)
     
    =
-    [%#span54] index_logic'5 seq (UIntSize.to_int self) = out
+    [%#span46] index_logic'5 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Item'0.t_item name)) =
-    [%#span55] UIntSize.to_int self < len'1 seq
+    [%#span47] UIntSize.to_int self < len'1 seq
   
   function shallow_model'0 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) : Seq'0.t_seq (Item'0.t_item name)
     
    =
-    [%#span66] shallow_model'3 self
+    [%#span58] shallow_model'3 self
   
-  let rec index'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (index:usize) (return'  (ret:Item'0.t_item name))= {[@expl:precondition] [%#span69] inv'3 index}
-    {[@expl:precondition] [%#span68] inv'2 self}
-    {[@expl:precondition] [%#span67] in_bounds'0 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (index:usize) (return'  (ret:Item'0.t_item name))= {[@expl:precondition] [%#span61] inv'3 index}
+    {[@expl:precondition] [%#span60] inv'2 self}
+    {[@expl:precondition] [%#span59] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:Item'0.t_item name)-> {[%#span71] inv'0 result}
-      {[%#span70] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:Item'0.t_item name)-> {[%#span63] inv'0 result}
+      {[%#span62] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
   function m'0 [#"../knapsack.rs" 34 0 34 57] (items : Seq'0.t_seq (Item'0.t_item name)) (i : int) (w : int) : int
   
   axiom m'0_def : forall items : Seq'0.t_seq (Item'0.t_item name), i : int, w : int . m'0 items i w
-  = ([%#span77] if i = 0 then
+  = ([%#span68] if i = 0 then
     0
   else
     if UIntSize.to_int (Knapsack_Item_Type.item_weight (index_logic'5 items (i - 1))) > w then
@@ -895,27 +801,27 @@ module Knapsack_Knapsack01Dyn
     
   )
   
-  axiom m'0_spec : forall items : Seq'0.t_seq (Item'0.t_item name), i : int, w : int . ([%#span72] 0 <= i
-  /\ i <= len'1 items)  -> ([%#span73] 0 <= w)  -> ([%#span74] inv'6 items)  -> ([%#span75] m'0 items i w >= 0)
+  axiom m'0_spec : forall items : Seq'0.t_seq (Item'0.t_item name), i : int, w : int . ([%#span64] 0 <= i
+  /\ i <= len'1 items)  -> ([%#span65] 0 <= w)  -> ([%#span66] m'0 items i w >= 0)
   
-  let rec from_elem'1 (elem:Vec'0.t_vec usize (Global'0.t_global)) (n:usize) (return'  (ret:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))= {[@expl:precondition] [%#span78] inv'4 elem}
+  let rec from_elem'1 (elem:Vec'0.t_vec usize (Global'0.t_global)) (n:usize) (return'  (ret:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))= {[@expl:precondition] [%#span69] inv'4 elem}
     any
-    [ return' (result:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))-> {[%#span81] inv'5 result}
-      {[%#span80] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
-      {[%#span79] len'2 (shallow_model'1 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))-> {[%#span72] inv'5 result}
+      {[%#span71] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
+      {[%#span70] len'2 (shallow_model'1 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span82] inv'2 self}
+  let rec len'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span73] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span83] UIntSize.to_int result = len'1 (shallow_model'0 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span74] UIntSize.to_int result = len'1 (shallow_model'0 self)} (! return' {result}) ]
     
   
-  let rec from_elem'0 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span78] inv'3 elem}
+  let rec from_elem'0 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span69] inv'3 elem}
     any
-    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span81] inv'4 result}
-      {[%#span80] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'3 result i = elem}
-      {[%#span79] len'3 (shallow_model'2 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span72] inv'4 result}
+      {[%#span71] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'3 result i = elem}
+      {[%#span70] len'3 (shallow_model'2 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/knapsack_full.coma b/creusot/tests/should_succeed/knapsack_full.coma
index 9daa891751..896becea67 100644
--- a/creusot/tests/should_succeed/knapsack_full.coma
+++ b/creusot/tests/should_succeed/knapsack_full.coma
@@ -27,22 +27,7 @@ module KnapsackFull_Max
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module KnapsackFull_Item_Type
   use prelude.prelude.UIntSize
@@ -75,57 +60,35 @@ module KnapsackFull_SumWeights_Impl
   
   let%span sknapsack_full0 = "../knapsack_full.rs" 25 11 25 33
   
-  let%span sknapsack_full1 = "../knapsack_full.rs" 27 21 27 22
-  
-  let%span sknapsack_full2 = "../knapsack_full.rs" 26 10 26 21
-  
-  let%span sknapsack_full3 = "../knapsack_full.rs" 24 10 24 19
-  
-  let%span sseq24 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span sknapsack_full1 = "../knapsack_full.rs" 26 10 26 21
   
-  let%span sseq25 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span sknapsack_full2 = "../knapsack_full.rs" 24 10 24 19
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  use prelude.prelude.Int
   
   use KnapsackFull_Item_Type as Item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq (Item'0.t_item name))
-  
-  predicate inv'0 (_x : Seq'0.t_seq (Item'0.t_item name))
-  
-  axiom inv'0 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#sseq24] inv'0 self)
-   -> ([%#sseq25] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#sseq23] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (Item'0.t_item name) = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq (Item'0.t_item name)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   use KnapsackFull_Item_Type as KnapsackFull_Item_Type
   
@@ -137,20 +100,18 @@ module KnapsackFull_SumWeights_Impl
   
   function sum_weights [#"../knapsack_full.rs" 27 0 27 56] (s : Seq'0.t_seq (Item'0.t_item name)) (i : int) : int
   
-  goal vc_sum_weights : ([%#sknapsack_full1] inv'0 s)
-   -> ([%#sknapsack_full0] 0 <= i /\ i <= len'0 s)
-   -> ([%#sseq24] inv'0 s)
-  /\ (([%#sseq25] len'0 s >= 0)
+  goal vc_sum_weights : ([%#sknapsack_full0] 0 <= i /\ i <= len'0 s)
+   -> ([%#sseq23] len'0 s >= 0)
    -> match i = len'0 s with
-    | True -> [%#sknapsack_full2] 0 >= 0
-    | False -> ((([%#sknapsack_full1] inv'0 s) && ([%#sknapsack_full0] 0 <= i + 1 /\ i + 1 <= len'0 s))
-    /\ 0 <= ([%#sknapsack_full3] len'0 s - i)
-    /\ ([%#sknapsack_full3] len'0 s - (i + 1)) < ([%#sknapsack_full3] len'0 s - i))
-    /\ (([%#sknapsack_full2] sum_weights s (i + 1) >= 0)
-     -> ([%#sknapsack_full2] UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 s i))
+    | True -> [%#sknapsack_full1] 0 >= 0
+    | False -> (([%#sknapsack_full0] 0 <= i + 1 /\ i + 1 <= len'0 s)
+    /\ 0 <= ([%#sknapsack_full2] len'0 s - i)
+    /\ ([%#sknapsack_full2] len'0 s - (i + 1)) < ([%#sknapsack_full2] len'0 s - i))
+    /\ (([%#sknapsack_full1] sum_weights s (i + 1) >= 0)
+     -> ([%#sknapsack_full1] UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 s i))
     + sum_weights s (i + 1)
     >= 0))
-    end)
+    end
 end
 module KnapsackFull_SumValues_Impl
   type name
@@ -159,51 +120,31 @@ module KnapsackFull_SumValues_Impl
   
   let%span sknapsack_full1 = "../knapsack_full.rs" 35 10 35 19
   
-  let%span sseq22 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span sseq22 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span3 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  use prelude.prelude.Int
   
   use KnapsackFull_Item_Type as Item'0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq (Item'0.t_item name))
-  
-  predicate inv'0 (_x : Seq'0.t_seq (Item'0.t_item name))
-  
-  axiom inv'0 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#sseq22] inv'0 self)
-   -> ([%#sseq23] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#sseq22] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (Item'0.t_item name) = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq (Item'0.t_item name)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   use KnapsackFull_Item_Type as KnapsackFull_Item_Type
   
@@ -216,14 +157,13 @@ module KnapsackFull_SumValues_Impl
   function sum_values [#"../knapsack_full.rs" 37 0 37 55] (s : Seq'0.t_seq (Item'0.t_item name)) (i : int) : int
   
   goal vc_sum_values : ([%#sknapsack_full0] i >= 0 /\ i <= len'0 s)
-   -> ([%#sseq22] inv'0 s)
-  /\ (([%#sseq23] len'0 s >= 0)
+   -> ([%#sseq22] len'0 s >= 0)
    -> match i = len'0 s with
     | True -> true
     | False -> ([%#sknapsack_full0] i + 1 >= 0 /\ i + 1 <= len'0 s)
     /\ 0 <= ([%#sknapsack_full1] len'0 s - i)
     /\ ([%#sknapsack_full1] len'0 s - (i + 1)) < ([%#sknapsack_full1] len'0 s - i)
-    end)
+    end
 end
 module KnapsackFull_SubseqRev_Impl
   type t
@@ -234,67 +174,37 @@ module KnapsackFull_SubseqRev_Impl
   
   let%span sknapsack_full2 = "../knapsack_full.rs" 45 10 45 12
   
-  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span sseq24 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'1 (self : Seq'0.t_seq t)
+  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  predicate inv'1 (_x : Seq'0.t_seq t)
-  
-  axiom inv'1 : forall x : Seq'0.t_seq t . inv'1 x = true
-  
-  predicate invariant'0 (self : Seq'0.t_seq t)
-  
-  predicate inv'0 (_x : Seq'0.t_seq t)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq t . inv'0 x = true
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#sseq23] inv'1 self)  -> ([%#sseq24] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span5] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#sseq23] len'1 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span7] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span4] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#sseq23] inv'0 self)  -> ([%#sseq24] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#sseq23] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   use prelude.prelude.Borrow
   
@@ -312,9 +222,8 @@ module KnapsackFull_SubseqRev_Impl
   goal vc_subseq_rev : ([%#sknapsack_full1] 0 <= i2 /\ i2 <= len'1 s2)
    -> ([%#sknapsack_full0] 0 <= i1 /\ i1 <= len'0 s1)
    -> match i2 = 0 with
-    | True -> [%#sseq23] inv'0 s1
-    | False -> ([%#sseq23] inv'0 s1)
-    /\ (([%#sseq24] len'0 s1 >= 0)
+    | True -> true
+    | False -> ([%#sseq23] len'0 s1 >= 0)
      -> (if i1 < len'0 s1 then
       if index_logic'0 s1 i1 = index_logic'1 s2 (i2 - 1) then
         ((([%#sknapsack_full1] 0 <= i2 - 1 /\ i2 - 1 <= len'1 s2)
@@ -329,7 +238,7 @@ module KnapsackFull_SubseqRev_Impl
     else
       (([%#sknapsack_full1] 0 <= i2 - 1 /\ i2 - 1 <= len'1 s2) && ([%#sknapsack_full0] 0 <= i1 /\ i1 <= len'0 s1))
       /\ 0 <= ([%#sknapsack_full2] i2) /\ ([%#sknapsack_full2] i2 - 1) < ([%#sknapsack_full2] i2)
-    ))
+    )
     end
 end
 module KnapsackFull_M_Impl
@@ -339,95 +248,63 @@ module KnapsackFull_M_Impl
   
   let%span sknapsack_full1 = "../knapsack_full.rs" 61 11 61 17
   
-  let%span sknapsack_full2 = "../knapsack_full.rs" 66 11 66 16
-  
-  let%span sknapsack_full3 = "../knapsack_full.rs" 62 10 62 21
-  
-  let%span sknapsack_full4 = "../knapsack_full.rs" 63 0 65 2
+  let%span sknapsack_full2 = "../knapsack_full.rs" 62 10 62 21
   
-  let%span sknapsack_full5 = "../knapsack_full.rs" 59 10 59 11
+  let%span sknapsack_full3 = "../knapsack_full.rs" 63 0 65 2
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span sknapsack_full4 = "../knapsack_full.rs" 59 10 59 11
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span7 = "../knapsack_full.rs" 36 11 36 33
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span8 = "../knapsack_full.rs" 35 10 35 19
   
-  let%span span11 = "../knapsack_full.rs" 36 11 36 33
+  let%span span9 = "../knapsack_full.rs" 38 4 41 5
   
-  let%span span12 = "../knapsack_full.rs" 35 10 35 19
+  let%span span10 = "../knapsack_full.rs" 25 11 25 33
   
-  let%span span13 = "../knapsack_full.rs" 38 4 41 5
+  let%span span11 = "../knapsack_full.rs" 26 10 26 21
   
-  let%span span14 = "../knapsack_full.rs" 25 11 25 33
+  let%span span12 = "../knapsack_full.rs" 24 10 24 19
   
-  let%span span15 = "../knapsack_full.rs" 27 21 27 22
+  let%span span13 = "../knapsack_full.rs" 28 4 31 5
   
-  let%span span16 = "../knapsack_full.rs" 26 10 26 21
+  let%span span14 = "../knapsack_full.rs" 46 11 46 36
   
-  let%span span17 = "../knapsack_full.rs" 24 10 24 19
+  let%span span15 = "../knapsack_full.rs" 47 11 47 36
   
-  let%span span18 = "../knapsack_full.rs" 28 4 31 5
+  let%span span16 = "../knapsack_full.rs" 45 10 45 12
   
-  let%span span19 = "../knapsack_full.rs" 46 11 46 36
-  
-  let%span span20 = "../knapsack_full.rs" 47 11 47 36
-  
-  let%span span21 = "../knapsack_full.rs" 45 10 45 12
-  
-  let%span span22 = "../knapsack_full.rs" 49 4 55 5
+  let%span span17 = "../knapsack_full.rs" 49 4 55 5
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
   use KnapsackFull_Item_Type as Item'0
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq (Item'0.t_item name))
-  
   function len'1 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#span6] inv'1 self)
-   -> ([%#span7] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq (Item'0.t_item name) = [%#span8] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#span5] len'1 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span10] ()
+  constant empty'1 : Seq'0.t_seq (Item'0.t_item name)
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span9] len'1 (empty'1 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  predicate invariant'1 (self : Seq'0.t_seq (Item'0.t_item name))
-  
-  axiom inv'1 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'1 x = true
-  
-  predicate invariant'0 (self : Seq'0.t_seq (Item'0.t_item name))
-  
-  predicate inv'0 (_x : Seq'0.t_seq (Item'0.t_item name))
-  
-  axiom inv'0 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'0 x = true
-  
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'1 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   function len'0 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#span6] inv'0 self)
-   -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#span5] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (Item'0.t_item name) = [%#span8] ()
+  constant empty'0 : Seq'0.t_seq (Item'0.t_item name)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   use int.MinMax
   
@@ -437,20 +314,16 @@ module KnapsackFull_M_Impl
   
   use prelude.prelude.UIntSize
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
-  function index_logic'1 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'1 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   use prelude.prelude.Borrow
   
   function sum_values'0 [#"../knapsack_full.rs" 37 0 37 55] (s : Seq'0.t_seq (Item'0.t_item name)) (i : int) : int
   
   axiom sum_values'0_def : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . sum_values'0 s i
-  = ([%#span13] if i = len'1 s then
+  = ([%#span9] if i = len'1 s then
     0
   else
     UIntSize.to_int (KnapsackFull_Item_Type.item_value (index_logic'1 s i)) + sum_values'0 s (i + 1)
@@ -459,20 +332,20 @@ module KnapsackFull_M_Impl
   function sum_weights'0 [#"../knapsack_full.rs" 27 0 27 56] (s : Seq'0.t_seq (Item'0.t_item name)) (i : int) : int
   
   axiom sum_weights'0_def : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . sum_weights'0 s i
-  = ([%#span18] if i = len'1 s then
+  = ([%#span13] if i = len'1 s then
     0
   else
     UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'1 s i)) + sum_weights'0 s (i + 1)
   )
   
-  axiom sum_weights'0_spec : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . ([%#span14] 0 <= i /\ i <= len'1 s)
-   -> ([%#span15] inv'1 s)  -> ([%#span16] sum_weights'0 s i >= 0)
+  axiom sum_weights'0_spec : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . ([%#span10] 0 <= i /\ i <= len'1 s)
+   -> ([%#span11] sum_weights'0 s i >= 0)
   
   predicate subseq_rev'0 [#"../knapsack_full.rs" 48 0 48 67] (s1 : Seq'0.t_seq (Item'0.t_item name)) (i1 : int) (s2 : Seq'0.t_seq (Item'0.t_item name)) (i2 : int)
     
   
   axiom subseq_rev'0_def : forall s1 : Seq'0.t_seq (Item'0.t_item name), i1 : int, s2 : Seq'0.t_seq (Item'0.t_item name), i2 : int . subseq_rev'0 s1 i1 s2 i2
-  = ([%#span22] if i2 = 0 then
+  = ([%#span17] if i2 = 0 then
     i1 = len'1 s1
   else
     i1 < len'1 s1 /\ index_logic'1 s1 i1 = index_logic'0 s2 (i2 - 1) /\ subseq_rev'0 s1 (i1 + 1) s2 (i2 - 1)
@@ -487,53 +360,49 @@ module KnapsackFull_M_Impl
   
   function m [#"../knapsack_full.rs" 66 0 66 57] (items : Seq'0.t_seq (Item'0.t_item name)) (i : int) (w : int) : int
   
-  goal vc_m : ([%#sknapsack_full2] inv'0 items)
-   -> ([%#sknapsack_full1] 0 <= w)
+  goal vc_m : ([%#sknapsack_full1] 0 <= w)
    -> ([%#sknapsack_full0] 0 <= i /\ i <= len'0 items)
    -> match i = 0 with
-    | True -> let result = 0 in ([%#sknapsack_full4] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . inv'1 s
-     -> 0 <= j /\ j <= len'1 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w  -> sum_values'0 s j <= result)
-    && ([%#sknapsack_full3] result >= 0)
+    | True -> let result = 0 in ([%#sknapsack_full3] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . 0
+    <= j
+    /\ j <= len'1 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w  -> sum_values'0 s j <= result)
+    && ([%#sknapsack_full2] result >= 0)
     | False -> match UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 items (i - 1))) > w with
-      | True -> ((([%#sknapsack_full2] inv'0 items)
-      && ([%#sknapsack_full1] 0 <= w) && ([%#sknapsack_full0] 0 <= i - 1 /\ i - 1 <= len'0 items))
-      /\ 0 <= ([%#sknapsack_full5] i) /\ ([%#sknapsack_full5] i - 1) < ([%#sknapsack_full5] i))
-      /\ (([%#sknapsack_full4] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . inv'1 s
-       -> 0 <= j /\ j <= len'1 s /\ subseq_rev'0 s j items (i - 1) /\ sum_weights'0 s j <= w
+      | True -> ((([%#sknapsack_full1] 0 <= w) && ([%#sknapsack_full0] 0 <= i - 1 /\ i - 1 <= len'0 items))
+      /\ 0 <= ([%#sknapsack_full4] i) /\ ([%#sknapsack_full4] i - 1) < ([%#sknapsack_full4] i))
+      /\ (([%#sknapsack_full3] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . 0 <= j
+      /\ j <= len'1 s /\ subseq_rev'0 s j items (i - 1) /\ sum_weights'0 s j <= w
        -> sum_values'0 s j <= m items (i - 1) w)
-      && ([%#sknapsack_full3] m items (i - 1) w >= 0)
+      && ([%#sknapsack_full2] m items (i - 1) w >= 0)
        -> (let result = m items (i
-      - 1) w in ([%#sknapsack_full4] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . inv'1 s
-       -> 0 <= j /\ j <= len'1 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w  -> sum_values'0 s j <= result)
-      && ([%#sknapsack_full3] result >= 0)))
-      | False -> ((([%#sknapsack_full2] inv'0 items)
-      && ([%#sknapsack_full1] 0 <= w) && ([%#sknapsack_full0] 0 <= i - 1 /\ i - 1 <= len'0 items))
-      /\ 0 <= ([%#sknapsack_full5] i) /\ ([%#sknapsack_full5] i - 1) < ([%#sknapsack_full5] i))
-      /\ (([%#sknapsack_full4] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . inv'1 s
-       -> 0 <= j /\ j <= len'1 s /\ subseq_rev'0 s j items (i - 1) /\ sum_weights'0 s j <= w
+      - 1) w in ([%#sknapsack_full3] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . 0 <= j
+      /\ j <= len'1 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w  -> sum_values'0 s j <= result)
+      && ([%#sknapsack_full2] result >= 0)))
+      | False -> ((([%#sknapsack_full1] 0 <= w) && ([%#sknapsack_full0] 0 <= i - 1 /\ i - 1 <= len'0 items))
+      /\ 0 <= ([%#sknapsack_full4] i) /\ ([%#sknapsack_full4] i - 1) < ([%#sknapsack_full4] i))
+      /\ (([%#sknapsack_full3] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . 0 <= j
+      /\ j <= len'1 s /\ subseq_rev'0 s j items (i - 1) /\ sum_weights'0 s j <= w
        -> sum_values'0 s j <= m items (i - 1) w)
-      && ([%#sknapsack_full3] m items (i - 1) w >= 0)
-       -> ((([%#sknapsack_full2] inv'0 items)
-      && ([%#sknapsack_full1] 0
+      && ([%#sknapsack_full2] m items (i - 1) w >= 0)
+       -> ((([%#sknapsack_full1] 0
       <= w - UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 items (i - 1))))
       && ([%#sknapsack_full0] 0 <= i - 1 /\ i - 1 <= len'0 items))
-      /\ 0 <= ([%#sknapsack_full5] i) /\ ([%#sknapsack_full5] i - 1) < ([%#sknapsack_full5] i))
-      /\ (([%#sknapsack_full4] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . inv'1 s
-       -> 0 <= j
+      /\ 0 <= ([%#sknapsack_full4] i) /\ ([%#sknapsack_full4] i - 1) < ([%#sknapsack_full4] i))
+      /\ (([%#sknapsack_full3] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . 0 <= j
       /\ j <= len'1 s
       /\ subseq_rev'0 s j items (i - 1)
       /\ sum_weights'0 s j <= w - UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 items (i - 1)))
        -> sum_values'0 s j
       <= m items (i - 1) (w - UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 items (i - 1)))))
-      && ([%#sknapsack_full3] m items (i - 1) (w
+      && ([%#sknapsack_full2] m items (i - 1) (w
       - UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 items (i - 1))))
       >= 0)
        -> (let result = MinMax.max (m items (i - 1) w) (m items (i - 1) (w
       - UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'0 items (i - 1))))
       + UIntSize.to_int (KnapsackFull_Item_Type.item_value (index_logic'0 items (i
-      - 1)))) in ([%#sknapsack_full4] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . inv'1 s
-       -> 0 <= j /\ j <= len'1 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w  -> sum_values'0 s j <= result)
-      && ([%#sknapsack_full3] result >= 0))))
+      - 1)))) in ([%#sknapsack_full3] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . 0 <= j
+      /\ j <= len'1 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w  -> sum_values'0 s j <= result)
+      && ([%#sknapsack_full2] result >= 0))))
       end
     end
 end
@@ -773,471 +642,425 @@ module KnapsackFull_Knapsack01Dyn
   
   let%span sknapsack_full29 = "../knapsack_full.rs" 85 75 85 91
   
-  let%span span30 = "" 0 0 0 0
+  let%span span30 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span31 = "" 0 0 0 0
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span34 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span35 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span35 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span36 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span37 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span39 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span40 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span40 = "../../../../creusot-contracts/src/std/ops.rs" 207 20 207 24
   
-  let%span span41 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span41 = "../../../../creusot-contracts/src/std/ops.rs" 206 4 206 88
   
-  let%span span42 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span42 = "../../../../creusot-contracts/src/std/iter/range.rs" 46 62 46 63
   
-  let%span span43 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span43 = "../../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
   
-  let%span span44 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span44 = "../../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
   
-  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span45 = "../../../../creusot-contracts/src/std/iter/range.rs" 65 8 71 9
   
-  let%span span46 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span46 = "../../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
   
-  let%span span47 = "../../../../creusot-contracts/src/std/ops.rs" 207 20 207 24
+  let%span span47 = "../../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
   
-  let%span span48 = "../../../../creusot-contracts/src/std/ops.rs" 206 4 206 88
+  let%span span48 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 22 84 23
   
-  let%span span49 = "../../../../creusot-contracts/src/std/iter/range.rs" 46 62 46 63
+  let%span span49 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 52 84 53
   
-  let%span span50 = "../../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
+  let%span span50 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 82 84 83
   
-  let%span span51 = "../../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
+  let%span span51 = "../../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
   
-  let%span span52 = "../../../../creusot-contracts/src/std/iter/range.rs" 65 8 71 9
+  let%span span52 = "../../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
   
-  let%span span53 = "../../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
+  let%span span53 = "../../../../creusot-contracts/src/std/iter/range.rs" 77 21 77 25
   
-  let%span span54 = "../../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
+  let%span span54 = "../../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
   
-  let%span span55 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 22 84 23
+  let%span span55 = "../../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
   
-  let%span span56 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 31 84 33
+  let%span span56 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span57 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 52 84 53
+  let%span span57 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span58 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 61 84 63
+  let%span span58 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span59 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 82 84 83
+  let%span span59 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span60 = "../../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
+  let%span span60 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span61 = "../../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
+  let%span span61 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span62 = "../../../../creusot-contracts/src/std/iter/range.rs" 77 21 77 25
+  let%span span62 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span63 = "../../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
+  let%span span63 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span64 = "../../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
+  let%span span64 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span65 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span65 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span66 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span66 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span67 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span67 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span68 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span68 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span69 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span69 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span70 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span70 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span71 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span71 = "" 0 0 0 0
   
-  let%span span72 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span72 = "" 0 0 0 0
   
-  let%span span73 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span73 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span74 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span74 = "../knapsack_full.rs" 46 11 46 36
   
-  let%span span75 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span75 = "../knapsack_full.rs" 47 11 47 36
   
-  let%span span76 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span76 = "../knapsack_full.rs" 45 10 45 12
   
-  let%span span77 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span77 = "../knapsack_full.rs" 49 4 55 5
   
-  let%span span78 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span78 = "../knapsack_full.rs" 36 11 36 33
   
-  let%span span79 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span79 = "../knapsack_full.rs" 35 10 35 19
   
-  let%span span80 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span80 = "../knapsack_full.rs" 38 4 41 5
   
-  let%span span81 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span81 = "../knapsack_full.rs" 25 11 25 33
   
-  let%span span82 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span82 = "../knapsack_full.rs" 26 10 26 21
   
-  let%span span83 = "" 0 0 0 0
+  let%span span83 = "../knapsack_full.rs" 24 10 24 19
   
-  let%span span84 = "" 0 0 0 0
+  let%span span84 = "../knapsack_full.rs" 28 4 31 5
   
-  let%span span85 = "../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span85 = "../../../../creusot-contracts/src/std/vec.rs" 73 26 73 44
   
-  let%span span86 = "../knapsack_full.rs" 46 11 46 36
+  let%span span86 = "" 0 0 0 0
   
-  let%span span87 = "../knapsack_full.rs" 47 11 47 36
+  let%span span87 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span88 = "../knapsack_full.rs" 45 10 45 12
+  let%span span88 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span89 = "../knapsack_full.rs" 49 4 55 5
+  let%span span89 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span90 = "../knapsack_full.rs" 36 11 36 33
+  let%span span90 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span91 = "../knapsack_full.rs" 35 10 35 19
+  let%span span91 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span92 = "../knapsack_full.rs" 38 4 41 5
+  let%span span92 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span93 = "../knapsack_full.rs" 25 11 25 33
+  let%span span93 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span94 = "../knapsack_full.rs" 27 21 27 22
+  let%span span94 = "" 0 0 0 0
   
-  let%span span95 = "../knapsack_full.rs" 26 10 26 21
+  let%span span95 = "" 0 0 0 0
   
-  let%span span96 = "../knapsack_full.rs" 24 10 24 19
+  let%span span96 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span97 = "../knapsack_full.rs" 28 4 31 5
+  let%span span97 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span98 = "../../../../creusot-contracts/src/std/vec.rs" 73 26 73 44
+  let%span span98 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span99 = "" 0 0 0 0
+  let%span span99 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span100 = "../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span100 = "" 0 0 0 0
   
-  let%span span101 = "../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span101 = "../knapsack_full.rs" 14 10 14 31
   
-  let%span span102 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span102 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span103 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span103 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span104 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span104 = "" 0 0 0 0
   
-  let%span span105 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span105 = "" 0 0 0 0
   
-  let%span span106 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span106 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
   let%span span107 = "" 0 0 0 0
   
-  let%span span108 = "" 0 0 0 0
+  let%span span108 = "../../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
   
-  let%span span109 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span109 = "" 0 0 0 0
   
-  let%span span110 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span110 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span111 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span111 = "" 0 0 0 0
   
-  let%span span112 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span112 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span113 = "" 0 0 0 0
+  let%span span113 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span114 = "../knapsack_full.rs" 14 10 14 31
+  let%span span114 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span115 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span115 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span116 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span116 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
   let%span span117 = "" 0 0 0 0
   
   let%span span118 = "" 0 0 0 0
   
-  let%span span119 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span119 = "" 0 0 0 0
   
   let%span span120 = "" 0 0 0 0
   
-  let%span span121 = "../../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
+  let%span span121 = "../../../../creusot-contracts/src/std/ops.rs" 220 26 220 53
   
-  let%span span122 = "" 0 0 0 0
+  let%span span122 = "../../../../creusot-contracts/src/std/ops.rs" 221 26 221 49
   
-  let%span span123 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span123 = "../../../../creusot-contracts/src/std/ops.rs" 222 16 222 93
   
   let%span span124 = "" 0 0 0 0
   
-  let%span span125 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span125 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span126 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span126 = "" 0 0 0 0
   
-  let%span span127 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
+  let%span span127 = "" 0 0 0 0
   
-  let%span span128 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
+  let%span span128 = "../knapsack_full.rs" 60 11 60 37
   
-  let%span span129 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span129 = "../knapsack_full.rs" 61 11 61 17
   
-  let%span span130 = "" 0 0 0 0
+  let%span span130 = "../knapsack_full.rs" 62 10 62 21
   
-  let%span span131 = "" 0 0 0 0
+  let%span span131 = "../knapsack_full.rs" 63 0 65 2
   
-  let%span span132 = "" 0 0 0 0
+  let%span span132 = "../knapsack_full.rs" 59 10 59 11
   
-  let%span span133 = "" 0 0 0 0
+  let%span span133 = "../knapsack_full.rs" 67 4 74 5
   
-  let%span span134 = "../../../../creusot-contracts/src/std/ops.rs" 220 26 220 53
+  let%span span134 = "" 0 0 0 0
   
-  let%span span135 = "../../../../creusot-contracts/src/std/ops.rs" 221 26 221 49
+  let%span span135 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span136 = "../../../../creusot-contracts/src/std/ops.rs" 222 16 222 93
+  let%span span136 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
   let%span span137 = "" 0 0 0 0
   
-  let%span span138 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
-  
-  let%span span139 = "" 0 0 0 0
-  
-  let%span span140 = "" 0 0 0 0
+  let%span span138 = "" 0 0 0 0
   
-  let%span span141 = "../knapsack_full.rs" 60 11 60 37
+  let%span span139 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span142 = "../knapsack_full.rs" 61 11 61 17
-  
-  let%span span143 = "../knapsack_full.rs" 66 11 66 16
+  use KnapsackFull_Item_Type as Item'0
   
-  let%span span144 = "../knapsack_full.rs" 62 10 62 21
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span145 = "../knapsack_full.rs" 63 0 65 2
+  predicate invariant'22 (self : Seq'0.t_seq (Item'0.t_item name))
   
-  let%span span146 = "../knapsack_full.rs" 59 10 59 11
+  predicate inv'22 (_x : Seq'0.t_seq (Item'0.t_item name))
   
-  let%span span147 = "../knapsack_full.rs" 67 4 74 5
+  axiom inv'22 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'22 x = true
   
-  let%span span148 = "" 0 0 0 0
+  use Alloc_Alloc_Global_Type as Global'0
   
-  let%span span149 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
+  use prelude.prelude.UIntSize
   
-  let%span span150 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
+  use Alloc_Vec_Vec_Type as Vec'0
   
-  let%span span151 = "" 0 0 0 0
+  predicate invariant'21 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span30] true
   
-  let%span span152 = "" 0 0 0 0
+  predicate inv'21 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   
-  let%span span153 = "../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  axiom inv'21 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'21 x = true
   
-  use KnapsackFull_Item_Type as Item'0
+  predicate invariant'20 (self : Seq'0.t_seq (Item'0.t_item name))
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'20 (_x : Seq'0.t_seq (Item'0.t_item name))
   
-  predicate inv'10 (_x : Seq'0.t_seq (Item'0.t_item name))
-  
-  use Alloc_Alloc_Global_Type as Global'0
-  
-  use Alloc_Vec_Vec_Type as Vec'0
-  
-  use prelude.prelude.UIntSize
+  axiom inv'20 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'20 x = true
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.Int
   
-  constant max'1 : usize = [%#span30] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'1 : usize = [%#span31] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#span31] inv'10 self)
-   -> ([%#span32] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#span32] len'1 self >= 0
   
-  predicate inv'22 (_x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
+  predicate inv'19 (_x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
   
   function shallow_model'4 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) : Seq'0.t_seq (Item'0.t_item name)
     
   
-  axiom shallow_model'4_spec : forall self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . ([%#span33] inv'22 self)
-   -> ([%#span35] inv'10 (shallow_model'4 self))
-  && ([%#span34] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'1 : usize))
+  axiom shallow_model'4_spec : forall self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . ([%#span33] inv'19 self)
+   -> ([%#span34] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'1 : usize))
   
-  predicate invariant'22 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) =
-    [%#span36] inv'10 (shallow_model'4 self)
+  predicate invariant'19 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) =
+    [%#span35] inv'22 (shallow_model'4 self)
   
-  axiom inv'22 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'22 x = true
+  axiom inv'19 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'19 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'21 (self : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
+  predicate invariant'18 (self : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
   
-  predicate inv'21 (_x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
+  predicate inv'18 (_x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))
   
-  axiom inv'21 : forall x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) . inv'21 x = true
+  axiom inv'18 : forall x : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) . inv'18 x = true
   
-  predicate invariant'20 (self : borrowed usize) =
-    [%#span37] true
+  predicate invariant'17 (self : borrowed usize) =
+    [%#span30] true
   
-  predicate inv'20 (_x : borrowed usize)
+  predicate inv'17 (_x : borrowed usize)
   
-  axiom inv'20 : forall x : borrowed usize . inv'20 x = true
+  axiom inv'17 : forall x : borrowed usize . inv'17 x = true
   
-  predicate invariant'19 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span37] true
+  predicate invariant'16 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span30] true
   
-  predicate inv'19 (_x : borrowed (Vec'0.t_vec usize (Global'0.t_global)))
+  predicate inv'16 (_x : borrowed (Vec'0.t_vec usize (Global'0.t_global)))
   
-  axiom inv'19 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'19 x = true
+  axiom inv'16 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'16 x = true
   
-  predicate invariant'18 (self : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) =
-    [%#span37] true
+  predicate invariant'15 (self : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) =
+    [%#span30] true
   
-  predicate inv'18 (_x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))
+  predicate inv'15 (_x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))
   
-  axiom inv'18 : forall x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) . inv'18 x
+  axiom inv'15 : forall x : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) . inv'15 x
   = true
   
-  predicate invariant'17 (self : usize) =
-    [%#span37] true
+  predicate invariant'14 (self : usize) =
+    [%#span30] true
   
-  predicate inv'17 (_x : usize)
+  predicate inv'14 (_x : usize)
   
-  axiom inv'17 : forall x : usize . inv'17 x = true
+  axiom inv'14 : forall x : usize . inv'14 x = true
   
-  predicate invariant'16 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span37] true
+  predicate invariant'13 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span30] true
   
-  predicate inv'16 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'13 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
-  axiom inv'16 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'16 x = true
+  axiom inv'13 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'13 x = true
   
-  predicate invariant'15 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span37] true
+  predicate invariant'12 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
+    [%#span30] true
   
-  predicate inv'15 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
+  predicate inv'12 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
-  axiom inv'15 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'15 x = true
+  axiom inv'12 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'12 x = true
   
   use Core_Ops_Range_RangeInclusive_Type as RangeInclusive'0
   
-  predicate invariant'14 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
-    [%#span37] true
+  predicate invariant'11 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
+    [%#span30] true
   
-  predicate inv'14 (_x : borrowed (RangeInclusive'0.t_rangeinclusive usize))
+  predicate inv'11 (_x : borrowed (RangeInclusive'0.t_rangeinclusive usize))
   
-  axiom inv'14 : forall x : borrowed (RangeInclusive'0.t_rangeinclusive usize) . inv'14 x = true
+  axiom inv'11 : forall x : borrowed (RangeInclusive'0.t_rangeinclusive usize) . inv'11 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'13 (self : Option'0.t_option usize) =
-    [%#span37] true
+  predicate invariant'10 (self : Option'0.t_option usize) =
+    [%#span30] true
   
-  predicate inv'13 (_x : Option'0.t_option usize)
+  predicate inv'10 (_x : Option'0.t_option usize)
   
-  axiom inv'13 : forall x : Option'0.t_option usize . inv'13 x = true
+  axiom inv'10 : forall x : Option'0.t_option usize . inv'10 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
-  predicate invariant'12 (self : borrowed (Range'0.t_range usize)) =
-    [%#span37] true
-  
-  predicate inv'12 (_x : borrowed (Range'0.t_range usize))
-  
-  axiom inv'12 : forall x : borrowed (Range'0.t_range usize) . inv'12 x = true
-  
-  predicate invariant'11 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span37] true
-  
-  predicate inv'11 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
-  
-  axiom inv'11 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'11 x = true
-  
-  predicate invariant'10 (self : Seq'0.t_seq (Item'0.t_item name))
+  predicate invariant'9 (self : borrowed (Range'0.t_range usize)) =
+    [%#span30] true
   
-  axiom inv'10 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'10 x = true
+  predicate inv'9 (_x : borrowed (Range'0.t_range usize))
   
-  predicate invariant'9 (self : Seq'0.t_seq usize) =
-    [%#span37] true
+  axiom inv'9 : forall x : borrowed (Range'0.t_range usize) . inv'9 x = true
   
-  predicate inv'9 (_x : Seq'0.t_seq usize)
+  predicate invariant'8 (self : Seq'0.t_seq usize) =
+    [%#span30] true
   
-  axiom inv'9 : forall x : Seq'0.t_seq usize . inv'9 x = true
+  predicate inv'8 (_x : Seq'0.t_seq usize)
   
-  use seq.Seq
+  axiom inv'8 : forall x : Seq'0.t_seq usize . inv'8 x = true
   
   function len'2 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span31] inv'11 self)
-   -> ([%#span32] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . [%#span32] len'2 self >= 0
   
-  predicate inv'8 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
+  predicate inv'7 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span33] inv'8 self)
-   -> ([%#span35] inv'11 (shallow_model'1 self))
-  && ([%#span34] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'1 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span33] inv'7 self)
+   -> ([%#span34] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'1 : usize))
   
-  predicate invariant'8 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span36] inv'11 (shallow_model'1 self)
+  predicate invariant'7 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
+    [%#span35] inv'21 (shallow_model'1 self)
   
-  axiom inv'8 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'8 x = true
-  
-  use seq.Seq
+  axiom inv'7 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'7 x = true
   
   function len'3 (self : Seq'0.t_seq usize) : int
   
-  axiom len'3_spec : forall self : Seq'0.t_seq usize . ([%#span31] inv'9 self)  -> ([%#span32] len'3 self >= 0)
+  axiom len'3_spec : forall self : Seq'0.t_seq usize . [%#span32] len'3 self >= 0
   
-  predicate inv'7 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'6 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span33] inv'7 self)
-   -> ([%#span35] inv'9 (shallow_model'2 self))
-  && ([%#span34] len'3 (shallow_model'2 self) <= UIntSize.to_int (max'1 : usize))
-  
-  predicate invariant'7 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span36] inv'9 (shallow_model'2 self)
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span33] inv'6 self)
+   -> ([%#span34] len'3 (shallow_model'2 self) <= UIntSize.to_int (max'1 : usize))
   
-  axiom inv'7 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'7 x = true
+  predicate invariant'6 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span35] inv'8 (shallow_model'2 self)
   
-  predicate invariant'6 (self : usize) =
-    [%#span37] true
+  axiom inv'6 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'6 x = true
   
-  predicate inv'6 (_x : usize)
+  predicate invariant'5 (self : usize) =
+    [%#span30] true
   
-  axiom inv'6 : forall x : usize . inv'6 x = true
+  predicate inv'5 (_x : usize)
   
-  predicate inv'4 (_x : Seq'0.t_seq (Item'0.t_item name))
-  
-  use seq.Seq
+  axiom inv'5 : forall x : usize . inv'5 x = true
   
   function len'4 (self : Seq'0.t_seq (Item'0.t_item name)) : int
   
-  axiom len'4_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . ([%#span31] inv'4 self)
-   -> ([%#span32] len'4 self >= 0)
+  axiom len'4_spec : forall self : Seq'0.t_seq (Item'0.t_item name) . [%#span32] len'4 self >= 0
   
-  predicate inv'5 (_x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
+  predicate inv'4 (_x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) : Seq'0.t_seq (Item'0.t_item name)
     
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . ([%#span33] inv'5 self)
-   -> ([%#span35] inv'4 (shallow_model'3 self))
-  && ([%#span34] len'4 (shallow_model'3 self) <= UIntSize.to_int (max'1 : usize))
-  
-  predicate invariant'5 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) =
-    [%#span36] inv'4 (shallow_model'3 self)
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . ([%#span33] inv'4 self)
+   -> ([%#span34] len'4 (shallow_model'3 self) <= UIntSize.to_int (max'1 : usize))
   
-  axiom inv'5 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'5 x = true
+  predicate invariant'4 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) =
+    [%#span35] inv'20 (shallow_model'3 self)
   
-  constant empty'3 : Seq'0.t_seq (Item'0.t_item name) = [%#span38] ()
+  axiom inv'4 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'4 x = true
   
-  function empty_len'3 (_1 : ()) : () =
-    [%#span40] ()
+  constant empty'3 : Seq'0.t_seq (Item'0.t_item name)
   
-  axiom empty_len'3_spec : forall _1 : () . [%#span39] len'4 (empty'3 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  function empty_len'3 (_1 : ()) : ()
   
-  predicate invariant'4 (self : Seq'0.t_seq (Item'0.t_item name))
-  
-  axiom inv'4 : forall x : Seq'0.t_seq (Item'0.t_item name) . inv'4 x = true
+  axiom empty_len'3_spec : forall _1 : () . [%#span36] len'4 (empty'3 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   predicate invariant'3 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
   
@@ -1245,21 +1068,15 @@ module KnapsackFull_Knapsack01Dyn
   
   axiom inv'3 : forall x : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global) . inv'3 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span41] inv'9 self)
-   -> ([%#span42] inv'9 other)
-   -> ([%#span45] inv'9 (concat'0 self other))
-  && ([%#span44] forall i : int . 0 <= i /\ i < len'3 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span38] forall i : int . 0 <= i
+  /\ i < len'3 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'3 self then index_logic'1 self i else index_logic'1 other (i - len'3 self)))
-  && ([%#span43] len'3 (concat'0 self other) = len'3 self + len'3 other)
+  && ([%#span37] len'3 (concat'0 self other) = len'3 self + len'3 other)
   
   predicate inv'2 (_x : RangeInclusive'0.t_rangeinclusive usize)
   
@@ -1268,7 +1085,7 @@ module KnapsackFull_Knapsack01Dyn
   function start_log'0 (self : RangeInclusive'0.t_rangeinclusive usize) : usize
   
   function deep_model'0 (self : usize) : int =
-    [%#span46] UIntSize.to_int self
+    [%#span39] UIntSize.to_int self
   
   function end_log'0 (self : RangeInclusive'0.t_rangeinclusive usize) : usize
   
@@ -1276,19 +1093,19 @@ module KnapsackFull_Knapsack01Dyn
   
   function is_empty_log'0 (self : RangeInclusive'0.t_rangeinclusive usize) : bool
   
-  axiom is_empty_log'0_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span47] inv'2 self)
-   -> ([%#span48] not is_empty_log'0 self  -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self))
+  axiom is_empty_log'0_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span40] inv'2 self)
+   -> ([%#span41] not is_empty_log'0 self  -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self))
   
   function range_inclusive_len'0 (r : RangeInclusive'0.t_rangeinclusive usize) : int =
-    [%#span51] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+    [%#span44] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
   
-  axiom range_inclusive_len'0_spec : forall r : RangeInclusive'0.t_rangeinclusive usize . ([%#span49] inv'2 r)
-   -> ([%#span50] is_empty_log'0 r = (range_inclusive_len'0 r = 0))
+  axiom range_inclusive_len'0_spec : forall r : RangeInclusive'0.t_rangeinclusive usize . ([%#span42] inv'2 r)
+   -> ([%#span43] is_empty_log'0 r = (range_inclusive_len'0 r = 0))
   
   predicate produces'1 (self : RangeInclusive'0.t_rangeinclusive usize) (visited : Seq'0.t_seq usize) (o : RangeInclusive'0.t_rangeinclusive usize)
     
    =
-    [%#span52] len'3 visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    [%#span45] len'3 visited = range_inclusive_len'0 self - range_inclusive_len'0 o
     /\ (is_empty_log'0 self  -> is_empty_log'0 o)
     /\ (is_empty_log'0 o \/ end_log'0 self = end_log'0 o)
     /\ (forall i : int . 0 <= i /\ i < len'3 visited
@@ -1297,25 +1114,23 @@ module KnapsackFull_Knapsack01Dyn
   function produces_trans'1 (a : RangeInclusive'0.t_rangeinclusive usize) (ab : Seq'0.t_seq usize) (b : RangeInclusive'0.t_rangeinclusive usize) (bc : Seq'0.t_seq usize) (c : RangeInclusive'0.t_rangeinclusive usize) : ()
     
    =
-    [%#span61] ()
+    [%#span52] ()
   
-  axiom produces_trans'1_spec : forall a : RangeInclusive'0.t_rangeinclusive usize, ab : Seq'0.t_seq usize, b : RangeInclusive'0.t_rangeinclusive usize, bc : Seq'0.t_seq usize, c : RangeInclusive'0.t_rangeinclusive usize . ([%#span53] produces'1 a ab b)
-   -> ([%#span54] produces'1 b bc c)
-   -> ([%#span55] inv'2 a)
-   -> ([%#span56] inv'9 ab)
-   -> ([%#span57] inv'2 b)
-   -> ([%#span58] inv'9 bc)  -> ([%#span59] inv'2 c)  -> ([%#span60] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : RangeInclusive'0.t_rangeinclusive usize, ab : Seq'0.t_seq usize, b : RangeInclusive'0.t_rangeinclusive usize, bc : Seq'0.t_seq usize, c : RangeInclusive'0.t_rangeinclusive usize . ([%#span46] produces'1 a ab b)
+   -> ([%#span47] produces'1 b bc c)
+   -> ([%#span48] inv'2 a)
+   -> ([%#span49] inv'2 b)  -> ([%#span50] inv'2 c)  -> ([%#span51] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span38] ()
+  constant empty'0 : Seq'0.t_seq usize
   
   function produces_refl'1 (self : RangeInclusive'0.t_rangeinclusive usize) : () =
-    [%#span64] ()
+    [%#span55] ()
   
-  axiom produces_refl'1_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span62] inv'2 self)
-   -> ([%#span63] produces'1 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'1_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span53] inv'2 self)
+   -> ([%#span54] produces'1 self (empty'0 : Seq'0.t_seq usize) self)
   
   predicate invariant'2 (self : RangeInclusive'0.t_rangeinclusive usize) =
-    [%#span37] true
+    [%#span30] true
   
   axiom inv'2 : forall x : RangeInclusive'0.t_rangeinclusive usize . inv'2 x = true
   
@@ -1325,27 +1140,25 @@ module KnapsackFull_Knapsack01Dyn
   
   axiom inv'1 : forall x : Item'0.t_item name . inv'1 x = true
   
-  constant empty'2 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) = [%#span38] ()
+  constant empty'2 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span40] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span39] len'2 (empty'2 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom empty_len'2_spec : forall _1 : () . [%#span36] len'2 (empty'2 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   = 0
   
-  constant empty'1 : Seq'0.t_seq (Item'0.t_item name) = [%#span38] ()
+  constant empty'1 : Seq'0.t_seq (Item'0.t_item name)
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span40] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span39] len'1 (empty'1 : Seq'0.t_seq (Item'0.t_item name)) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span36] len'1 (empty'1 : Seq'0.t_seq (Item'0.t_item name)) = 0
   
   predicate inv'0 (_x : Range'0.t_range usize)
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span65] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span56] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'3 visited > 0
@@ -1358,82 +1171,69 @@ module KnapsackFull_Knapsack01Dyn
   function produces_trans'0 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span66] produces'0 a ab b)
-   -> ([%#span67] produces'0 b bc c)
-   -> ([%#span68] inv'0 a)
-   -> ([%#span69] inv'9 ab)
-   -> ([%#span70] inv'0 b)
-   -> ([%#span71] inv'9 bc)  -> ([%#span72] inv'0 c)  -> ([%#span73] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span57] produces'0 a ab b)
+   -> ([%#span58] produces'0 b bc c)
+   -> ([%#span59] inv'0 a)
+   -> ([%#span60] inv'0 b)  -> ([%#span61] inv'0 c)  -> ([%#span62] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span74] inv'0 self)
-   -> ([%#span75] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span63] inv'0 self)
+   -> ([%#span64] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
   
   predicate invariant'0 (self : Range'0.t_range usize) =
-    [%#span37] true
+    [%#span30] true
   
   axiom inv'0 : forall x : Range'0.t_range usize . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span40] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span39] len'3 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span36] len'3 (empty'0 : Seq'0.t_seq usize) = 0
   
   use KnapsackFull_Item_Type as KnapsackFull_Item_Type
   
-  use seq.Seq
-  
-  function index_logic'7 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'7 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   function index_logic'4 [@inline:trivial] (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (ix : int) : Item'0.t_item name
     
    =
-    [%#span76] index_logic'7 (shallow_model'4 self) ix
+    [%#span65] index_logic'7 (shallow_model'4 self) ix
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq (Item'0.t_item name)) (x : int) : Item'0.t_item name
+  function index_logic'3 (self : Seq'0.t_seq (Item'0.t_item name)) (_2 : int) : Item'0.t_item name
   
   function concat'1 (self : Seq'0.t_seq (Item'0.t_item name)) (other : Seq'0.t_seq (Item'0.t_item name)) : Seq'0.t_seq (Item'0.t_item name)
     
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name), other : Seq'0.t_seq (Item'0.t_item name) . ([%#span41] inv'4 self)
-   -> ([%#span42] inv'4 other)
-   -> ([%#span45] inv'4 (concat'1 self other))
-  && ([%#span44] forall i : int . 0 <= i /\ i < len'4 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq (Item'0.t_item name), other : Seq'0.t_seq (Item'0.t_item name) . ([%#span38] forall i : int . 0
+  <= i
+  /\ i < len'4 (concat'1 self other)
    -> index_logic'3 (concat'1 self other) i
   = (if i < len'4 self then index_logic'3 self i else index_logic'3 other (i - len'4 self)))
-  && ([%#span43] len'4 (concat'1 self other) = len'4 self + len'4 other)
-  
-  use seq.Seq
+  && ([%#span37] len'4 (concat'1 self other) = len'4 self + len'4 other)
   
   function singleton'1 (v : Item'0.t_item name) : Seq'0.t_seq (Item'0.t_item name)
   
-  axiom singleton'1_spec : forall v : Item'0.t_item name . ([%#span77] inv'1 v)
-   -> ([%#span80] inv'4 (singleton'1 v))
-  && ([%#span79] index_logic'3 (singleton'1 v) 0 = v) && ([%#span78] len'4 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : Item'0.t_item name . ([%#span66] inv'1 v)
+   -> ([%#span68] index_logic'3 (singleton'1 v) 0 = v) && ([%#span67] len'4 (singleton'1 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq (Item'0.t_item name)) (v : Item'0.t_item name) : Seq'0.t_seq (Item'0.t_item name)
     
    =
-    [%#span81] concat'1 self (singleton'1 v)
+    [%#span69] concat'1 self (singleton'1 v)
   
   function shallow_model'9 (self : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))) : Seq'0.t_seq (Item'0.t_item name)
     
    =
-    [%#span82] shallow_model'3 ( * self)
+    [%#span70] shallow_model'3 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))) (value:Item'0.t_item name) (return'  (ret:()))= {[@expl:precondition] [%#span84] inv'1 value}
-    {[@expl:precondition] [%#span83] inv'21 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))) (value:Item'0.t_item name) (return'  (ret:()))= {[@expl:precondition] [%#span72] inv'1 value}
+    {[@expl:precondition] [%#span71] inv'18 self}
     any
-    [ return' (result:())-> {[%#span85] shallow_model'3 ( ^ self) = push'1 (shallow_model'9 self) value}
+    [ return' (result:())-> {[%#span73] shallow_model'3 ( ^ self) = push'1 (shallow_model'9 self) value}
       (! return' {result}) ]
     
   
@@ -1441,7 +1241,7 @@ module KnapsackFull_Knapsack01Dyn
     
   
   axiom subseq_rev'0_def : forall s1 : Seq'0.t_seq (Item'0.t_item name), i1 : int, s2 : Seq'0.t_seq (Item'0.t_item name), i2 : int . subseq_rev'0 s1 i1 s2 i2
-  = ([%#span89] if i2 = 0 then
+  = ([%#span77] if i2 = 0 then
     i1 = len'4 s1
   else
     i1 < len'4 s1 /\ index_logic'3 s1 i1 = index_logic'7 s2 (i2 - 1) /\ subseq_rev'0 s1 (i1 + 1) s2 (i2 - 1)
@@ -1451,7 +1251,7 @@ module KnapsackFull_Knapsack01Dyn
   function sum_values'0 [#"../knapsack_full.rs" 37 0 37 55] (s : Seq'0.t_seq (Item'0.t_item name)) (i : int) : int
   
   axiom sum_values'0_def : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . sum_values'0 s i
-  = ([%#span92] if i = len'4 s then
+  = ([%#span80] if i = len'4 s then
     0
   else
     UIntSize.to_int (KnapsackFull_Item_Type.item_value (index_logic'3 s i)) + sum_values'0 s (i + 1)
@@ -1460,165 +1260,160 @@ module KnapsackFull_Knapsack01Dyn
   function sum_weights'0 [#"../knapsack_full.rs" 27 0 27 56] (s : Seq'0.t_seq (Item'0.t_item name)) (i : int) : int
   
   axiom sum_weights'0_def : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . sum_weights'0 s i
-  = ([%#span97] if i = len'4 s then
+  = ([%#span84] if i = len'4 s then
     0
   else
     UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'3 s i)) + sum_weights'0 s (i + 1)
   )
   
-  axiom sum_weights'0_spec : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . ([%#span93] 0 <= i /\ i <= len'4 s)
-   -> ([%#span94] inv'4 s)  -> ([%#span95] sum_weights'0 s i >= 0)
+  axiom sum_weights'0_spec : forall s : Seq'0.t_seq (Item'0.t_item name), i : int . ([%#span81] 0 <= i /\ i <= len'4 s)
+   -> ([%#span82] sum_weights'0 s i >= 0)
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (ix : int) : Item'0.t_item name
     
    =
-    [%#span76] index_logic'3 (shallow_model'3 self) ix
+    [%#span65] index_logic'3 (shallow_model'3 self) ix
   
   let rec with_capacity'0 (capacity:usize) (return'  (ret:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))-> {[%#span99] inv'5 result}
-      {[%#span98] len'4 (shallow_model'3 result) = 0}
+    [ return' (result:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))-> {[%#span86] inv'4 result}
+      {[%#span85] len'4 (shallow_model'3 result) = 0}
       (! return' {result}) ]
     
   
   predicate resolve'6 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))
   
   predicate resolve'8 (self : usize) =
-    [%#span100] true
+    [%#span87] true
   
   function index_logic'5 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span76] index_logic'1 (shallow_model'2 self) ix
+    [%#span65] index_logic'1 (shallow_model'2 self) ix
   
   predicate resolve'7 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span101] forall i : int . 0 <= i /\ i < len'3 (shallow_model'2 self)  -> resolve'8 (index_logic'5 self i)
-  
-  use seq.Seq
+    [%#span88] forall i : int . 0 <= i /\ i < len'3 (shallow_model'2 self)  -> resolve'8 (index_logic'5 self i)
   
-  function index_logic'6 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (x : int) : Vec'0.t_vec usize (Global'0.t_global)
+  function index_logic'6 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (_2 : int) : Vec'0.t_vec usize (Global'0.t_global)
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (ix : int) : Vec'0.t_vec usize (Global'0.t_global)
     
    =
-    [%#span76] index_logic'6 (shallow_model'1 self) ix
+    [%#span65] index_logic'6 (shallow_model'1 self) ix
   
   predicate resolve'5 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span101] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)  -> resolve'7 (index_logic'0 self i)
+    [%#span88] forall i : int . 0 <= i /\ i < len'2 (shallow_model'1 self)  -> resolve'7 (index_logic'0 self i)
   
   predicate resolve'4 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span102]  ^ self =  * self
+    [%#span89]  ^ self =  * self
   
   predicate resolve'3 (self : borrowed usize) =
-    [%#span102]  ^ self =  * self
+    [%#span89]  ^ self =  * self
   
   use prelude.prelude.Slice
   
   predicate resolve_elswhere'1 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq usize) (fin : Seq'0.t_seq usize) =
-    [%#span103] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'3 old'
+    [%#span90] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'3 old'
      -> index_logic'1 old' i = index_logic'1 fin i
   
   predicate has_value'2 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span104] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span91] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'2 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span105] UIntSize.to_int self < len'3 seq
+    [%#span92] UIntSize.to_int self < len'3 seq
   
   function shallow_model'8 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span82] shallow_model'2 ( * self)
+    [%#span70] shallow_model'2 ( * self)
   
-  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span108] inv'6 index}
-    {[@expl:precondition] [%#span107] inv'19 self}
-    {[@expl:precondition] [%#span106] in_bounds'2 index (shallow_model'8 self)}
+  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span95] inv'5 index}
+    {[@expl:precondition] [%#span94] inv'16 self}
+    {[@expl:precondition] [%#span93] in_bounds'2 index (shallow_model'8 self)}
     any
-    [ return' (result:borrowed usize)-> {[%#span113] inv'20 result}
-      {[%#span112] len'3 (shallow_model'2 ( ^ self)) = len'3 (shallow_model'8 self)}
-      {[%#span111] resolve_elswhere'1 index (shallow_model'8 self) (shallow_model'2 ( ^ self))}
-      {[%#span110] has_value'2 index (shallow_model'2 ( ^ self)) ( ^ result)}
-      {[%#span109] has_value'2 index (shallow_model'8 self) ( * result)}
+    [ return' (result:borrowed usize)-> {[%#span100] inv'17 result}
+      {[%#span99] len'3 (shallow_model'2 ( ^ self)) = len'3 (shallow_model'8 self)}
+      {[%#span98] resolve_elswhere'1 index (shallow_model'8 self) (shallow_model'2 ( ^ self))}
+      {[%#span97] has_value'2 index (shallow_model'2 ( ^ self)) ( ^ result)}
+      {[%#span96] has_value'2 index (shallow_model'8 self) ( * result)}
       (! return' {result}) ]
     
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (fin : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
     
    =
-    [%#span103] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'2 old'
+    [%#span90] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'2 old'
      -> index_logic'6 old' i = index_logic'6 fin i
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (out : Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span104] index_logic'6 seq (UIntSize.to_int self) = out
+    [%#span91] index_logic'6 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span105] UIntSize.to_int self < len'2 seq
+    [%#span92] UIntSize.to_int self < len'2 seq
   
   function shallow_model'7 (self : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span82] shallow_model'1 ( * self)
+    [%#span70] shallow_model'1 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (Vec'0.t_vec usize (Global'0.t_global))))= {[@expl:precondition] [%#span108] inv'6 index}
-    {[@expl:precondition] [%#span107] inv'18 self}
-    {[@expl:precondition] [%#span106] in_bounds'1 index (shallow_model'7 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (Vec'0.t_vec usize (Global'0.t_global))))= {[@expl:precondition] [%#span95] inv'5 index}
+    {[@expl:precondition] [%#span94] inv'15 self}
+    {[@expl:precondition] [%#span93] in_bounds'1 index (shallow_model'7 self)}
     any
-    [ return' (result:borrowed (Vec'0.t_vec usize (Global'0.t_global)))-> {[%#span113] inv'19 result}
-      {[%#span112] len'2 (shallow_model'1 ( ^ self)) = len'2 (shallow_model'7 self)}
-      {[%#span111] resolve_elswhere'0 index (shallow_model'7 self) (shallow_model'1 ( ^ self))}
-      {[%#span110] has_value'1 index (shallow_model'1 ( ^ self)) ( ^ result)}
-      {[%#span109] has_value'1 index (shallow_model'7 self) ( * result)}
+    [ return' (result:borrowed (Vec'0.t_vec usize (Global'0.t_global)))-> {[%#span100] inv'16 result}
+      {[%#span99] len'2 (shallow_model'1 ( ^ self)) = len'2 (shallow_model'7 self)}
+      {[%#span98] resolve_elswhere'0 index (shallow_model'7 self) (shallow_model'1 ( ^ self))}
+      {[%#span97] has_value'1 index (shallow_model'1 ( ^ self)) ( ^ result)}
+      {[%#span96] has_value'1 index (shallow_model'7 self) ( * result)}
       (! return' {result}) ]
     
   
   use int.MinMax
   
   let rec max'0 (a:usize) (b:usize) (return'  (ret:usize))= any
-    [ return' (result:usize)-> {[%#span114] UIntSize.to_int result = MinMax.max (UIntSize.to_int a) (UIntSize.to_int b)}
+    [ return' (result:usize)-> {[%#span101] UIntSize.to_int result = MinMax.max (UIntSize.to_int a) (UIntSize.to_int b)}
       (! return' {result}) ]
     
   
   function shallow_model'6 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize =
-    [%#span115] shallow_model'2 self
+    [%#span102] shallow_model'2 self
   
-  let rec index'2 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span118] inv'6 index}
-    {[@expl:precondition] [%#span117] inv'16 self}
-    {[@expl:precondition] [%#span116] in_bounds'2 index (shallow_model'6 self)}
+  let rec index'2 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span105] inv'5 index}
+    {[@expl:precondition] [%#span104] inv'13 self}
+    {[@expl:precondition] [%#span103] in_bounds'2 index (shallow_model'6 self)}
     any
-    [ return' (result:usize)-> {[%#span120] inv'17 result}
-      {[%#span119] has_value'2 index (shallow_model'6 self) result}
+    [ return' (result:usize)-> {[%#span107] inv'14 result}
+      {[%#span106] has_value'2 index (shallow_model'6 self) result}
       (! return' {result}) ]
     
   
   function shallow_model'5 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span115] shallow_model'1 self
+    [%#span102] shallow_model'1 self
   
-  let rec index'1 (self:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (index:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span118] inv'6 index}
-    {[@expl:precondition] [%#span117] inv'15 self}
-    {[@expl:precondition] [%#span116] in_bounds'1 index (shallow_model'5 self)}
+  let rec index'1 (self:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (index:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span105] inv'5 index}
+    {[@expl:precondition] [%#span104] inv'12 self}
+    {[@expl:precondition] [%#span103] in_bounds'1 index (shallow_model'5 self)}
     any
-    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span120] inv'16 result}
-      {[%#span119] has_value'1 index (shallow_model'5 self) result}
+    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span107] inv'13 result}
+      {[%#span106] has_value'1 index (shallow_model'5 self) result}
       (! return' {result}) ]
     
   
   predicate resolve'2 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
-    [%#span102]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span89]  ^ self =  * self
   
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span77] inv'6 v)
-   -> ([%#span80] inv'9 (singleton'0 v))
-  && ([%#span79] index_logic'1 (singleton'0 v) 0 = v) && ([%#span78] len'3 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span66] inv'5 v)
+   -> ([%#span68] index_logic'1 (singleton'0 v) 0 = v) && ([%#span67] len'3 (singleton'0 v) = 1)
   
   predicate completed'1 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
-    [%#span121] is_empty_log'0 ( * self) /\ is_empty_log'0 ( ^ self)
+    [%#span108] is_empty_log'0 ( * self) /\ is_empty_log'0 ( ^ self)
   
-  let rec next'1 (self:borrowed (RangeInclusive'0.t_rangeinclusive usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span122] inv'14 self}
+  let rec next'1 (self:borrowed (RangeInclusive'0.t_rangeinclusive usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span109] inv'11 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span124] inv'13 result}
-      {[%#span123] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span111] inv'10 result}
+      {[%#span110] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -1634,32 +1429,32 @@ module KnapsackFull_Knapsack01Dyn
   function new'3 (x : RangeInclusive'0.t_rangeinclusive usize) : Snapshot'0.t_snapshot (RangeInclusive'0.t_rangeinclusive usize)
     
   
-  axiom new'3_spec : forall x : RangeInclusive'0.t_rangeinclusive usize . ([%#span125] inv'2 x)
-   -> ([%#span126] deref'2 (new'3 x) = x)
+  axiom new'3_spec : forall x : RangeInclusive'0.t_rangeinclusive usize . ([%#span112] inv'2 x)
+   -> ([%#span113] deref'2 (new'3 x) = x)
   
   predicate into_iter_post'1 (self : RangeInclusive'0.t_rangeinclusive usize) (res : RangeInclusive'0.t_rangeinclusive usize)
     
    =
-    [%#span127] self = res
+    [%#span114] self = res
   
   predicate into_iter_pre'1 (self : RangeInclusive'0.t_rangeinclusive usize) =
-    [%#span128] true
+    [%#span115] true
   
-  let rec into_iter'1 (self:RangeInclusive'0.t_rangeinclusive usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span130] inv'2 self}
-    {[@expl:precondition] [%#span129] into_iter_pre'1 self}
+  let rec into_iter'1 (self:RangeInclusive'0.t_rangeinclusive usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span117] inv'2 self}
+    {[@expl:precondition] [%#span116] into_iter_pre'1 self}
     any
-    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span131] inv'2 result}
-      {[%#span129] into_iter_post'1 self result}
+    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span118] inv'2 result}
+      {[%#span116] into_iter_post'1 self result}
       (! return' {result}) ]
     
   
-  let rec new'2 (start:usize) (end':usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span133] inv'6 end'}
-    {[@expl:precondition] [%#span132] inv'6 start}
+  let rec new'2 (start:usize) (end':usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span120] inv'5 end'}
+    {[@expl:precondition] [%#span119] inv'5 start}
     any
-    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span137] inv'2 result}
-      {[%#span136] deep_model'0 start <= deep_model'0 end'  -> not is_empty_log'0 result}
-      {[%#span135] end_log'0 result = end'}
-      {[%#span134] start_log'0 result = start}
+    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span124] inv'2 result}
+      {[%#span123] deep_model'0 start <= deep_model'0 end'  -> not is_empty_log'0 result}
+      {[%#span122] end_log'0 result = end'}
+      {[%#span121] start_log'0 result = start}
       (! return' {result}) ]
     
   
@@ -1668,37 +1463,37 @@ module KnapsackFull_Knapsack01Dyn
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Item'0.t_item name)) (out : Item'0.t_item name)
     
    =
-    [%#span104] index_logic'7 seq (UIntSize.to_int self) = out
+    [%#span91] index_logic'7 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Item'0.t_item name)) =
-    [%#span105] UIntSize.to_int self < len'1 seq
+    [%#span92] UIntSize.to_int self < len'1 seq
   
   function shallow_model'0 (self : Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) : Seq'0.t_seq (Item'0.t_item name)
     
    =
-    [%#span115] shallow_model'4 self
+    [%#span102] shallow_model'4 self
   
-  let rec index'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (index:usize) (return'  (ret:Item'0.t_item name))= {[@expl:precondition] [%#span118] inv'6 index}
-    {[@expl:precondition] [%#span117] inv'3 self}
-    {[@expl:precondition] [%#span116] in_bounds'0 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (index:usize) (return'  (ret:Item'0.t_item name))= {[@expl:precondition] [%#span105] inv'5 index}
+    {[@expl:precondition] [%#span104] inv'3 self}
+    {[@expl:precondition] [%#span103] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:Item'0.t_item name)-> {[%#span120] inv'1 result}
-      {[%#span119] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:Item'0.t_item name)-> {[%#span107] inv'1 result}
+      {[%#span106] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span102]  ^ self =  * self
+    [%#span89]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span138] resolve'0 self
+    [%#span125] resolve'0 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span139] inv'12 self}
+  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span126] inv'9 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span140] inv'13 result}
-      {[%#span123] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span127] inv'10 result}
+      {[%#span110] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -1708,7 +1503,7 @@ module KnapsackFull_Knapsack01Dyn
   function m'0 [#"../knapsack_full.rs" 66 0 66 57] (items : Seq'0.t_seq (Item'0.t_item name)) (i : int) (w : int) : int
   
   axiom m'0_def : forall items : Seq'0.t_seq (Item'0.t_item name), i : int, w : int . m'0 items i w
-  = ([%#span147] if i = 0 then
+  = ([%#span133] if i = 0 then
     0
   else
     if UIntSize.to_int (KnapsackFull_Item_Type.item_weight (index_logic'7 items (i - 1))) > w then
@@ -1720,14 +1515,12 @@ module KnapsackFull_Knapsack01Dyn
     
   )
   
-  axiom m'0_spec : forall items : Seq'0.t_seq (Item'0.t_item name), i : int, w : int . ([%#span141] 0 <= i
+  axiom m'0_spec : forall items : Seq'0.t_seq (Item'0.t_item name), i : int, w : int . ([%#span128] 0 <= i
   /\ i <= len'1 items)
-   -> ([%#span142] 0 <= w)
-   -> ([%#span143] inv'10 items)
-   -> ([%#span145] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . inv'4 s
-   -> 0 <= j /\ j <= len'4 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w
-   -> sum_values'0 s j <= m'0 items i w)
-  && ([%#span144] m'0 items i w >= 0)
+   -> ([%#span129] 0 <= w)
+   -> ([%#span131] forall j : int . forall s : Seq'0.t_seq (Item'0.t_item name) . 0 <= j
+  /\ j <= len'4 s /\ subseq_rev'0 s j items i /\ sum_weights'0 s j <= w  -> sum_values'0 s j <= m'0 items i w)
+  && ([%#span130] m'0 items i w >= 0)
   
   function deref'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
@@ -1739,45 +1532,45 @@ module KnapsackFull_Knapsack01Dyn
   
   function new'1 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq usize . ([%#span125] inv'9 x)  -> ([%#span126] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq usize . ([%#span112] inv'8 x)  -> ([%#span113] deref'0 (new'1 x) = x)
   
   function new'0 (x : Range'0.t_range usize) : Snapshot'0.t_snapshot (Range'0.t_range usize)
   
-  axiom new'0_spec : forall x : Range'0.t_range usize . ([%#span125] inv'0 x)  -> ([%#span126] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Range'0.t_range usize . ([%#span112] inv'0 x)  -> ([%#span113] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span127] self = res
+    [%#span114] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range usize) =
-    [%#span128] true
+    [%#span115] true
   
-  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span130] inv'0 self}
-    {[@expl:precondition] [%#span129] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span117] inv'0 self}
+    {[@expl:precondition] [%#span116] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range usize)-> {[%#span131] inv'0 result}
-      {[%#span129] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range usize)-> {[%#span118] inv'0 result}
+      {[%#span116] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec from_elem'1 (elem:Vec'0.t_vec usize (Global'0.t_global)) (n:usize) (return'  (ret:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))= {[@expl:precondition] [%#span148] inv'7 elem}
+  let rec from_elem'1 (elem:Vec'0.t_vec usize (Global'0.t_global)) (n:usize) (return'  (ret:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))= {[@expl:precondition] [%#span134] inv'6 elem}
     any
-    [ return' (result:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))-> {[%#span151] inv'8 result}
-      {[%#span150] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
-      {[%#span149] len'2 (shallow_model'1 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))-> {[%#span137] inv'7 result}
+      {[%#span136] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
+      {[%#span135] len'2 (shallow_model'1 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span152] inv'3 self}
+  let rec len'0 (self:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span138] inv'3 self}
     any
-    [ return' (result:usize)-> {[%#span153] UIntSize.to_int result = len'1 (shallow_model'0 self)}
+    [ return' (result:usize)-> {[%#span139] UIntSize.to_int result = len'1 (shallow_model'0 self)}
       (! return' {result}) ]
     
   
-  let rec from_elem'0 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span148] inv'6 elem}
+  let rec from_elem'0 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span134] inv'5 elem}
     any
-    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span151] inv'7 result}
-      {[%#span150] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'5 result i = elem}
-      {[%#span149] len'3 (shallow_model'2 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span137] inv'6 result}
+      {[%#span136] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'5 result i = elem}
+      {[%#span135] len'3 (shallow_model'2 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
@@ -2039,21 +1832,21 @@ module KnapsackFull_Knapsack01Dyn
     | bb54 = bb55
     | bb55 = bb56
     | bb56 = bb56
-      [ bb56 = {[@expl:loop invariant] [%#sknapsack_full18] forall r : Seq'0.t_seq (Item'0.t_item name) . inv'4 r
-         -> len'4 (shallow_model'3 result) <= len'4 r
+      [ bb56 = {[@expl:loop invariant] [%#sknapsack_full18] forall r : Seq'0.t_seq (Item'0.t_item name) . len'4 (shallow_model'3 result)
+        <= len'4 r
         /\ (forall i : int . 0 <= i /\ i < len'4 (shallow_model'3 result)
          -> index_logic'2 result i = index_logic'3 r i)
         /\ subseq_rev'0 r (len'4 (shallow_model'3 result)) (shallow_model'0 items) (UIntSize.to_int j)
          -> subseq_rev'0 r 0 (shallow_model'0 items) (len'1 (shallow_model'0 items))}
-        {[@expl:loop invariant] [%#sknapsack_full18] forall r : Seq'0.t_seq (Item'0.t_item name) . inv'4 r
-         -> len'4 (shallow_model'3 result) <= len'4 r
+        {[@expl:loop invariant] [%#sknapsack_full18] forall r : Seq'0.t_seq (Item'0.t_item name) . len'4 (shallow_model'3 result)
+        <= len'4 r
         /\ (forall i : int . 0 <= i /\ i < len'4 (shallow_model'3 result)
          -> index_logic'2 result i = index_logic'3 r i)
         /\ sum_values'0 r (len'4 (shallow_model'3 result))
         = m'0 (shallow_model'0 items) (UIntSize.to_int j) (UIntSize.to_int left_weight)
          -> sum_values'0 r 0 = m'0 (shallow_model'0 items) (len'1 (shallow_model'0 items)) (UIntSize.to_int max_weight)}
-        {[@expl:loop invariant] [%#sknapsack_full18] forall r : Seq'0.t_seq (Item'0.t_item name) . inv'4 r
-         -> len'4 (shallow_model'3 result) <= len'4 r
+        {[@expl:loop invariant] [%#sknapsack_full18] forall r : Seq'0.t_seq (Item'0.t_item name) . len'4 (shallow_model'3 result)
+        <= len'4 r
         /\ (forall i : int . 0 <= i /\ i < len'4 (shallow_model'3 result)
          -> index_logic'2 result i = index_logic'3 r i)
         /\ sum_weights'0 r (len'4 (shallow_model'3 result)) <= UIntSize.to_int left_weight
@@ -2095,7 +1888,7 @@ module KnapsackFull_Knapsack01Dyn
                  [ &_138 <- _ret' ] 
                  [ &result <-  ^ _138 ] 
                 s1)
-          | s1 = -{inv'5 ( ^ _138)}- s2
+          | s1 = -{inv'4 ( ^ _138)}- s2
           | s2 = push'0 {_138} {it1} (fun (_ret':()) ->  [ &_137 <- _ret' ] s3)
           | s3 = bb65 ]
           
@@ -2184,9 +1977,8 @@ module KnapsackFull_Knapsack01Dyn
     | & _137 : () = any_l ()
     | & _138 : borrowed (Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global)) = any_l () ]
     
-    [ return' (result:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))-> {[@expl:postcondition] [%#sknapsack_full29] inv'5 result}
-      {[@expl:postcondition] [%#sknapsack_full28] forall s : Seq'0.t_seq (Item'0.t_item name) . inv'4 s
-       -> subseq_rev'0 s 0 (shallow_model'0 items) (len'1 (shallow_model'0 items))
+    [ return' (result:Vec'0.t_vec (Item'0.t_item name) (Global'0.t_global))-> {[@expl:postcondition] [%#sknapsack_full29] inv'4 result}
+      {[@expl:postcondition] [%#sknapsack_full28] forall s : Seq'0.t_seq (Item'0.t_item name) . subseq_rev'0 s 0 (shallow_model'0 items) (len'1 (shallow_model'0 items))
       /\ sum_weights'0 s (len'4 s) <= UIntSize.to_int max_weight
        -> sum_values'0 s (len'4 s) <= sum_values'0 (shallow_model'3 result) (len'4 (shallow_model'3 result))}
       {[@expl:postcondition] [%#sknapsack_full27] subseq_rev'0 (shallow_model'3 result) 0 (shallow_model'0 items) (len'1 (shallow_model'0 items))}
diff --git a/creusot/tests/should_succeed/list_reversal_lasso.coma b/creusot/tests/should_succeed/list_reversal_lasso.coma
index 8eda9eb9c0..98f177d2d7 100644
--- a/creusot/tests/should_succeed/list_reversal_lasso.coma
+++ b/creusot/tests/should_succeed/list_reversal_lasso.coma
@@ -125,22 +125,7 @@ module ListReversalLasso_Memory_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module ListReversalLasso_Impl1_Index
   let%span slist_reversal_lasso0 = "../list_reversal_lasso.rs" 28 15 28 34
@@ -151,45 +136,37 @@ module ListReversalLasso_Impl1_Index
   
   let%span span3 = "" 0 0 0 0
   
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span5 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span6 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span6 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span7 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span7 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span9 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span10 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span11 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span12 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span13 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span14 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span14 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span15 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span16 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span16 = "" 0 0 0 0
   
-  let%span span17 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span17 = "" 0 0 0 0
   
-  let%span span18 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span18 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span19 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
-  
-  let%span span20 = "" 0 0 0 0
-  
-  let%span span21 = "" 0 0 0 0
-  
-  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
-  
-  let%span span23 = "" 0 0 0 0
+  let%span span19 = "" 0 0 0 0
   
   use prelude.prelude.UIntSize
   
@@ -212,33 +189,27 @@ module ListReversalLasso_Impl1_Index
   
   constant max'0 : usize = [%#span3] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span4] inv'4 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span4] len'0 self >= 0
   
   predicate inv'3 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span6] inv'3 self)
-   -> ([%#span8] inv'4 (shallow_model'1 self))
-  && ([%#span7] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span5] inv'3 self)
+   -> ([%#span6] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'3 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span9] inv'4 (shallow_model'1 self)
+    [%#span7] inv'4 (shallow_model'1 self)
   
   axiom inv'3 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'3 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   predicate invariant'2 (self : usize) =
     [%#span2] true
@@ -261,22 +232,20 @@ module ListReversalLasso_Impl1_Index
   
   axiom inv'0 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span13] index_logic'2 (shallow_model'1 self) (UIntSize.to_int ix)
+    [%#span9] index_logic'2 (shallow_model'1 self) (UIntSize.to_int ix)
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
   use ListReversalLasso_Memory_Type as Memory'0
   
   function index_logic'0 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span14] index_logic'1 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span10] index_logic'1 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span15] len'0 (shallow_model'1 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span11] len'0 (shallow_model'1 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'1 (ListReversalLasso_Memory_Type.memory_0 self))
   
   use prelude.prelude.Intrinsic
@@ -286,20 +255,20 @@ module ListReversalLasso_Impl1_Index
   use prelude.prelude.Slice
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span16] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span12] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span17] UIntSize.to_int self < len'0 seq
+    [%#span13] UIntSize.to_int self < len'0 seq
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize =
-    [%#span18] shallow_model'1 self
+    [%#span14] shallow_model'1 self
   
-  let rec index'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span21] inv'1 index}
-    {[@expl:precondition] [%#span20] inv'0 self}
-    {[@expl:precondition] [%#span19] in_bounds'0 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span17] inv'1 index}
+    {[@expl:precondition] [%#span16] inv'0 self}
+    {[@expl:precondition] [%#span15] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:usize)-> {[%#span23] inv'2 result}
-      {[%#span22] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:usize)-> {[%#span19] inv'2 result}
+      {[%#span18] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
@@ -338,55 +307,47 @@ module ListReversalLasso_Impl2_IndexMut
   
   let%span span6 = "" 0 0 0 0
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span16 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span12 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span17 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span13 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span18 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span14 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span19 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span15 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span20 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span16 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span21 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span17 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span22 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span18 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span23 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span19 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span20 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span25 = "" 0 0 0 0
+  let%span span21 = "" 0 0 0 0
   
-  let%span span26 = "" 0 0 0 0
+  let%span span22 = "" 0 0 0 0
   
-  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span25 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span30 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span31 = "" 0 0 0 0
+  let%span span27 = "" 0 0 0 0
   
   use prelude.prelude.UIntSize
   
@@ -409,24 +370,19 @@ module ListReversalLasso_Impl2_IndexMut
   
   constant max'0 : usize = [%#span6] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span7] inv'4 self)  -> ([%#span8] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span7] len'0 self >= 0
   
   predicate inv'3 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span9] inv'3 self)
-   -> ([%#span11] inv'4 (shallow_model'0 self))
-  && ([%#span10] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'3 self)
+   -> ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'3 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span12] inv'4 (shallow_model'0 self)
+    [%#span10] inv'4 (shallow_model'0 self)
   
   axiom inv'3 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'3 x = true
   
@@ -453,63 +409,60 @@ module ListReversalLasso_Impl2_IndexMut
   
   axiom inv'0 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span13] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span15] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span14] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span16] index_logic'2 (shallow_model'0 self) (UIntSize.to_int ix)
+    [%#span12] index_logic'2 (shallow_model'0 self) (UIntSize.to_int ix)
   
   use ListReversalLasso_Memory_Type as Memory'0
   
   function index_logic'0 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span17] index_logic'1 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span13] index_logic'1 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span18] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span14] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span19]  ^ self =  * self
+    [%#span15]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed usize) =
-    [%#span19]  ^ self =  * self
+    [%#span15]  ^ self =  * self
   
   use prelude.prelude.Slice
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq usize) (fin : Seq'0.t_seq usize) =
-    [%#span20] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
+    [%#span16] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
      -> index_logic'2 old' i = index_logic'2 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span21] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span17] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span22] UIntSize.to_int self < len'0 seq
+    [%#span18] UIntSize.to_int self < len'0 seq
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span23] shallow_model'0 ( * self)
+    [%#span19] shallow_model'0 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span26] inv'1 index}
-    {[@expl:precondition] [%#span25] inv'0 self}
-    {[@expl:precondition] [%#span24] in_bounds'0 index (shallow_model'1 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span22] inv'1 index}
+    {[@expl:precondition] [%#span21] inv'0 self}
+    {[@expl:precondition] [%#span20] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:borrowed usize)-> {[%#span31] inv'2 result}
-      {[%#span30] len'0 (shallow_model'0 ( ^ self)) = len'0 (shallow_model'1 self)}
-      {[%#span29] resolve_elswhere'0 index (shallow_model'1 self) (shallow_model'0 ( ^ self))}
-      {[%#span28] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
-      {[%#span27] has_value'0 index (shallow_model'1 self) ( * result)}
+    [ return' (result:borrowed usize)-> {[%#span27] inv'2 result}
+      {[%#span26] len'0 (shallow_model'0 ( ^ self)) = len'0 (shallow_model'1 self)}
+      {[%#span25] resolve_elswhere'0 index (shallow_model'1 self) (shallow_model'0 ( ^ self))}
+      {[%#span24] has_value'0 index (shallow_model'0 ( ^ self)) ( ^ result)}
+      {[%#span23] has_value'0 index (shallow_model'1 self) ( * result)}
       (! return' {result}) ]
     
   
@@ -584,53 +537,45 @@ module ListReversalLasso_Impl4_ListReversalSafe
   
   let%span span8 = "" 0 0 0 0
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span18 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span14 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span15 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span20 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span16 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span21 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span17 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span22 = "../list_reversal_lasso.rs" 36 15 36 34
+  let%span span18 = "../list_reversal_lasso.rs" 36 15 36 34
   
-  let%span span23 = "../list_reversal_lasso.rs" 37 14 37 47
+  let%span span19 = "../list_reversal_lasso.rs" 37 14 37 47
   
-  let%span span24 = "../list_reversal_lasso.rs" 38 14 38 47
+  let%span span20 = "../list_reversal_lasso.rs" 38 14 38 47
   
-  let%span span25 = "../list_reversal_lasso.rs" 39 14 39 47
+  let%span span21 = "../list_reversal_lasso.rs" 39 14 39 47
   
-  let%span span26 = "../list_reversal_lasso.rs" 40 4 40 113
+  let%span span22 = "../list_reversal_lasso.rs" 40 4 40 113
   
-  let%span span27 = "../list_reversal_lasso.rs" 28 15 28 34
+  let%span span23 = "../list_reversal_lasso.rs" 28 15 28 34
   
-  let%span span28 = "../list_reversal_lasso.rs" 29 14 29 44
+  let%span span24 = "../list_reversal_lasso.rs" 29 14 29 44
   
-  let%span span29 = "../list_reversal_lasso.rs" 13 0 13 15
+  let%span span25 = "../list_reversal_lasso.rs" 13 0 13 15
   
-  let%span span30 = "../list_reversal_lasso.rs" 56 8 58 9
+  let%span span26 = "../list_reversal_lasso.rs" 56 8 58 9
   
-  let%span span31 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span27 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span32 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span28 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
   use prelude.prelude.UIntSize
   
@@ -653,33 +598,27 @@ module ListReversalLasso_Impl4_ListReversalSafe
   
   constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span9] inv'2 self)  -> ([%#span10] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span9] len'0 self >= 0
   
   predicate inv'1 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span11] inv'1 self)
-   -> ([%#span13] inv'2 (shallow_model'0 self))
-  && ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span10] inv'1 self)
+   -> ([%#span11] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span14] inv'2 (shallow_model'0 self)
+    [%#span12] inv'2 (shallow_model'0 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'1 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span15] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span17] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use ListReversalLasso_Memory_Type as Memory'0
   
@@ -697,53 +636,51 @@ module ListReversalLasso_Impl4_ListReversalSafe
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed usize) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span19] index_logic'2 (shallow_model'0 self) (UIntSize.to_int ix)
+    [%#span15] index_logic'2 (shallow_model'0 self) (UIntSize.to_int ix)
   
   function index_logic'0 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span20] index_logic'1 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span16] index_logic'1 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span21] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span17] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
   
-  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span22] nonnull_ptr'0 ( * self) i}
+  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span18] nonnull_ptr'0 ( * self) i}
     any
-    [ return' (result:borrowed usize)-> {[%#span26] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
+    [ return' (result:borrowed usize)-> {[%#span22] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
        -> index_logic'0 ( ^ self) j = index_logic'0 ( * self) j}
-      {[%#span25] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
+      {[%#span21] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
       = len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( ^ self)))}
-      {[%#span24]  ^ result = index_logic'0 ( ^ self) i}
-      {[%#span23]  * result = index_logic'0 ( * self) i}
+      {[%#span20]  ^ result = index_logic'0 ( ^ self) i}
+      {[%#span19]  * result = index_logic'0 ( * self) i}
       (! return' {result}) ]
     
   
-  let rec index'0 (self:Memory'0.t_memory) (i:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span27] nonnull_ptr'0 self i}
-    any [ return' (result:usize)-> {[%#span28] result = index_logic'0 self i} (! return' {result}) ] 
+  let rec index'0 (self:Memory'0.t_memory) (i:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span23] nonnull_ptr'0 self i}
+    any [ return' (result:usize)-> {[%#span24] result = index_logic'0 self i} (! return' {result}) ] 
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))) : borrowed (Memory'0.t_memory)
   
-  constant null'0 : usize = [%#span29] (18446744073709551615 : usize)
+  constant null'0 : usize = [%#span25] (18446744073709551615 : usize)
   
   predicate mem_is_well_formed'0 [#"../list_reversal_lasso.rs" 55 4 55 43] (self : Memory'0.t_memory) =
-    [%#span30] forall i : usize . nonnull_ptr'0 self i
+    [%#span26] forall i : usize . nonnull_ptr'0 self i
      -> index_logic'0 self i = null'0 \/ nonnull_ptr'0 self (index_logic'0 self i)
   
   function new'0 (x : borrowed (Memory'0.t_memory)) : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))
   
-  axiom new'0_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span31] inv'0 x)
-   -> ([%#span32] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span27] inv'0 x)
+   -> ([%#span28] deref'0 (new'0 x) = x)
   
   let rec list_reversal_safe (self:borrowed (Memory'0.t_memory)) (l:usize) (return'  (ret:usize))= {[%#slist_reversal_lasso6] l
     = null'0
@@ -822,79 +759,72 @@ module ListReversalLasso_Impl4_ListReversalList
   
   let%span slist_reversal_lasso8 = "../list_reversal_lasso.rs" 98 14 98 47
   
-  let%span span9 = "" 0 0 0 0
+  let%span span9 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span10 = "" 0 0 0 0
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span16 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span16 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span17 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span18 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span19 = "../list_reversal_lasso.rs" 83 12 85 98
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span20 = "../list_reversal_lasso.rs" 13 0 13 15
   
-  let%span span21 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span21 = "../list_reversal_lasso.rs" 93 12 93 53
   
-  let%span span22 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span22 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span23 = "../list_reversal_lasso.rs" 83 12 85 98
+  let%span span23 = "" 0 0 0 0
   
-  let%span span24 = "../list_reversal_lasso.rs" 13 0 13 15
+  let%span span24 = "" 0 0 0 0
   
-  let%span span25 = "../list_reversal_lasso.rs" 93 12 93 53
+  let%span span25 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
   
-  let%span span26 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span26 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
   
   let%span span27 = "" 0 0 0 0
   
-  let%span span28 = "" 0 0 0 0
-  
-  let%span span29 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
-  
-  let%span span30 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
-  
-  let%span span31 = "" 0 0 0 0
-  
-  let%span span32 = "../list_reversal_lasso.rs" 36 15 36 34
+  let%span span28 = "../list_reversal_lasso.rs" 36 15 36 34
   
-  let%span span33 = "../list_reversal_lasso.rs" 37 14 37 47
+  let%span span29 = "../list_reversal_lasso.rs" 37 14 37 47
   
-  let%span span34 = "../list_reversal_lasso.rs" 38 14 38 47
+  let%span span30 = "../list_reversal_lasso.rs" 38 14 38 47
   
-  let%span span35 = "../list_reversal_lasso.rs" 39 14 39 47
+  let%span span31 = "../list_reversal_lasso.rs" 39 14 39 47
   
-  let%span span36 = "../list_reversal_lasso.rs" 40 4 40 113
+  let%span span32 = "../list_reversal_lasso.rs" 40 4 40 113
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 19 115 23
+  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 114 14 114 40
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 113 14 113 40
+  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 100
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 114 4 114 100
+  let%span span35 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span40 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 32
-  
-  let%span span41 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span42 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span36 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
   use prelude.prelude.UIntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq usize)
+  predicate invariant'5 (self : Seq'0.t_seq usize) =
+    [%#span9] true
+  
+  predicate inv'5 (_x : Seq'0.t_seq usize)
+  
+  axiom inv'5 : forall x : Seq'0.t_seq usize . inv'5 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -904,54 +834,44 @@ module ListReversalLasso_Impl4_ListReversalList
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span9] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span10] inv'2 self)  -> ([%#span11] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span11] len'0 self >= 0
   
-  predicate inv'5 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'4 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span12] inv'5 self)
-   -> ([%#span14] inv'2 (shallow_model'0 self))
-  && ([%#span13] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span12] inv'4 self)
+   -> ([%#span13] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'5 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span15] inv'2 (shallow_model'0 self)
+  predicate invariant'4 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span14] inv'5 (shallow_model'0 self)
   
-  axiom inv'5 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'5 x = true
+  axiom inv'4 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'4 x = true
   
-  predicate invariant'4 (self : usize) =
-    [%#span16] true
+  predicate invariant'3 (self : usize) =
+    [%#span9] true
   
-  predicate inv'4 (_x : usize)
+  predicate inv'3 (_x : usize)
   
-  axiom inv'4 : forall x : usize . inv'4 x = true
+  axiom inv'3 : forall x : usize . inv'3 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'3 (self : borrowed usize) =
-    [%#span16] true
-  
-  predicate inv'3 (_x : borrowed usize)
-  
-  axiom inv'3 : forall x : borrowed usize . inv'3 x = true
+  predicate invariant'2 (self : borrowed usize) =
+    [%#span9] true
   
-  predicate invariant'2 (self : Seq'0.t_seq usize) =
-    [%#span16] true
+  predicate inv'2 (_x : borrowed usize)
   
-  axiom inv'2 : forall x : Seq'0.t_seq usize . inv'2 x = true
+  axiom inv'2 : forall x : borrowed usize . inv'2 x = true
   
   use ListReversalLasso_Memory_Type as Memory'0
   
   predicate invariant'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span16] true
+    [%#span9] true
   
   predicate inv'1 (_x : borrowed (Memory'0.t_memory))
   
@@ -960,93 +880,86 @@ module ListReversalLasso_Impl4_ListReversalList
   use prelude.prelude.Int
   
   predicate invariant'0 (self : int) =
-    [%#span16] true
+    [%#span9] true
   
   predicate inv'0 (_x : int)
   
   axiom inv'0 : forall x : int . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span18] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'0 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span20] index_logic'0 (shallow_model'0 self) (UIntSize.to_int ix)
+    [%#span16] index_logic'0 (shallow_model'0 self) (UIntSize.to_int ix)
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
   function index_logic'1 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span21] index_logic'2 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span17] index_logic'2 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span22] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span18] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
   
   predicate list_seg'0 [#"../list_reversal_lasso.rs" 81 4 81 81] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize) (last : usize) (l : int) (h : int)
     
    =
-    [%#span23] first = (if h = l then last else index_logic'0 s l)
+    [%#span19] first = (if h = l then last else index_logic'0 s l)
     /\ (forall i : int . l <= i /\ i < h
      -> nonnull_ptr'0 self (index_logic'0 s i)
     /\ index_logic'1 self (index_logic'0 s i) = (if i = h - 1 then last else index_logic'0 s (i + 1)))
     /\ (forall j : int . forall i : int . l <= i /\ i < h /\ l <= j /\ j < h /\ i <> j
      -> index_logic'0 s i <> index_logic'0 s j)
   
-  constant null'0 : usize = [%#span24] (18446744073709551615 : usize)
+  constant null'0 : usize = [%#span20] (18446744073709551615 : usize)
   
   predicate list'0 [#"../list_reversal_lasso.rs" 91 4 91 54] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize)
     
    =
-    [%#span25] list_seg'0 self first s null'0 0 (len'0 s)
+    [%#span21] list_seg'0 self first s null'0 0 (len'0 s)
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span26]  ^ self =  * self
+    [%#span22]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed usize) =
-    [%#span26]  ^ self =  * self
+    [%#span22]  ^ self =  * self
   
-  let rec replace'0 (dest:borrowed usize) (src:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span28] inv'4 src}
-    {[@expl:precondition] [%#span27] inv'3 dest}
+  let rec replace'0 (dest:borrowed usize) (src:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span24] inv'3 src}
+    {[@expl:precondition] [%#span23] inv'2 dest}
     any
-    [ return' (result:usize)-> {[%#span31] inv'4 result}
-      {[%#span30] result =  * dest}
-      {[%#span29]  ^ dest = src}
+    [ return' (result:usize)-> {[%#span27] inv'3 result}
+      {[%#span26] result =  * dest}
+      {[%#span25]  ^ dest = src}
       (! return' {result}) ]
     
   
-  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span32] nonnull_ptr'0 ( * self) i}
+  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span28] nonnull_ptr'0 ( * self) i}
     any
-    [ return' (result:borrowed usize)-> {[%#span36] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
+    [ return' (result:borrowed usize)-> {[%#span32] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
        -> index_logic'1 ( ^ self) j = index_logic'1 ( * self) j}
-      {[%#span35] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
+      {[%#span31] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
       = len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( ^ self)))}
-      {[%#span34]  ^ result = index_logic'1 ( ^ self) i}
-      {[%#span33]  * result = index_logic'1 ( * self) i}
+      {[%#span30]  ^ result = index_logic'1 ( ^ self) i}
+      {[%#span29]  * result = index_logic'1 ( * self) i}
       (! return' {result}) ]
     
   
   function deref'2 (self : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))) : borrowed (Memory'0.t_memory)
   
-  use seq.Reverse
-  
   function reverse'0 (self : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom reverse'0_spec : forall self : Seq'0.t_seq usize . ([%#span37] inv'2 self)
-   -> ([%#span40] inv'2 (reverse'0 self))
-  && ([%#span39] forall i : int . 0 <= i /\ i < len'0 (reverse'0 self)
-   -> index_logic'0 (reverse'0 self) i = index_logic'0 self (len'0 self - 1 - i))
-  && ([%#span38] len'0 (reverse'0 self) = len'0 self)
+  axiom reverse'0_spec : forall self : Seq'0.t_seq usize . ([%#span34] forall i : int . 0 <= i
+  /\ i < len'0 (reverse'0 self)  -> index_logic'0 (reverse'0 self) i = index_logic'0 self (len'0 self - 1 - i))
+  && ([%#span33] len'0 (reverse'0 self) = len'0 self)
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
@@ -1054,12 +967,12 @@ module ListReversalLasso_Impl4_ListReversalList
   
   function new'1 (x : borrowed (Memory'0.t_memory)) : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))
   
-  axiom new'1_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span41] inv'1 x)
-   -> ([%#span42] deref'2 (new'1 x) = x)
+  axiom new'1_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span35] inv'1 x)
+   -> ([%#span36] deref'2 (new'1 x) = x)
   
   function new'0 (x : int) : Snapshot'0.t_snapshot int
   
-  axiom new'0_spec : forall x : int . ([%#span41] inv'0 x)  -> ([%#span42] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : int . ([%#span35] inv'0 x)  -> ([%#span36] deref'0 (new'0 x) = x)
   
   let rec list_reversal_list (self:borrowed (Memory'0.t_memory)) (l:usize) (s:Snapshot'0.t_snapshot (Seq'0.t_seq usize)) (return'  (ret:usize))= {[%#slist_reversal_lasso7] list'0 ( * self) l (deref'1 s)}
     (! bb0
@@ -1165,109 +1078,90 @@ module ListReversalLasso_Impl4_ListReversalLoop
   
   let%span slist_reversal_lasso10 = "../list_reversal_lasso.rs" 124 14 124 101
   
-  let%span span11 = "" 0 0 0 0
+  let%span span11 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span12 = "" 0 0 0 0
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span16 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span17 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span18 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span16 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span23 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span18 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span24 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span19 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span25 = "../list_reversal_lasso.rs" 83 12 85 98
+  let%span span20 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span26 = "../list_reversal_lasso.rs" 118 12 118 53
+  let%span span21 = "../list_reversal_lasso.rs" 83 12 85 98
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span22 = "../list_reversal_lasso.rs" 118 12 118 53
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span35 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span31 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span32 = "" 0 0 0 0
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span33 = "" 0 0 0 0
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span34 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
   
-  let%span span40 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span35 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
   
-  let%span span41 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span36 = "" 0 0 0 0
   
-  let%span span42 = "" 0 0 0 0
+  let%span span37 = "../list_reversal_lasso.rs" 36 15 36 34
   
-  let%span span43 = "" 0 0 0 0
+  let%span span38 = "../list_reversal_lasso.rs" 37 14 37 47
   
-  let%span span44 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
+  let%span span39 = "../list_reversal_lasso.rs" 38 14 38 47
   
-  let%span span45 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
+  let%span span40 = "../list_reversal_lasso.rs" 39 14 39 47
   
-  let%span span46 = "" 0 0 0 0
+  let%span span41 = "../list_reversal_lasso.rs" 40 4 40 113
   
-  let%span span47 = "../list_reversal_lasso.rs" 36 15 36 34
+  let%span span42 = "../../../../creusot-contracts/src/logic/seq2.rs" 114 14 114 40
   
-  let%span span48 = "../list_reversal_lasso.rs" 37 14 37 47
+  let%span span43 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 100
   
-  let%span span49 = "../list_reversal_lasso.rs" 38 14 38 47
+  let%span span44 = "../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
   
-  let%span span50 = "../list_reversal_lasso.rs" 39 14 39 47
+  let%span span45 = "../list_reversal_lasso.rs" 13 0 13 15
   
-  let%span span51 = "../list_reversal_lasso.rs" 40 4 40 113
+  let%span span46 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span52 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 19 115 23
-  
-  let%span span53 = "../../../../creusot-contracts/src/logic/seq2.rs" 113 14 113 40
-  
-  let%span span54 = "../../../../creusot-contracts/src/logic/seq2.rs" 114 4 114 100
-  
-  let%span span55 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 32
-  
-  let%span span56 = "../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
-  
-  let%span span57 = "../list_reversal_lasso.rs" 13 0 13 15
-  
-  let%span span58 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span59 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span47 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
   use prelude.prelude.UIntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq usize)
+  predicate invariant'5 (self : Seq'0.t_seq usize) =
+    [%#span11] true
+  
+  predicate inv'5 (_x : Seq'0.t_seq usize)
+  
+  axiom inv'5 : forall x : Seq'0.t_seq usize . inv'5 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1277,54 +1171,44 @@ module ListReversalLasso_Impl4_ListReversalLoop
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span12] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span12] inv'2 self)  -> ([%#span13] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span13] len'0 self >= 0
   
-  predicate inv'5 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'4 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span14] inv'5 self)
-   -> ([%#span16] inv'2 (shallow_model'0 self))
-  && ([%#span15] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span14] inv'4 self)
+   -> ([%#span15] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'5 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span17] inv'2 (shallow_model'0 self)
+  predicate invariant'4 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span16] inv'5 (shallow_model'0 self)
   
-  axiom inv'5 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'5 x = true
+  axiom inv'4 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'4 x = true
   
-  predicate invariant'4 (self : usize) =
-    [%#span18] true
+  predicate invariant'3 (self : usize) =
+    [%#span11] true
   
-  predicate inv'4 (_x : usize)
+  predicate inv'3 (_x : usize)
   
-  axiom inv'4 : forall x : usize . inv'4 x = true
+  axiom inv'3 : forall x : usize . inv'3 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'3 (self : borrowed usize) =
-    [%#span18] true
-  
-  predicate inv'3 (_x : borrowed usize)
-  
-  axiom inv'3 : forall x : borrowed usize . inv'3 x = true
+  predicate invariant'2 (self : borrowed usize) =
+    [%#span11] true
   
-  predicate invariant'2 (self : Seq'0.t_seq usize) =
-    [%#span18] true
+  predicate inv'2 (_x : borrowed usize)
   
-  axiom inv'2 : forall x : Seq'0.t_seq usize . inv'2 x = true
+  axiom inv'2 : forall x : borrowed usize . inv'2 x = true
   
   use ListReversalLasso_Memory_Type as Memory'0
   
   predicate invariant'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span18] true
+    [%#span11] true
   
   predicate inv'1 (_x : borrowed (Memory'0.t_memory))
   
@@ -1333,39 +1217,36 @@ module ListReversalLasso_Impl4_ListReversalLoop
   use prelude.prelude.Int
   
   predicate invariant'0 (self : int) =
-    [%#span18] true
+    [%#span11] true
   
   predicate inv'0 (_x : int)
   
   axiom inv'0 : forall x : int . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span19] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span21] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'0 (empty'0 : Seq'0.t_seq usize) = 0
-  
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'3 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span22] index_logic'2 (shallow_model'0 self) (UIntSize.to_int ix)
+    [%#span18] index_logic'2 (shallow_model'0 self) (UIntSize.to_int ix)
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
   function index_logic'1 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span23] index_logic'3 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span19] index_logic'3 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span24] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span20] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
   
   predicate list_seg'0 [#"../list_reversal_lasso.rs" 81 4 81 81] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize) (last : usize) (l : int) (h : int)
     
    =
-    [%#span25] first = (if h = l then last else index_logic'2 s l)
+    [%#span21] first = (if h = l then last else index_logic'2 s l)
     /\ (forall i : int . l <= i /\ i < h
      -> nonnull_ptr'0 self (index_logic'2 s i)
     /\ index_logic'1 self (index_logic'2 s i) = (if i = h - 1 then last else index_logic'2 s (i + 1)))
@@ -1375,99 +1256,84 @@ module ListReversalLasso_Impl4_ListReversalLoop
   predicate loop'0 [#"../list_reversal_lasso.rs" 116 4 116 55] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize)
     
    =
-    [%#span26] list_seg'0 self first s (index_logic'2 s 0) 0 (len'0 s)
+    [%#span22] list_seg'0 self first s (index_logic'2 s 0) 0 (len'0 s)
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span27] inv'2 self)
-   -> ([%#span28] inv'2 other)
-   -> ([%#span31] inv'2 (concat'0 self other))
-  && ([%#span30] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span24] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'0 self then index_logic'2 self i else index_logic'2 other (i - len'0 self)))
-  && ([%#span29] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use prelude.seq_ext.SeqExt
+  && ([%#span23] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function subsequence'0 (self : Seq'0.t_seq usize) (n : int) (m : int) : Seq'0.t_seq usize
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#span32] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#span25] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span33] inv'2 self)
-   -> ([%#span36] inv'2 (subsequence'0 self n m))
-  && ([%#span35] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span27] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'2 (subsequence'0 self n m) i = index_logic'2 self (n + i))
-  && ([%#span34] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span26] len'0 (subsequence'0 self n m) = m - n)
   
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span37] inv'4 v)
-   -> ([%#span40] inv'2 (singleton'0 v))
-  && ([%#span39] index_logic'2 (singleton'0 v) 0 = v) && ([%#span38] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span28] inv'3 v)
+   -> ([%#span30] index_logic'2 (singleton'0 v) 0 = v) && ([%#span29] len'0 (singleton'0 v) = 1)
   
   predicate resolve'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span41]  ^ self =  * self
+    [%#span31]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed usize) =
-    [%#span41]  ^ self =  * self
+    [%#span31]  ^ self =  * self
   
-  let rec replace'0 (dest:borrowed usize) (src:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span43] inv'4 src}
-    {[@expl:precondition] [%#span42] inv'3 dest}
+  let rec replace'0 (dest:borrowed usize) (src:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span33] inv'3 src}
+    {[@expl:precondition] [%#span32] inv'2 dest}
     any
-    [ return' (result:usize)-> {[%#span46] inv'4 result}
-      {[%#span45] result =  * dest}
-      {[%#span44]  ^ dest = src}
+    [ return' (result:usize)-> {[%#span36] inv'3 result}
+      {[%#span35] result =  * dest}
+      {[%#span34]  ^ dest = src}
       (! return' {result}) ]
     
   
-  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span47] nonnull_ptr'0 ( * self) i}
+  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span37] nonnull_ptr'0 ( * self) i}
     any
-    [ return' (result:borrowed usize)-> {[%#span51] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
+    [ return' (result:borrowed usize)-> {[%#span41] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
        -> index_logic'1 ( ^ self) j = index_logic'1 ( * self) j}
-      {[%#span50] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
+      {[%#span40] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
       = len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( ^ self)))}
-      {[%#span49]  ^ result = index_logic'1 ( ^ self) i}
-      {[%#span48]  * result = index_logic'1 ( * self) i}
+      {[%#span39]  ^ result = index_logic'1 ( ^ self) i}
+      {[%#span38]  * result = index_logic'1 ( * self) i}
       (! return' {result}) ]
     
   
   function deref'2 (self : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))) : borrowed (Memory'0.t_memory)
   
-  use seq.Reverse
-  
   function reverse'0 (self : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom reverse'0_spec : forall self : Seq'0.t_seq usize . ([%#span52] inv'2 self)
-   -> ([%#span55] inv'2 (reverse'0 self))
-  && ([%#span54] forall i : int . 0 <= i /\ i < len'0 (reverse'0 self)
-   -> index_logic'2 (reverse'0 self) i = index_logic'2 self (len'0 self - 1 - i))
-  && ([%#span53] len'0 (reverse'0 self) = len'0 self)
+  axiom reverse'0_spec : forall self : Seq'0.t_seq usize . ([%#span43] forall i : int . 0 <= i
+  /\ i < len'0 (reverse'0 self)  -> index_logic'2 (reverse'0 self) i = index_logic'2 self (len'0 self - 1 - i))
+  && ([%#span42] len'0 (reverse'0 self) = len'0 self)
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
   function index_logic'0 [@inline:trivial] (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) (ix : int) : usize =
-    [%#span56] index_logic'2 (deref'1 self) ix
+    [%#span44] index_logic'2 (deref'1 self) ix
   
-  constant null'0 : usize = [%#span57] (18446744073709551615 : usize)
+  constant null'0 : usize = [%#span45] (18446744073709551615 : usize)
   
   function deref'0 (self : Snapshot'0.t_snapshot int) : int
   
   function new'1 (x : borrowed (Memory'0.t_memory)) : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))
   
-  axiom new'1_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span58] inv'1 x)
-   -> ([%#span59] deref'2 (new'1 x) = x)
+  axiom new'1_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span46] inv'1 x)
+   -> ([%#span47] deref'2 (new'1 x) = x)
   
   function new'0 (x : int) : Snapshot'0.t_snapshot int
   
-  axiom new'0_spec : forall x : int . ([%#span58] inv'0 x)  -> ([%#span59] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : int . ([%#span46] inv'0 x)  -> ([%#span47] deref'0 (new'0 x) = x)
   
   let rec list_reversal_loop (self:borrowed (Memory'0.t_memory)) (l:usize) (s:Snapshot'0.t_snapshot (Seq'0.t_seq usize)) (return'  (ret:usize))= {[%#slist_reversal_lasso9] loop'0 ( * self) l (deref'1 s)}
     {[%#slist_reversal_lasso8] len'0 (deref'1 s) > 0}
@@ -1587,81 +1453,74 @@ module ListReversalLasso_Impl4_ListReversalLasso
   
   let%span slist_reversal_lasso7 = "../list_reversal_lasso.rs" 162 14 162 54
   
-  let%span span8 = "" 0 0 0 0
+  let%span span8 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span9 = "" 0 0 0 0
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span15 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span16 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span17 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span18 = "../list_reversal_lasso.rs" 83 12 85 98
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span19 = "../list_reversal_lasso.rs" 152 8 158 9
   
-  let%span span20 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span20 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span21 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span21 = "" 0 0 0 0
   
-  let%span span22 = "../list_reversal_lasso.rs" 83 12 85 98
+  let%span span22 = "" 0 0 0 0
   
-  let%span span23 = "../list_reversal_lasso.rs" 152 8 158 9
+  let%span span23 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
   
-  let%span span24 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span24 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
   
   let%span span25 = "" 0 0 0 0
   
-  let%span span26 = "" 0 0 0 0
-  
-  let%span span27 = "../../../../creusot-contracts/src/std/mem.rs" 8 22 8 34
+  let%span span26 = "../list_reversal_lasso.rs" 36 15 36 34
   
-  let%span span28 = "../../../../creusot-contracts/src/std/mem.rs" 9 22 9 37
+  let%span span27 = "../list_reversal_lasso.rs" 37 14 37 47
   
-  let%span span29 = "" 0 0 0 0
+  let%span span28 = "../list_reversal_lasso.rs" 38 14 38 47
   
-  let%span span30 = "../list_reversal_lasso.rs" 36 15 36 34
+  let%span span29 = "../list_reversal_lasso.rs" 39 14 39 47
   
-  let%span span31 = "../list_reversal_lasso.rs" 37 14 37 47
+  let%span span30 = "../list_reversal_lasso.rs" 40 4 40 113
   
-  let%span span32 = "../list_reversal_lasso.rs" 38 14 38 47
+  let%span span31 = "../list_reversal_lasso.rs" 13 0 13 15
   
-  let%span span33 = "../list_reversal_lasso.rs" 39 14 39 47
+  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 114 14 114 40
   
-  let%span span34 = "../list_reversal_lasso.rs" 40 4 40 113
+  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 100
   
-  let%span span35 = "../list_reversal_lasso.rs" 13 0 13 15
+  let%span span34 = "../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 19 115 23
+  let%span span35 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 113 14 113 40
-  
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 114 4 114 100
-  
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 115 4 115 32
-  
-  let%span span40 = "../../../../creusot-contracts/src/logic/ops.rs" 87 8 87 33
-  
-  let%span span41 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span42 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span36 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
   use prelude.prelude.UIntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : Seq'0.t_seq usize)
+  predicate invariant'5 (self : Seq'0.t_seq usize) =
+    [%#span8] true
+  
+  predicate inv'5 (_x : Seq'0.t_seq usize)
+  
+  axiom inv'5 : forall x : Seq'0.t_seq usize . inv'5 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1671,54 +1530,44 @@ module ListReversalLasso_Impl4_ListReversalLasso
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span9] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span9] inv'2 self)  -> ([%#span10] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span10] len'0 self >= 0
   
-  predicate inv'5 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'4 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span11] inv'5 self)
-   -> ([%#span13] inv'2 (shallow_model'0 self))
-  && ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span11] inv'4 self)
+   -> ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'5 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span14] inv'2 (shallow_model'0 self)
+  predicate invariant'4 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span13] inv'5 (shallow_model'0 self)
   
-  axiom inv'5 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'5 x = true
+  axiom inv'4 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'4 x = true
   
-  predicate invariant'4 (self : usize) =
-    [%#span15] true
+  predicate invariant'3 (self : usize) =
+    [%#span8] true
   
-  predicate inv'4 (_x : usize)
+  predicate inv'3 (_x : usize)
   
-  axiom inv'4 : forall x : usize . inv'4 x = true
+  axiom inv'3 : forall x : usize . inv'3 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'3 (self : borrowed usize) =
-    [%#span15] true
-  
-  predicate inv'3 (_x : borrowed usize)
-  
-  axiom inv'3 : forall x : borrowed usize . inv'3 x = true
+  predicate invariant'2 (self : borrowed usize) =
+    [%#span8] true
   
-  predicate invariant'2 (self : Seq'0.t_seq usize) =
-    [%#span15] true
+  predicate inv'2 (_x : borrowed usize)
   
-  axiom inv'2 : forall x : Seq'0.t_seq usize . inv'2 x = true
+  axiom inv'2 : forall x : borrowed usize . inv'2 x = true
   
   use ListReversalLasso_Memory_Type as Memory'0
   
   predicate invariant'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span15] true
+    [%#span8] true
   
   predicate inv'1 (_x : borrowed (Memory'0.t_memory))
   
@@ -1727,39 +1576,36 @@ module ListReversalLasso_Impl4_ListReversalLasso
   use prelude.prelude.Int
   
   predicate invariant'0 (self : int) =
-    [%#span15] true
+    [%#span8] true
   
   predicate inv'0 (_x : int)
   
   axiom inv'0 : forall x : int . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span16] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span18] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span14] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'3 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span19] index_logic'1 (shallow_model'0 self) (UIntSize.to_int ix)
+    [%#span15] index_logic'1 (shallow_model'0 self) (UIntSize.to_int ix)
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
   function index_logic'2 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span20] index_logic'3 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span16] index_logic'3 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span21] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span17] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
   
   predicate list_seg'0 [#"../list_reversal_lasso.rs" 81 4 81 81] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize) (last : usize) (l : int) (h : int)
     
    =
-    [%#span22] first = (if h = l then last else index_logic'1 s l)
+    [%#span18] first = (if h = l then last else index_logic'1 s l)
     /\ (forall i : int . l <= i /\ i < h
      -> nonnull_ptr'0 self (index_logic'1 s i)
     /\ index_logic'2 self (index_logic'1 s i) = (if i = h - 1 then last else index_logic'1 s (i + 1)))
@@ -1769,7 +1615,7 @@ module ListReversalLasso_Impl4_ListReversalLasso
   predicate lasso'0 [#"../list_reversal_lasso.rs" 151 4 151 70] (self : Memory'0.t_memory) (first : usize) (s1 : Seq'0.t_seq usize) (s2 : Seq'0.t_seq usize)
     
    =
-    [%#span23] let mid = if len'0 s2 = 0 then index_logic'1 s1 (len'0 s1 - 1) else index_logic'1 s2 0 in len'0 s1 > 0
+    [%#span19] let mid = if len'0 s2 = 0 then index_logic'1 s1 (len'0 s1 - 1) else index_logic'1 s2 0 in len'0 s1 > 0
     /\ (forall j : int . forall i : int . 0 <= i /\ i < len'0 s1 /\ 0 <= j /\ j < len'0 s2
      -> index_logic'1 s1 i <> index_logic'1 s2 j)
     /\ list_seg'0 self first s1 mid 0 (len'0 s1)
@@ -1780,60 +1626,56 @@ module ListReversalLasso_Impl4_ListReversalLasso
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed (Memory'0.t_memory)) =
-    [%#span24]  ^ self =  * self
+    [%#span20]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed usize) =
-    [%#span24]  ^ self =  * self
+    [%#span20]  ^ self =  * self
   
-  let rec replace'0 (dest:borrowed usize) (src:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span26] inv'4 src}
-    {[@expl:precondition] [%#span25] inv'3 dest}
+  let rec replace'0 (dest:borrowed usize) (src:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span22] inv'3 src}
+    {[@expl:precondition] [%#span21] inv'2 dest}
     any
-    [ return' (result:usize)-> {[%#span29] inv'4 result}
-      {[%#span28] result =  * dest}
-      {[%#span27]  ^ dest = src}
+    [ return' (result:usize)-> {[%#span25] inv'3 result}
+      {[%#span24] result =  * dest}
+      {[%#span23]  ^ dest = src}
       (! return' {result}) ]
     
   
-  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span30] nonnull_ptr'0 ( * self) i}
+  let rec index_mut'0 (self:borrowed (Memory'0.t_memory)) (i:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span26] nonnull_ptr'0 ( * self) i}
     any
-    [ return' (result:borrowed usize)-> {[%#span34] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
+    [ return' (result:borrowed usize)-> {[%#span30] forall j : usize . nonnull_ptr'0 ( * self) j /\ i <> j
        -> index_logic'2 ( ^ self) j = index_logic'2 ( * self) j}
-      {[%#span33] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
+      {[%#span29] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( * self)))
       = len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 ( ^ self)))}
-      {[%#span32]  ^ result = index_logic'2 ( ^ self) i}
-      {[%#span31]  * result = index_logic'2 ( * self) i}
+      {[%#span28]  ^ result = index_logic'2 ( ^ self) i}
+      {[%#span27]  * result = index_logic'2 ( * self) i}
       (! return' {result}) ]
     
   
   function deref'2 (self : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))) : borrowed (Memory'0.t_memory)
   
-  constant null'0 : usize = [%#span35] (18446744073709551615 : usize)
-  
-  use seq.Reverse
+  constant null'0 : usize = [%#span31] (18446744073709551615 : usize)
   
   function reverse'0 (self : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom reverse'0_spec : forall self : Seq'0.t_seq usize . ([%#span36] inv'2 self)
-   -> ([%#span39] inv'2 (reverse'0 self))
-  && ([%#span38] forall i : int . 0 <= i /\ i < len'0 (reverse'0 self)
-   -> index_logic'1 (reverse'0 self) i = index_logic'1 self (len'0 self - 1 - i))
-  && ([%#span37] len'0 (reverse'0 self) = len'0 self)
+  axiom reverse'0_spec : forall self : Seq'0.t_seq usize . ([%#span33] forall i : int . 0 <= i
+  /\ i < len'0 (reverse'0 self)  -> index_logic'1 (reverse'0 self) i = index_logic'1 self (len'0 self - 1 - i))
+  && ([%#span32] len'0 (reverse'0 self) = len'0 self)
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
   function index_logic'0 [@inline:trivial] (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) (ix : int) : usize =
-    [%#span40] index_logic'1 (deref'1 self) ix
+    [%#span34] index_logic'1 (deref'1 self) ix
   
   function deref'0 (self : Snapshot'0.t_snapshot int) : int
   
   function new'1 (x : borrowed (Memory'0.t_memory)) : Snapshot'0.t_snapshot (borrowed (Memory'0.t_memory))
   
-  axiom new'1_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span41] inv'1 x)
-   -> ([%#span42] deref'2 (new'1 x) = x)
+  axiom new'1_spec : forall x : borrowed (Memory'0.t_memory) . ([%#span35] inv'1 x)
+   -> ([%#span36] deref'2 (new'1 x) = x)
   
   function new'0 (x : int) : Snapshot'0.t_snapshot int
   
-  axiom new'0_spec : forall x : int . ([%#span41] inv'0 x)  -> ([%#span42] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : int . ([%#span35] inv'0 x)  -> ([%#span36] deref'0 (new'0 x) = x)
   
   let rec list_reversal_lasso (self:borrowed (Memory'0.t_memory)) (l:usize) (s1:Snapshot'0.t_snapshot (Seq'0.t_seq usize)) (s2:Snapshot'0.t_snapshot (Seq'0.t_seq usize)) (return'  (ret:usize))= {[%#slist_reversal_lasso6] lasso'0 ( * self) l (deref'1 s1) (deref'1 s2)}
     (! bb0
@@ -1965,51 +1807,29 @@ module ListReversalLasso_Impl4_FindPtrInSeq_Impl
   
   let%span slist_reversal_lasso2 = "../list_reversal_lasso.rs" 203 14 203 25
   
-  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span sseq24 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span5 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span sseq23 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  use prelude.prelude.Int
   
   use prelude.prelude.UIntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq usize) =
-    [%#span5] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq usize)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq usize . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#sseq23] inv'0 self)  -> ([%#sseq24] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#sseq23] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span4] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use prelude.prelude.UIntSize
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'0 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   use prelude.prelude.Int
   
@@ -2025,8 +1845,7 @@ module ListReversalLasso_Impl4_FindPtrInSeq_Impl
     
   
   goal vc_find_ptr_in_seq : ([%#slist_reversal_lasso0] 0 <= i /\ i <= len'0 s)
-   -> ([%#sseq23] inv'0 s)
-  /\ (([%#sseq24] len'0 s >= 0)
+   -> ([%#sseq23] len'0 s >= 0)
    -> match i = len'0 s with
     | True -> [%#slist_reversal_lasso1] match Option'0.C_None with
       | Option'0.C_None -> forall j : int . i <= j /\ j < len'0 s  -> UIntSize.to_int (index_logic'0 s j) <> p
@@ -2049,7 +1868,7 @@ module ListReversalLasso_Impl4_FindPtrInSeq_Impl
         | Option'0.C_Some j -> i <= j /\ j < len'0 s /\ UIntSize.to_int (index_logic'0 s j) = p
         end))
       end
-    end)
+    end
 end
 module ListReversalLasso_Impl4_Pigeon_Impl
   let%span slist_reversal_lasso0 = "../list_reversal_lasso.rs" 213 15 213 21
@@ -2070,95 +1889,56 @@ module ListReversalLasso_Impl4_Pigeon_Impl
   
   let%span slist_reversal_lasso8 = "../list_reversal_lasso.rs" 203 14 203 25
   
-  let%span sseq29 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
-  
-  let%span sseq210 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
-  
-  let%span sseq211 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
-  
-  let%span sseq212 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span sseq29 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span sseq213 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span sseq210 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span sseq214 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span sseq211 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span sseq215 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span sseq212 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span sseq216 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span sseq213 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span sseq217 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span sseq214 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span sseq218 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span sseq219 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span16 = "../list_reversal_lasso.rs" 205 8 209 9
   
-  let%span sseq220 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span21 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span25 = "../list_reversal_lasso.rs" 205 8 209 9
+  use prelude.prelude.Int
   
   use prelude.prelude.UIntSize
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq usize) =
-    [%#span21] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq usize)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq usize . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#sseq214] inv'0 self)  -> ([%#sseq215] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq usize = [%#span22] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#sseq212] len'0 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span24] ()
-  
-  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  constant empty'0 : Seq'0.t_seq usize
   
-  use seq.Seq
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
-  function index_logic'0 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'0 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#sseq216] inv'0 self)
-   -> ([%#sseq217] inv'0 other)
-   -> ([%#sseq220] inv'0 (concat'0 self other))
-  && ([%#sseq219] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#sseq214] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#sseq218] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use prelude.seq_ext.SeqExt
+  && ([%#sseq213] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function subsequence'0 (self : Seq'0.t_seq usize) (n : int) (m : int) : Seq'0.t_seq usize
   
   axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#sseq29] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#sseq210] inv'0 self)
-   -> ([%#sseq213] inv'0 (subsequence'0 self n m))
-  && ([%#sseq212] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#sseq211] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#sseq211] len'0 (subsequence'0 self n m) = m - n)
+  && ([%#sseq210] len'0 (subsequence'0 self n m) = m - n)
   
   use prelude.prelude.Int
   
@@ -2170,7 +1950,7 @@ module ListReversalLasso_Impl4_Pigeon_Impl
     
   
   axiom find_ptr_in_seq'0_def : forall s : Seq'0.t_seq usize, i : int, p : int . find_ptr_in_seq'0 s i p
-  = ([%#span25] if i = len'0 s then
+  = ([%#span16] if i = len'0 s then
     Option'0.C_None
   else
     if UIntSize.to_int (index_logic'0 s i) = p then Option'0.C_Some i else find_ptr_in_seq'0 s (i + 1) p
@@ -2215,21 +1995,16 @@ module ListReversalLasso_Impl4_Pigeon_Impl
         | Option'0.C_Some j -> i + 1 <= j /\ j < len'0 s /\ UIntSize.to_int (index_logic'0 s j) = n - 1
         end)
        -> match find_ptr_in_seq'0 s (i + 1) (n - 1) with
-        | Option'0.C_None -> (([%#sseq210] inv'0 s) && ([%#sseq29] 0 <= 0 /\ 0 <= i /\ i <= len'0 s))
-        /\ (([%#sseq213] inv'0 (subsequence'0 s 0 i))
-        && ([%#sseq212] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s 0 i)
+        | Option'0.C_None -> ([%#sseq29] 0 <= 0 /\ 0 <= i /\ i <= len'0 s)
+        /\ (([%#sseq211] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s 0 i)
          -> index_logic'0 (subsequence'0 s 0 i) i' = index_logic'0 s (0 + i'))
-        && ([%#sseq211] len'0 (subsequence'0 s 0 i) = i - 0)
-         -> ([%#sseq214] inv'0 s)
-        /\ (([%#sseq215] len'0 s >= 0)
-         -> (([%#sseq210] inv'0 s) && ([%#sseq29] 0 <= i + 1 /\ i + 1 <= len'0 s /\ len'0 s <= len'0 s))
-        /\ (([%#sseq213] inv'0 (subsequence'0 s (i + 1) (len'0 s)))
-        && ([%#sseq212] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s (i + 1) (len'0 s))
+        && ([%#sseq210] len'0 (subsequence'0 s 0 i) = i - 0)
+         -> ([%#sseq212] len'0 s >= 0)
+         -> ([%#sseq29] 0 <= i + 1 /\ i + 1 <= len'0 s /\ len'0 s <= len'0 s)
+        /\ (([%#sseq211] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s (i + 1) (len'0 s))
          -> index_logic'0 (subsequence'0 s (i + 1) (len'0 s)) i' = index_logic'0 s (i + 1 + i'))
-        && ([%#sseq211] len'0 (subsequence'0 s (i + 1) (len'0 s)) = len'0 s - (i + 1))
-         -> (([%#sseq217] inv'0 (subsequence'0 s (i + 1) (len'0 s))) && ([%#sseq216] inv'0 (subsequence'0 s 0 i)))
-        /\ (([%#sseq220] inv'0 (concat'0 (subsequence'0 s 0 i) (subsequence'0 s (i + 1) (len'0 s))))
-        && ([%#sseq219] forall i' : int . 0 <= i'
+        && ([%#sseq210] len'0 (subsequence'0 s (i + 1) (len'0 s)) = len'0 s - (i + 1))
+         -> ([%#sseq214] forall i' : int . 0 <= i'
         /\ i' < len'0 (concat'0 (subsequence'0 s 0 i) (subsequence'0 s (i + 1) (len'0 s)))
          -> index_logic'0 (concat'0 (subsequence'0 s 0 i) (subsequence'0 s (i + 1) (len'0 s))) i'
         = (if i' < len'0 (subsequence'0 s 0 i) then
@@ -2237,7 +2012,7 @@ module ListReversalLasso_Impl4_Pigeon_Impl
         else
           index_logic'0 (subsequence'0 s (i + 1) (len'0 s)) (i' - len'0 (subsequence'0 s 0 i))
         ))
-        && ([%#sseq218] len'0 (concat'0 (subsequence'0 s 0 i) (subsequence'0 s (i + 1) (len'0 s)))
+        && ([%#sseq213] len'0 (concat'0 (subsequence'0 s 0 i) (subsequence'0 s (i + 1) (len'0 s)))
         = len'0 (subsequence'0 s 0 i) + len'0 (subsequence'0 s (i + 1) (len'0 s)))
          -> ((([%#slist_reversal_lasso2] forall j : int . forall i' : int . 0 <= i'
         /\ i' < len'0 (concat'0 (subsequence'0 s 0 i) (subsequence'0 s (i + 1) (len'0 s)))
@@ -2256,7 +2031,7 @@ module ListReversalLasso_Impl4_Pigeon_Impl
         <= n - 1)
          -> ([%#slist_reversal_lasso4] pigeon (concat'0 (subsequence'0 s 0 i) (subsequence'0 s (i + 1) (len'0 s))) (n
         - 1))
-        && ([%#slist_reversal_lasso3] len'0 s <= n))))))
+        && ([%#slist_reversal_lasso3] len'0 s <= n))))
         | Option'0.C_Some _ -> ([%#slist_reversal_lasso4] true) && ([%#slist_reversal_lasso3] len'0 s <= n)
         end)
       end)
@@ -2283,103 +2058,83 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
   
   let%span svec9 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span svec10 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span sseq211 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span sseq212 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span slist_reversal_lasso13 = "../list_reversal_lasso.rs" 213 15 213 21
+  let%span sseq210 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span slist_reversal_lasso14 = "../list_reversal_lasso.rs" 214 4 214 67
+  let%span slist_reversal_lasso11 = "../list_reversal_lasso.rs" 213 15 213 21
   
-  let%span slist_reversal_lasso15 = "../list_reversal_lasso.rs" 215 4 215 113
+  let%span slist_reversal_lasso12 = "../list_reversal_lasso.rs" 214 4 214 67
   
-  let%span slist_reversal_lasso16 = "../list_reversal_lasso.rs" 216 14 216 26
+  let%span slist_reversal_lasso13 = "../list_reversal_lasso.rs" 215 4 215 113
   
-  let%span slist_reversal_lasso17 = "../list_reversal_lasso.rs" 217 14 217 20
+  let%span slist_reversal_lasso14 = "../list_reversal_lasso.rs" 216 14 216 26
   
-  let%span slist_reversal_lasso18 = "../list_reversal_lasso.rs" 218 14 218 15
+  let%span slist_reversal_lasso15 = "../list_reversal_lasso.rs" 217 14 217 20
   
-  let%span sseq219 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span slist_reversal_lasso16 = "../list_reversal_lasso.rs" 218 14 218 15
   
-  let%span sseq220 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span sseq217 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span sseq221 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span sseq218 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span sseq222 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
-  
-  let%span sseq223 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
-  
-  let%span span24 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span25 = "" 0 0 0 0
+  let%span sseq219 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span20 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span21 = "" 0 0 0 0
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span22 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span35 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span40 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span30 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span41 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span31 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span42 = "../list_reversal_lasso.rs" 205 8 209 9
+  let%span span32 = "../list_reversal_lasso.rs" 205 8 209 9
   
-  let%span span43 = "../list_reversal_lasso.rs" 220 8 232 9
+  let%span span33 = "../list_reversal_lasso.rs" 220 8 232 9
   
-  let%span span44 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span34 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span45 = "../list_reversal_lasso.rs" 83 12 85 98
+  let%span span35 = "../list_reversal_lasso.rs" 83 12 85 98
   
-  let%span span46 = "../list_reversal_lasso.rs" 152 8 158 9
+  let%span span36 = "../list_reversal_lasso.rs" 152 8 158 9
   
-  let%span span47 = "../list_reversal_lasso.rs" 13 0 13 15
+  let%span span37 = "../list_reversal_lasso.rs" 13 0 13 15
   
-  let%span span48 = "../list_reversal_lasso.rs" 93 12 93 53
+  let%span span38 = "../list_reversal_lasso.rs" 93 12 93 53
   
-  let%span span49 = "../list_reversal_lasso.rs" 56 8 58 9
+  let%span span39 = "../list_reversal_lasso.rs" 56 8 58 9
   
   use prelude.prelude.UIntSize
   
-  predicate invariant'2 (self : usize) =
-    [%#span24] true
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'2 (_x : usize)
+  predicate invariant'2 (self : Seq'0.t_seq usize) =
+    [%#span20] true
   
-  axiom inv'2 : forall x : usize . inv'2 x = true
+  predicate inv'2 (_x : Seq'0.t_seq usize)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'2 : forall x : Seq'0.t_seq usize . inv'2 x = true
   
-  predicate invariant'1 (self : Seq'0.t_seq usize) =
-    [%#span24] true
+  predicate invariant'1 (self : usize) =
+    [%#span20] true
   
-  predicate inv'1 (_x : Seq'0.t_seq usize)
+  predicate inv'1 (_x : usize)
   
-  axiom inv'1 : forall x : Seq'0.t_seq usize . inv'1 x = true
+  axiom inv'1 : forall x : usize . inv'1 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -2389,84 +2144,65 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span25] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span21] (18446744073709551615 : usize)
   
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#sseq211] inv'1 self)  -> ([%#sseq212] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#sseq210] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
   axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#svec8] inv'0 self)
-   -> ([%#svec10] inv'1 (shallow_model'0 self))
-  && ([%#svec9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+   -> ([%#svec9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span26] inv'1 (shallow_model'0 self)
+    [%#span22] inv'2 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span27] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span29] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span28] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use prelude.seq_ext.SeqExt
-  
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
-  function index_logic'0 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'0 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function subsequence'0 (self : Seq'0.t_seq usize) (n : int) (m : int) : Seq'0.t_seq usize
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#sseq219] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#sseq217] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#sseq220] inv'1 self)
-   -> ([%#sseq223] inv'1 (subsequence'0 self n m))
-  && ([%#sseq222] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#sseq219] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#sseq221] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#sseq218] len'0 (subsequence'0 self n m) = m - n)
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span30] inv'1 self)
-   -> ([%#span31] inv'1 other)
-   -> ([%#span34] inv'1 (concat'0 self other))
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span25] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span32] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span24] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span35] inv'2 v)
-   -> ([%#span38] inv'1 (singleton'0 v))
-  && ([%#span37] index_logic'0 (singleton'0 v) 0 = v) && ([%#span36] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span26] inv'1 v)
+   -> ([%#span28] index_logic'0 (singleton'0 v) 0 = v) && ([%#span27] len'0 (singleton'0 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq usize) (v : usize) : Seq'0.t_seq usize =
-    [%#span39] concat'0 self (singleton'0 v)
+    [%#span29] concat'0 self (singleton'0 v)
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span40] index_logic'0 (shallow_model'0 self) (UIntSize.to_int ix)
+    [%#span30] index_logic'0 (shallow_model'0 self) (UIntSize.to_int ix)
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
   use ListReversalLasso_Memory_Type as Memory'0
   
   function index_logic'1 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span41] index_logic'2 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span31] index_logic'2 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   use prelude.prelude.Int
   
@@ -2476,7 +2212,7 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
     
   
   axiom find_ptr_in_seq'0_def : forall s : Seq'0.t_seq usize, i : int, p : int . find_ptr_in_seq'0 s i p
-  = ([%#span42] if i = len'0 s then
+  = ([%#span32] if i = len'0 s then
     Option'0.C_None
   else
     if UIntSize.to_int (index_logic'0 s i) = p then Option'0.C_Some i else find_ptr_in_seq'0 s (i + 1) p
@@ -2492,7 +2228,7 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
   function pigeon'0 [#"../list_reversal_lasso.rs" 219 4 219 42] (s : Seq'0.t_seq usize) (n : int) : bool
   
   axiom pigeon'0_def : forall s : Seq'0.t_seq usize, n : int . pigeon'0 s n
-  = ([%#span43] if n = 0 then
+  = ([%#span33] if n = 0 then
     true
   else
     match find_ptr_in_seq'0 s 0 (n - 1) with
@@ -2504,20 +2240,20 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
       end
   )
   
-  axiom pigeon'0_spec : forall s : Seq'0.t_seq usize, n : int . ([%#slist_reversal_lasso13] 0 <= n)
-   -> ([%#slist_reversal_lasso14] forall i : int . 0 <= i /\ i < len'0 s  -> UIntSize.to_int (index_logic'0 s i) < n)
-   -> ([%#slist_reversal_lasso15] forall j : int . forall i : int . 0 <= i
+  axiom pigeon'0_spec : forall s : Seq'0.t_seq usize, n : int . ([%#slist_reversal_lasso11] 0 <= n)
+   -> ([%#slist_reversal_lasso12] forall i : int . 0 <= i /\ i < len'0 s  -> UIntSize.to_int (index_logic'0 s i) < n)
+   -> ([%#slist_reversal_lasso13] forall j : int . forall i : int . 0 <= i
   /\ i < len'0 s /\ 0 <= j /\ j < len'0 s /\ i <> j  -> index_logic'0 s i <> index_logic'0 s j)
-   -> ([%#slist_reversal_lasso17] pigeon'0 s n) && ([%#slist_reversal_lasso16] len'0 s <= n)
+   -> ([%#slist_reversal_lasso15] pigeon'0 s n) && ([%#slist_reversal_lasso14] len'0 s <= n)
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span44] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span34] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
   
   predicate list_seg'0 [#"../list_reversal_lasso.rs" 81 4 81 81] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize) (last : usize) (l : int) (h : int)
     
    =
-    [%#span45] first = (if h = l then last else index_logic'0 s l)
+    [%#span35] first = (if h = l then last else index_logic'0 s l)
     /\ (forall i : int . l <= i /\ i < h
      -> nonnull_ptr'0 self (index_logic'0 s i)
     /\ index_logic'1 self (index_logic'0 s i) = (if i = h - 1 then last else index_logic'0 s (i + 1)))
@@ -2527,21 +2263,21 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
   predicate lasso'0 [#"../list_reversal_lasso.rs" 151 4 151 70] (self : Memory'0.t_memory) (first : usize) (s1 : Seq'0.t_seq usize) (s2 : Seq'0.t_seq usize)
     
    =
-    [%#span46] let mid = if len'0 s2 = 0 then index_logic'0 s1 (len'0 s1 - 1) else index_logic'0 s2 0 in len'0 s1 > 0
+    [%#span36] let mid = if len'0 s2 = 0 then index_logic'0 s1 (len'0 s1 - 1) else index_logic'0 s2 0 in len'0 s1 > 0
     /\ (forall j : int . forall i : int . 0 <= i /\ i < len'0 s1 /\ 0 <= j /\ j < len'0 s2
      -> index_logic'0 s1 i <> index_logic'0 s2 j)
     /\ list_seg'0 self first s1 mid 0 (len'0 s1)
     /\ list_seg'0 self mid s2 (index_logic'0 s1 (len'0 s1 - 1)) 0 (len'0 s2)
   
-  constant null'0 : usize = [%#span47] (18446744073709551615 : usize)
+  constant null'0 : usize = [%#span37] (18446744073709551615 : usize)
   
   predicate list'0 [#"../list_reversal_lasso.rs" 91 4 91 54] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize)
     
    =
-    [%#span48] list_seg'0 self first s null'0 0 (len'0 s)
+    [%#span38] list_seg'0 self first s null'0 0 (len'0 s)
   
   predicate mem_is_well_formed'0 [#"../list_reversal_lasso.rs" 55 4 55 43] (self : Memory'0.t_memory) =
-    [%#span49] forall i : usize . nonnull_ptr'0 self i
+    [%#span39] forall i : usize . nonnull_ptr'0 self i
      -> index_logic'1 self i = null'0 \/ nonnull_ptr'0 self (index_logic'1 self i)
   
   constant self  : Memory'0.t_memory
@@ -2571,18 +2307,16 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
       end)
      -> match find_ptr_in_seq'0 s 0 (UIntSize.to_int last) with
       | Option'0.C_None -> ([%#svec8] inv'0 (ListReversalLasso_Memory_Type.memory_0 self))
-      /\ (([%#svec10] inv'1 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)))
-      && ([%#svec9] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
+      /\ (([%#svec9] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
       <= UIntSize.to_int (max'0 : usize))
-       -> ([%#sseq211] inv'1 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)))
-      /\ (([%#sseq212] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) >= 0)
-       -> (([%#slist_reversal_lasso15] forall j : int . forall i : int . 0 <= i
+       -> ([%#sseq210] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) >= 0)
+       -> (([%#slist_reversal_lasso13] forall j : int . forall i : int . 0 <= i
       /\ i < len'0 s /\ 0 <= j /\ j < len'0 s /\ i <> j  -> index_logic'0 s i <> index_logic'0 s j)
-      && ([%#slist_reversal_lasso14] forall i : int . 0 <= i /\ i < len'0 s
+      && ([%#slist_reversal_lasso12] forall i : int . 0 <= i /\ i < len'0 s
        -> UIntSize.to_int (index_logic'0 s i) < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)))
-      && ([%#slist_reversal_lasso13] 0 <= len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))))
-      /\ (([%#slist_reversal_lasso17] pigeon'0 s (len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))))
-      && ([%#slist_reversal_lasso16] len'0 s <= len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)))
+      && ([%#slist_reversal_lasso11] 0 <= len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))))
+      /\ (([%#slist_reversal_lasso15] pigeon'0 s (len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))))
+      && ([%#slist_reversal_lasso14] len'0 s <= len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)))
        -> match pigeon'0 s (len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))) with
         | True -> ((([%#slist_reversal_lasso2] list_seg'0 self first (push'0 s last) (index_logic'1 self last) 0 (len'0 (push'0 s last)))
         && ([%#slist_reversal_lasso1] index_logic'1 self last = null'0 \/ nonnull_ptr'0 self (index_logic'1 self last))
@@ -2604,24 +2338,21 @@ module ListReversalLasso_Impl4_FindLassoAux_Impl
           | (s, Option'0.C_None) -> list'0 self first s
           | (s1, Option'0.C_Some s2) -> lasso'0 self first s1 s2
           end
-        end)))
-      | Option'0.C_Some i -> (([%#sseq220] inv'1 s) && ([%#sseq219] 0 <= 0 /\ 0 <= i + 1 /\ i + 1 <= len'0 s))
-      /\ (([%#sseq223] inv'1 (subsequence'0 s 0 (i + 1)))
-      && ([%#sseq222] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s 0 (i + 1))
+        end))
+      | Option'0.C_Some i -> ([%#sseq217] 0 <= 0 /\ 0 <= i + 1 /\ i + 1 <= len'0 s)
+      /\ (([%#sseq219] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s 0 (i + 1))
        -> index_logic'0 (subsequence'0 s 0 (i + 1)) i' = index_logic'0 s (0 + i'))
-      && ([%#sseq221] len'0 (subsequence'0 s 0 (i + 1)) = i + 1 - 0)
-       -> ([%#sseq211] inv'1 s)
-      /\ (([%#sseq212] len'0 s >= 0)
-       -> (([%#sseq220] inv'1 s) && ([%#sseq219] 0 <= i + 1 /\ i + 1 <= len'0 s /\ len'0 s <= len'0 s))
-      /\ (([%#sseq223] inv'1 (subsequence'0 s (i + 1) (len'0 s)))
-      && ([%#sseq222] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s (i + 1) (len'0 s))
+      && ([%#sseq218] len'0 (subsequence'0 s 0 (i + 1)) = i + 1 - 0)
+       -> ([%#sseq210] len'0 s >= 0)
+       -> ([%#sseq217] 0 <= i + 1 /\ i + 1 <= len'0 s /\ len'0 s <= len'0 s)
+      /\ (([%#sseq219] forall i' : int . 0 <= i' /\ i' < len'0 (subsequence'0 s (i + 1) (len'0 s))
        -> index_logic'0 (subsequence'0 s (i + 1) (len'0 s)) i' = index_logic'0 s (i + 1 + i'))
-      && ([%#sseq221] len'0 (subsequence'0 s (i + 1) (len'0 s)) = len'0 s - (i + 1))
+      && ([%#sseq218] len'0 (subsequence'0 s (i + 1) (len'0 s)) = len'0 s - (i + 1))
        -> ([%#slist_reversal_lasso3] match (subsequence'0 s 0 (i + 1), Option'0.C_Some (subsequence'0 s (i
       + 1) (len'0 s))) with
         | (s, Option'0.C_None) -> list'0 self first s
         | (s1, Option'0.C_Some s2) -> lasso'0 self first s1 s2
-        end))))
+        end)))
       end)
     end
 end
@@ -2646,106 +2377,91 @@ module ListReversalLasso_Impl4_FindLasso_Impl
   
   let%span span9 = "" 0 0 0 0
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
+  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span20 = "../list_reversal_lasso.rs" 21 8 21 31
+  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span21 = "../list_reversal_lasso.rs" 50 20 50 70
+  let%span span15 = "../../../../creusot-contracts/src/logic/ops.rs" 31 8 31 32
   
-  let%span span22 = "../list_reversal_lasso.rs" 83 12 85 98
+  let%span span16 = "../list_reversal_lasso.rs" 21 8 21 31
   
-  let%span span23 = "../list_reversal_lasso.rs" 198 15 198 37
+  let%span span17 = "../list_reversal_lasso.rs" 50 20 50 70
   
-  let%span span24 = "../list_reversal_lasso.rs" 199 14 202 5
+  let%span span18 = "../list_reversal_lasso.rs" 83 12 85 98
   
-  let%span span25 = "../list_reversal_lasso.rs" 203 14 203 25
+  let%span span19 = "../list_reversal_lasso.rs" 198 15 198 37
   
-  let%span span26 = "../list_reversal_lasso.rs" 205 8 209 9
+  let%span span20 = "../list_reversal_lasso.rs" 199 14 202 5
   
-  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span21 = "../list_reversal_lasso.rs" 203 14 203 25
   
-  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span22 = "../list_reversal_lasso.rs" 205 8 209 9
   
-  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span35 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span32 = "../list_reversal_lasso.rs" 213 15 213 21
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span33 = "../list_reversal_lasso.rs" 214 4 214 67
   
-  let%span span40 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span34 = "../list_reversal_lasso.rs" 215 4 215 113
   
-  let%span span41 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span35 = "../list_reversal_lasso.rs" 216 14 216 26
   
-  let%span span42 = "../list_reversal_lasso.rs" 213 15 213 21
+  let%span span36 = "../list_reversal_lasso.rs" 217 14 217 20
   
-  let%span span43 = "../list_reversal_lasso.rs" 214 4 214 67
+  let%span span37 = "../list_reversal_lasso.rs" 218 14 218 15
   
-  let%span span44 = "../list_reversal_lasso.rs" 215 4 215 113
+  let%span span38 = "../list_reversal_lasso.rs" 220 8 232 9
   
-  let%span span45 = "../list_reversal_lasso.rs" 216 14 216 26
+  let%span span39 = "../list_reversal_lasso.rs" 152 8 158 9
   
-  let%span span46 = "../list_reversal_lasso.rs" 217 14 217 20
+  let%span span40 = "../list_reversal_lasso.rs" 13 0 13 15
   
-  let%span span47 = "../list_reversal_lasso.rs" 218 14 218 15
+  let%span span41 = "../list_reversal_lasso.rs" 93 12 93 53
   
-  let%span span48 = "../list_reversal_lasso.rs" 220 8 232 9
+  let%span span42 = "../list_reversal_lasso.rs" 56 8 58 9
   
-  let%span span49 = "../list_reversal_lasso.rs" 152 8 158 9
+  let%span span43 = "../list_reversal_lasso.rs" 245 8 259 9
   
-  let%span span50 = "../list_reversal_lasso.rs" 13 0 13 15
+  use prelude.prelude.UIntSize
   
-  let%span span51 = "../list_reversal_lasso.rs" 93 12 93 53
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span52 = "../list_reversal_lasso.rs" 56 8 58 9
+  predicate invariant'2 (self : Seq'0.t_seq usize) =
+    [%#span8] true
   
-  let%span span53 = "../list_reversal_lasso.rs" 245 8 259 9
+  predicate inv'2 (_x : Seq'0.t_seq usize)
   
-  use prelude.prelude.UIntSize
+  axiom inv'2 : forall x : Seq'0.t_seq usize . inv'2 x = true
   
-  predicate invariant'2 (self : usize) =
+  predicate invariant'1 (self : usize) =
     [%#span8] true
   
-  predicate inv'2 (_x : usize)
-  
-  axiom inv'2 : forall x : usize . inv'2 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'1 (_x : usize)
   
-  predicate inv'0 (_x : Seq'0.t_seq usize)
+  axiom inv'1 : forall x : usize . inv'1 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -2757,61 +2473,48 @@ module ListReversalLasso_Impl4_FindLasso_Impl
   
   constant max'0 : usize = [%#span9] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span10] inv'0 self)  -> ([%#span11] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span10] len'0 self >= 0
   
-  predicate inv'1 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'0 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span12] inv'1 self)
-   -> ([%#span14] inv'0 (shallow_model'0 self))
-  && ([%#span13] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'1 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span15] inv'0 (shallow_model'0 self)
-  
-  axiom inv'1 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'1 x = true
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span11] inv'0 self)
+   -> ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'0 (self : Seq'0.t_seq usize) =
-    [%#span8] true
+  predicate invariant'0 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span13] inv'2 (shallow_model'0 self)
   
-  axiom inv'0 : forall x : Seq'0.t_seq usize . inv'0 x = true
+  axiom inv'0 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span16] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span18] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span14] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use ListReversalLasso_Memory_Type as ListReversalLasso_Memory_Type
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : usize) : usize =
-    [%#span19] index_logic'1 (shallow_model'0 self) (UIntSize.to_int ix)
+    [%#span15] index_logic'1 (shallow_model'0 self) (UIntSize.to_int ix)
   
   use ListReversalLasso_Memory_Type as Memory'0
   
   function index_logic'0 [#"../list_reversal_lasso.rs" 20 4 20 39] (self : Memory'0.t_memory) (i : usize) : usize =
-    [%#span20] index_logic'2 (ListReversalLasso_Memory_Type.memory_0 self) i
+    [%#span16] index_logic'2 (ListReversalLasso_Memory_Type.memory_0 self) i
   
   predicate nonnull_ptr'0 [#"../list_reversal_lasso.rs" 49 4 49 44] (self : Memory'0.t_memory) (i : usize) =
-    [%#span21] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
+    [%#span17] len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self)) <= UIntSize.to_int (max'0 : usize)
     /\ UIntSize.to_int i < len'0 (shallow_model'0 (ListReversalLasso_Memory_Type.memory_0 self))
   
   predicate list_seg'0 [#"../list_reversal_lasso.rs" 81 4 81 81] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize) (last : usize) (l : int) (h : int)
     
    =
-    [%#span22] first = (if h = l then last else index_logic'1 s l)
+    [%#span18] first = (if h = l then last else index_logic'1 s l)
     /\ (forall i : int . l <= i /\ i < h
      -> nonnull_ptr'0 self (index_logic'1 s i)
     /\ index_logic'0 self (index_logic'1 s i) = (if i = h - 1 then last else index_logic'1 s (i + 1)))
@@ -2826,57 +2529,46 @@ module ListReversalLasso_Impl4_FindLasso_Impl
     
   
   axiom find_ptr_in_seq'0_def : forall s : Seq'0.t_seq usize, i : int, p : int . find_ptr_in_seq'0 s i p
-  = ([%#span26] if i = len'0 s then
+  = ([%#span22] if i = len'0 s then
     Option'0.C_None
   else
     if UIntSize.to_int (index_logic'1 s i) = p then Option'0.C_Some i else find_ptr_in_seq'0 s (i + 1) p
   )
   
-  axiom find_ptr_in_seq'0_spec : forall s : Seq'0.t_seq usize, i : int, p : int . ([%#span23] 0 <= i /\ i <= len'0 s)
-   -> ([%#span24] match find_ptr_in_seq'0 s i p with
+  axiom find_ptr_in_seq'0_spec : forall s : Seq'0.t_seq usize, i : int, p : int . ([%#span19] 0 <= i /\ i <= len'0 s)
+   -> ([%#span20] match find_ptr_in_seq'0 s i p with
     | Option'0.C_None -> forall j : int . i <= j /\ j < len'0 s  -> UIntSize.to_int (index_logic'1 s j) <> p
     | Option'0.C_Some j -> i <= j /\ j < len'0 s /\ UIntSize.to_int (index_logic'1 s j) = p
     end)
   
-  use prelude.seq_ext.SeqExt
-  
   function subsequence'0 (self : Seq'0.t_seq usize) (n : int) (m : int) : Seq'0.t_seq usize
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#span27] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#span23] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span28] inv'0 self)
-   -> ([%#span31] inv'0 (subsequence'0 self n m))
-  && ([%#span30] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span25] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span29] len'0 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span24] len'0 (subsequence'0 self n m) = m - n)
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span32] inv'0 self)
-   -> ([%#span33] inv'0 other)
-   -> ([%#span36] inv'0 (concat'0 self other))
-  && ([%#span35] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span27] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span34] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span26] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span37] inv'2 v)
-   -> ([%#span40] inv'0 (singleton'0 v))
-  && ([%#span39] index_logic'1 (singleton'0 v) 0 = v) && ([%#span38] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span28] inv'1 v)
+   -> ([%#span30] index_logic'1 (singleton'0 v) 0 = v) && ([%#span29] len'0 (singleton'0 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq usize) (v : usize) : Seq'0.t_seq usize =
-    [%#span41] concat'0 self (singleton'0 v)
+    [%#span31] concat'0 self (singleton'0 v)
   
   function pigeon'0 [#"../list_reversal_lasso.rs" 219 4 219 42] (s : Seq'0.t_seq usize) (n : int) : bool
   
   axiom pigeon'0_def : forall s : Seq'0.t_seq usize, n : int . pigeon'0 s n
-  = ([%#span48] if n = 0 then
+  = ([%#span38] if n = 0 then
     true
   else
     match find_ptr_in_seq'0 s 0 (n - 1) with
@@ -2888,36 +2580,36 @@ module ListReversalLasso_Impl4_FindLasso_Impl
       end
   )
   
-  axiom pigeon'0_spec : forall s : Seq'0.t_seq usize, n : int . ([%#span42] 0 <= n)
-   -> ([%#span43] forall i : int . 0 <= i /\ i < len'0 s  -> UIntSize.to_int (index_logic'1 s i) < n)
-   -> ([%#span44] forall j : int . forall i : int . 0 <= i /\ i < len'0 s /\ 0 <= j /\ j < len'0 s /\ i <> j
-   -> index_logic'1 s i <> index_logic'1 s j)  -> ([%#span46] pigeon'0 s n) && ([%#span45] len'0 s <= n)
+  axiom pigeon'0_spec : forall s : Seq'0.t_seq usize, n : int . ([%#span32] 0 <= n)
+   -> ([%#span33] forall i : int . 0 <= i /\ i < len'0 s  -> UIntSize.to_int (index_logic'1 s i) < n)
+   -> ([%#span34] forall j : int . forall i : int . 0 <= i /\ i < len'0 s /\ 0 <= j /\ j < len'0 s /\ i <> j
+   -> index_logic'1 s i <> index_logic'1 s j)  -> ([%#span36] pigeon'0 s n) && ([%#span35] len'0 s <= n)
   
   predicate lasso'0 [#"../list_reversal_lasso.rs" 151 4 151 70] (self : Memory'0.t_memory) (first : usize) (s1 : Seq'0.t_seq usize) (s2 : Seq'0.t_seq usize)
     
    =
-    [%#span49] let mid = if len'0 s2 = 0 then index_logic'1 s1 (len'0 s1 - 1) else index_logic'1 s2 0 in len'0 s1 > 0
+    [%#span39] let mid = if len'0 s2 = 0 then index_logic'1 s1 (len'0 s1 - 1) else index_logic'1 s2 0 in len'0 s1 > 0
     /\ (forall j : int . forall i : int . 0 <= i /\ i < len'0 s1 /\ 0 <= j /\ j < len'0 s2
      -> index_logic'1 s1 i <> index_logic'1 s2 j)
     /\ list_seg'0 self first s1 mid 0 (len'0 s1)
     /\ list_seg'0 self mid s2 (index_logic'1 s1 (len'0 s1 - 1)) 0 (len'0 s2)
   
-  constant null'0 : usize = [%#span50] (18446744073709551615 : usize)
+  constant null'0 : usize = [%#span40] (18446744073709551615 : usize)
   
   predicate list'0 [#"../list_reversal_lasso.rs" 91 4 91 54] (self : Memory'0.t_memory) (first : usize) (s : Seq'0.t_seq usize)
     
    =
-    [%#span51] list_seg'0 self first s null'0 0 (len'0 s)
+    [%#span41] list_seg'0 self first s null'0 0 (len'0 s)
   
   predicate mem_is_well_formed'0 [#"../list_reversal_lasso.rs" 55 4 55 43] (self : Memory'0.t_memory) =
-    [%#span52] forall i : usize . nonnull_ptr'0 self i
+    [%#span42] forall i : usize . nonnull_ptr'0 self i
      -> index_logic'0 self i = null'0 \/ nonnull_ptr'0 self (index_logic'0 self i)
   
   function find_lasso_aux'0 [#"../list_reversal_lasso.rs" 244 4 244 95] (self : Memory'0.t_memory) (first : usize) (last : usize) (s : Seq'0.t_seq usize) : (Seq'0.t_seq usize, Option'0.t_option (Seq'0.t_seq usize))
     
   
   axiom find_lasso_aux'0_def : forall self : Memory'0.t_memory, first : usize, last : usize, s : Seq'0.t_seq usize . find_lasso_aux'0 self first last s
-  = ([%#span53] if last = null'0 then
+  = ([%#span43] if last = null'0 then
     (s, Option'0.C_None)
   else
     match find_ptr_in_seq'0 s 0 (UIntSize.to_int last) with
diff --git a/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma b/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma
index 05b727ccb3..db751792d2 100644
--- a/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma
+++ b/creusot/tests/should_succeed/rusthorn/inc_max_repeat.coma
@@ -88,22 +88,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -144,84 +129,66 @@ module IncMaxRepeat_IncMaxRepeat
   
   let%span span10 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span14 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span15 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span16 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span17 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span18 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span19 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span20 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span23 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span25 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span26 = "../inc_max_repeat.rs" 4 0 5 56
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span31 = "" 0 0 0 0
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span32 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span33 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span33 = "" 0 0 0 0
   
-  let%span span34 = "../inc_max_repeat.rs" 4 0 5 56
+  let%span span34 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span35 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span36 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span37 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span37 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span38 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span39 = "" 0 0 0 0
   
   let%span span40 = "" 0 0 0 0
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
-  
-  let%span span42 = "" 0 0 0 0
-  
-  let%span span43 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span44 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span45 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span47 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span48 = "" 0 0 0 0
-  
-  let%span span49 = "" 0 0 0 0
-  
   use prelude.prelude.UInt32
   
   predicate invariant'4 (self : uint32) =
@@ -260,31 +227,22 @@ module IncMaxRepeat_IncMaxRepeat
   
   axiom inv'1 : forall x : Seq'0.t_seq uint32 . inv'1 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span11] inv'1 self)  -> ([%#span12] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span11] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span13] inv'1 self)
-   -> ([%#span14] inv'1 other)
-   -> ([%#span17] inv'1 (concat'0 self other))
-  && ([%#span16] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span13] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span15] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span12] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : Range'0.t_range uint32)
   
@@ -293,12 +251,12 @@ module IncMaxRepeat_IncMaxRepeat
   use prelude.prelude.UInt32
   
   function deep_model'0 (self : uint32) : int =
-    [%#span18] UInt32.to_int self
+    [%#span14] UInt32.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range uint32) (visited : Seq'0.t_seq uint32) (o : Range'0.t_range uint32) =
-    [%#span19] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span15] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'0 visited > 0
@@ -311,39 +269,36 @@ module IncMaxRepeat_IncMaxRepeat
   function produces_trans'0 (a : Range'0.t_range uint32) (ab : Seq'0.t_seq uint32) (b : Range'0.t_range uint32) (bc : Seq'0.t_seq uint32) (c : Range'0.t_range uint32) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range uint32, ab : Seq'0.t_seq uint32, b : Range'0.t_range uint32, bc : Seq'0.t_seq uint32, c : Range'0.t_range uint32 . ([%#span20] produces'0 a ab b)
-   -> ([%#span21] produces'0 b bc c)
-   -> ([%#span22] inv'0 a)
-   -> ([%#span23] inv'1 ab)
-   -> ([%#span24] inv'0 b)
-   -> ([%#span25] inv'1 bc)  -> ([%#span26] inv'0 c)  -> ([%#span27] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range uint32, ab : Seq'0.t_seq uint32, b : Range'0.t_range uint32, bc : Seq'0.t_seq uint32, c : Range'0.t_range uint32 . ([%#span16] produces'0 a ab b)
+   -> ([%#span17] produces'0 b bc c)
+   -> ([%#span18] inv'0 a)
+   -> ([%#span19] inv'0 b)  -> ([%#span20] inv'0 c)  -> ([%#span21] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span28] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   function produces_refl'0 (self : Range'0.t_range uint32) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range uint32 . ([%#span29] inv'0 self)
-   -> ([%#span30] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range uint32 . ([%#span22] inv'0 self)
+   -> ([%#span23] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   predicate invariant'0 (self : Range'0.t_range uint32) =
     [%#span10] true
   
   axiom inv'0 : forall x : Range'0.t_range uint32 . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span32] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span31] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span24] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : borrowed uint32) =
-    [%#span33]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
   let rec take_max'0 (ma:borrowed uint32) (mb:borrowed uint32) (return'  (ret:borrowed uint32))= any
-    [ return' (result:borrowed uint32)-> {[%#span34] if  * ma >=  * mb then
+    [ return' (result:borrowed uint32)-> {[%#span26] if  * ma >=  * mb then
          * mb =  ^ mb /\ result = ma
       else
          * ma =  ^ ma /\ result = mb
@@ -351,26 +306,23 @@ module IncMaxRepeat_IncMaxRepeat
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span35] inv'4 v)
-   -> ([%#span38] inv'1 (singleton'0 v))
-  && ([%#span37] index_logic'0 (singleton'0 v) 0 = v) && ([%#span36] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span27] inv'4 v)
+   -> ([%#span29] index_logic'0 (singleton'0 v) 0 = v) && ([%#span28] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Range'0.t_range uint32)) =
-    [%#span33]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range uint32)) =
-    [%#span39] resolve'0 self
+    [%#span30] resolve'0 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range uint32)) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span40] inv'2 self}
+  let rec next'0 (self:borrowed (Range'0.t_range uint32)) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span31] inv'2 self}
     any
-    [ return' (result:Option'0.t_option uint32)-> {[%#span42] inv'3 result}
-      {[%#span41] match result with
+    [ return' (result:Option'0.t_option uint32)-> {[%#span33] inv'3 result}
+      {[%#span32] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -387,23 +339,23 @@ module IncMaxRepeat_IncMaxRepeat
   
   function new'1 (x : Seq'0.t_seq uint32) : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq uint32 . ([%#span43] inv'1 x)  -> ([%#span44] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq uint32 . ([%#span34] inv'1 x)  -> ([%#span35] deref'0 (new'1 x) = x)
   
   function new'0 (x : Range'0.t_range uint32) : Snapshot'0.t_snapshot (Range'0.t_range uint32)
   
-  axiom new'0_spec : forall x : Range'0.t_range uint32 . ([%#span43] inv'0 x)  -> ([%#span44] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Range'0.t_range uint32 . ([%#span34] inv'0 x)  -> ([%#span35] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range uint32) (res : Range'0.t_range uint32) =
-    [%#span45] self = res
+    [%#span36] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range uint32) =
-    [%#span46] true
+    [%#span37] true
   
-  let rec into_iter'0 (self:Range'0.t_range uint32) (return'  (ret:Range'0.t_range uint32))= {[@expl:precondition] [%#span48] inv'0 self}
-    {[@expl:precondition] [%#span47] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range uint32) (return'  (ret:Range'0.t_range uint32))= {[@expl:precondition] [%#span39] inv'0 self}
+    {[@expl:precondition] [%#span38] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range uint32)-> {[%#span49] inv'0 result}
-      {[%#span47] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range uint32)-> {[%#span40] inv'0 result}
+      {[%#span38] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/slices/01.coma b/creusot/tests/should_succeed/slices/01.coma
index d4e1ca8a2c..616790e2a3 100644
--- a/creusot/tests/should_succeed/slices/01.coma
+++ b/creusot/tests/should_succeed/slices/01.coma
@@ -1,21 +1,6 @@
 
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C01_IndexSlice
   let%span s010 = "../01.rs" 7 6 7 8
@@ -26,79 +11,58 @@ module C01_IndexSlice
   
   let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span6 = "" 0 0 0 0
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span7 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span8 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span9 = "" 0 0 0 0
-  
-  let%span span10 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
-  
-  let%span span12 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
-  
-  let%span span13 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span9 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
   use prelude.prelude.UInt32
   
   use prelude.prelude.Slice
   
-  predicate invariant'1 (self : slice uint32) =
+  predicate invariant'0 (self : slice uint32) =
     [%#span3] true
   
-  predicate inv'1 (_x : slice uint32)
-  
-  axiom inv'1 : forall x : slice uint32 . inv'1 x = true
+  predicate inv'0 (_x : slice uint32)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'0 (self : Seq'0.t_seq uint32) =
-    [%#span3] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq uint32 . inv'0 x = true
+  axiom inv'0 : forall x : slice uint32 . inv'0 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span4] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span9] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span6] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice uint32) : Seq'0.t_seq uint32
   
-  axiom shallow_model'1_spec : forall self : slice uint32 . ([%#span10] inv'1 self)
-   -> ([%#span12] inv'0 (shallow_model'1 self))
-  && ([%#span11] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice uint32 . ([%#span7] inv'0 self)
+   -> ([%#span8] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   use prelude.prelude.Borrow
   
   function shallow_model'0 (self : slice uint32) : Seq'0.t_seq uint32 =
-    [%#span13] shallow_model'1 self
+    [%#span9] shallow_model'1 self
   
   use prelude.prelude.Intrinsic
   
@@ -133,97 +97,74 @@ module C01_IndexMutSlice
   
   let%span span5 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "" 0 0 0 0
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span8 = "" 0 0 0 0
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span10 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span11 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span16 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span12 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span17 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span13 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
   use prelude.prelude.UInt32
   
   use prelude.prelude.Slice
   
-  predicate invariant'1 (self : slice uint32) =
+  predicate invariant'0 (self : slice uint32) =
     [%#span5] true
   
-  predicate inv'1 (_x : slice uint32)
+  predicate inv'0 (_x : slice uint32)
   
-  axiom inv'1 : forall x : slice uint32 . inv'1 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'0 (self : Seq'0.t_seq uint32) =
-    [%#span5] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq uint32 . inv'0 x = true
+  axiom inv'0 : forall x : slice uint32 . inv'0 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span6] inv'0 self)  -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span6] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span8] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.UInt32
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice uint32) : Seq'0.t_seq uint32
   
-  axiom shallow_model'1_spec : forall self : slice uint32 . ([%#span12] inv'1 self)
-   -> ([%#span14] inv'0 (shallow_model'1 self))
-  && ([%#span13] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice uint32 . ([%#span9] inv'0 self)
+   -> ([%#span10] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'0 [@inline:trivial] (self : slice uint32) (ix : int) : uint32 =
-    [%#span15] index_logic'1 (shallow_model'1 self) ix
+    [%#span11] index_logic'1 (shallow_model'1 self) ix
   
   use prelude.prelude.Borrow
   
   function shallow_model'0 (self : borrowed (slice uint32)) : Seq'0.t_seq uint32 =
-    [%#span16] shallow_model'1 ( * self)
+    [%#span12] shallow_model'1 ( * self)
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed (slice uint32)) =
-    [%#span17]  ^ self =  * self
+    [%#span13]  ^ self =  * self
   
   let rec index_mut_slice (a:borrowed (slice uint32)) (return'  (ret:()))= {[%#s013] len'0 (shallow_model'0 a) = 5}
     (! bb0
@@ -284,47 +225,31 @@ module C01_SliceFirst
   
   let%span s015 = "../01.rs" 20 34 20 44
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span8 = "" 0 0 0 0
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span11 = "" 0 0 0 0
+  let%span span10 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span11 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span12 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span13 = "" 0 0 0 0
   
-  let%span span15 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span16 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
-  
-  let%span span17 = "" 0 0 0 0
-  
-  let%span span18 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span14 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
   use prelude.prelude.Slice
   
-  predicate invariant'4 (self : slice t)
+  predicate invariant'3 (self : slice t)
   
-  predicate inv'4 (_x : slice t)
-  
-  axiom inv'4 : forall x : slice t . inv'4 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'3 (_x : slice t)
   
-  predicate invariant'3 (self : Seq'0.t_seq t)
-  
-  predicate inv'3 (_x : Seq'0.t_seq t)
-  
-  axiom inv'3 : forall x : Seq'0.t_seq t . inv'3 x = true
+  axiom inv'3 : forall x : slice t . inv'3 x = true
   
   use Core_Option_Option_Type as Option'0
   
@@ -336,20 +261,17 @@ module C01_SliceFirst
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span6] inv'3 self)  -> ([%#span7] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span6] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span8] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'1 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'1 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'1 (self : t)
   
@@ -367,25 +289,22 @@ module C01_SliceFirst
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : slice t . ([%#span12] inv'4 self)
-   -> ([%#span14] inv'3 (shallow_model'1 self))
-  && ([%#span13] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice t . ([%#span9] inv'3 self)
+   -> ([%#span10] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   use prelude.prelude.Borrow
   
   function shallow_model'0 (self : slice t) : Seq'0.t_seq t =
-    [%#span15] shallow_model'1 self
-  
-  use seq.Seq
+    [%#span11] shallow_model'1 self
   
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'0 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span16] index_logic'1 (shallow_model'1 self) ix
+    [%#span12] index_logic'1 (shallow_model'1 self) ix
   
   use prelude.prelude.Intrinsic
   
@@ -393,9 +312,9 @@ module C01_SliceFirst
   
   predicate resolve'0 (self : slice t)
   
-  let rec len'0 (self:slice t) (return'  (ret:usize))= {[@expl:precondition] [%#span17] inv'0 self}
+  let rec len'0 (self:slice t) (return'  (ret:usize))= {[@expl:precondition] [%#span13] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span18] len'1 (shallow_model'0 self) = UIntSize.to_int result} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span14] len'1 (shallow_model'0 self) = UIntSize.to_int result} (! return' {result}) ]
     
   
   let rec slice_first (a:slice t) (return'  (ret:Option'0.t_option t))= {[%#s013] inv'0 a}
diff --git a/creusot/tests/should_succeed/slices/02_std.coma b/creusot/tests/should_succeed/slices/02_std.coma
index b6dc5c5389..8110aaf912 100644
--- a/creusot/tests/should_succeed/slices/02_std.coma
+++ b/creusot/tests/should_succeed/slices/02_std.coma
@@ -17,22 +17,7 @@ module Core_Result_Result_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Cmp_Ordering_Type
   type t_ordering  =
@@ -65,94 +50,66 @@ module C02Std_BinarySearch
   
   let%span span4 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span10 = "" 0 0 0 0
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
-  
-  let%span span12 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span7 = "" 0 0 0 0
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/result.rs" 53 16 53 55
+  let%span span8 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span17 = "" 0 0 0 0
+  let%span span9 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/result.rs" 18 0 135 1
+  let%span span10 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span19 = "" 0 0 0 0
+  let%span span11 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span12 = "../../../../../creusot-contracts/src/std/result.rs" 53 16 53 55
   
-  let%span span21 = "../../../../../creusot-contracts/src/model.rs" 81 8 81 28
+  let%span span13 = "" 0 0 0 0
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 31 18 31 22
+  let%span span14 = "../../../../../creusot-contracts/src/std/result.rs" 18 0 135 1
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 29 14 29 44
+  let%span span15 = "" 0 0 0 0
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 30 4 30 98
+  let%span span16 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 31 4 31 44
+  let%span span17 = "../../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 156 8 158 9
+  let%span span18 = "../../../../../creusot-contracts/src/std/slice.rs" 31 18 31 22
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 167 8 167 40
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 29 14 29 44
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 30 4 30 98
   
-  let%span span29 = "" 0 0 0 0
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 157 8 159 9
   
-  let%span span30 = "" 0 0 0 0
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 168 8 168 40
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 299 8 299 118
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 223 0 332 1
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 300 8 301 96
+  let%span span24 = "" 0 0 0 0
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 302 8 303 78
+  let%span span25 = "" 0 0 0 0
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 304 8 305 99
+  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 299 8 299 118
   
-  use prelude.prelude.Int
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 300 8 301 96
   
-  predicate invariant'6 (self : Seq'0.t_seq int) =
-    [%#span4] true
+  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 302 8 303 78
   
-  predicate inv'6 (_x : Seq'0.t_seq int)
-  
-  axiom inv'6 : forall x : Seq'0.t_seq int . inv'6 x = true
+  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 304 8 305 99
   
   use prelude.prelude.UInt32
   
   use prelude.prelude.Slice
   
-  predicate invariant'5 (self : slice uint32) =
-    [%#span4] true
-  
-  predicate inv'5 (_x : slice uint32)
-  
-  axiom inv'5 : forall x : slice uint32 . inv'5 x = true
-  
-  predicate invariant'4 (self : Seq'0.t_seq uint32) =
+  predicate invariant'4 (self : slice uint32) =
     [%#span4] true
   
-  predicate inv'4 (_x : Seq'0.t_seq uint32)
+  predicate inv'4 (_x : slice uint32)
   
-  axiom inv'4 : forall x : Seq'0.t_seq uint32 . inv'4 x = true
+  axiom inv'4 : forall x : slice uint32 . inv'4 x = true
   
   use prelude.prelude.UIntSize
   
@@ -188,112 +145,102 @@ module C02Std_BinarySearch
   
   use prelude.prelude.Int
   
-  use seq.Seq
+  use prelude.prelude.Int
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'1 (self : Seq'0.t_seq int) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq int . ([%#span5] inv'6 self)  -> ([%#span6] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq int . [%#span5] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq int = [%#span7] ()
+  constant empty'1 : Seq'0.t_seq int
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span8] len'1 (empty'1 : Seq'0.t_seq int) = 0
-  
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'1 (empty'1 : Seq'0.t_seq int) = 0
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span5] inv'4 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span5] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.UInt32
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'2 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
   function shallow_model'1 (self : slice uint32) : Seq'0.t_seq uint32
   
-  axiom shallow_model'1_spec : forall self : slice uint32 . ([%#span11] inv'5 self)
-   -> ([%#span13] inv'4 (shallow_model'1 self))
-  && ([%#span12] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : slice uint32 . ([%#span8] inv'4 self)
+   -> ([%#span9] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'0 [@inline:trivial] (self : slice uint32) (ix : int) : uint32 =
-    [%#span14] index_logic'2 (shallow_model'1 self) ix
+    [%#span10] index_logic'2 (shallow_model'1 self) ix
   
   use prelude.prelude.Borrow
   
   function shallow_model'0 (self : slice uint32) : Seq'0.t_seq uint32 =
-    [%#span15] shallow_model'1 self
+    [%#span11] shallow_model'1 self
   
   use prelude.prelude.Intrinsic
   
-  let rec unwrap'0 (self:Result'0.t_result usize usize) (return'  (ret:usize))= {[@expl:precondition] [%#span17] inv'3 self}
-    {[@expl:precondition] [%#span16] exists t : usize . inv'2 t /\ self = Result'0.C_Ok t}
+  let rec unwrap'0 (self:Result'0.t_result usize usize) (return'  (ret:usize))= {[@expl:precondition] [%#span13] inv'3 self}
+    {[@expl:precondition] [%#span12] exists t : usize . inv'2 t /\ self = Result'0.C_Ok t}
     any
-    [ return' (result:usize)-> {[%#span19] inv'2 result} {[%#span18] Result'0.C_Ok result = self} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span15] inv'2 result} {[%#span14] Result'0.C_Ok result = self} (! return' {result}) ]
     
   
   use int.Int
   
   function deep_model'3 (self : uint32) : int =
-    [%#span20] UInt32.to_int self
+    [%#span16] UInt32.to_int self
   
   function deep_model'2 (self : uint32) : int =
-    [%#span21] deep_model'3 self
-  
-  use seq.Seq
+    [%#span17] deep_model'3 self
   
-  function index_logic'1 (self : Seq'0.t_seq int) (x : int) : int
+  function index_logic'1 (self : Seq'0.t_seq int) (_2 : int) : int
   
   function deep_model'1 (self : slice uint32) : Seq'0.t_seq int
   
-  axiom deep_model'1_spec : forall self : slice uint32 . ([%#span22] inv'5 self)
-   -> ([%#span25] inv'6 (deep_model'1 self))
-  && ([%#span24] forall i : int . 0 <= i /\ i < len'1 (deep_model'1 self)
+  axiom deep_model'1_spec : forall self : slice uint32 . ([%#span18] inv'4 self)
+   -> ([%#span20] forall i : int . 0 <= i /\ i < len'1 (deep_model'1 self)
    -> index_logic'1 (deep_model'1 self) i = deep_model'3 (index_logic'0 self i))
-  && ([%#span23] len'0 (shallow_model'0 self) = len'1 (deep_model'1 self))
+  && ([%#span19] len'0 (shallow_model'0 self) = len'1 (deep_model'1 self))
   
   use int.Int
   
   predicate sorted_range'0 (self : Seq'0.t_seq int) (l : int) (u : int) =
-    [%#span26] forall j : int . forall i : int . l <= i /\ i <= j /\ j < u
+    [%#span21] forall j : int . forall i : int . l <= i /\ i <= j /\ j < u
      -> index_logic'1 self i <= index_logic'1 self j
   
   predicate sorted'0 (self : Seq'0.t_seq int) =
-    [%#span27] sorted_range'0 self 0 (len'1 self)
+    [%#span22] sorted_range'0 self 0 (len'1 self)
   
   function deep_model'0 (self : slice uint32) : Seq'0.t_seq int =
-    [%#span21] deep_model'1 self
+    [%#span17] deep_model'1 self
   
-  let rec binary_search'0 (self:slice uint32) (x:uint32) (return'  (ret:Result'0.t_result usize usize))= {[@expl:precondition] [%#span30] inv'1 x}
-    {[@expl:precondition] [%#span29] inv'0 self}
-    {[@expl:precondition] [%#span28] sorted'0 (deep_model'0 self)}
+  let rec binary_search'0 (self:slice uint32) (x:uint32) (return'  (ret:Result'0.t_result usize usize))= {[@expl:precondition] [%#span25] inv'1 x}
+    {[@expl:precondition] [%#span24] inv'0 self}
+    {[@expl:precondition] [%#span23] sorted'0 (deep_model'0 self)}
     any
-    [ return' (result:Result'0.t_result usize usize)-> {[%#span34] forall i : usize . result = Result'0.C_Err i
+    [ return' (result:Result'0.t_result usize usize)-> {[%#span29] forall i : usize . result = Result'0.C_Err i
        -> (forall j : usize . i <= j /\ UIntSize.to_int j < len'0 (shallow_model'0 self)
        -> deep_model'2 x < index_logic'1 (deep_model'0 self) (UIntSize.to_int j))}
-      {[%#span33] forall i : usize . result = Result'0.C_Err i
+      {[%#span28] forall i : usize . result = Result'0.C_Err i
        -> (forall j : usize . j < i  -> index_logic'1 (deep_model'0 self) (UIntSize.to_int j) < deep_model'2 x)}
-      {[%#span32] forall i : usize . result = Result'0.C_Err i
+      {[%#span27] forall i : usize . result = Result'0.C_Err i
        -> UIntSize.to_int i <= len'0 (shallow_model'0 self)
       /\ (forall j : int . 0 <= j /\ j < len'0 (shallow_model'0 self)
        -> index_logic'1 (deep_model'0 self) j <> deep_model'2 x)}
-      {[%#span31] forall i : usize . result = Result'0.C_Ok i
+      {[%#span26] forall i : usize . result = Result'0.C_Ok i
        -> UIntSize.to_int i < len'0 (shallow_model'0 self)
       /\ index_logic'1 (deep_model'1 self) (UIntSize.to_int i) = deep_model'2 x}
       (! return' {result}) ]
diff --git a/creusot/tests/should_succeed/sparse_array.coma b/creusot/tests/should_succeed/sparse_array.coma
index 6017815eac..5c4efb982b 100644
--- a/creusot/tests/should_succeed/sparse_array.coma
+++ b/creusot/tests/should_succeed/sparse_array.coma
@@ -150,22 +150,7 @@ module SparseArray_Sparse_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -196,81 +181,80 @@ module SparseArray_Impl2_Get
   
   let%span ssparse_array4 = "../sparse_array.rs" 89 35 89 45
   
-  let%span span5 = "" 0 0 0 0
+  let%span span5 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span6 = "" 0 0 0 0
   
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span12 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span12 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 22 15 22 23
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 25 25 25 29
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 33
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 28 15 28 23
+  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 24 4 24 87
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 25 31 29
+  let%span span17 = "../sparse_array.rs" 73 20 74 52
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 29 14 29 33
+  let%span span18 = "../sparse_array.rs" 40 12 41 82
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 30 4 30 87
+  let%span span19 = "../sparse_array.rs" 50 8 61 9
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 4 31 55
+  let%span span20 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span22 = "../sparse_array.rs" 73 20 74 52
+  let%span span21 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span23 = "../sparse_array.rs" 40 12 41 82
+  let%span span22 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span24 = "../sparse_array.rs" 50 8 61 9
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span25 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span24 = "" 0 0 0 0
   
-  let%span span26 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span25 = "" 0 0 0 0
   
-  let%span span27 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span27 = "" 0 0 0 0
   
-  let%span span29 = "" 0 0 0 0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span30 = "" 0 0 0 0
+  predicate invariant'12 (self : Seq'0.t_seq t)
   
-  let%span span31 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  predicate inv'12 (_x : Seq'0.t_seq t)
   
-  let%span span32 = "" 0 0 0 0
+  axiom inv'12 : forall x : Seq'0.t_seq t . inv'12 x = true
   
-  use Core_Option_Option_Type as Option'0
+  use prelude.prelude.UIntSize
   
-  use prelude.prelude.Int
+  predicate invariant'11 (self : Seq'0.t_seq usize) =
+    [%#span5] true
   
-  use map.Map
+  predicate inv'11 (_x : Seq'0.t_seq usize)
   
-  predicate invariant'13 (self : Map.map int (Option'0.t_option t))
+  axiom inv'11 : forall x : Seq'0.t_seq usize . inv'11 x = true
   
-  predicate inv'13 (_x : Map.map int (Option'0.t_option t))
+  use Core_Option_Option_Type as Option'0
   
-  axiom inv'13 : forall x : Map.map int (Option'0.t_option t) . inv'13 x = true
+  use prelude.prelude.Int
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use map.Map
   
-  predicate invariant'12 (self : Seq'0.t_seq t)
+  predicate invariant'10 (self : Map.map int (Option'0.t_option t))
   
-  predicate inv'12 (_x : Seq'0.t_seq t)
+  predicate inv'10 (_x : Map.map int (Option'0.t_option t))
   
-  axiom inv'12 : forall x : Seq'0.t_seq t . inv'12 x = true
+  axiom inv'10 : forall x : Map.map int (Option'0.t_option t) . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -278,116 +262,84 @@ module SparseArray_Impl2_Get
   
   use prelude.prelude.UIntSize
   
-  use prelude.prelude.UIntSize
-  
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span6] (18446744073709551615 : usize)
   
   function len'2 (self : Seq'0.t_seq t) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq t . ([%#span6] inv'12 self)  -> ([%#span7] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq t . [%#span7] len'2 self >= 0
   
-  predicate inv'11 (_x : Vec'0.t_vec t (Global'0.t_global))
+  predicate inv'9 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'5 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'5_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span8] inv'11 self)
-   -> ([%#span10] inv'12 (shallow_model'5 self))
-  && ([%#span9] len'2 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'5_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span8] inv'9 self)
+   -> ([%#span9] len'2 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'11 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span11] inv'12 (shallow_model'5 self)
+  predicate invariant'9 (self : Vec'0.t_vec t (Global'0.t_global)) =
+    [%#span10] inv'12 (shallow_model'5 self)
   
-  axiom inv'11 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'11 x = true
-  
-  predicate invariant'10 (self : Seq'0.t_seq usize) =
-    [%#span12] true
-  
-  predicate inv'10 (_x : Seq'0.t_seq usize)
-  
-  axiom inv'10 : forall x : Seq'0.t_seq usize . inv'10 x = true
-  
-  use seq.Seq
+  axiom inv'9 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'9 x = true
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span6] inv'10 self)  -> ([%#span7] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span7] len'1 self >= 0
   
-  predicate inv'9 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'8 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'4 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'4_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'9 self)
-   -> ([%#span10] inv'10 (shallow_model'4 self))
-  && ([%#span9] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'9 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span11] inv'10 (shallow_model'4 self)
+  axiom shallow_model'4_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'8 self)
+   -> ([%#span9] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
-  axiom inv'9 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'9 x = true
+  predicate invariant'8 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span10] inv'11 (shallow_model'4 self)
   
-  constant empty'2 : Seq'0.t_seq t = [%#span13] ()
+  axiom inv'8 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'8 x = true
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span15] ()
+  constant empty'2 : Seq'0.t_seq t
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span14] len'2 (empty'2 : Seq'0.t_seq t) = 0
+  function empty_len'2 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span11] len'2 (empty'2 : Seq'0.t_seq t) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'4 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span16] index_logic'1 (shallow_model'4 self) ix
+    [%#span12] index_logic'1 (shallow_model'4 self) ix
   
   use SparseArray_Sparse_Type as SparseArray_Sparse_Type
   
-  use seq.Seq
-  
-  predicate inv'7 (_x : Seq'0.t_seq (Option'0.t_option t))
-  
   function len'0 (self : Seq'0.t_seq (Option'0.t_option t)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . ([%#span6] inv'7 self)
-   -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . [%#span7] len'0 self >= 0
   
   use prelude.prelude.Borrow
   
-  use seq.Seq
-  
   use map.Map
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option t)) (x : int) : Option'0.t_option t
+  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option t)) (_2 : int) : Option'0.t_option t
   
   function new'0 (len : int) (data : Map.map int (Option'0.t_option t)) : Seq'0.t_seq (Option'0.t_option t)
   
-  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span17] len >= 0)
-   -> ([%#span18] inv'13 data)
-   -> ([%#span21] inv'7 (new'0 len data))
-  && ([%#span20] forall i : int . 0 <= i /\ i < len'0 (new'0 len data)
+  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span13] len >= 0)
+   -> ([%#span14] inv'10 data)
+   -> ([%#span16] forall i : int . 0 <= i /\ i < len'0 (new'0 len data)
    -> index_logic'0 (new'0 len data) i = Map.get data i)
-  && ([%#span19] len'0 (new'0 len data) = len)
+  && ([%#span15] len'0 (new'0 len data) = len)
   
   use prelude.prelude.Mapping
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'3 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span16] index_logic'2 (shallow_model'5 self) ix
+    [%#span12] index_logic'2 (shallow_model'5 self) ix
   
   use SparseArray_Sparse_Type as Sparse'0
   
   function is_elt'0 [#"../sparse_array.rs" 72 4 72 36] (self : Sparse'0.t_sparse t) (i : int) : bool =
-    [%#span22] UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_idx self) i)
+    [%#span17] UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_idx self) i)
     < UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     /\ UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_back self) (UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_idx self) i)))
     = i
@@ -395,14 +347,14 @@ module SparseArray_Impl2_Get
   function shallow_model'3 [#"../sparse_array.rs" 38 4 38 50] (self : Sparse'0.t_sparse t) : Seq'0.t_seq (Option'0.t_option t)
     
    =
-    [%#span23] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
+    [%#span18] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
       Option'0.C_Some (index_logic'3 (SparseArray_Sparse_Type.sparse_values self) i)
     else
       Option'0.C_None
     ))
   
-  predicate invariant'8 [#"../sparse_array.rs" 49 4 49 30] (self : Sparse'0.t_sparse t) =
-    [%#span24] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
+  predicate invariant'7 [#"../sparse_array.rs" 49 4 49 30] (self : Sparse'0.t_sparse t) =
+    [%#span19] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     <= UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'0 (shallow_model'3 self) = UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'2 (shallow_model'5 (SparseArray_Sparse_Type.sparse_values self))
@@ -418,24 +370,19 @@ module SparseArray_Impl2_Get
       /\ UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_idx self) (UIntSize.to_int j)) = i
       end)
   
-  predicate inv'8 (_x : Sparse'0.t_sparse t)
+  predicate inv'7 (_x : Sparse'0.t_sparse t)
   
-  axiom inv'8 : forall x : Sparse'0.t_sparse t . inv'8 x
-  = (invariant'8 x
+  axiom inv'7 : forall x : Sparse'0.t_sparse t . inv'7 x
+  = (invariant'7 x
   /\ match x with
     | Sparse'0.C_Sparse size n values idx back -> true
     end)
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span13] ()
+  constant empty'1 : Seq'0.t_seq usize
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span15] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span14] len'1 (empty'1 : Seq'0.t_seq usize) = 0
-  
-  predicate invariant'7 (self : Seq'0.t_seq (Option'0.t_option t))
-  
-  axiom inv'7 : forall x : Seq'0.t_seq (Option'0.t_option t) . inv'7 x = true
+  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
   predicate invariant'6 (self : Vec'0.t_vec t (Global'0.t_global))
   
@@ -444,21 +391,21 @@ module SparseArray_Impl2_Get
   axiom inv'6 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'6 x = true
   
   predicate invariant'5 (self : usize) =
-    [%#span12] true
+    [%#span5] true
   
   predicate inv'5 (_x : usize)
   
   axiom inv'5 : forall x : usize . inv'5 x = true
   
   predicate invariant'4 (self : usize) =
-    [%#span12] true
+    [%#span5] true
   
   predicate inv'4 (_x : usize)
   
   axiom inv'4 : forall x : usize . inv'4 x = true
   
   predicate invariant'3 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span12] true
+    [%#span5] true
   
   predicate inv'3 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
@@ -470,12 +417,11 @@ module SparseArray_Impl2_Get
   
   axiom inv'2 : forall x : Option'0.t_option t . inv'2 x = true
   
-  constant empty'0 : Seq'0.t_seq (Option'0.t_option t) = [%#span13] ()
+  constant empty'0 : Seq'0.t_seq (Option'0.t_option t)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span15] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span14] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option t)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option t)) = 0
   
   predicate invariant'1 (self : t)
   
@@ -487,10 +433,10 @@ module SparseArray_Impl2_Get
   
   predicate inv'0 (_x : Sparse'0.t_sparse t)
   
-  axiom inv'0 : forall x : Sparse'0.t_sparse t . inv'0 x = inv'8 x
+  axiom inv'0 : forall x : Sparse'0.t_sparse t . inv'0 x = inv'7 x
   
   function shallow_model'0 (self : Sparse'0.t_sparse t) : Seq'0.t_seq (Option'0.t_option t) =
-    [%#span25] shallow_model'3 self
+    [%#span20] shallow_model'3 self
   
   use prelude.prelude.Intrinsic
   
@@ -499,40 +445,40 @@ module SparseArray_Impl2_Get
   use prelude.prelude.Slice
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) (out : t) =
-    [%#span26] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span21] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) =
-    [%#span27] UIntSize.to_int self < len'2 seq
+    [%#span22] UIntSize.to_int self < len'2 seq
   
   function shallow_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t =
-    [%#span25] shallow_model'5 self
+    [%#span20] shallow_model'5 self
   
-  let rec index'1 (self:Vec'0.t_vec t (Global'0.t_global)) (index:usize) (return'  (ret:t))= {[@expl:precondition] [%#span30] inv'4 index}
-    {[@expl:precondition] [%#span29] inv'6 self}
-    {[@expl:precondition] [%#span28] in_bounds'1 index (shallow_model'2 self)}
+  let rec index'1 (self:Vec'0.t_vec t (Global'0.t_global)) (index:usize) (return'  (ret:t))= {[@expl:precondition] [%#span25] inv'4 index}
+    {[@expl:precondition] [%#span24] inv'6 self}
+    {[@expl:precondition] [%#span23] in_bounds'1 index (shallow_model'2 self)}
     any
-    [ return' (result:t)-> {[%#span32] inv'1 result}
-      {[%#span31] has_value'1 index (shallow_model'2 self) result}
+    [ return' (result:t)-> {[%#span27] inv'1 result}
+      {[%#span26] has_value'1 index (shallow_model'2 self) result}
       (! return' {result}) ]
     
   
   predicate resolve'0 (self : Sparse'0.t_sparse t)
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span26] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span21] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span27] UIntSize.to_int self < len'1 seq
+    [%#span22] UIntSize.to_int self < len'1 seq
   
   function shallow_model'1 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize =
-    [%#span25] shallow_model'4 self
+    [%#span20] shallow_model'4 self
   
-  let rec index'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span30] inv'4 index}
-    {[@expl:precondition] [%#span29] inv'3 self}
-    {[@expl:precondition] [%#span28] in_bounds'0 index (shallow_model'1 self)}
+  let rec index'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span25] inv'4 index}
+    {[@expl:precondition] [%#span24] inv'3 self}
+    {[@expl:precondition] [%#span23] in_bounds'0 index (shallow_model'1 self)}
     any
-    [ return' (result:usize)-> {[%#span32] inv'5 result}
-      {[%#span31] has_value'0 index (shallow_model'1 self) result}
+    [ return' (result:usize)-> {[%#span27] inv'5 result}
+      {[%#span26] has_value'0 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
@@ -622,76 +568,60 @@ module SparseArray_Impl2_LemmaPermutation_Impl
   
   let%span span5 = "" 0 0 0 0
   
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span10 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span7 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span8 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span9 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span11 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 28 15 28 23
+  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 22 15 22 23
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 25 31 29
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 25 25 25 29
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 29 14 29 33
+  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 33
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 30 4 30 87
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 24 4 24 87
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 4 31 55
+  let%span span16 = "../sparse_array.rs" 73 20 74 52
   
-  let%span span21 = "../sparse_array.rs" 73 20 74 52
-  
-  let%span span22 = "../sparse_array.rs" 40 12 41 82
-  
-  let%span span23 = "../sparse_array.rs" 50 8 61 9
-  
-  use Core_Option_Option_Type as Option'0
-  
-  use prelude.prelude.Int
+  let%span span17 = "../sparse_array.rs" 40 12 41 82
   
-  use map.Map
+  let%span span18 = "../sparse_array.rs" 50 8 61 9
   
-  predicate invariant'6 (self : Map.map int (Option'0.t_option t))
+  use prelude.prelude.UIntSize
   
-  predicate inv'6 (_x : Map.map int (Option'0.t_option t))
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  axiom inv'6 : forall x : Map.map int (Option'0.t_option t) . inv'6 x = true
+  predicate invariant'5 (self : Seq'0.t_seq usize) =
+    [%#span4] true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate inv'5 (_x : Seq'0.t_seq usize)
   
-  predicate invariant'5 (self : Seq'0.t_seq t)
+  axiom inv'5 : forall x : Seq'0.t_seq usize . inv'5 x = true
   
-  predicate inv'5 (_x : Seq'0.t_seq t)
+  predicate invariant'4 (self : Seq'0.t_seq t)
   
-  axiom inv'5 : forall x : Seq'0.t_seq t . inv'5 x = true
+  predicate inv'4 (_x : Seq'0.t_seq t)
   
-  predicate invariant'4 (self : Seq'0.t_seq (Option'0.t_option t))
+  axiom inv'4 : forall x : Seq'0.t_seq t . inv'4 x = true
   
-  predicate inv'4 (_x : Seq'0.t_seq (Option'0.t_option t))
+  use Core_Option_Option_Type as Option'0
   
-  axiom inv'4 : forall x : Seq'0.t_seq (Option'0.t_option t) . inv'4 x = true
+  use prelude.prelude.Int
   
-  use prelude.prelude.UIntSize
+  use map.Map
   
-  predicate invariant'3 (self : Seq'0.t_seq usize) =
-    [%#span4] true
+  predicate invariant'3 (self : Map.map int (Option'0.t_option t))
   
-  predicate inv'3 (_x : Seq'0.t_seq usize)
+  predicate inv'3 (_x : Map.map int (Option'0.t_option t))
   
-  axiom inv'3 : forall x : Seq'0.t_seq usize . inv'3 x = true
+  axiom inv'3 : forall x : Map.map int (Option'0.t_option t) . inv'3 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -703,115 +633,92 @@ module SparseArray_Impl2_LemmaPermutation_Impl
   
   constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq usize) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq usize . ([%#span6] inv'3 self)  -> ([%#span7] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq usize . [%#span6] len'2 self >= 0
   
   predicate inv'2 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'2 self)
-   -> ([%#span10] inv'3 (shallow_model'0 self))
-  && ([%#span9] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span7] inv'2 self)
+   -> ([%#span8] len'2 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'2 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span11] inv'3 (shallow_model'0 self)
+    [%#span9] inv'5 (shallow_model'0 self)
   
   axiom inv'2 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'2 x = true
   
-  constant empty'2 : Seq'0.t_seq usize = [%#span12] ()
+  constant empty'2 : Seq'0.t_seq usize
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span14] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span13] len'2 (empty'2 : Seq'0.t_seq usize) = 0
-  
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span10] len'2 (empty'2 : Seq'0.t_seq usize) = 0
   
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span6] inv'5 self)  -> ([%#span7] len'1 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq t = [%#span12] ()
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span6] len'1 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span14] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span13] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span10] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
   function len'0 (self : Seq'0.t_seq (Option'0.t_option t)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . ([%#span6] inv'4 self)
-   -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . [%#span6] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (Option'0.t_option t) = [%#span12] ()
+  constant empty'0 : Seq'0.t_seq (Option'0.t_option t)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span14] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option t)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option t)) = 0
   
   predicate inv'1 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span8] inv'1 self)
-   -> ([%#span10] inv'5 (shallow_model'2 self))
-  && ([%#span9] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span7] inv'1 self)
+   -> ([%#span8] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span11] inv'5 (shallow_model'2 self)
+    [%#span9] inv'4 (shallow_model'2 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'1 x = true
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span15] index_logic'1 (shallow_model'0 self) ix
+    [%#span11] index_logic'1 (shallow_model'0 self) ix
   
   use SparseArray_Sparse_Type as SparseArray_Sparse_Type
   
   use prelude.prelude.Borrow
   
-  use seq.Seq
-  
   use map.Map
   
-  use seq.Seq
-  
-  function index_logic'4 (self : Seq'0.t_seq (Option'0.t_option t)) (x : int) : Option'0.t_option t
+  function index_logic'4 (self : Seq'0.t_seq (Option'0.t_option t)) (_2 : int) : Option'0.t_option t
   
   function new'0 (len : int) (data : Map.map int (Option'0.t_option t)) : Seq'0.t_seq (Option'0.t_option t)
   
-  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span16] len >= 0)
-   -> ([%#span17] inv'6 data)
-   -> ([%#span20] inv'4 (new'0 len data))
-  && ([%#span19] forall i : int . 0 <= i /\ i < len'0 (new'0 len data)
+  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span12] len >= 0)
+   -> ([%#span13] inv'3 data)
+   -> ([%#span15] forall i : int . 0 <= i /\ i < len'0 (new'0 len data)
    -> index_logic'4 (new'0 len data) i = Map.get data i)
-  && ([%#span18] len'0 (new'0 len data) = len)
+  && ([%#span14] len'0 (new'0 len data) = len)
   
   use prelude.prelude.Mapping
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'3 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span15] index_logic'3 (shallow_model'2 self) ix
+    [%#span11] index_logic'3 (shallow_model'2 self) ix
   
   use SparseArray_Sparse_Type as Sparse'0
   
   function is_elt'0 [#"../sparse_array.rs" 72 4 72 36] (self : Sparse'0.t_sparse t) (i : int) : bool =
-    [%#span21] UIntSize.to_int (index_logic'0 (SparseArray_Sparse_Type.sparse_idx self) i)
+    [%#span16] UIntSize.to_int (index_logic'0 (SparseArray_Sparse_Type.sparse_idx self) i)
     < UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     /\ UIntSize.to_int (index_logic'0 (SparseArray_Sparse_Type.sparse_back self) (UIntSize.to_int (index_logic'0 (SparseArray_Sparse_Type.sparse_idx self) i)))
     = i
@@ -819,14 +726,14 @@ module SparseArray_Impl2_LemmaPermutation_Impl
   function shallow_model'1 [#"../sparse_array.rs" 38 4 38 50] (self : Sparse'0.t_sparse t) : Seq'0.t_seq (Option'0.t_option t)
     
    =
-    [%#span22] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
+    [%#span17] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
       Option'0.C_Some (index_logic'2 (SparseArray_Sparse_Type.sparse_values self) i)
     else
       Option'0.C_None
     ))
   
   predicate invariant'0 [#"../sparse_array.rs" 49 4 49 30] (self : Sparse'0.t_sparse t) =
-    [%#span23] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
+    [%#span18] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     <= UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'0 (shallow_model'1 self) = UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'1 (shallow_model'2 (SparseArray_Sparse_Type.sparse_values self))
@@ -889,116 +796,112 @@ module SparseArray_Impl2_Set
   
   let%span span10 = "" 0 0 0 0
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span16 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span16 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 22 15 22 23
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 25 25 25 29
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 33
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 24 4 24 87
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 28 15 28 23
+  let%span span21 = "../sparse_array.rs" 73 20 74 52
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 25 31 29
+  let%span span22 = "../sparse_array.rs" 40 12 41 82
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 29 14 29 33
+  let%span span23 = "../sparse_array.rs" 50 8 61 9
   
-  let%span span24 = "../../../../creusot-contracts/src/logic/seq2.rs" 30 4 30 87
+  let%span span24 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 4 31 55
+  let%span span25 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span26 = "../sparse_array.rs" 73 20 74 52
+  let%span span26 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span27 = "../sparse_array.rs" 40 12 41 82
+  let%span span27 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span28 = "../sparse_array.rs" 50 8 61 9
+  let%span span28 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span29 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span30 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span30 = "" 0 0 0 0
   
-  let%span span31 = "../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span31 = "" 0 0 0 0
   
-  let%span span32 = "../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span32 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span33 = "../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span33 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span34 = "../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span34 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span35 = "" 0 0 0 0
+  let%span span35 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
   let%span span36 = "" 0 0 0 0
   
-  let%span span37 = "../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span37 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span38 = "../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span38 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span39 = "../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span39 = "../sparse_array.rs" 101 15 101 34
   
-  let%span span40 = "../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span40 = "../sparse_array.rs" 102 15 102 39
   
-  let%span span41 = "" 0 0 0 0
+  let%span span41 = "../sparse_array.rs" 104 25 104 29
   
-  let%span span42 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span42 = "../sparse_array.rs" 103 14 103 28
   
-  let%span span43 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span43 = "../sparse_array.rs" 100 4 100 12
   
-  let%span span44 = "../sparse_array.rs" 101 15 101 34
+  let%span span44 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span45 = "../sparse_array.rs" 102 15 102 39
+  let%span span45 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span46 = "../sparse_array.rs" 104 25 104 29
+  let%span span46 = "" 0 0 0 0
   
-  let%span span47 = "../sparse_array.rs" 103 14 103 28
+  let%span span47 = "" 0 0 0 0
   
-  let%span span48 = "../sparse_array.rs" 100 4 100 12
+  let%span span48 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span49 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span49 = "" 0 0 0 0
   
-  let%span span50 = "../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
-  
-  let%span span51 = "" 0 0 0 0
-  
-  let%span span52 = "" 0 0 0 0
+  use prelude.prelude.UIntSize
   
-  let%span span53 = "../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span54 = "" 0 0 0 0
+  predicate invariant'15 (self : Seq'0.t_seq usize) =
+    [%#span9] true
   
-  use Core_Option_Option_Type as Option'0
+  predicate inv'15 (_x : Seq'0.t_seq usize)
   
-  use prelude.prelude.Int
+  axiom inv'15 : forall x : Seq'0.t_seq usize . inv'15 x = true
   
-  use map.Map
+  predicate invariant'14 (self : Seq'0.t_seq t)
   
-  predicate invariant'16 (self : Map.map int (Option'0.t_option t))
+  predicate inv'14 (_x : Seq'0.t_seq t)
   
-  predicate inv'16 (_x : Map.map int (Option'0.t_option t))
+  axiom inv'14 : forall x : Seq'0.t_seq t . inv'14 x = true
   
-  axiom inv'16 : forall x : Map.map int (Option'0.t_option t) . inv'16 x = true
+  use Core_Option_Option_Type as Option'0
   
-  use prelude.prelude.UIntSize
+  use prelude.prelude.Int
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use map.Map
   
-  predicate invariant'15 (self : Seq'0.t_seq usize) =
-    [%#span9] true
+  predicate invariant'13 (self : Map.map int (Option'0.t_option t))
   
-  predicate inv'15 (_x : Seq'0.t_seq usize)
+  predicate inv'13 (_x : Map.map int (Option'0.t_option t))
   
-  axiom inv'15 : forall x : Seq'0.t_seq usize . inv'15 x = true
+  axiom inv'13 : forall x : Map.map int (Option'0.t_option t) . inv'13 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1010,38 +913,21 @@ module SparseArray_Impl2_Set
   
   constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq usize) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq usize . ([%#span11] inv'15 self)  -> ([%#span12] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq usize . [%#span11] len'2 self >= 0
   
-  predicate inv'14 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'12 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'6 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'6_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span13] inv'14 self)
-   -> ([%#span15] inv'15 (shallow_model'6 self))
-  && ([%#span14] len'2 (shallow_model'6 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'14 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span16] inv'15 (shallow_model'6 self)
-  
-  axiom inv'14 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'14 x = true
+  axiom shallow_model'6_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span12] inv'12 self)
+   -> ([%#span13] len'2 (shallow_model'6 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'13 (self : Seq'0.t_seq t)
+  predicate invariant'12 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span14] inv'15 (shallow_model'6 self)
   
-  predicate inv'13 (_x : Seq'0.t_seq t)
-  
-  axiom inv'13 : forall x : Seq'0.t_seq t . inv'13 x = true
-  
-  predicate invariant'12 (self : Seq'0.t_seq (Option'0.t_option t))
-  
-  predicate inv'12 (_x : Seq'0.t_seq (Option'0.t_option t))
-  
-  axiom inv'12 : forall x : Seq'0.t_seq (Option'0.t_option t) . inv'12 x = true
+  axiom inv'12 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'12 x = true
   
   use prelude.prelude.Borrow
   
@@ -1052,12 +938,11 @@ module SparseArray_Impl2_Set
   
   axiom inv'11 : forall x : borrowed usize . inv'11 x = true
   
-  constant empty'2 : Seq'0.t_seq usize = [%#span17] ()
+  constant empty'2 : Seq'0.t_seq usize
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span18] len'2 (empty'2 : Seq'0.t_seq usize) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span15] len'2 (empty'2 : Seq'0.t_seq usize) = 0
   
   predicate invariant'10 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
     [%#span9] true
@@ -1074,64 +959,49 @@ module SparseArray_Impl2_Set
   
   predicate inv'0 (_x : Vec'0.t_vec t (Global'0.t_global))
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'3 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'4 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span20] index_logic'3 (shallow_model'6 self) ix
+    [%#span16] index_logic'3 (shallow_model'6 self) ix
   
   use SparseArray_Sparse_Type as SparseArray_Sparse_Type
   
-  use seq.Seq
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span11] inv'13 self)  -> ([%#span12] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span11] len'1 self >= 0
   
   function shallow_model'3 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span13] inv'0 self)
-   -> ([%#span15] inv'13 (shallow_model'3 self))
-  && ([%#span14] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
-  
-  use seq.Seq
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span12] inv'0 self)
+   -> ([%#span13] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   function len'0 (self : Seq'0.t_seq (Option'0.t_option t)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . ([%#span11] inv'12 self)
-   -> ([%#span12] len'0 self >= 0)
-  
-  use seq.Seq
+  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . [%#span11] len'0 self >= 0
   
   use map.Map
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option t)) (x : int) : Option'0.t_option t
+  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option t)) (_2 : int) : Option'0.t_option t
   
   function new'1 (len : int) (data : Map.map int (Option'0.t_option t)) : Seq'0.t_seq (Option'0.t_option t)
   
-  axiom new'1_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span21] len >= 0)
-   -> ([%#span22] inv'16 data)
-   -> ([%#span25] inv'12 (new'1 len data))
-  && ([%#span24] forall i : int . 0 <= i /\ i < len'0 (new'1 len data)
+  axiom new'1_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span17] len >= 0)
+   -> ([%#span18] inv'13 data)
+   -> ([%#span20] forall i : int . 0 <= i /\ i < len'0 (new'1 len data)
    -> index_logic'0 (new'1 len data) i = Map.get data i)
-  && ([%#span23] len'0 (new'1 len data) = len)
+  && ([%#span19] len'0 (new'1 len data) = len)
   
   use prelude.prelude.Mapping
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span20] index_logic'2 (shallow_model'3 self) ix
+    [%#span16] index_logic'2 (shallow_model'3 self) ix
   
   use SparseArray_Sparse_Type as Sparse'0
   
   function is_elt'0 [#"../sparse_array.rs" 72 4 72 36] (self : Sparse'0.t_sparse t) (i : int) : bool =
-    [%#span26] UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_idx self) i)
+    [%#span21] UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_idx self) i)
     < UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     /\ UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_back self) (UIntSize.to_int (index_logic'4 (SparseArray_Sparse_Type.sparse_idx self) i)))
     = i
@@ -1139,14 +1009,14 @@ module SparseArray_Impl2_Set
   function shallow_model'1 [#"../sparse_array.rs" 38 4 38 50] (self : Sparse'0.t_sparse t) : Seq'0.t_seq (Option'0.t_option t)
     
    =
-    [%#span27] new'1 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
+    [%#span22] new'1 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
       Option'0.C_Some (index_logic'1 (SparseArray_Sparse_Type.sparse_values self) i)
     else
       Option'0.C_None
     ))
   
   predicate invariant'8 [#"../sparse_array.rs" 49 4 49 30] (self : Sparse'0.t_sparse t) =
-    [%#span28] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
+    [%#span23] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     <= UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'0 (shallow_model'1 self) = UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'1 (shallow_model'3 (SparseArray_Sparse_Type.sparse_values self))
@@ -1184,12 +1054,11 @@ module SparseArray_Impl2_Set
   
   axiom inv'6 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'6 x = true
   
-  constant empty'1 : Seq'0.t_seq t = [%#span17] ()
+  constant empty'1 : Seq'0.t_seq t
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span18] len'1 (empty'1 : Seq'0.t_seq t) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span15] len'1 (empty'1 : Seq'0.t_seq t) = 0
   
   predicate invariant'5 (self : usize) =
     [%#span9] true
@@ -1204,12 +1073,11 @@ module SparseArray_Impl2_Set
   
   axiom inv'4 : forall x : borrowed (Vec'0.t_vec t (Global'0.t_global)) . inv'4 x = true
   
-  constant empty'0 : Seq'0.t_seq (Option'0.t_option t) = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq (Option'0.t_option t)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span18] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option t)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option t)) = 0
   
   predicate invariant'3 (self : borrowed (Sparse'0.t_sparse t))
   
@@ -1230,44 +1098,44 @@ module SparseArray_Impl2_Set
   axiom inv'1 : forall x : t . inv'1 x = true
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span16] inv'13 (shallow_model'3 self)
+    [%#span14] inv'14 (shallow_model'3 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
   function shallow_model'0 (self : borrowed (Sparse'0.t_sparse t)) : Seq'0.t_seq (Option'0.t_option t) =
-    [%#span29] shallow_model'1 ( * self)
+    [%#span24] shallow_model'1 ( * self)
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'4 (self : borrowed usize) =
-    [%#span30]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
   use prelude.prelude.Slice
   
   predicate resolve_elswhere'1 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq usize) (fin : Seq'0.t_seq usize) =
-    [%#span31] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'2 old'
+    [%#span26] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'2 old'
      -> index_logic'3 old' i = index_logic'3 fin i
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span32] index_logic'3 seq (UIntSize.to_int self) = out
+    [%#span27] index_logic'3 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span33] UIntSize.to_int self < len'2 seq
+    [%#span28] UIntSize.to_int self < len'2 seq
   
   function shallow_model'5 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span29] shallow_model'6 ( * self)
+    [%#span24] shallow_model'6 ( * self)
   
-  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span36] inv'5 index}
-    {[@expl:precondition] [%#span35] inv'10 self}
-    {[@expl:precondition] [%#span34] in_bounds'1 index (shallow_model'5 self)}
+  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span31] inv'5 index}
+    {[@expl:precondition] [%#span30] inv'10 self}
+    {[@expl:precondition] [%#span29] in_bounds'1 index (shallow_model'5 self)}
     any
-    [ return' (result:borrowed usize)-> {[%#span41] inv'11 result}
-      {[%#span40] len'2 (shallow_model'6 ( ^ self)) = len'2 (shallow_model'5 self)}
-      {[%#span39] resolve_elswhere'1 index (shallow_model'5 self) (shallow_model'6 ( ^ self))}
-      {[%#span38] has_value'1 index (shallow_model'6 ( ^ self)) ( ^ result)}
-      {[%#span37] has_value'1 index (shallow_model'5 self) ( * result)}
+    [ return' (result:borrowed usize)-> {[%#span36] inv'11 result}
+      {[%#span35] len'2 (shallow_model'6 ( ^ self)) = len'2 (shallow_model'5 self)}
+      {[%#span34] resolve_elswhere'1 index (shallow_model'5 self) (shallow_model'6 ( ^ self))}
+      {[%#span33] has_value'1 index (shallow_model'6 ( ^ self)) ( ^ result)}
+      {[%#span32] has_value'1 index (shallow_model'5 self) ( * result)}
       (! return' {result}) ]
     
   
@@ -1277,58 +1145,58 @@ module SparseArray_Impl2_Set
   
   function new'0 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'0_spec : forall x : () . ([%#span42] inv'9 x)  -> ([%#span43] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : () . ([%#span37] inv'9 x)  -> ([%#span38] deref'0 (new'0 x) = x)
   
   function lemma_permutation'0 [#"../sparse_array.rs" 104 4 104 38] (self : Sparse'0.t_sparse t) (i : int) : () =
-    [%#span48] ()
+    [%#span43] ()
   
-  axiom lemma_permutation'0_spec : forall self : Sparse'0.t_sparse t, i : int . ([%#span44] SparseArray_Sparse_Type.sparse_n self
+  axiom lemma_permutation'0_spec : forall self : Sparse'0.t_sparse t, i : int . ([%#span39] SparseArray_Sparse_Type.sparse_n self
   = SparseArray_Sparse_Type.sparse_size self)
-   -> ([%#span45] 0 <= i /\ i < UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self))
-   -> ([%#span46] inv'8 self)  -> ([%#span47] is_elt'0 self i)
+   -> ([%#span40] 0 <= i /\ i < UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self))
+   -> ([%#span41] inv'8 self)  -> ([%#span42] is_elt'0 self i)
   
   predicate resolve'2 (self : borrowed (Sparse'0.t_sparse t)) =
-    [%#span30]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
   function shallow_model'4 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize =
-    [%#span49] shallow_model'6 self
+    [%#span44] shallow_model'6 self
   
-  let rec index'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span52] inv'5 index}
-    {[@expl:precondition] [%#span51] inv'6 self}
-    {[@expl:precondition] [%#span50] in_bounds'1 index (shallow_model'4 self)}
+  let rec index'0 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span47] inv'5 index}
+    {[@expl:precondition] [%#span46] inv'6 self}
+    {[@expl:precondition] [%#span45] in_bounds'1 index (shallow_model'4 self)}
     any
-    [ return' (result:usize)-> {[%#span54] inv'7 result}
-      {[%#span53] has_value'1 index (shallow_model'4 self) result}
+    [ return' (result:usize)-> {[%#span49] inv'7 result}
+      {[%#span48] has_value'1 index (shallow_model'4 self) result}
       (! return' {result}) ]
     
   
   predicate resolve'1 (self : borrowed t) =
-    [%#span30]  ^ self =  * self
+    [%#span25]  ^ self =  * self
   
   predicate resolve'0 (self : t)
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq t) (fin : Seq'0.t_seq t) =
-    [%#span31] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
+    [%#span26] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
      -> index_logic'2 old' i = index_logic'2 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) (out : t) =
-    [%#span32] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span27] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) =
-    [%#span33] UIntSize.to_int self < len'1 seq
+    [%#span28] UIntSize.to_int self < len'1 seq
   
   function shallow_model'2 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span29] shallow_model'3 ( * self)
+    [%#span24] shallow_model'3 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:usize) (return'  (ret:borrowed t))= {[@expl:precondition] [%#span36] inv'5 index}
-    {[@expl:precondition] [%#span35] inv'4 self}
-    {[@expl:precondition] [%#span34] in_bounds'0 index (shallow_model'2 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:usize) (return'  (ret:borrowed t))= {[@expl:precondition] [%#span31] inv'5 index}
+    {[@expl:precondition] [%#span30] inv'4 self}
+    {[@expl:precondition] [%#span29] in_bounds'0 index (shallow_model'2 self)}
     any
-    [ return' (result:borrowed t)-> {[%#span41] inv'2 result}
-      {[%#span40] len'1 (shallow_model'3 ( ^ self)) = len'1 (shallow_model'2 self)}
-      {[%#span39] resolve_elswhere'0 index (shallow_model'2 self) (shallow_model'3 ( ^ self))}
-      {[%#span38] has_value'0 index (shallow_model'3 ( ^ self)) ( ^ result)}
-      {[%#span37] has_value'0 index (shallow_model'2 self) ( * result)}
+    [ return' (result:borrowed t)-> {[%#span36] inv'2 result}
+      {[%#span35] len'1 (shallow_model'3 ( ^ self)) = len'1 (shallow_model'2 self)}
+      {[%#span34] resolve_elswhere'0 index (shallow_model'2 self) (shallow_model'3 ( ^ self))}
+      {[%#span33] has_value'0 index (shallow_model'3 ( ^ self)) ( ^ result)}
+      {[%#span32] has_value'0 index (shallow_model'2 self) ( * result)}
       (! return' {result}) ]
     
   
@@ -1502,104 +1370,82 @@ module SparseArray_Create
   
   let%span span7 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span10 = "" 0 0 0 0
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span11 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span13 = "" 0 0 0 0
+  let%span span12 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span14 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span13 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span15 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span14 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span16 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 22 15 22 23
   
-  let%span span17 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 25 25 25 29
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 33
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 28 15 28 23
+  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 24 4 24 87
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 25 31 29
+  let%span span19 = "../sparse_array.rs" 73 20 74 52
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 29 14 29 33
+  let%span span20 = "../sparse_array.rs" 40 12 41 82
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 30 4 30 87
+  let%span span21 = "../sparse_array.rs" 50 8 61 9
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 4 31 55
+  let%span span22 = "" 0 0 0 0
   
-  let%span span24 = "../sparse_array.rs" 73 20 74 52
+  let%span span23 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span25 = "../sparse_array.rs" 40 12 41 82
+  let%span span24 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
-  let%span span26 = "../sparse_array.rs" 50 8 61 9
+  let%span span25 = "" 0 0 0 0
   
-  let%span span27 = "" 0 0 0 0
+  use prelude.prelude.UIntSize
   
-  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
+  predicate invariant'7 (self : Seq'0.t_seq usize) =
+    [%#span7] true
   
-  let%span span30 = "" 0 0 0 0
+  predicate inv'7 (_x : Seq'0.t_seq usize)
   
-  use Core_Option_Option_Type as Option'0
+  axiom inv'7 : forall x : Seq'0.t_seq usize . inv'7 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate invariant'6 (self : Seq'0.t_seq t)
   
-  predicate invariant'8 (self : Seq'0.t_seq (Option'0.t_option t))
+  predicate inv'6 (_x : Seq'0.t_seq t)
   
-  predicate inv'8 (_x : Seq'0.t_seq (Option'0.t_option t))
+  axiom inv'6 : forall x : Seq'0.t_seq t . inv'6 x = true
   
-  axiom inv'8 : forall x : Seq'0.t_seq (Option'0.t_option t) . inv'8 x = true
+  use Core_Option_Option_Type as Option'0
   
   use prelude.prelude.Int
   
   use map.Map
   
-  predicate invariant'7 (self : Map.map int (Option'0.t_option t))
-  
-  predicate inv'7 (_x : Map.map int (Option'0.t_option t))
-  
-  axiom inv'7 : forall x : Map.map int (Option'0.t_option t) . inv'7 x = true
+  predicate invariant'5 (self : Map.map int (Option'0.t_option t))
   
-  use prelude.prelude.UIntSize
-  
-  predicate invariant'6 (self : Seq'0.t_seq usize) =
-    [%#span7] true
-  
-  predicate inv'6 (_x : Seq'0.t_seq usize)
-  
-  axiom inv'6 : forall x : Seq'0.t_seq usize . inv'6 x = true
-  
-  predicate invariant'5 (self : Seq'0.t_seq t)
+  predicate inv'5 (_x : Map.map int (Option'0.t_option t))
   
-  predicate inv'5 (_x : Seq'0.t_seq t)
-  
-  axiom inv'5 : forall x : Seq'0.t_seq t . inv'5 x = true
+  axiom inv'5 : forall x : Map.map int (Option'0.t_option t) . inv'5 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq (Option'0.t_option t)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . ([%#span8] inv'8 self)
-   -> ([%#span9] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (Option'0.t_option t) . [%#span8] len'2 self >= 0
   
-  constant empty'2 : Seq'0.t_seq (Option'0.t_option t) = [%#span10] ()
+  constant empty'2 : Seq'0.t_seq (Option'0.t_option t)
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span11] len'2 (empty'2 : Seq'0.t_seq (Option'0.t_option t)) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span9] len'2 (empty'2 : Seq'0.t_seq (Option'0.t_option t)) = 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1607,33 +1453,29 @@ module SparseArray_Create
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span13] (18446744073709551615 : usize)
-  
-  use seq.Seq
+  constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span8] inv'6 self)  -> ([%#span9] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span8] len'1 self >= 0
   
   predicate inv'4 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span14] inv'4 self)
-   -> ([%#span16] inv'6 (shallow_model'2 self))
-  && ([%#span15] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span11] inv'4 self)
+   -> ([%#span12] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'4 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span17] inv'6 (shallow_model'2 self)
+    [%#span13] inv'7 (shallow_model'2 self)
   
   axiom inv'4 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'4 x = true
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span10] ()
+  constant empty'1 : Seq'0.t_seq usize
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span11] len'1 (empty'1 : Seq'0.t_seq usize) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span9] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
   predicate invariant'3 (self : usize) =
     [%#span7] true
@@ -1642,73 +1484,60 @@ module SparseArray_Create
   
   axiom inv'3 : forall x : usize . inv'3 x = true
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span8] inv'5 self)  -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span8] len'0 self >= 0
   
   predicate inv'2 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span14] inv'2 self)
-   -> ([%#span16] inv'5 (shallow_model'1 self))
-  && ([%#span15] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span11] inv'2 self)
+   -> ([%#span12] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'2 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span17] inv'5 (shallow_model'1 self)
+    [%#span13] inv'6 (shallow_model'1 self)
   
   axiom inv'2 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'2 x = true
   
-  constant empty'0 : Seq'0.t_seq t = [%#span10] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
-  function index_logic'4 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'4 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span18] index_logic'4 (shallow_model'2 self) ix
+    [%#span14] index_logic'4 (shallow_model'2 self) ix
   
   use SparseArray_Sparse_Type as SparseArray_Sparse_Type
   
   use prelude.prelude.Borrow
   
-  use seq.Seq
-  
   use map.Map
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option t)) (x : int) : Option'0.t_option t
+  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option t)) (_2 : int) : Option'0.t_option t
   
   function new'0 (len : int) (data : Map.map int (Option'0.t_option t)) : Seq'0.t_seq (Option'0.t_option t)
   
-  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span19] len >= 0)
-   -> ([%#span20] inv'7 data)
-   -> ([%#span23] inv'8 (new'0 len data))
-  && ([%#span22] forall i : int . 0 <= i /\ i < len'2 (new'0 len data)
+  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option t) . ([%#span15] len >= 0)
+   -> ([%#span16] inv'5 data)
+   -> ([%#span18] forall i : int . 0 <= i /\ i < len'2 (new'0 len data)
    -> index_logic'0 (new'0 len data) i = Map.get data i)
-  && ([%#span21] len'2 (new'0 len data) = len)
+  && ([%#span17] len'2 (new'0 len data) = len)
   
   use prelude.prelude.Mapping
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'3 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span18] index_logic'3 (shallow_model'1 self) ix
+    [%#span14] index_logic'3 (shallow_model'1 self) ix
   
   use SparseArray_Sparse_Type as Sparse'0
   
   function is_elt'0 [#"../sparse_array.rs" 72 4 72 36] (self : Sparse'0.t_sparse t) (i : int) : bool =
-    [%#span24] UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_idx self) i)
+    [%#span19] UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_idx self) i)
     < UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     /\ UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_back self) (UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_idx self) i)))
     = i
@@ -1716,14 +1545,14 @@ module SparseArray_Create
   function shallow_model'0 [#"../sparse_array.rs" 38 4 38 50] (self : Sparse'0.t_sparse t) : Seq'0.t_seq (Option'0.t_option t)
     
    =
-    [%#span25] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
+    [%#span20] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
       Option'0.C_Some (index_logic'1 (SparseArray_Sparse_Type.sparse_values self) i)
     else
       Option'0.C_None
     ))
   
   predicate invariant'1 [#"../sparse_array.rs" 49 4 49 30] (self : Sparse'0.t_sparse t) =
-    [%#span26] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
+    [%#span21] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     <= UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'2 (shallow_model'0 self) = UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'0 (shallow_model'1 (SparseArray_Sparse_Type.sparse_values self))
@@ -1755,19 +1584,19 @@ module SparseArray_Create
   
   use prelude.prelude.Intrinsic
   
-  let rec from_elem'1 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span27] inv'3 elem}
+  let rec from_elem'1 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span22] inv'3 elem}
     any
-    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span30] inv'4 result}
-      {[%#span29] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'2 result i = elem}
-      {[%#span28] len'1 (shallow_model'2 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span25] inv'4 result}
+      {[%#span24] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'2 result i = elem}
+      {[%#span23] len'1 (shallow_model'2 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
-  let rec from_elem'0 (elem:t) (n:usize) (return'  (ret:Vec'0.t_vec t (Global'0.t_global)))= {[@expl:precondition] [%#span27] inv'0 elem}
+  let rec from_elem'0 (elem:t) (n:usize) (return'  (ret:Vec'0.t_vec t (Global'0.t_global)))= {[@expl:precondition] [%#span22] inv'0 elem}
     any
-    [ return' (result:Vec'0.t_vec t (Global'0.t_global))-> {[%#span30] inv'2 result}
-      {[%#span29] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'1 result i = elem}
-      {[%#span28] len'0 (shallow_model'1 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec t (Global'0.t_global))-> {[%#span25] inv'2 result}
+      {[%#span24] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'1 result i = elem}
+      {[%#span23] len'0 (shallow_model'1 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
@@ -1871,86 +1700,85 @@ module SparseArray_F
   
   let%span span24 = "" 0 0 0 0
   
-  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span25 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span26 = "../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span27 = "../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span29 = "../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span28 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span30 = "../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span30 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 22 15 22 23
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 25 25 25 29
   
-  let%span span34 = "../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 33
   
-  let%span span35 = "../../../../creusot-contracts/src/logic/seq2.rs" 28 15 28 23
+  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 24 4 24 87
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 25 31 29
+  let%span span35 = "../sparse_array.rs" 73 20 74 52
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 29 14 29 33
+  let%span span36 = "../sparse_array.rs" 40 12 41 82
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 30 4 30 87
+  let%span span37 = "../sparse_array.rs" 50 8 61 9
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 31 4 31 55
+  let%span span38 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span40 = "../sparse_array.rs" 73 20 74 52
+  let%span span39 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span41 = "../sparse_array.rs" 40 12 41 82
+  let%span span40 = "../sparse_array.rs" 108 15 108 31
   
-  let%span span42 = "../sparse_array.rs" 50 8 61 9
+  let%span span41 = "../sparse_array.rs" 112 20 112 24
   
-  let%span span43 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span42 = "../sparse_array.rs" 112 36 112 37
   
-  let%span span44 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span43 = "../sparse_array.rs" 109 14 109 43
   
-  let%span span45 = "../sparse_array.rs" 108 15 108 31
+  let%span span44 = "../sparse_array.rs" 110 4 110 95
   
-  let%span span46 = "../sparse_array.rs" 112 20 112 24
+  let%span span45 = "../sparse_array.rs" 111 14 111 37
   
-  let%span span47 = "../sparse_array.rs" 112 36 112 37
+  let%span span46 = "../sparse_array.rs" 80 15 80 31
   
-  let%span span48 = "../sparse_array.rs" 109 14 109 43
+  let%span span47 = "../sparse_array.rs" 89 16 89 20
   
-  let%span span49 = "../sparse_array.rs" 110 4 110 95
+  let%span span48 = "../sparse_array.rs" 81 14 84 5
   
-  let%span span50 = "../sparse_array.rs" 111 14 111 37
+  let%span span49 = "../sparse_array.rs" 85 14 88 5
   
-  let%span span51 = "../sparse_array.rs" 80 15 80 31
+  let%span span50 = "../sparse_array.rs" 89 35 89 45
   
-  let%span span52 = "../sparse_array.rs" 89 16 89 20
+  let%span span51 = "../sparse_array.rs" 134 42 134 47
   
-  let%span span53 = "../sparse_array.rs" 81 14 84 5
+  let%span span52 = "../sparse_array.rs" 132 10 132 27
   
-  let%span span54 = "../sparse_array.rs" 85 14 88 5
+  let%span span53 = "../sparse_array.rs" 133 0 133 67
   
-  let%span span55 = "../sparse_array.rs" 89 35 89 45
+  let%span span54 = "../sparse_array.rs" 134 55 134 64
   
-  let%span span56 = "../sparse_array.rs" 134 42 134 47
+  use prelude.prelude.UIntSize
   
-  let%span span57 = "../sparse_array.rs" 132 10 132 27
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span58 = "../sparse_array.rs" 133 0 133 67
+  predicate invariant'9 (self : Seq'0.t_seq usize) =
+    [%#span23] true
   
-  let%span span59 = "../sparse_array.rs" 134 55 134 64
+  predicate inv'9 (_x : Seq'0.t_seq usize)
   
-  use prelude.prelude.UIntSize
+  axiom inv'9 : forall x : Seq'0.t_seq usize . inv'9 x = true
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  use prelude.prelude.Int32
   
-  predicate invariant'10 (self : Seq'0.t_seq usize) =
+  predicate invariant'8 (self : Seq'0.t_seq int32) =
     [%#span23] true
   
-  predicate inv'10 (_x : Seq'0.t_seq usize)
+  predicate inv'8 (_x : Seq'0.t_seq int32)
   
-  axiom inv'10 : forall x : Seq'0.t_seq usize . inv'10 x = true
+  axiom inv'8 : forall x : Seq'0.t_seq int32 . inv'8 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -1962,55 +1790,37 @@ module SparseArray_F
   
   constant max'0 : usize = [%#span24] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq usize) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq usize . ([%#span25] inv'10 self)  -> ([%#span26] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq usize . [%#span25] len'2 self >= 0
   
-  predicate inv'9 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'7 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'5 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'5_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span27] inv'9 self)
-   -> ([%#span29] inv'10 (shallow_model'5 self))
-  && ([%#span28] len'2 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'9 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span30] inv'10 (shallow_model'5 self)
-  
-  axiom inv'9 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'9 x = true
-  
-  use prelude.prelude.Int32
-  
-  predicate invariant'8 (self : Seq'0.t_seq int32) =
-    [%#span23] true
-  
-  predicate inv'8 (_x : Seq'0.t_seq int32)
+  axiom shallow_model'5_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span26] inv'7 self)
+   -> ([%#span27] len'2 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
   
-  axiom inv'8 : forall x : Seq'0.t_seq int32 . inv'8 x = true
+  predicate invariant'7 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span28] inv'9 (shallow_model'5 self)
   
-  constant empty'2 : Seq'0.t_seq usize = [%#span31] ()
+  axiom inv'7 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'7 x = true
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span33] ()
+  constant empty'2 : Seq'0.t_seq usize
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span32] len'2 (empty'2 : Seq'0.t_seq usize) = 0
+  function empty_len'2 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'2_spec : forall _1 : () . [%#span29] len'2 (empty'2 : Seq'0.t_seq usize) = 0
   
   function len'1 (self : Seq'0.t_seq int32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq int32 . ([%#span25] inv'8 self)  -> ([%#span26] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq int32 . [%#span25] len'1 self >= 0
   
-  constant empty'1 : Seq'0.t_seq int32 = [%#span31] ()
+  constant empty'1 : Seq'0.t_seq int32
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span33] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span32] len'1 (empty'1 : Seq'0.t_seq int32) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span29] len'1 (empty'1 : Seq'0.t_seq int32) = 0
   
   use Core_Option_Option_Type as Option'0
   
@@ -2018,32 +1828,24 @@ module SparseArray_F
   
   use map.Map
   
-  predicate invariant'7 (self : Map.map int (Option'0.t_option int32)) =
+  predicate invariant'6 (self : Map.map int (Option'0.t_option int32)) =
     [%#span23] true
   
-  predicate inv'7 (_x : Map.map int (Option'0.t_option int32))
+  predicate inv'6 (_x : Map.map int (Option'0.t_option int32))
   
-  axiom inv'7 : forall x : Map.map int (Option'0.t_option int32) . inv'7 x = true
+  axiom inv'6 : forall x : Map.map int (Option'0.t_option int32) . inv'6 x = true
   
-  predicate inv'6 (_x : Vec'0.t_vec int32 (Global'0.t_global))
+  predicate inv'5 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'4 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'4_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span27] inv'6 self)
-   -> ([%#span29] inv'8 (shallow_model'4 self))
-  && ([%#span28] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'6 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span30] inv'8 (shallow_model'4 self)
-  
-  axiom inv'6 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'6 x = true
-  
-  predicate invariant'5 (self : Seq'0.t_seq (Option'0.t_option int32)) =
-    [%#span23] true
+  axiom shallow_model'4_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span26] inv'5 self)
+   -> ([%#span27] len'1 (shallow_model'4 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate inv'5 (_x : Seq'0.t_seq (Option'0.t_option int32))
+  predicate invariant'5 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
+    [%#span28] inv'8 (shallow_model'4 self)
   
-  axiom inv'5 : forall x : Seq'0.t_seq (Option'0.t_option int32) . inv'5 x = true
+  axiom inv'5 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'5 x = true
   
   use SparseArray_Sparse_Type as Sparse'0
   
@@ -2072,19 +1874,15 @@ module SparseArray_F
   
   axiom inv'2 : forall x : Sparse'0.t_sparse int32 . inv'2 x = inv'0 x
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq (Option'0.t_option int32)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option int32) . ([%#span25] inv'5 self)
-   -> ([%#span26] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Option'0.t_option int32) . [%#span25] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq (Option'0.t_option int32) = [%#span31] ()
+  constant empty'0 : Seq'0.t_seq (Option'0.t_option int32)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span33] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span32] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option int32)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span29] len'0 (empty'0 : Seq'0.t_seq (Option'0.t_option int32)) = 0
   
   predicate invariant'1 (self : int32) =
     [%#span23] true
@@ -2093,43 +1891,34 @@ module SparseArray_F
   
   axiom inv'1 : forall x : int32 . inv'1 x = true
   
-  use seq.Seq
-  
-  function index_logic'4 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'4 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span34] index_logic'4 (shallow_model'5 self) ix
+    [%#span30] index_logic'4 (shallow_model'5 self) ix
   
   use SparseArray_Sparse_Type as SparseArray_Sparse_Type
   
-  use seq.Seq
-  
   use map.Map
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option int32)) (x : int) : Option'0.t_option int32
+  function index_logic'0 (self : Seq'0.t_seq (Option'0.t_option int32)) (_2 : int) : Option'0.t_option int32
   
   function new'0 (len : int) (data : Map.map int (Option'0.t_option int32)) : Seq'0.t_seq (Option'0.t_option int32)
   
-  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option int32) . ([%#span35] len >= 0)
-   -> ([%#span36] inv'7 data)
-   -> ([%#span39] inv'5 (new'0 len data))
-  && ([%#span38] forall i : int . 0 <= i /\ i < len'0 (new'0 len data)
+  axiom new'0_spec : forall len : int, data : Map.map int (Option'0.t_option int32) . ([%#span31] len >= 0)
+   -> ([%#span32] inv'6 data)
+   -> ([%#span34] forall i : int . 0 <= i /\ i < len'0 (new'0 len data)
    -> index_logic'0 (new'0 len data) i = Map.get data i)
-  && ([%#span37] len'0 (new'0 len data) = len)
+  && ([%#span33] len'0 (new'0 len data) = len)
   
   use prelude.prelude.Mapping
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'3 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span34] index_logic'3 (shallow_model'4 self) ix
+    [%#span30] index_logic'3 (shallow_model'4 self) ix
   
   function is_elt'0 [#"../sparse_array.rs" 72 4 72 36] (self : Sparse'0.t_sparse int32) (i : int) : bool =
-    [%#span40] UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_idx self) i)
+    [%#span35] UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_idx self) i)
     < UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     /\ UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_back self) (UIntSize.to_int (index_logic'2 (SparseArray_Sparse_Type.sparse_idx self) i)))
     = i
@@ -2137,14 +1926,14 @@ module SparseArray_F
   function shallow_model'1 [#"../sparse_array.rs" 38 4 38 50] (self : Sparse'0.t_sparse int32) : Seq'0.t_seq (Option'0.t_option int32)
     
    =
-    [%#span41] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
+    [%#span36] new'0 (UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)) (Mapping.from_fn (fun (i : int) -> if is_elt'0 self i then
       Option'0.C_Some (index_logic'1 (SparseArray_Sparse_Type.sparse_values self) i)
     else
       Option'0.C_None
     ))
   
   predicate invariant'0 [#"../sparse_array.rs" 49 4 49 30] (self : Sparse'0.t_sparse int32) =
-    [%#span42] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
+    [%#span37] UIntSize.to_int (SparseArray_Sparse_Type.sparse_n self)
     <= UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'0 (shallow_model'1 self) = UIntSize.to_int (SparseArray_Sparse_Type.sparse_size self)
     /\ len'1 (shallow_model'4 (SparseArray_Sparse_Type.sparse_values self))
@@ -2171,47 +1960,47 @@ module SparseArray_F
   use prelude.prelude.Int32
   
   function shallow_model'0 (self : int32) : int =
-    [%#span43] Int32.to_int self
+    [%#span38] Int32.to_int self
   
   function shallow_model'3 (self : borrowed (Sparse'0.t_sparse int32)) : Seq'0.t_seq (Option'0.t_option int32) =
-    [%#span44] shallow_model'1 ( * self)
+    [%#span39] shallow_model'1 ( * self)
   
-  let rec set'0 (self:borrowed (Sparse'0.t_sparse int32)) (i:usize) (v:int32) (return'  (ret:()))= {[@expl:precondition] [%#span47] inv'1 v}
-    {[@expl:precondition] [%#span46] inv'4 self}
-    {[@expl:precondition] [%#span45] UIntSize.to_int i < len'0 (shallow_model'3 self)}
+  let rec set'0 (self:borrowed (Sparse'0.t_sparse int32)) (i:usize) (v:int32) (return'  (ret:()))= {[@expl:precondition] [%#span42] inv'1 v}
+    {[@expl:precondition] [%#span41] inv'4 self}
+    {[@expl:precondition] [%#span40] UIntSize.to_int i < len'0 (shallow_model'3 self)}
     any
-    [ return' (result:())-> {[%#span50] index_logic'0 (shallow_model'1 ( ^ self)) (UIntSize.to_int i)
+    [ return' (result:())-> {[%#span45] index_logic'0 (shallow_model'1 ( ^ self)) (UIntSize.to_int i)
       = Option'0.C_Some v}
-      {[%#span49] forall j : int . 0 <= j /\ j < len'0 (shallow_model'3 self) /\ j <> UIntSize.to_int i
+      {[%#span44] forall j : int . 0 <= j /\ j < len'0 (shallow_model'3 self) /\ j <> UIntSize.to_int i
        -> index_logic'0 (shallow_model'1 ( ^ self)) j = index_logic'0 (shallow_model'3 self) j}
-      {[%#span48] len'0 (shallow_model'1 ( ^ self)) = len'0 (shallow_model'3 self)}
+      {[%#span43] len'0 (shallow_model'1 ( ^ self)) = len'0 (shallow_model'3 self)}
       (! return' {result}) ]
     
   
   function shallow_model'2 (self : Sparse'0.t_sparse int32) : Seq'0.t_seq (Option'0.t_option int32) =
-    [%#span43] shallow_model'1 self
+    [%#span38] shallow_model'1 self
   
-  let rec get'0 (self:Sparse'0.t_sparse int32) (i:usize) (return'  (ret:Option'0.t_option int32))= {[@expl:precondition] [%#span52] inv'2 self}
-    {[@expl:precondition] [%#span51] UIntSize.to_int i < len'0 (shallow_model'2 self)}
+  let rec get'0 (self:Sparse'0.t_sparse int32) (i:usize) (return'  (ret:Option'0.t_option int32))= {[@expl:precondition] [%#span47] inv'2 self}
+    {[@expl:precondition] [%#span46] UIntSize.to_int i < len'0 (shallow_model'2 self)}
     any
-    [ return' (result:Option'0.t_option int32)-> {[%#span55] inv'3 result}
-      {[%#span54] match index_logic'0 (shallow_model'2 self) (UIntSize.to_int i) with
+    [ return' (result:Option'0.t_option int32)-> {[%#span50] inv'3 result}
+      {[%#span49] match index_logic'0 (shallow_model'2 self) (UIntSize.to_int i) with
         | Option'0.C_None -> result = Option'0.C_None
         | Option'0.C_Some _ -> true
         end}
-      {[%#span53] match result with
+      {[%#span48] match result with
         | Option'0.C_None -> index_logic'0 (shallow_model'2 self) (UIntSize.to_int i) = Option'0.C_None
         | Option'0.C_Some x -> index_logic'0 (shallow_model'2 self) (UIntSize.to_int i) = Option'0.C_Some x
         end}
       (! return' {result}) ]
     
   
-  let rec create'0 (sz:usize) (dummy:int32) (return'  (ret:Sparse'0.t_sparse int32))= {[@expl:precondition] [%#span56] inv'1 dummy}
+  let rec create'0 (sz:usize) (dummy:int32) (return'  (ret:Sparse'0.t_sparse int32))= {[@expl:precondition] [%#span51] inv'1 dummy}
     any
-    [ return' (result:Sparse'0.t_sparse int32)-> {[%#span59] inv'0 result}
-      {[%#span58] forall i : int . 0 <= i /\ i < UIntSize.to_int sz
+    [ return' (result:Sparse'0.t_sparse int32)-> {[%#span54] inv'0 result}
+      {[%#span53] forall i : int . 0 <= i /\ i < UIntSize.to_int sz
        -> index_logic'0 (shallow_model'1 result) i = Option'0.C_None}
-      {[%#span57] SparseArray_Sparse_Type.sparse_size result = sz}
+      {[%#span52] SparseArray_Sparse_Type.sparse_size result = sz}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/sum.coma b/creusot/tests/should_succeed/sum.coma
index 884001832b..d23a907b5e 100644
--- a/creusot/tests/should_succeed/sum.coma
+++ b/creusot/tests/should_succeed/sum.coma
@@ -15,22 +15,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Cmp_Ordering_Type
   type t_ordering  =
@@ -89,107 +74,89 @@ module Sum_SumFirstN
   
   let%span span9 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span13 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span14 = "../../../../creusot-contracts/src/std/ops.rs" 207 20 207 24
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span15 = "../../../../creusot-contracts/src/std/ops.rs" 206 4 206 88
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span16 = "../../../../creusot-contracts/src/std/iter/range.rs" 46 62 46 63
   
-  let%span span17 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span17 = "../../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
   
-  let%span span18 = "../../../../creusot-contracts/src/std/ops.rs" 207 20 207 24
+  let%span span18 = "../../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
   
-  let%span span19 = "../../../../creusot-contracts/src/std/ops.rs" 206 4 206 88
+  let%span span19 = "../../../../creusot-contracts/src/std/iter/range.rs" 65 8 71 9
   
-  let%span span20 = "../../../../creusot-contracts/src/std/iter/range.rs" 46 62 46 63
+  let%span span20 = "../../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
   
-  let%span span21 = "../../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
+  let%span span21 = "../../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
   
-  let%span span22 = "../../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
+  let%span span22 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 22 84 23
   
-  let%span span23 = "../../../../creusot-contracts/src/std/iter/range.rs" 65 8 71 9
+  let%span span23 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 52 84 53
   
-  let%span span24 = "../../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
+  let%span span24 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 82 84 83
   
-  let%span span25 = "../../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
+  let%span span25 = "../../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
   
-  let%span span26 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 22 84 23
+  let%span span26 = "../../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
   
-  let%span span27 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 31 84 33
+  let%span span27 = "../../../../creusot-contracts/src/std/iter/range.rs" 77 21 77 25
   
-  let%span span28 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 52 84 53
+  let%span span28 = "../../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
   
-  let%span span29 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 61 84 63
+  let%span span29 = "../../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
   
-  let%span span30 = "../../../../creusot-contracts/src/std/iter/range.rs" 84 82 84 83
+  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span31 = "../../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
+  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span32 = "../../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
+  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span34 = "../../../../creusot-contracts/src/std/iter/range.rs" 77 21 77 25
+  let%span span34 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span35 = "../../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
+  let%span span35 = "../../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
   
-  let%span span36 = "../../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
+  let%span span36 = "" 0 0 0 0
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span37 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span38 = "" 0 0 0 0
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span39 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span40 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span40 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span41 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span41 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span42 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span42 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span43 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span43 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span44 = "../../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
+  let%span span44 = "" 0 0 0 0
   
   let%span span45 = "" 0 0 0 0
   
-  let%span span46 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span46 = "" 0 0 0 0
   
   let%span span47 = "" 0 0 0 0
   
-  let%span span48 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span49 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span50 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span51 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span52 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span48 = "../../../../creusot-contracts/src/std/ops.rs" 220 26 220 53
   
-  let%span span53 = "" 0 0 0 0
+  let%span span49 = "../../../../creusot-contracts/src/std/ops.rs" 221 26 221 49
   
-  let%span span54 = "" 0 0 0 0
+  let%span span50 = "../../../../creusot-contracts/src/std/ops.rs" 222 16 222 93
   
-  let%span span55 = "" 0 0 0 0
-  
-  let%span span56 = "" 0 0 0 0
-  
-  let%span span57 = "../../../../creusot-contracts/src/std/ops.rs" 220 26 220 53
-  
-  let%span span58 = "../../../../creusot-contracts/src/std/ops.rs" 221 26 221 49
-  
-  let%span span59 = "../../../../creusot-contracts/src/std/ops.rs" 222 16 222 93
-  
-  let%span span60 = "" 0 0 0 0
+  let%span span51 = "" 0 0 0 0
   
   use prelude.prelude.UInt32
   
@@ -229,31 +196,22 @@ module Sum_SumFirstN
   
   axiom inv'1 : forall x : uint32 . inv'1 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span10] inv'2 self)  -> ([%#span11] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span10] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span12] inv'2 self)
-   -> ([%#span13] inv'2 other)
-   -> ([%#span16] inv'2 (concat'0 self other))
-  && ([%#span15] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span12] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span11] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : RangeInclusive'0.t_rangeinclusive uint32)
   
@@ -264,7 +222,7 @@ module Sum_SumFirstN
   use prelude.prelude.UInt32
   
   function deep_model'0 (self : uint32) : int =
-    [%#span17] UInt32.to_int self
+    [%#span13] UInt32.to_int self
   
   function end_log'0 (self : RangeInclusive'0.t_rangeinclusive uint32) : uint32
   
@@ -272,19 +230,19 @@ module Sum_SumFirstN
   
   function is_empty_log'0 (self : RangeInclusive'0.t_rangeinclusive uint32) : bool
   
-  axiom is_empty_log'0_spec : forall self : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span18] inv'0 self)
-   -> ([%#span19] not is_empty_log'0 self  -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self))
+  axiom is_empty_log'0_spec : forall self : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span14] inv'0 self)
+   -> ([%#span15] not is_empty_log'0 self  -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self))
   
   function range_inclusive_len'0 (r : RangeInclusive'0.t_rangeinclusive uint32) : int =
-    [%#span22] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+    [%#span18] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
   
-  axiom range_inclusive_len'0_spec : forall r : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span20] inv'0 r)
-   -> ([%#span21] is_empty_log'0 r = (range_inclusive_len'0 r = 0))
+  axiom range_inclusive_len'0_spec : forall r : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span16] inv'0 r)
+   -> ([%#span17] is_empty_log'0 r = (range_inclusive_len'0 r = 0))
   
   predicate produces'0 (self : RangeInclusive'0.t_rangeinclusive uint32) (visited : Seq'0.t_seq uint32) (o : RangeInclusive'0.t_rangeinclusive uint32)
     
    =
-    [%#span23] len'0 visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    [%#span19] len'0 visited = range_inclusive_len'0 self - range_inclusive_len'0 o
     /\ (is_empty_log'0 self  -> is_empty_log'0 o)
     /\ (is_empty_log'0 o \/ end_log'0 self = end_log'0 o)
     /\ (forall i : int . 0 <= i /\ i < len'0 visited
@@ -293,55 +251,49 @@ module Sum_SumFirstN
   function produces_trans'0 (a : RangeInclusive'0.t_rangeinclusive uint32) (ab : Seq'0.t_seq uint32) (b : RangeInclusive'0.t_rangeinclusive uint32) (bc : Seq'0.t_seq uint32) (c : RangeInclusive'0.t_rangeinclusive uint32) : ()
     
    =
-    [%#span32] ()
+    [%#span26] ()
   
-  axiom produces_trans'0_spec : forall a : RangeInclusive'0.t_rangeinclusive uint32, ab : Seq'0.t_seq uint32, b : RangeInclusive'0.t_rangeinclusive uint32, bc : Seq'0.t_seq uint32, c : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span24] produces'0 a ab b)
-   -> ([%#span25] produces'0 b bc c)
-   -> ([%#span26] inv'0 a)
-   -> ([%#span27] inv'2 ab)
-   -> ([%#span28] inv'0 b)
-   -> ([%#span29] inv'2 bc)  -> ([%#span30] inv'0 c)  -> ([%#span31] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : RangeInclusive'0.t_rangeinclusive uint32, ab : Seq'0.t_seq uint32, b : RangeInclusive'0.t_rangeinclusive uint32, bc : Seq'0.t_seq uint32, c : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span20] produces'0 a ab b)
+   -> ([%#span21] produces'0 b bc c)
+   -> ([%#span22] inv'0 a)
+   -> ([%#span23] inv'0 b)  -> ([%#span24] inv'0 c)  -> ([%#span25] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span33] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   function produces_refl'0 (self : RangeInclusive'0.t_rangeinclusive uint32) : () =
-    [%#span36] ()
+    [%#span29] ()
   
-  axiom produces_refl'0_spec : forall self : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span34] inv'0 self)
-   -> ([%#span35] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'0_spec : forall self : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span27] inv'0 self)
+   -> ([%#span28] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   predicate invariant'0 (self : RangeInclusive'0.t_rangeinclusive uint32) =
     [%#span9] true
   
   axiom inv'0 : forall x : RangeInclusive'0.t_rangeinclusive uint32 . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span38] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span37] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span30] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span39] inv'1 v)
-   -> ([%#span42] inv'2 (singleton'0 v))
-  && ([%#span41] index_logic'0 (singleton'0 v) 0 = v) && ([%#span40] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span31] inv'1 v)
+   -> ([%#span33] index_logic'0 (singleton'0 v) 0 = v) && ([%#span32] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (RangeInclusive'0.t_rangeinclusive uint32)) =
-    [%#span43]  ^ self =  * self
+    [%#span34]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (RangeInclusive'0.t_rangeinclusive uint32)) =
-    [%#span44] is_empty_log'0 ( * self) /\ is_empty_log'0 ( ^ self)
+    [%#span35] is_empty_log'0 ( * self) /\ is_empty_log'0 ( ^ self)
   
-  let rec next'0 (self:borrowed (RangeInclusive'0.t_rangeinclusive uint32)) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span45] inv'3 self}
+  let rec next'0 (self:borrowed (RangeInclusive'0.t_rangeinclusive uint32)) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span36] inv'3 self}
     any
-    [ return' (result:Option'0.t_option uint32)-> {[%#span47] inv'4 result}
-      {[%#span46] match result with
+    [ return' (result:Option'0.t_option uint32)-> {[%#span38] inv'4 result}
+      {[%#span37] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -360,37 +312,37 @@ module Sum_SumFirstN
   
   function new'2 (x : Seq'0.t_seq uint32) : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)
   
-  axiom new'2_spec : forall x : Seq'0.t_seq uint32 . ([%#span48] inv'2 x)  -> ([%#span49] deref'0 (new'2 x) = x)
+  axiom new'2_spec : forall x : Seq'0.t_seq uint32 . ([%#span39] inv'2 x)  -> ([%#span40] deref'0 (new'2 x) = x)
   
   function new'1 (x : RangeInclusive'0.t_rangeinclusive uint32) : Snapshot'0.t_snapshot (RangeInclusive'0.t_rangeinclusive uint32)
     
   
-  axiom new'1_spec : forall x : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span48] inv'0 x)
-   -> ([%#span49] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : RangeInclusive'0.t_rangeinclusive uint32 . ([%#span39] inv'0 x)
+   -> ([%#span40] deref'1 (new'1 x) = x)
   
   predicate into_iter_post'0 (self : RangeInclusive'0.t_rangeinclusive uint32) (res : RangeInclusive'0.t_rangeinclusive uint32)
     
    =
-    [%#span50] self = res
+    [%#span41] self = res
   
   predicate into_iter_pre'0 (self : RangeInclusive'0.t_rangeinclusive uint32) =
-    [%#span51] true
+    [%#span42] true
   
-  let rec into_iter'0 (self:RangeInclusive'0.t_rangeinclusive uint32) (return'  (ret:RangeInclusive'0.t_rangeinclusive uint32))= {[@expl:precondition] [%#span53] inv'0 self}
-    {[@expl:precondition] [%#span52] into_iter_pre'0 self}
+  let rec into_iter'0 (self:RangeInclusive'0.t_rangeinclusive uint32) (return'  (ret:RangeInclusive'0.t_rangeinclusive uint32))= {[@expl:precondition] [%#span44] inv'0 self}
+    {[@expl:precondition] [%#span43] into_iter_pre'0 self}
     any
-    [ return' (result:RangeInclusive'0.t_rangeinclusive uint32)-> {[%#span54] inv'0 result}
-      {[%#span52] into_iter_post'0 self result}
+    [ return' (result:RangeInclusive'0.t_rangeinclusive uint32)-> {[%#span45] inv'0 result}
+      {[%#span43] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec new'0 (start:uint32) (end':uint32) (return'  (ret:RangeInclusive'0.t_rangeinclusive uint32))= {[@expl:precondition] [%#span56] inv'1 end'}
-    {[@expl:precondition] [%#span55] inv'1 start}
+  let rec new'0 (start:uint32) (end':uint32) (return'  (ret:RangeInclusive'0.t_rangeinclusive uint32))= {[@expl:precondition] [%#span47] inv'1 end'}
+    {[@expl:precondition] [%#span46] inv'1 start}
     any
-    [ return' (result:RangeInclusive'0.t_rangeinclusive uint32)-> {[%#span60] inv'0 result}
-      {[%#span59] deep_model'0 start <= deep_model'0 end'  -> not is_empty_log'0 result}
-      {[%#span58] end_log'0 result = end'}
-      {[%#span57] start_log'0 result = start}
+    [ return' (result:RangeInclusive'0.t_rangeinclusive uint32)-> {[%#span51] inv'0 result}
+      {[%#span50] deep_model'0 start <= deep_model'0 end'  -> not is_empty_log'0 result}
+      {[%#span49] end_log'0 result = end'}
+      {[%#span48] start_log'0 result = start}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/sum_of_odds.coma b/creusot/tests/should_succeed/sum_of_odds.coma
index 3967ea33f7..8074d5eac6 100644
--- a/creusot/tests/should_succeed/sum_of_odds.coma
+++ b/creusot/tests/should_succeed/sum_of_odds.coma
@@ -73,22 +73,7 @@ module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Option_Option_Type
   type t_option 't =
@@ -133,96 +118,78 @@ module SumOfOdds_ComputeSumOfOdd
   
   let%span span12 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span15 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span16 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span16 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span17 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span17 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span18 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span18 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span19 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span20 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span20 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span21 = "../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span21 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span22 = "../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span22 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span23 = "../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span23 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span24 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span24 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span25 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span25 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span26 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span27 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span27 = "../sum_of_odds.rs" 8 4 8 9
   
-  let%span span28 = "../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span28 = "../sum_of_odds.rs" 17 10 17 11
   
-  let%span span29 = "../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span29 = "../sum_of_odds.rs" 16 0 16 8
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span30 = "../sum_of_odds.rs" 27 11 27 17
   
-  let%span span31 = "../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span31 = "../sum_of_odds.rs" 28 10 28 33
   
-  let%span span32 = "../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span32 = "../sum_of_odds.rs" 29 10 29 11
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span33 = "../sum_of_odds.rs" 31 4 31 65
   
-  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span35 = "../sum_of_odds.rs" 8 4 8 9
+  let%span span35 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span36 = "../sum_of_odds.rs" 17 10 17 11
+  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span37 = "../sum_of_odds.rs" 16 0 16 8
+  let%span span37 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span38 = "../sum_of_odds.rs" 27 11 27 17
+  let%span span38 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span39 = "../sum_of_odds.rs" 28 10 28 33
+  let%span span39 = "" 0 0 0 0
   
-  let%span span40 = "../sum_of_odds.rs" 29 10 29 11
+  let%span span40 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span41 = "../sum_of_odds.rs" 31 4 31 65
+  let%span span41 = "" 0 0 0 0
   
-  let%span span42 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span42 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span43 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span43 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span44 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span44 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span45 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span45 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span46 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span46 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span47 = "../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span47 = "" 0 0 0 0
   
   let%span span48 = "" 0 0 0 0
   
-  let%span span49 = "../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
-  
-  let%span span50 = "" 0 0 0 0
-  
-  let%span span51 = "../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span52 = "../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span53 = "../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span54 = "../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span55 = "../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
-  
-  let%span span56 = "" 0 0 0 0
-  
-  let%span span57 = "" 0 0 0 0
-  
   use prelude.prelude.UInt32
   
   predicate invariant'4 (self : uint32) =
@@ -261,31 +228,22 @@ module SumOfOdds_ComputeSumOfOdd
   
   axiom inv'1 : forall x : Seq'0.t_seq uint32 . inv'1 x = true
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  use seq.Seq
-  
   use prelude.prelude.Int
   
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span13] inv'1 self)  -> ([%#span14] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span13] len'0 self >= 0
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span15] inv'1 self)
-   -> ([%#span16] inv'1 other)
-   -> ([%#span19] inv'1 (concat'0 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span15] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span17] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span14] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : Range'0.t_range uint32)
   
@@ -294,12 +252,12 @@ module SumOfOdds_ComputeSumOfOdd
   use prelude.prelude.UInt32
   
   function deep_model'0 (self : uint32) : int =
-    [%#span20] UInt32.to_int self
+    [%#span16] UInt32.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range uint32) (visited : Seq'0.t_seq uint32) (o : Range'0.t_range uint32) =
-    [%#span21] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span17] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'0 visited > 0
@@ -312,69 +270,63 @@ module SumOfOdds_ComputeSumOfOdd
   function produces_trans'0 (a : Range'0.t_range uint32) (ab : Seq'0.t_seq uint32) (b : Range'0.t_range uint32) (bc : Seq'0.t_seq uint32) (c : Range'0.t_range uint32) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range uint32, ab : Seq'0.t_seq uint32, b : Range'0.t_range uint32, bc : Seq'0.t_seq uint32, c : Range'0.t_range uint32 . ([%#span22] produces'0 a ab b)
-   -> ([%#span23] produces'0 b bc c)
-   -> ([%#span24] inv'0 a)
-   -> ([%#span25] inv'1 ab)
-   -> ([%#span26] inv'0 b)
-   -> ([%#span27] inv'1 bc)  -> ([%#span28] inv'0 c)  -> ([%#span29] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range uint32, ab : Seq'0.t_seq uint32, b : Range'0.t_range uint32, bc : Seq'0.t_seq uint32, c : Range'0.t_range uint32 . ([%#span18] produces'0 a ab b)
+   -> ([%#span19] produces'0 b bc c)
+   -> ([%#span20] inv'0 a)
+   -> ([%#span21] inv'0 b)  -> ([%#span22] inv'0 c)  -> ([%#span23] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span30] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
   function produces_refl'0 (self : Range'0.t_range uint32) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range uint32 . ([%#span31] inv'0 self)
-   -> ([%#span32] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range uint32 . ([%#span24] inv'0 self)
+   -> ([%#span25] produces'0 self (empty'0 : Seq'0.t_seq uint32) self)
   
   predicate invariant'0 (self : Range'0.t_range uint32) =
     [%#span12] true
   
   axiom inv'0 : forall x : Range'0.t_range uint32 . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span34] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span33] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span26] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   function sqr'0 [#"../sum_of_odds.rs" 7 0 7 21] (x : int) : int =
-    [%#span35] x * x
+    [%#span27] x * x
   
   function sum_of_odd'0 [#"../sum_of_odds.rs" 18 0 18 28] (x : int) : int
   
   axiom sum_of_odd'0_def : forall x : int . sum_of_odd'0 x
-  = ([%#span37] if x <= 0 then 0 else sum_of_odd'0 (x - 1) + 2 * x - 1)
+  = ([%#span29] if x <= 0 then 0 else sum_of_odd'0 (x - 1) + 2 * x - 1)
   
   function sum_of_odd_is_sqr'0 [#"../sum_of_odds.rs" 30 0 30 28] (x : int) : ()
   
   axiom sum_of_odd_is_sqr'0_def : forall x : int . sum_of_odd_is_sqr'0 x
-  = ([%#span41] if x > 0 then sum_of_odd_is_sqr'0 (x - 1) else ())
-  
-  axiom sum_of_odd_is_sqr'0_spec : forall x : int . ([%#span38] x >= 0)  -> ([%#span39] sum_of_odd'0 x = sqr'0 x)
+  = ([%#span33] if x > 0 then sum_of_odd_is_sqr'0 (x - 1) else ())
   
-  use seq.Seq
+  axiom sum_of_odd_is_sqr'0_spec : forall x : int . ([%#span30] x >= 0)  -> ([%#span31] sum_of_odd'0 x = sqr'0 x)
   
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span42] inv'4 v)
-   -> ([%#span45] inv'1 (singleton'0 v))
-  && ([%#span44] index_logic'0 (singleton'0 v) 0 = v) && ([%#span43] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span34] inv'4 v)
+   -> ([%#span36] index_logic'0 (singleton'0 v) 0 = v) && ([%#span35] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Range'0.t_range uint32)) =
-    [%#span46]  ^ self =  * self
+    [%#span37]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range uint32)) =
-    [%#span47] resolve'0 self
+    [%#span38] resolve'0 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range uint32)) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span48] inv'2 self}
+  let rec next'0 (self:borrowed (Range'0.t_range uint32)) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span39] inv'2 self}
     any
-    [ return' (result:Option'0.t_option uint32)-> {[%#span50] inv'3 result}
-      {[%#span49] match result with
+    [ return' (result:Option'0.t_option uint32)-> {[%#span41] inv'3 result}
+      {[%#span40] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -391,23 +343,23 @@ module SumOfOdds_ComputeSumOfOdd
   
   function new'1 (x : Seq'0.t_seq uint32) : Snapshot'0.t_snapshot (Seq'0.t_seq uint32)
   
-  axiom new'1_spec : forall x : Seq'0.t_seq uint32 . ([%#span51] inv'1 x)  -> ([%#span52] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq uint32 . ([%#span42] inv'1 x)  -> ([%#span43] deref'0 (new'1 x) = x)
   
   function new'0 (x : Range'0.t_range uint32) : Snapshot'0.t_snapshot (Range'0.t_range uint32)
   
-  axiom new'0_spec : forall x : Range'0.t_range uint32 . ([%#span51] inv'0 x)  -> ([%#span52] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : Range'0.t_range uint32 . ([%#span42] inv'0 x)  -> ([%#span43] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range uint32) (res : Range'0.t_range uint32) =
-    [%#span53] self = res
+    [%#span44] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range uint32) =
-    [%#span54] true
+    [%#span45] true
   
-  let rec into_iter'0 (self:Range'0.t_range uint32) (return'  (ret:Range'0.t_range uint32))= {[@expl:precondition] [%#span56] inv'0 self}
-    {[@expl:precondition] [%#span55] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range uint32) (return'  (ret:Range'0.t_range uint32))= {[@expl:precondition] [%#span47] inv'0 self}
+    {[@expl:precondition] [%#span46] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range uint32)-> {[%#span57] inv'0 result}
-      {[%#span55] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range uint32)-> {[%#span48] inv'0 result}
+      {[%#span46] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/syntax/06_logic_function_contracts.coma b/creusot/tests/should_succeed/syntax/06_logic_function_contracts.coma
index e70b5f4f77..0bd26e87eb 100644
--- a/creusot/tests/should_succeed/syntax/06_logic_function_contracts.coma
+++ b/creusot/tests/should_succeed/syntax/06_logic_function_contracts.coma
@@ -1,207 +1,124 @@
 
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C06LogicFunctionContracts_Sum_Impl
   let%span s06_logic_function_contracts0 = "../06_logic_function_contracts.rs" 9 10 9 19
   
-  let%span sseq21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span sseq22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span sseq23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
-  
-  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
-  
-  let%span sseq25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
-  
-  let%span sseq26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span sseq21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span sseq27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span sseq22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span8 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span sseq23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
   use prelude.prelude.Int
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'0 (self : Seq'0.t_seq int) =
-    [%#span8] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq int)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq int . inv'0 x = true
-  
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq int) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int . ([%#sseq21] inv'0 self)  -> ([%#sseq22] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq int = [%#span9] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq int . [%#sseq21] len'0 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span11] ()
+  constant empty'0 : Seq'0.t_seq int
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq int) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use prelude.seq_ext.SeqExt
+  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq int) = 0
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq int) (x : int) : int
+  function index_logic'0 (self : Seq'0.t_seq int) (_2 : int) : int
   
   function subsequence'0 (self : Seq'0.t_seq int) (n : int) (m : int) : Seq'0.t_seq int
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq int, n : int, m : int . ([%#sseq23] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq int, n : int, m : int . ([%#sseq22] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#sseq24] inv'0 self)
-   -> ([%#sseq27] inv'0 (subsequence'0 self n m))
-  && ([%#sseq26] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#sseq24] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#sseq25] len'0 (subsequence'0 self n m) = m - n)
+  && ([%#sseq23] len'0 (subsequence'0 self n m) = m - n)
   
   constant seq  : Seq'0.t_seq int
   
   function sum [#"../06_logic_function_contracts.rs" 10 0 10 32] (seq : Seq'0.t_seq int) : int
   
-  goal vc_sum : ([%#sseq21] inv'0 seq)
-  /\ (([%#sseq22] len'0 seq >= 0)
+  goal vc_sum : ([%#sseq21] len'0 seq >= 0)
    -> match len'0 seq = 0 with
     | True -> true
-    | False -> ([%#sseq21] inv'0 seq)
-    /\ (([%#sseq22] len'0 seq >= 0)
-     -> ([%#sseq21] inv'0 seq)
-    /\ (([%#sseq22] len'0 seq >= 0)
-     -> (([%#sseq24] inv'0 seq) && ([%#sseq23] 0 <= 0 /\ 0 <= len'0 seq - 1 /\ len'0 seq - 1 <= len'0 seq))
-    /\ (([%#sseq27] inv'0 (subsequence'0 seq 0 (len'0 seq - 1)))
-    && ([%#sseq26] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 seq 0 (len'0 seq - 1))
+    | False -> ([%#sseq21] len'0 seq >= 0)
+     -> ([%#sseq21] len'0 seq >= 0)
+     -> ([%#sseq22] 0 <= 0 /\ 0 <= len'0 seq - 1 /\ len'0 seq - 1 <= len'0 seq)
+    /\ (([%#sseq24] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 seq 0 (len'0 seq - 1))
      -> index_logic'0 (subsequence'0 seq 0 (len'0 seq - 1)) i = index_logic'0 seq (0 + i))
-    && ([%#sseq25] len'0 (subsequence'0 seq 0 (len'0 seq - 1)) = len'0 seq - 1 - 0)
+    && ([%#sseq23] len'0 (subsequence'0 seq 0 (len'0 seq - 1)) = len'0 seq - 1 - 0)
      -> 0 <= ([%#s06_logic_function_contracts0] len'0 seq)
     /\ ([%#s06_logic_function_contracts0] len'0 (subsequence'0 seq 0 (len'0 seq - 1)))
-    < ([%#s06_logic_function_contracts0] len'0 seq))))
-    end)
+    < ([%#s06_logic_function_contracts0] len'0 seq))
+    end
 end
 module C06LogicFunctionContracts_AllZero_Impl
   let%span s06_logic_function_contracts0 = "../06_logic_function_contracts.rs" 21 10 21 19
   
-  let%span sseq21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span sseq22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span sseq23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
-  
-  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span sseq21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span sseq25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span sseq22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span sseq26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span sseq23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span sseq27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span sseq24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span8 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
   use prelude.prelude.Int
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'0 (self : Seq'0.t_seq int) =
-    [%#span8] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq int)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq int . inv'0 x = true
-  
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq int) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int . ([%#sseq21] inv'0 self)  -> ([%#sseq22] len'0 self >= 0)
-  
-  constant empty'0 : Seq'0.t_seq int = [%#span9] ()
+  axiom len'0_spec : forall self : Seq'0.t_seq int . [%#sseq21] len'0 self >= 0
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span11] ()
+  constant empty'0 : Seq'0.t_seq int
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq int) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use prelude.seq_ext.SeqExt
+  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq int) = 0
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq int) (x : int) : int
+  function index_logic'0 (self : Seq'0.t_seq int) (_2 : int) : int
   
   function subsequence'0 (self : Seq'0.t_seq int) (n : int) (m : int) : Seq'0.t_seq int
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq int, n : int, m : int . ([%#sseq23] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq int, n : int, m : int . ([%#sseq22] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#sseq24] inv'0 self)
-   -> ([%#sseq27] inv'0 (subsequence'0 self n m))
-  && ([%#sseq26] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#sseq24] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#sseq25] len'0 (subsequence'0 self n m) = m - n)
+  && ([%#sseq23] len'0 (subsequence'0 self n m) = m - n)
   
   constant seq  : Seq'0.t_seq int
   
   predicate all_zero [#"../06_logic_function_contracts.rs" 22 0 22 38] (seq : Seq'0.t_seq int)
   
-  goal vc_all_zero : ([%#sseq21] inv'0 seq)
-  /\ (([%#sseq22] len'0 seq >= 0)
+  goal vc_all_zero : ([%#sseq21] len'0 seq >= 0)
    -> match len'0 seq = 0 with
     | True -> true
-    | False -> ([%#sseq21] inv'0 seq)
-    /\ (([%#sseq22] len'0 seq >= 0)
+    | False -> ([%#sseq21] len'0 seq >= 0)
      -> (if index_logic'0 seq (len'0 seq - 1) = 0 then
-      ([%#sseq21] inv'0 seq)
-      /\ (([%#sseq22] len'0 seq >= 0)
-       -> (([%#sseq24] inv'0 seq) && ([%#sseq23] 0 <= 0 /\ 0 <= len'0 seq - 1 /\ len'0 seq - 1 <= len'0 seq))
-      /\ (([%#sseq27] inv'0 (subsequence'0 seq 0 (len'0 seq - 1)))
-      && ([%#sseq26] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 seq 0 (len'0 seq - 1))
+      ([%#sseq21] len'0 seq >= 0)
+       -> ([%#sseq22] 0 <= 0 /\ 0 <= len'0 seq - 1 /\ len'0 seq - 1 <= len'0 seq)
+      /\ (([%#sseq24] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 seq 0 (len'0 seq - 1))
        -> index_logic'0 (subsequence'0 seq 0 (len'0 seq - 1)) i = index_logic'0 seq (0 + i))
-      && ([%#sseq25] len'0 (subsequence'0 seq 0 (len'0 seq - 1)) = len'0 seq - 1 - 0)
+      && ([%#sseq23] len'0 (subsequence'0 seq 0 (len'0 seq - 1)) = len'0 seq - 1 - 0)
        -> 0 <= ([%#s06_logic_function_contracts0] len'0 seq)
       /\ ([%#s06_logic_function_contracts0] len'0 (subsequence'0 seq 0 (len'0 seq - 1)))
-      < ([%#s06_logic_function_contracts0] len'0 seq)))
+      < ([%#s06_logic_function_contracts0] len'0 seq))
     else
       true
-    ))
-    end)
+    )
+    end
 end
 module C06LogicFunctionContracts_Stupid_Impl
   type t
diff --git a/creusot/tests/should_succeed/syntax/08_const.coma b/creusot/tests/should_succeed/syntax/08_const.coma
index 60b4e4b9a7..09ff978568 100644
--- a/creusot/tests/should_succeed/syntax/08_const.coma
+++ b/creusot/tests/should_succeed/syntax/08_const.coma
@@ -1,14 +1,4 @@
 
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
+  type t_seq 't
 end
diff --git a/creusot/tests/should_succeed/syntax/11_array_types.coma b/creusot/tests/should_succeed/syntax/11_array_types.coma
index b8aa65e6ec..2c4a207c41 100644
--- a/creusot/tests/should_succeed/syntax/11_array_types.coma
+++ b/creusot/tests/should_succeed/syntax/11_array_types.coma
@@ -22,22 +22,7 @@ module C11ArrayTypes_UsesArray_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C11ArrayTypes_Omg
   let%span s11_array_types0 = "../11_array_types.rs" 9 8 9 9
@@ -50,55 +35,35 @@ module C11ArrayTypes_Omg
   
   let%span s11_array_types4 = "../11_array_types.rs" 7 11 7 53
   
-  let%span span5 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span7 = "" 0 0 0 0
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span8 = "../../../../../creusot-contracts/src/logic/ops.rs" 65 8 65 31
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span11 = "" 0 0 0 0
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/ops.rs" 65 8 65 31
+  use prelude.prelude.Int
   
   use prelude.prelude.Int64
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq int64) =
-    [%#span5] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq int64)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq int64 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq int64) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int64 . ([%#span6] inv'0 self)  -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int64 . [%#span5] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq int64 = [%#span8] ()
+  constant empty'0 : Seq'0.t_seq int64
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq int64) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq int64) = 0
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
   use prelude.prelude.Slice
   
@@ -106,14 +71,12 @@ module C11ArrayTypes_Omg
   
   use prelude.prelude.Int64
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq int64) (x : int) : int64
+  function index_logic'1 (self : Seq'0.t_seq int64) (_2 : int) : int64
   
   use prelude.prelude.Slice
   
   function index_logic'0 [@inline:trivial] (self : array int64) (ix : int) : int64 =
-    [%#span12] index_logic'1 (Slice.id self) ix
+    [%#span8] index_logic'1 (Slice.id self) ix
   
   use C11ArrayTypes_UsesArray_Type as C11ArrayTypes_UsesArray_Type
   
@@ -155,49 +118,29 @@ module C11ArrayTypes_CallOmg
   
   let%span s11_array_types1 = "../11_array_types.rs" 15 15 15 20
   
-  let%span span2 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span4 = "" 0 0 0 0
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span5 = "../11_array_types.rs" 7 11 7 53
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span8 = "" 0 0 0 0
-  
-  let%span span9 = "../11_array_types.rs" 7 11 7 53
+  use prelude.prelude.Int
   
   use prelude.prelude.Int64
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate invariant'0 (self : Seq'0.t_seq int64) =
-    [%#span2] true
-  
-  predicate inv'0 (_x : Seq'0.t_seq int64)
-  
-  axiom inv'0 : forall x : Seq'0.t_seq int64 . inv'0 x = true
-  
-  use prelude.prelude.Int
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq int64) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int64 . ([%#span3] inv'0 self)  -> ([%#span4] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int64 . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq int64 = [%#span5] ()
+  constant empty'0 : Seq'0.t_seq int64
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span7] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq int64) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq int64) = 0
   
   use prelude.prelude.Intrinsic
   
@@ -207,13 +150,13 @@ module C11ArrayTypes_CallOmg
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   use prelude.prelude.Slice
   
   use C11ArrayTypes_UsesArray_Type as C11ArrayTypes_UsesArray_Type
   
-  let rec omg'0 (x:UsesArray'0.t_usesarray) (return'  (ret:()))= {[@expl:precondition] [%#span9] len'0 (Slice.id (C11ArrayTypes_UsesArray_Type.usesarray_0 x))
+  let rec omg'0 (x:UsesArray'0.t_usesarray) (return'  (ret:()))= {[@expl:precondition] [%#span5] len'0 (Slice.id (C11ArrayTypes_UsesArray_Type.usesarray_0 x))
     > 0
     /\ len'0 (Slice.id (C11ArrayTypes_UsesArray_Type.usesarray_0 x)) < UIntSize.to_int (max'0 : usize)}
     any [ return' (result:())-> (! return' {result}) ] 
diff --git a/creusot/tests/should_succeed/syntax/12_ghost_code.coma b/creusot/tests/should_succeed/syntax/12_ghost_code.coma
index 4763f5d803..e76ef673aa 100644
--- a/creusot/tests/should_succeed/syntax/12_ghost_code.coma
+++ b/creusot/tests/should_succeed/syntax/12_ghost_code.coma
@@ -142,22 +142,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C12GhostCode_GhostVec
   let%span s12_ghost_code0 = "../12_ghost_code.rs" 9 22 9 32
@@ -168,37 +153,29 @@ module C12GhostCode_GhostVec
   
   let%span span3 = "" 0 0 0 0
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span13 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span9 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span14 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span10 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span15 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span11 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span12 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
-  let%span span19 = "" 0 0 0 0
+  let%span span15 = "" 0 0 0 0
   
   use prelude.prelude.UInt32
   
@@ -223,33 +200,27 @@ module C12GhostCode_GhostVec
   
   constant max'0 : usize = [%#span3] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span4] inv'1 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span4] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span6] inv'0 self)
-   -> ([%#span8] inv'1 (shallow_model'0 self))
-  && ([%#span7] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span5] inv'0 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span9] inv'1 (shallow_model'0 self)
+    [%#span7] inv'1 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
@@ -263,25 +234,23 @@ module C12GhostCode_GhostVec
   function new'1 (x : Vec'0.t_vec uint32 (Global'0.t_global)) : Snapshot'0.t_snapshot (Vec'0.t_vec uint32 (Global'0.t_global))
     
   
-  axiom new'1_spec : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span13] inv'0 x)
-   -> ([%#span14] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span9] inv'0 x)
+   -> ([%#span10] deref'0 (new'1 x) = x)
   
   predicate resolve'1 (self : uint32) =
-    [%#span15] true
-  
-  use seq.Seq
+    [%#span11] true
   
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span16] index_logic'1 (shallow_model'0 self) ix
+    [%#span12] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span17] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
+    [%#span13] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
   
   let rec new'0 (_1:()) (return'  (ret:Vec'0.t_vec uint32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span19] inv'0 result}
-      {[%#span18] len'0 (shallow_model'0 result) = 0}
+    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span15] inv'0 result}
+      {[%#span14] len'0 (shallow_model'0 result) = 0}
       (! return' {result}) ]
     
   
@@ -308,39 +277,25 @@ module C12GhostCode_GhostCopy
   
   let%span span3 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span9 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span10 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
-  
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
   use prelude.prelude.Int32
   
@@ -362,20 +317,15 @@ module C12GhostCode_GhostCopy
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq int32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq int32 . ([%#span4] inv'0 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq int32 . [%#span4] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq int32) = 0
   
   use prelude.prelude.Intrinsic
   
@@ -387,34 +337,25 @@ module C12GhostCode_GhostCopy
   
   function new'0 (x : Seq'0.t_seq int32) : Snapshot'0.t_snapshot (Seq'0.t_seq int32)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq int32 . ([%#span9] inv'0 x)  -> ([%#span10] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Seq'0.t_seq int32 . ([%#span6] inv'0 x)  -> ([%#span7] deref'0 (new'0 x) = x)
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'0 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function concat'0 (self : Seq'0.t_seq int32) (other : Seq'0.t_seq int32) : Seq'0.t_seq int32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span11] inv'0 self)
-   -> ([%#span12] inv'0 other)
-   -> ([%#span15] inv'0 (concat'0 self other))
-  && ([%#span14] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span9] forall i : int . 0 <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'0 self then index_logic'0 self i else index_logic'0 other (i - len'0 self)))
-  && ([%#span13] len'0 (concat'0 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span8] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   function singleton'0 (v : int32) : Seq'0.t_seq int32
   
-  axiom singleton'0_spec : forall v : int32 . ([%#span16] inv'1 v)
-   -> ([%#span19] inv'0 (singleton'0 v))
-  && ([%#span18] index_logic'0 (singleton'0 v) 0 = v) && ([%#span17] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : int32 . ([%#span10] inv'1 v)
+   -> ([%#span12] index_logic'0 (singleton'0 v) 0 = v) && ([%#span11] len'0 (singleton'0 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq int32) (v : int32) : Seq'0.t_seq int32 =
-    [%#span20] concat'0 self (singleton'0 v)
+    [%#span13] concat'0 self (singleton'0 v)
   
   let rec ghost_copy (_1:()) (return'  (ret:()))= (! bb0
     [ bb0 = s0
@@ -513,73 +454,57 @@ module C12GhostCode_GhostCheck
   
   let%span span6 = "" 0 0 0 0
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span12 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span13 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span16 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span15 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span16 = "" 0 0 0 0
   
-  let%span span19 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span20 = "" 0 0 0 0
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span24 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span25 = "" 0 0 0 0
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span26 = "" 0 0 0 0
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span28 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span29 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span32 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span30 = "../12_ghost_code.rs" 32 0 32 8
   
-  let%span span33 = "" 0 0 0 0
+  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
-  let%span span34 = "" 0 0 0 0
-  
-  let%span span35 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
-  
-  let%span span36 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span37 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span38 = "../12_ghost_code.rs" 32 0 32 8
-  
-  let%span span39 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
-  
-  let%span span40 = "" 0 0 0 0
+  let%span span32 = "" 0 0 0 0
   
   use prelude.prelude.Int32
   
@@ -634,89 +559,74 @@ module C12GhostCode_GhostCheck
   
   constant max'0 : usize = [%#span6] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq int32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq int32 . ([%#span7] inv'5 self)  -> ([%#span8] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq int32 . [%#span7] len'1 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span9] inv'0 self)
-   -> ([%#span11] inv'5 (shallow_model'0 self))
-  && ([%#span10] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span8] inv'0 self)
+   -> ([%#span9] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span12] inv'5 (shallow_model'0 self)
+    [%#span10] inv'5 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq int32 = [%#span13] ()
+  constant empty'0 : Seq'0.t_seq int32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span15] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span14] len'1 (empty'0 : Seq'0.t_seq int32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'1 (empty'0 : Seq'0.t_seq int32) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'1 (self : int32) =
-    [%#span16] true
-  
-  use seq.Seq
+    [%#span12] true
   
-  function index_logic'1 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'1 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span17] index_logic'1 (shallow_model'0 self) ix
+    [%#span13] index_logic'1 (shallow_model'0 self) ix
   
   predicate resolve'0 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span18] forall i : int . 0 <= i /\ i < len'1 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
+    [%#span14] forall i : int . 0 <= i /\ i < len'1 (shallow_model'0 self)  -> resolve'1 (index_logic'0 self i)
   
   function shallow_model'2 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32 =
-    [%#span19] shallow_model'0 self
+    [%#span15] shallow_model'0 self
   
-  let rec len'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span20] inv'4 self}
+  let rec len'0 (self:Vec'0.t_vec int32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span16] inv'4 self}
     any
-    [ return' (result:usize)-> {[%#span21] UIntSize.to_int result = len'1 (shallow_model'2 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span17] UIntSize.to_int result = len'1 (shallow_model'2 self)} (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq int32) (other : Seq'0.t_seq int32) : Seq'0.t_seq int32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span22] inv'5 self)
-   -> ([%#span23] inv'5 other)
-   -> ([%#span26] inv'5 (concat'0 self other))
-  && ([%#span25] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq int32, other : Seq'0.t_seq int32 . ([%#span19] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span24] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span18] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function singleton'0 (v : int32) : Seq'0.t_seq int32
   
-  axiom singleton'0_spec : forall v : int32 . ([%#span27] inv'3 v)
-   -> ([%#span30] inv'5 (singleton'0 v))
-  && ([%#span29] index_logic'1 (singleton'0 v) 0 = v) && ([%#span28] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : int32 . ([%#span20] inv'3 v)
+   -> ([%#span22] index_logic'1 (singleton'0 v) 0 = v) && ([%#span21] len'1 (singleton'0 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq int32) (v : int32) : Seq'0.t_seq int32 =
-    [%#span31] concat'0 self (singleton'0 v)
+    [%#span23] concat'0 self (singleton'0 v)
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec int32 (Global'0.t_global))) : Seq'0.t_seq int32 =
-    [%#span32] shallow_model'0 ( * self)
+    [%#span24] shallow_model'0 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (value:int32) (return'  (ret:()))= {[@expl:precondition] [%#span34] inv'3 value}
-    {[@expl:precondition] [%#span33] inv'2 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec int32 (Global'0.t_global))) (value:int32) (return'  (ret:()))= {[@expl:precondition] [%#span26] inv'3 value}
+    {[@expl:precondition] [%#span25] inv'2 self}
     any
-    [ return' (result:())-> {[%#span35] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
+    [ return' (result:())-> {[%#span27] shallow_model'0 ( ^ self) = push'1 (shallow_model'1 self) value}
       (! return' {result}) ]
     
   
@@ -724,14 +634,14 @@ module C12GhostCode_GhostCheck
   
   function new'1 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'1_spec : forall x : () . ([%#span36] inv'1 x)  -> ([%#span37] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : () . ([%#span28] inv'1 x)  -> ([%#span29] deref'0 (new'1 x) = x)
   
   function logi_drop'0 [#"../12_ghost_code.rs" 33 0 33 21] (_1 : Vec'0.t_vec int32 (Global'0.t_global)) : () =
-    [%#span38] ()
+    [%#span30] ()
   
   let rec new'0 (_1:()) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span40] inv'0 result}
-      {[%#span39] len'1 (shallow_model'0 result) = 0}
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span32] inv'0 result}
+      {[%#span31] len'1 (shallow_model'0 result) = 0}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/syntax/13_vec_macro.coma b/creusot/tests/should_succeed/syntax/13_vec_macro.coma
index 19f61663f3..742c36ca2c 100644
--- a/creusot/tests/should_succeed/syntax/13_vec_macro.coma
+++ b/creusot/tests/should_succeed/syntax/13_vec_macro.coma
@@ -101,22 +101,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Alloc_Boxed_Box_Type
   use Core_Ptr_Unique_Unique_Type as Unique'0
@@ -149,82 +134,81 @@ module C13VecMacro_X
   
   let%span span10 = "" 0 0 0 0
   
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span17 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span18 = "../../../../../creusot-contracts/src/std/boxed.rs" 20 8 20 31
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span19 = "" 0 0 0 0
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 310 18 310 35
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span21 = "" 0 0 0 0
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span22 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/boxed.rs" 20 8 20 31
+  let%span span23 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span24 = "" 0 0 0 0
+  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 310 18 310 35
+  let%span span25 = "" 0 0 0 0
   
-  let%span span26 = "" 0 0 0 0
+  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span27 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span28 = "" 0 0 0 0
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
   let%span span30 = "" 0 0 0 0
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
-  
-  let%span span32 = "../../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
+  use prelude.prelude.Int32
   
-  let%span span33 = "" 0 0 0 0
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
+  predicate invariant'6 (self : Seq'0.t_seq int32) =
+    [%#span9] true
   
-  let%span span35 = "" 0 0 0 0
+  predicate inv'6 (_x : Seq'0.t_seq int32)
   
-  use prelude.prelude.Int32
+  axiom inv'6 : forall x : Seq'0.t_seq int32 . inv'6 x = true
   
-  use prelude.prelude.Slice
+  use prelude.prelude.UInt32
   
-  predicate invariant'6 (self : slice int32) =
+  predicate invariant'5 (self : Seq'0.t_seq uint32) =
     [%#span9] true
   
-  predicate inv'6 (_x : slice int32)
+  predicate inv'5 (_x : Seq'0.t_seq uint32)
   
-  axiom inv'6 : forall x : slice int32 . inv'6 x = true
+  axiom inv'5 : forall x : Seq'0.t_seq uint32 . inv'5 x = true
   
-  predicate invariant'5 (self : slice int32) =
-    [%#span9] true
+  use prelude.prelude.Slice
   
-  predicate inv'5 (_x : slice int32)
+  predicate invariant'4 (self : slice int32) =
+    [%#span9] true
   
-  axiom inv'5 : forall x : slice int32 . inv'5 x = true
+  predicate inv'4 (_x : slice int32)
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'4 : forall x : slice int32 . inv'4 x = true
   
-  predicate invariant'4 (self : Seq'0.t_seq int32) =
+  predicate invariant'3 (self : slice int32) =
     [%#span9] true
   
-  predicate inv'4 (_x : Seq'0.t_seq int32)
+  predicate inv'3 (_x : slice int32)
   
-  axiom inv'4 : forall x : Seq'0.t_seq int32 . inv'4 x = true
+  axiom inv'3 : forall x : slice int32 . inv'3 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -238,131 +222,107 @@ module C13VecMacro_X
   
   constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq int32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq int32 . ([%#span11] inv'4 self)  -> ([%#span12] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq int32 . [%#span11] len'1 self >= 0
   
-  predicate inv'3 (_x : Vec'0.t_vec int32 (Global'0.t_global))
+  predicate inv'2 (_x : Vec'0.t_vec int32 (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) : Seq'0.t_seq int32
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span13] inv'3 self)
-   -> ([%#span15] inv'4 (shallow_model'1 self))
-  && ([%#span14] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'3 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span16] inv'4 (shallow_model'1 self)
-  
-  axiom inv'3 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'3 x = true
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec int32 (Global'0.t_global) . ([%#span12] inv'2 self)
+   -> ([%#span13] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'2 (self : int32) =
-    [%#span9] true
-  
-  predicate inv'2 (_x : int32)
+  predicate invariant'2 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
+    [%#span14] inv'6 (shallow_model'1 self)
   
-  axiom inv'2 : forall x : int32 . inv'2 x = true
-  
-  use prelude.prelude.UInt32
+  axiom inv'2 : forall x : Vec'0.t_vec int32 (Global'0.t_global) . inv'2 x = true
   
-  predicate invariant'1 (self : Seq'0.t_seq uint32) =
+  predicate invariant'1 (self : int32) =
     [%#span9] true
   
-  predicate inv'1 (_x : Seq'0.t_seq uint32)
+  predicate inv'1 (_x : int32)
   
-  axiom inv'1 : forall x : Seq'0.t_seq uint32 . inv'1 x = true
-  
-  use seq.Seq
+  axiom inv'1 : forall x : int32 . inv'1 x = true
   
   function len'0 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . ([%#span11] inv'1 self)  -> ([%#span12] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq uint32 . [%#span11] len'0 self >= 0
   
   predicate inv'0 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span13] inv'0 self)
-   -> ([%#span15] inv'1 (shallow_model'0 self))
-  && ([%#span14] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span12] inv'0 self)
+   -> ([%#span13] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span16] inv'1 (shallow_model'0 self)
+    [%#span14] inv'5 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'1 : Seq'0.t_seq int32 = [%#span17] ()
+  constant empty'1 : Seq'0.t_seq int32
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span18] len'1 (empty'1 : Seq'0.t_seq int32) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span15] len'1 (empty'1 : Seq'0.t_seq int32) = 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span17] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span19] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span18] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'0 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.Intrinsic
   
   function shallow_model'3 (self : slice int32) : Seq'0.t_seq int32
   
-  axiom shallow_model'3_spec : forall self : slice int32 . ([%#span20] inv'6 self)
-   -> ([%#span22] inv'4 (shallow_model'3 self))
-  && ([%#span21] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : slice int32 . ([%#span16] inv'4 self)
+   -> ([%#span17] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   function shallow_model'2 (self : slice int32) : Seq'0.t_seq int32 =
-    [%#span23] shallow_model'3 self
+    [%#span18] shallow_model'3 self
   
-  let rec into_vec'0 (self:slice int32) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span24] inv'5 self}
+  let rec into_vec'0 (self:slice int32) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span19] inv'3 self}
     any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span26] inv'3 result}
-      {[%#span25] shallow_model'1 result = shallow_model'2 self}
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span21] inv'2 result}
+      {[%#span20] shallow_model'1 result = shallow_model'2 self}
       (! return' {result}) ]
     
   
   predicate resolve'3 (self : int32) =
-    [%#span27] true
-  
-  use seq.Seq
+    [%#span22] true
   
-  function index_logic'3 (self : Seq'0.t_seq int32) (x : int) : int32
+  function index_logic'3 (self : Seq'0.t_seq int32) (_2 : int) : int32
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec int32 (Global'0.t_global)) (ix : int) : int32 =
-    [%#span28] index_logic'3 (shallow_model'1 self) ix
+    [%#span23] index_logic'3 (shallow_model'1 self) ix
   
   predicate resolve'1 (self : Vec'0.t_vec int32 (Global'0.t_global)) =
-    [%#span29] forall i : int . 0 <= i /\ i < len'1 (shallow_model'1 self)  -> resolve'3 (index_logic'1 self i)
+    [%#span24] forall i : int . 0 <= i /\ i < len'1 (shallow_model'1 self)  -> resolve'3 (index_logic'1 self i)
   
-  let rec from_elem'0 (elem:int32) (n:usize) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span30] inv'2 elem}
+  let rec from_elem'0 (elem:int32) (n:usize) (return'  (ret:Vec'0.t_vec int32 (Global'0.t_global)))= {[@expl:precondition] [%#span25] inv'1 elem}
     any
-    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span33] inv'3 result}
-      {[%#span32] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'1 result i = elem}
-      {[%#span31] len'1 (shallow_model'1 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec int32 (Global'0.t_global))-> {[%#span28] inv'2 result}
+      {[%#span27] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'1 result i = elem}
+      {[%#span26] len'1 (shallow_model'1 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
   predicate resolve'2 (self : uint32) =
-    [%#span27] true
-  
-  use seq.Seq
+    [%#span22] true
   
-  function index_logic'2 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'2 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span28] index_logic'2 (shallow_model'0 self) ix
+    [%#span23] index_logic'2 (shallow_model'0 self) ix
   
   predicate resolve'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span29] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
+    [%#span24] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'2 (index_logic'0 self i)
   
   let rec new'0 (_1:()) (return'  (ret:Vec'0.t_vec uint32 (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span35] inv'0 result}
-      {[%#span34] len'0 (shallow_model'0 result) = 0}
+    [ return' (result:Vec'0.t_vec uint32 (Global'0.t_global))-> {[%#span30] inv'0 result}
+      {[%#span29] len'0 (shallow_model'0 result) = 0}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/syntax/derive_macros.coma b/creusot/tests/should_succeed/syntax/derive_macros.coma
index ae63b1bafd..f1f55c7de5 100644
--- a/creusot/tests/should_succeed/syntax/derive_macros.coma
+++ b/creusot/tests/should_succeed/syntax/derive_macros.coma
@@ -724,22 +724,7 @@ module DeriveMacros_Product2_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module DeriveMacros_Sum2_Type
   type t_sum2 'a 'b =
diff --git a/creusot/tests/should_succeed/take_first_mut.coma b/creusot/tests/should_succeed/take_first_mut.coma
index b2874fd5fd..3202b967f1 100644
--- a/creusot/tests/should_succeed/take_first_mut.coma
+++ b/creusot/tests/should_succeed/take_first_mut.coma
@@ -16,22 +16,7 @@ module Core_Option_Option_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module TakeFirstMut_TakeFirstMut
   type t
@@ -44,65 +29,45 @@ module TakeFirstMut_TakeFirstMut
   
   let%span stake_first_mut3 = "../take_first_mut.rs" 14 57 14 74
   
-  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span4 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span5 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span11 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span6 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span12 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span7 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span13 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span8 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span14 = "../../../../creusot-contracts/src/logic/seq2.rs" 66 8 66 39
+  let%span span9 = "../../../../creusot-contracts/src/logic/seq2.rs" 62 8 62 39
   
-  let%span span15 = "" 0 0 0 0
+  let%span span10 = "" 0 0 0 0
   
-  let%span span16 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span11 = "../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span17 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span12 = "../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span18 = "../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span13 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span14 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span20 = "../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span15 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span21 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span16 = "" 0 0 0 0
   
-  let%span span22 = "" 0 0 0 0
+  let%span span17 = "../../../../creusot-contracts/src/std/slice.rs" 257 18 265 9
   
-  let%span span23 = "../../../../creusot-contracts/src/std/slice.rs" 257 18 265 9
+  let%span span18 = "" 0 0 0 0
   
-  let%span span24 = "" 0 0 0 0
+  let%span span19 = "../../../../creusot-contracts/src/std/slice.rs" 40 20 40 65
   
-  let%span span25 = "../../../../creusot-contracts/src/std/slice.rs" 40 20 40 65
+  let%span span20 = "" 0 0 0 0
   
-  let%span span26 = "" 0 0 0 0
+  let%span span21 = "../../../../creusot-contracts/src/std/mem.rs" 17 22 17 37
   
-  let%span span27 = "../../../../creusot-contracts/src/std/mem.rs" 17 22 17 37
+  let%span span22 = "../../../../creusot-contracts/src/std/mem.rs" 18 22 18 42
   
-  let%span span28 = "../../../../creusot-contracts/src/std/mem.rs" 18 22 18 42
-  
-  let%span span29 = "" 0 0 0 0
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'7 (self : Seq'0.t_seq t)
-  
-  predicate inv'7 (_x : Seq'0.t_seq t)
-  
-  axiom inv'7 : forall x : Seq'0.t_seq t . inv'7 x = true
+  let%span span23 = "" 0 0 0 0
   
   use prelude.prelude.Borrow
   
@@ -116,20 +81,17 @@ module TakeFirstMut_TakeFirstMut
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span4] inv'7 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span4] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'5 (self : borrowed t)
   
@@ -169,60 +131,53 @@ module TakeFirstMut_TakeFirstMut
   
   axiom inv'0 : forall x : borrowed (slice t) . inv'0 x = true
   
-  use prelude.seq_ext.SeqExt
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function subsequence'0 (self : Seq'0.t_seq t) (n : int) (m : int) : Seq'0.t_seq t
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq t, n : int, m : int . ([%#span9] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq t, n : int, m : int . ([%#span6] 0 <= n
   /\ n <= m /\ m <= len'0 self)
-   -> ([%#span10] inv'7 self)
-   -> ([%#span13] inv'7 (subsequence'0 self n m))
-  && ([%#span12] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
+   -> ([%#span8] forall i : int . 0 <= i /\ i < len'0 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span11] len'0 (subsequence'0 self n m) = m - n)
+  && ([%#span7] len'0 (subsequence'0 self n m) = m - n)
   
   function tail'0 [@inline:trivial] (self : Seq'0.t_seq t) : Seq'0.t_seq t =
-    [%#span14] subsequence'0 self 1 (len'0 self)
+    [%#span9] subsequence'0 self 1 (len'0 self)
   
   use prelude.prelude.UIntSize
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span15] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
   
   function shallow_model'0 (self : slice t) : Seq'0.t_seq t
   
-  axiom shallow_model'0_spec : forall self : slice t . ([%#span16] inv'1 self)
-   -> ([%#span18] inv'7 (shallow_model'0 self))
-  && ([%#span17] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : slice t . ([%#span11] inv'1 self)
+   -> ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'0 [@inline:trivial] (self : slice t) (ix : int) : t =
-    [%#span19] index_logic'1 (shallow_model'0 self) ix
+    [%#span13] index_logic'1 (shallow_model'0 self) ix
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'3 (self : borrowed t) =
-    [%#span20]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   predicate resolve'2 (self : borrowed (slice t)) =
-    [%#span20]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   predicate resolve'1 (self : Option'0.t_option (borrowed t, borrowed (slice t)))
   
   predicate resolve'0 (self : borrowed (borrowed (slice t))) =
-    [%#span20]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   function shallow_model'1 (self : borrowed (slice t)) : Seq'0.t_seq t =
-    [%#span21] shallow_model'0 ( * self)
+    [%#span15] shallow_model'0 ( * self)
   
-  let rec split_first_mut'0 (self:borrowed (slice t)) (return'  (ret:Option'0.t_option (borrowed t, borrowed (slice t))))= {[@expl:precondition] [%#span22] inv'0 self}
+  let rec split_first_mut'0 (self:borrowed (slice t)) (return'  (ret:Option'0.t_option (borrowed t, borrowed (slice t))))= {[@expl:precondition] [%#span16] inv'0 self}
     any
-    [ return' (result:Option'0.t_option (borrowed t, borrowed (slice t)))-> {[%#span24] inv'3 result}
-      {[%#span23] match result with
+    [ return' (result:Option'0.t_option (borrowed t, borrowed (slice t)))-> {[%#span18] inv'3 result}
+      {[%#span17] match result with
         | Option'0.C_Some (first, tail) ->  * first = index_logic'0 ( * self) 0
         /\  ^ first = index_logic'0 ( ^ self) 0
         /\ len'0 (shallow_model'0 ( * self)) > 0
@@ -236,13 +191,13 @@ module TakeFirstMut_TakeFirstMut
     
   
   predicate is_default'0 (self : borrowed (slice t)) =
-    [%#span25] shallow_model'1 self = (empty'0 : Seq'0.t_seq t) /\ shallow_model'0 ( ^ self) = (empty'0 : Seq'0.t_seq t)
+    [%#span19] shallow_model'1 self = (empty'0 : Seq'0.t_seq t) /\ shallow_model'0 ( ^ self) = (empty'0 : Seq'0.t_seq t)
   
-  let rec take'0 (dest:borrowed (borrowed (slice t))) (return'  (ret:borrowed (slice t)))= {[@expl:precondition] [%#span26] inv'2 dest}
+  let rec take'0 (dest:borrowed (borrowed (slice t))) (return'  (ret:borrowed (slice t)))= {[@expl:precondition] [%#span20] inv'2 dest}
     any
-    [ return' (result:borrowed (slice t))-> {[%#span29] inv'0 result}
-      {[%#span28] is_default'0 ( ^ dest)}
-      {[%#span27] result =  * dest}
+    [ return' (result:borrowed (slice t))-> {[%#span23] inv'0 result}
+      {[%#span22] is_default'0 ( ^ dest)}
+      {[%#span21] result =  * dest}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/traits/16_impl_cloning.coma b/creusot/tests/should_succeed/traits/16_impl_cloning.coma
index 82373b2d37..93b8f6ac32 100644
--- a/creusot/tests/should_succeed/traits/16_impl_cloning.coma
+++ b/creusot/tests/should_succeed/traits/16_impl_cloning.coma
@@ -116,17 +116,7 @@ module C16ImplCloning_Vec_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
+  type t_seq 't
 end
 module C16ImplCloning_Test
   type t
diff --git a/creusot/tests/should_succeed/vecdeque.coma b/creusot/tests/should_succeed/vecdeque.coma
index 2d4469560f..742348cca5 100644
--- a/creusot/tests/should_succeed/vecdeque.coma
+++ b/creusot/tests/should_succeed/vecdeque.coma
@@ -118,22 +118,7 @@ module Core_Option_Option_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Vecdeque_TestDeque
   let%span svecdeque0 = "../vecdeque.rs" 6 55 6 56
@@ -174,125 +159,96 @@ module Vecdeque_TestDeque
   
   let%span span18 = "../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span19 = "../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span20 = "../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span21 = "../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span21 = "" 0 0 0 0
   
-  let%span span22 = "../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span22 = "../../../../creusot-contracts/src/std/deque.rs" 12 21 12 25
   
-  let%span span23 = "../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span23 = "../../../../creusot-contracts/src/std/deque.rs" 11 14 11 41
   
   let%span span24 = "" 0 0 0 0
   
-  let%span span25 = "../../../../creusot-contracts/src/std/deque.rs" 12 21 12 25
+  let%span span25 = "../../../../creusot-contracts/src/std/deque.rs" 76 26 76 45
   
-  let%span span26 = "../../../../creusot-contracts/src/std/deque.rs" 11 14 11 41
+  let%span span26 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span27 = "../../../../creusot-contracts/src/std/deque.rs" 12 4 12 36
+  let%span span27 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span28 = "" 0 0 0 0
+  let%span span28 = "../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span29 = "../../../../creusot-contracts/src/std/deque.rs" 76 26 76 45
+  let%span span29 = "../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span30 = "../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span31 = "../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span32 = "../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span32 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span33 = "../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span33 = "" 0 0 0 0
   
-  let%span span34 = "../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span34 = "" 0 0 0 0
   
-  let%span span35 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span35 = "../../../../creusot-contracts/src/std/deque.rs" 103 26 103 55
   
-  let%span span36 = "../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span36 = "" 0 0 0 0
   
-  let%span span37 = "../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span37 = "" 0 0 0 0
   
-  let%span span38 = "../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span38 = "../../../../creusot-contracts/src/std/deque.rs" 98 26 98 59
   
-  let%span span39 = "../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span39 = "../../../../creusot-contracts/src/std/deque.rs" 99 26 99 73
   
-  let%span span40 = "../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span40 = "../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span41 = "" 0 0 0 0
+  let%span span41 = "../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span42 = "" 0 0 0 0
+  let%span span42 = "../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span43 = "../../../../creusot-contracts/src/std/deque.rs" 103 26 103 55
+  let%span span43 = "" 0 0 0 0
   
-  let%span span44 = "" 0 0 0 0
+  let%span span44 = "../../../../creusot-contracts/src/std/deque.rs" 89 26 94 17
   
   let%span span45 = "" 0 0 0 0
   
-  let%span span46 = "../../../../creusot-contracts/src/std/deque.rs" 98 26 98 59
+  let%span span46 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span47 = "../../../../creusot-contracts/src/std/deque.rs" 99 26 99 73
+  let%span span47 = "../../../../creusot-contracts/src/std/option.rs" 10 8 13 9
   
-  let%span span48 = "../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span48 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
-  let%span span49 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span49 = "" 0 0 0 0
   
-  let%span span50 = "../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span50 = "" 0 0 0 0
   
-  let%span span51 = "../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span51 = "../../../../creusot-contracts/src/std/option.rs" 22 26 22 75
   
-  let%span span52 = "../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span52 = "" 0 0 0 0
   
-  let%span span53 = "" 0 0 0 0
+  let%span span53 = "../../../../creusot-contracts/src/std/deque.rs" 80 26 85 17
   
-  let%span span54 = "../../../../creusot-contracts/src/std/deque.rs" 89 26 94 17
+  let%span span54 = "" 0 0 0 0
   
-  let%span span55 = "" 0 0 0 0
+  let%span span55 = "../../../../creusot-contracts/src/std/deque.rs" 58 26 58 44
   
-  let%span span56 = "../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span56 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span57 = "../../../../creusot-contracts/src/std/option.rs" 10 8 13 9
+  let%span span57 = "" 0 0 0 0
   
-  let%span span58 = "../../../../creusot-contracts/src/model.rs" 81 8 81 28
+  let%span span58 = "../../../../creusot-contracts/src/std/deque.rs" 68 26 68 48
   
   let%span span59 = "" 0 0 0 0
   
-  let%span span60 = "" 0 0 0 0
-  
-  let%span span61 = "../../../../creusot-contracts/src/std/option.rs" 22 26 22 75
-  
-  let%span span62 = "" 0 0 0 0
-  
-  let%span span63 = "../../../../creusot-contracts/src/std/deque.rs" 80 26 85 17
-  
-  let%span span64 = "" 0 0 0 0
-  
-  let%span span65 = "../../../../creusot-contracts/src/std/deque.rs" 58 26 58 44
-  
-  let%span span66 = "../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span67 = "" 0 0 0 0
-  
-  let%span span68 = "../../../../creusot-contracts/src/std/deque.rs" 68 26 68 48
-  
-  let%span span69 = "" 0 0 0 0
+  let%span span60 = "../../../../creusot-contracts/src/std/deque.rs" 72 26 72 54
   
-  let%span span70 = "../../../../creusot-contracts/src/std/deque.rs" 72 26 72 54
+  let%span span61 = "../../../../creusot-contracts/src/std/deque.rs" 62 26 62 44
   
-  let%span span71 = "../../../../creusot-contracts/src/std/deque.rs" 62 26 62 44
+  use Alloc_Alloc_Global_Type as Global'0
   
   use prelude.prelude.UInt32
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate invariant'6 (self : Seq'0.t_seq uint32) =
-    [%#span18] true
-  
-  predicate inv'6 (_x : Seq'0.t_seq uint32)
-  
-  axiom inv'6 : forall x : Seq'0.t_seq uint32 . inv'6 x = true
-  
-  use Alloc_Alloc_Global_Type as Global'0
-  
   use Alloc_Collections_VecDeque_VecDeque_Type as VecDeque'0
   
   predicate invariant'5 (self : VecDeque'0.t_vecdeque uint32 (Global'0.t_global)) =
@@ -343,20 +299,17 @@ module Vecdeque_TestDeque
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
   function len'1 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . ([%#span19] inv'6 self)  -> ([%#span20] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . [%#span19] len'1 self >= 0
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span21] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span23] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span22] len'1 (empty'0 : Seq'0.t_seq uint32) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'1 (empty'0 : Seq'0.t_seq uint32) = 0
   
   use prelude.prelude.Intrinsic
   
@@ -364,78 +317,65 @@ module Vecdeque_TestDeque
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span24] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span21] (18446744073709551615 : usize)
   
   function shallow_model'0 (self : VecDeque'0.t_vecdeque uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'0_spec : forall self : VecDeque'0.t_vecdeque uint32 (Global'0.t_global) . ([%#span25] inv'5 self)
-   -> ([%#span27] inv'6 (shallow_model'0 self))
-  && ([%#span26] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
-  
-  let rec clear'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (return'  (ret:()))= {[@expl:precondition] [%#span28] inv'1 self}
-    any [ return' (result:())-> {[%#span29] len'1 (shallow_model'0 ( ^ self)) = 0} (! return' {result}) ] 
+  axiom shallow_model'0_spec : forall self : VecDeque'0.t_vecdeque uint32 (Global'0.t_global) . ([%#span22] inv'5 self)
+   -> ([%#span23] len'1 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  use seq.Seq
+  let rec clear'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (return'  (ret:()))= {[@expl:precondition] [%#span24] inv'1 self}
+    any [ return' (result:())-> {[%#span25] len'1 (shallow_model'0 ( ^ self)) = 0} (! return' {result}) ] 
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'0 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   function concat'0 (self : Seq'0.t_seq uint32) (other : Seq'0.t_seq uint32) : Seq'0.t_seq uint32
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span30] inv'6 self)
-   -> ([%#span31] inv'6 other)
-   -> ([%#span34] inv'6 (concat'0 self other))
-  && ([%#span33] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq uint32, other : Seq'0.t_seq uint32 . ([%#span27] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'1 self then index_logic'0 self i else index_logic'0 other (i - len'1 self)))
-  && ([%#span32] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span26] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function singleton'0 (v : uint32) : Seq'0.t_seq uint32
   
-  axiom singleton'0_spec : forall v : uint32 . ([%#span35] inv'4 v)
-   -> ([%#span38] inv'6 (singleton'0 v))
-  && ([%#span37] index_logic'0 (singleton'0 v) 0 = v) && ([%#span36] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : uint32 . ([%#span28] inv'4 v)
+   -> ([%#span30] index_logic'0 (singleton'0 v) 0 = v) && ([%#span29] len'1 (singleton'0 v) = 1)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq uint32) (v : uint32) : Seq'0.t_seq uint32 =
-    [%#span39] concat'0 self (singleton'0 v)
+    [%#span31] concat'0 self (singleton'0 v)
   
   function shallow_model'2 (self : borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) : Seq'0.t_seq uint32 =
-    [%#span40] shallow_model'0 ( * self)
+    [%#span32] shallow_model'0 ( * self)
   
-  let rec push_back'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (value:uint32) (return'  (ret:()))= {[@expl:precondition] [%#span42] inv'4 value}
-    {[@expl:precondition] [%#span41] inv'1 self}
+  let rec push_back'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (value:uint32) (return'  (ret:()))= {[@expl:precondition] [%#span34] inv'4 value}
+    {[@expl:precondition] [%#span33] inv'1 self}
     any
-    [ return' (result:())-> {[%#span43] shallow_model'0 ( ^ self) = push'0 (shallow_model'2 self) value}
+    [ return' (result:())-> {[%#span35] shallow_model'0 ( ^ self) = push'0 (shallow_model'2 self) value}
       (! return' {result}) ]
     
   
-  let rec push_front'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (value:uint32) (return'  (ret:()))= {[@expl:precondition] [%#span45] inv'4 value}
-    {[@expl:precondition] [%#span44] inv'1 self}
+  let rec push_front'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (value:uint32) (return'  (ret:()))= {[@expl:precondition] [%#span37] inv'4 value}
+    {[@expl:precondition] [%#span36] inv'1 self}
     any
-    [ return' (result:())-> {[%#span47] shallow_model'0 ( ^ self) = concat'0 (singleton'0 value) (shallow_model'2 self)}
-      {[%#span46] len'1 (shallow_model'0 ( ^ self)) = len'1 (shallow_model'2 self) + 1}
+    [ return' (result:())-> {[%#span39] shallow_model'0 ( ^ self) = concat'0 (singleton'0 value) (shallow_model'2 self)}
+      {[%#span38] len'1 (shallow_model'0 ( ^ self)) = len'1 (shallow_model'2 self) + 1}
       (! return' {result}) ]
     
   
-  use prelude.seq_ext.SeqExt
-  
   function subsequence'0 (self : Seq'0.t_seq uint32) (n : int) (m : int) : Seq'0.t_seq uint32
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span48] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq uint32, n : int, m : int . ([%#span40] 0 <= n
   /\ n <= m /\ m <= len'1 self)
-   -> ([%#span49] inv'6 self)
-   -> ([%#span52] inv'6 (subsequence'0 self n m))
-  && ([%#span51] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
+   -> ([%#span42] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
    -> index_logic'0 (subsequence'0 self n m) i = index_logic'0 self (n + i))
-  && ([%#span50] len'1 (subsequence'0 self n m) = m - n)
+  && ([%#span41] len'1 (subsequence'0 self n m) = m - n)
   
-  let rec pop_back'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span53] inv'1 self}
+  let rec pop_back'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span43] inv'1 self}
     any
-    [ return' (result:Option'0.t_option uint32)-> {[%#span55] inv'2 result}
-      {[%#span54] match result with
+    [ return' (result:Option'0.t_option uint32)-> {[%#span45] inv'2 result}
+      {[%#span44] match result with
         | Option'0.C_Some t -> shallow_model'0 ( ^ self)
         = subsequence'0 (shallow_model'2 self) 0 (len'1 (shallow_model'2 self) - 1)
         /\ shallow_model'2 self = push'0 (shallow_model'0 ( ^ self)) t
@@ -449,25 +389,25 @@ module Vecdeque_TestDeque
   use prelude.prelude.UInt32
   
   function deep_model'2 (self : uint32) : int =
-    [%#span56] UInt32.to_int self
+    [%#span46] UInt32.to_int self
   
   function deep_model'1 (self : Option'0.t_option uint32) : Option'0.t_option int =
-    [%#span57] match self with
+    [%#span47] match self with
       | Option'0.C_Some t -> Option'0.C_Some (deep_model'2 t)
       | Option'0.C_None -> Option'0.C_None
       end
   
   function deep_model'0 (self : Option'0.t_option uint32) : Option'0.t_option int =
-    [%#span58] deep_model'1 self
+    [%#span48] deep_model'1 self
   
-  let rec eq'0 (self:Option'0.t_option uint32) (other:Option'0.t_option uint32) (return'  (ret:bool))= {[@expl:precondition] [%#span60] inv'3 other}
-    {[@expl:precondition] [%#span59] inv'3 self}
-    any [ return' (result:bool)-> {[%#span61] result = (deep_model'0 self = deep_model'0 other)} (! return' {result}) ] 
+  let rec eq'0 (self:Option'0.t_option uint32) (other:Option'0.t_option uint32) (return'  (ret:bool))= {[@expl:precondition] [%#span50] inv'3 other}
+    {[@expl:precondition] [%#span49] inv'3 self}
+    any [ return' (result:bool)-> {[%#span51] result = (deep_model'0 self = deep_model'0 other)} (! return' {result}) ] 
   
-  let rec pop_front'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span62] inv'1 self}
+  let rec pop_front'0 (self:borrowed (VecDeque'0.t_vecdeque uint32 (Global'0.t_global))) (return'  (ret:Option'0.t_option uint32))= {[@expl:precondition] [%#span52] inv'1 self}
     any
-    [ return' (result:Option'0.t_option uint32)-> {[%#span64] inv'2 result}
-      {[%#span63] match result with
+    [ return' (result:Option'0.t_option uint32)-> {[%#span54] inv'2 result}
+      {[%#span53] match result with
         | Option'0.C_Some t -> shallow_model'0 ( ^ self)
         = subsequence'0 (shallow_model'2 self) 1 (len'1 (shallow_model'2 self))
         /\ shallow_model'2 self = concat'0 (singleton'0 t) (shallow_model'0 ( ^ self))
@@ -477,24 +417,24 @@ module Vecdeque_TestDeque
     
   
   let rec new'0 (_1:()) (return'  (ret:VecDeque'0.t_vecdeque uint32 (Global'0.t_global)))= any
-    [ return' (result:VecDeque'0.t_vecdeque uint32 (Global'0.t_global))-> {[%#span65] len'1 (shallow_model'0 result)
+    [ return' (result:VecDeque'0.t_vecdeque uint32 (Global'0.t_global))-> {[%#span55] len'1 (shallow_model'0 result)
       = 0}
       (! return' {result}) ]
     
   
   function shallow_model'1 (self : VecDeque'0.t_vecdeque uint32 (Global'0.t_global)) : Seq'0.t_seq uint32 =
-    [%#span66] shallow_model'0 self
+    [%#span56] shallow_model'0 self
   
-  let rec len'0 (self:VecDeque'0.t_vecdeque uint32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span67] inv'0 self}
+  let rec len'0 (self:VecDeque'0.t_vecdeque uint32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span57] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span68] UIntSize.to_int result = len'1 (shallow_model'1 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span58] UIntSize.to_int result = len'1 (shallow_model'1 self)} (! return' {result}) ]
     
   
-  let rec is_empty'0 (self:VecDeque'0.t_vecdeque uint32 (Global'0.t_global)) (return'  (ret:bool))= {[@expl:precondition] [%#span69] inv'0 self}
-    any [ return' (result:bool)-> {[%#span70] result = (len'1 (shallow_model'1 self) = 0)} (! return' {result}) ] 
+  let rec is_empty'0 (self:VecDeque'0.t_vecdeque uint32 (Global'0.t_global)) (return'  (ret:bool))= {[@expl:precondition] [%#span59] inv'0 self}
+    any [ return' (result:bool)-> {[%#span60] result = (len'1 (shallow_model'1 self) = 0)} (! return' {result}) ] 
   
   let rec with_capacity'0 (capacity:usize) (return'  (ret:VecDeque'0.t_vecdeque uint32 (Global'0.t_global)))= any
-    [ return' (result:VecDeque'0.t_vecdeque uint32 (Global'0.t_global))-> {[%#span71] len'1 (shallow_model'0 result)
+    [ return' (result:VecDeque'0.t_vecdeque uint32 (Global'0.t_global))-> {[%#span61] len'1 (shallow_model'0 result)
       = 0}
       (! return' {result}) ]
     
diff --git a/creusot/tests/should_succeed/vector/01.coma b/creusot/tests/should_succeed/vector/01.coma
index 43022b6515..185acae084 100644
--- a/creusot/tests/should_succeed/vector/01.coma
+++ b/creusot/tests/should_succeed/vector/01.coma
@@ -24,22 +24,7 @@ module Core_Ops_Range_Range_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Ptr_NonNull_NonNull_Type
   use prelude.prelude.Opaque
@@ -181,133 +166,118 @@ module C01_AllZero
   
   let%span s0110 = "../01.rs" 6 10 6 33
   
-  let%span span11 = "" 0 0 0 0
+  let%span span11 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span12 = "" 0 0 0 0
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span18 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span20 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span23 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span24 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span25 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span26 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span27 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span28 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span30 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span34 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span35 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span36 = "" 0 0 0 0
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span37 = "" 0 0 0 0
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span38 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span39 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span39 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span40 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span41 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span42 = "" 0 0 0 0
   
-  let%span span43 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span45 = "" 0 0 0 0
+  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span46 = "" 0 0 0 0
+  let%span span46 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span47 = "" 0 0 0 0
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span48 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span49 = "" 0 0 0 0
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span50 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span51 = "" 0 0 0 0
+  let%span span51 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span52 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span52 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
   
-  let%span span53 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span53 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span54 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span55 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span55 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span56 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span57 = "" 0 0 0 0
+  let%span span57 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span58 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span58 = "" 0 0 0 0
   
   let%span span59 = "" 0 0 0 0
   
-  let%span span60 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
-  
-  let%span span61 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
-  
-  let%span span62 = "../../../../../creusot-contracts/src/snapshot.rs" 27 20 27 48
-  
-  let%span span63 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
-  
-  let%span span64 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
-  
-  let%span span65 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
-  
-  let%span span66 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
-  
-  let%span span67 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span60 = "" 0 0 0 0
   
-  let%span span68 = "" 0 0 0 0
-  
-  let%span span69 = "" 0 0 0 0
-  
-  let%span span70 = "" 0 0 0 0
-  
-  let%span span71 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span61 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'4 (_x : Seq'0.t_seq uint32)
+  predicate invariant'9 (self : Seq'0.t_seq uint32) =
+    [%#span11] true
+  
+  predicate inv'9 (_x : Seq'0.t_seq uint32)
+  
+  axiom inv'9 : forall x : Seq'0.t_seq uint32 . inv'9 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -319,129 +289,110 @@ module C01_AllZero
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span12] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . ([%#span12] inv'4 self)  -> ([%#span13] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . [%#span13] len'1 self >= 0
   
-  predicate inv'9 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
+  predicate inv'8 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span14] inv'9 self)
-   -> ([%#span16] inv'4 (shallow_model'2 self))
-  && ([%#span15] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span14] inv'8 self)
+   -> ([%#span15] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'9 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span17] inv'4 (shallow_model'2 self)
+  predicate invariant'8 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
+    [%#span16] inv'9 (shallow_model'2 self)
   
-  axiom inv'9 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'9 x = true
+  axiom inv'8 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'8 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'8 (self : borrowed uint32) =
-    [%#span18] true
+  predicate invariant'7 (self : borrowed uint32) =
+    [%#span11] true
   
-  predicate inv'8 (_x : borrowed uint32)
+  predicate inv'7 (_x : borrowed uint32)
   
-  axiom inv'8 : forall x : borrowed uint32 . inv'8 x = true
+  axiom inv'7 : forall x : borrowed uint32 . inv'7 x = true
   
-  predicate invariant'7 (self : usize) =
-    [%#span18] true
+  predicate invariant'6 (self : usize) =
+    [%#span11] true
   
-  predicate inv'7 (_x : usize)
+  predicate inv'6 (_x : usize)
   
-  axiom inv'7 : forall x : usize . inv'7 x = true
+  axiom inv'6 : forall x : usize . inv'6 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'6 (self : Option'0.t_option usize) =
-    [%#span18] true
+  predicate invariant'5 (self : Option'0.t_option usize) =
+    [%#span11] true
   
-  predicate inv'6 (_x : Option'0.t_option usize)
+  predicate inv'5 (_x : Option'0.t_option usize)
   
-  axiom inv'6 : forall x : Option'0.t_option usize . inv'6 x = true
+  axiom inv'5 : forall x : Option'0.t_option usize . inv'5 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
-  predicate invariant'5 (self : borrowed (Range'0.t_range usize)) =
-    [%#span18] true
+  predicate invariant'4 (self : borrowed (Range'0.t_range usize)) =
+    [%#span11] true
   
-  predicate inv'5 (_x : borrowed (Range'0.t_range usize))
+  predicate inv'4 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'5 : forall x : borrowed (Range'0.t_range usize) . inv'5 x = true
-  
-  predicate invariant'4 (self : Seq'0.t_seq uint32) =
-    [%#span18] true
-  
-  axiom inv'4 : forall x : Seq'0.t_seq uint32 . inv'4 x = true
+  axiom inv'4 : forall x : borrowed (Range'0.t_range usize) . inv'4 x = true
   
   predicate invariant'3 (self : Seq'0.t_seq usize) =
-    [%#span18] true
+    [%#span11] true
   
   predicate inv'3 (_x : Seq'0.t_seq usize)
   
   axiom inv'3 : forall x : Seq'0.t_seq usize . inv'3 x = true
   
   predicate invariant'2 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span18] true
+    [%#span11] true
   
   predicate inv'2 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   axiom inv'2 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'2 x = true
   
   predicate invariant'1 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) =
-    [%#span18] true
+    [%#span11] true
   
   predicate inv'1 (_x : borrowed (Vec'0.t_vec uint32 (Global'0.t_global)))
   
   axiom inv'1 : forall x : borrowed (Vec'0.t_vec uint32 (Global'0.t_global)) . inv'1 x = true
   
-  constant empty'1 : Seq'0.t_seq uint32 = [%#span19] ()
-  
-  function empty_len'1 (_1 : ()) : () =
-    [%#span21] ()
-  
-  axiom empty_len'1_spec : forall _1 : () . [%#span20] len'1 (empty'1 : Seq'0.t_seq uint32) = 0
+  constant empty'1 : Seq'0.t_seq uint32
   
-  use seq.Seq
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span17] len'1 (empty'1 : Seq'0.t_seq uint32) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
-  
-  use seq.Seq
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function len'2 (self : Seq'0.t_seq usize) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq usize . ([%#span12] inv'3 self)  -> ([%#span13] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq usize . [%#span13] len'2 self >= 0
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span22] inv'3 self)
-   -> ([%#span23] inv'3 other)
-   -> ([%#span26] inv'3 (concat'0 self other))
-  && ([%#span25] forall i : int . 0 <= i /\ i < len'2 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span19] forall i : int . 0 <= i
+  /\ i < len'2 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'2 self then index_logic'1 self i else index_logic'1 other (i - len'2 self)))
-  && ([%#span24] len'2 (concat'0 self other) = len'2 self + len'2 other)
+  && ([%#span18] len'2 (concat'0 self other) = len'2 self + len'2 other)
   
   predicate inv'0 (_x : Range'0.t_range usize)
   
   use prelude.prelude.Int
   
   function deep_model'0 (self : usize) : int =
-    [%#span27] UIntSize.to_int self
+    [%#span20] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span28] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span21] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'2 visited > 0
@@ -454,91 +405,83 @@ module C01_AllZero
   function produces_trans'0 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span29] produces'0 a ab b)
-   -> ([%#span30] produces'0 b bc c)
-   -> ([%#span31] inv'0 a)
-   -> ([%#span32] inv'3 ab)
-   -> ([%#span33] inv'0 b)
-   -> ([%#span34] inv'3 bc)  -> ([%#span35] inv'0 c)  -> ([%#span36] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span22] produces'0 a ab b)
+   -> ([%#span23] produces'0 b bc c)
+   -> ([%#span24] inv'0 a)
+   -> ([%#span25] inv'0 b)  -> ([%#span26] inv'0 c)  -> ([%#span27] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span19] ()
+  constant empty'0 : Seq'0.t_seq usize
   
   function produces_refl'0 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span37] inv'0 self)
-   -> ([%#span38] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span28] inv'0 self)
+   -> ([%#span29] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
   
   predicate invariant'0 (self : Range'0.t_range usize) =
-    [%#span18] true
+    [%#span11] true
   
   axiom inv'0 : forall x : Range'0.t_range usize . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span21] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'2 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span17] len'2 (empty'0 : Seq'0.t_seq usize) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) =
-    [%#span39]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate resolve'1 (self : borrowed uint32) =
-    [%#span39]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   use prelude.prelude.Slice
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'2 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq uint32) (fin : Seq'0.t_seq uint32) =
-    [%#span40] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
+    [%#span31] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
      -> index_logic'2 old' i = index_logic'2 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq uint32) (out : uint32) =
-    [%#span41] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span32] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq uint32) =
-    [%#span42] UIntSize.to_int self < len'1 seq
+    [%#span33] UIntSize.to_int self < len'1 seq
   
   function shallow_model'0 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) : Seq'0.t_seq uint32 =
-    [%#span43] shallow_model'2 ( * self)
+    [%#span34] shallow_model'2 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) (index:usize) (return'  (ret:borrowed uint32))= {[@expl:precondition] [%#span46] inv'7 index}
-    {[@expl:precondition] [%#span45] inv'1 self}
-    {[@expl:precondition] [%#span44] in_bounds'0 index (shallow_model'0 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) (index:usize) (return'  (ret:borrowed uint32))= {[@expl:precondition] [%#span37] inv'6 index}
+    {[@expl:precondition] [%#span36] inv'1 self}
+    {[@expl:precondition] [%#span35] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:borrowed uint32)-> {[%#span51] inv'8 result}
-      {[%#span50] len'1 (shallow_model'2 ( ^ self)) = len'1 (shallow_model'0 self)}
-      {[%#span49] resolve_elswhere'0 index (shallow_model'0 self) (shallow_model'2 ( ^ self))}
-      {[%#span48] has_value'0 index (shallow_model'2 ( ^ self)) ( ^ result)}
-      {[%#span47] has_value'0 index (shallow_model'0 self) ( * result)}
+    [ return' (result:borrowed uint32)-> {[%#span42] inv'7 result}
+      {[%#span41] len'1 (shallow_model'2 ( ^ self)) = len'1 (shallow_model'0 self)}
+      {[%#span40] resolve_elswhere'0 index (shallow_model'0 self) (shallow_model'2 ( ^ self))}
+      {[%#span39] has_value'0 index (shallow_model'2 ( ^ self)) ( ^ result)}
+      {[%#span38] has_value'0 index (shallow_model'0 self) ( * result)}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span52] inv'7 v)
-   -> ([%#span55] inv'3 (singleton'0 v))
-  && ([%#span54] index_logic'1 (singleton'0 v) 0 = v) && ([%#span53] len'2 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span43] inv'6 v)
+   -> ([%#span45] index_logic'1 (singleton'0 v) 0 = v) && ([%#span44] len'2 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span39]  ^ self =  * self
+    [%#span30]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span56] resolve'0 self
+    [%#span46] resolve'0 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span57] inv'5 self}
+  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span47] inv'4 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span59] inv'6 result}
-      {[%#span58] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span49] inv'5 result}
+      {[%#span48] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -546,12 +489,12 @@ module C01_AllZero
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span60] index_logic'2 (shallow_model'2 self) ix
+    [%#span50] index_logic'2 (shallow_model'2 self) ix
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
   function shallow_model'4 (self : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) : Seq'0.t_seq uint32 =
-    [%#span61] shallow_model'0 self
+    [%#span51] shallow_model'0 self
   
   function deref'0 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec uint32 (Global'0.t_global)))) : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))
     
@@ -559,7 +502,7 @@ module C01_AllZero
   function shallow_model'1 (self : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec uint32 (Global'0.t_global)))) : Seq'0.t_seq uint32
     
    =
-    [%#span62] shallow_model'4 (deref'0 self)
+    [%#span52] shallow_model'4 (deref'0 self)
   
   function inner'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
@@ -569,39 +512,39 @@ module C01_AllZero
   
   function new'2 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'2_spec : forall x : Seq'0.t_seq usize . ([%#span63] inv'3 x)  -> ([%#span64] deref'1 (new'2 x) = x)
+  axiom new'2_spec : forall x : Seq'0.t_seq usize . ([%#span53] inv'3 x)  -> ([%#span54] deref'1 (new'2 x) = x)
   
   function new'1 (x : Range'0.t_range usize) : Snapshot'0.t_snapshot (Range'0.t_range usize)
   
-  axiom new'1_spec : forall x : Range'0.t_range usize . ([%#span63] inv'0 x)  -> ([%#span64] deref'2 (new'1 x) = x)
+  axiom new'1_spec : forall x : Range'0.t_range usize . ([%#span53] inv'0 x)  -> ([%#span54] deref'2 (new'1 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span65] self = res
+    [%#span55] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range usize) =
-    [%#span66] true
+    [%#span56] true
   
-  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span68] inv'0 self}
-    {[@expl:precondition] [%#span67] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span58] inv'0 self}
+    {[@expl:precondition] [%#span57] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range usize)-> {[%#span69] inv'0 result}
-      {[%#span67] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range usize)-> {[%#span59] inv'0 result}
+      {[%#span57] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
   function shallow_model'3 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32 =
-    [%#span61] shallow_model'2 self
+    [%#span51] shallow_model'2 self
   
-  let rec len'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span70] inv'2 self}
+  let rec len'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span60] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span71] UIntSize.to_int result = len'1 (shallow_model'3 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span61] UIntSize.to_int result = len'1 (shallow_model'3 self)} (! return' {result}) ]
     
   
   function new'0 (x : borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) : Snapshot'0.t_snapshot (borrowed (Vec'0.t_vec uint32 (Global'0.t_global)))
     
   
-  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec uint32 (Global'0.t_global)) . ([%#span63] inv'1 x)
-   -> ([%#span64] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : borrowed (Vec'0.t_vec uint32 (Global'0.t_global)) . ([%#span53] inv'1 x)
+   -> ([%#span54] deref'0 (new'0 x) = x)
   
   let rec all_zero (v:borrowed (Vec'0.t_vec uint32 (Global'0.t_global))) (return'  (ret:()))= (! bb0
     [ bb0 = s0 [ s0 =  [ &old_v <- [%#s010] new'0 v ] s1 | s1 = bb1 ] 
diff --git a/creusot/tests/should_succeed/vector/04_binary_search.coma b/creusot/tests/should_succeed/vector/04_binary_search.coma
index 4479e35524..7a79c1d273 100644
--- a/creusot/tests/should_succeed/vector/04_binary_search.coma
+++ b/creusot/tests/should_succeed/vector/04_binary_search.coma
@@ -1,21 +1,6 @@
 
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Ptr_NonNull_NonNull_Type
   use prelude.prelude.Opaque
@@ -164,59 +149,56 @@ module C04BinarySearch_BinarySearch
   
   let%span s04_binary_search13 = "../04_binary_search.rs" 24 0 25 65
   
-  let%span span14 = "" 0 0 0 0
+  let%span span14 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span15 = "" 0 0 0 0
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span21 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span21 = "../04_binary_search.rs" 9 4 11 5
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span22 = "../04_binary_search.rs" 16 4 16 31
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span25 = "../04_binary_search.rs" 9 4 11 5
+  let%span span25 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span26 = "../04_binary_search.rs" 16 4 16 31
+  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span27 = "" 0 0 0 0
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span28 = "" 0 0 0 0
   
-  let%span span29 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span30 = "" 0 0 0 0
   
-  let%span span31 = "" 0 0 0 0
+  let%span span31 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
   let%span span32 = "" 0 0 0 0
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
-  
-  let%span span34 = "" 0 0 0 0
-  
-  let%span span35 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
-  
-  let%span span36 = "" 0 0 0 0
-  
-  let%span span37 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
   use prelude.prelude.UInt32
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'1 (_x : Seq'0.t_seq uint32)
+  predicate invariant'4 (self : Seq'0.t_seq uint32) =
+    [%#span14] true
+  
+  predicate inv'4 (_x : Seq'0.t_seq uint32)
+  
+  axiom inv'4 : forall x : Seq'0.t_seq uint32 . inv'4 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -228,71 +210,58 @@ module C04BinarySearch_BinarySearch
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span14] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span15] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq uint32) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . ([%#span15] inv'1 self)  -> ([%#span16] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq uint32 . [%#span16] len'1 self >= 0
   
-  predicate inv'4 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
+  predicate inv'3 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span17] inv'4 self)
-   -> ([%#span19] inv'1 (shallow_model'1 self))
-  && ([%#span18] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'4 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span20] inv'1 (shallow_model'1 self)
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec uint32 (Global'0.t_global) . ([%#span17] inv'3 self)
+   -> ([%#span18] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
-  axiom inv'4 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'4 x = true
+  predicate invariant'3 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
+    [%#span19] inv'4 (shallow_model'1 self)
   
-  predicate invariant'3 (self : uint32) =
-    [%#span21] true
+  axiom inv'3 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'3 x = true
   
-  predicate inv'3 (_x : uint32)
+  predicate invariant'2 (self : uint32) =
+    [%#span14] true
   
-  axiom inv'3 : forall x : uint32 . inv'3 x = true
+  predicate inv'2 (_x : uint32)
   
-  predicate invariant'2 (self : usize) =
-    [%#span21] true
+  axiom inv'2 : forall x : uint32 . inv'2 x = true
   
-  predicate inv'2 (_x : usize)
+  predicate invariant'1 (self : usize) =
+    [%#span14] true
   
-  axiom inv'2 : forall x : usize . inv'2 x = true
+  predicate inv'1 (_x : usize)
   
-  predicate invariant'1 (self : Seq'0.t_seq uint32) =
-    [%#span21] true
-  
-  axiom inv'1 : forall x : Seq'0.t_seq uint32 . inv'1 x = true
+  axiom inv'1 : forall x : usize . inv'1 x = true
   
   predicate invariant'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) =
-    [%#span21] true
+    [%#span14] true
   
   predicate inv'0 (_x : Vec'0.t_vec uint32 (Global'0.t_global))
   
   axiom inv'0 : forall x : Vec'0.t_vec uint32 (Global'0.t_global) . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq uint32 = [%#span22] ()
-  
-  function empty_len'0 (_1 : ()) : () =
-    [%#span24] ()
+  constant empty'0 : Seq'0.t_seq uint32
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span23] len'1 (empty'0 : Seq'0.t_seq uint32) = 0
+  function empty_len'0 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'0_spec : forall _1 : () . [%#span20] len'1 (empty'0 : Seq'0.t_seq uint32) = 0
   
-  function index_logic'1 (self : Seq'0.t_seq uint32) (x : int) : uint32
+  function index_logic'1 (self : Seq'0.t_seq uint32) (_2 : int) : uint32
   
   predicate sorted_range'0 [#"../04_binary_search.rs" 8 0 8 52] (s : Seq'0.t_seq uint32) (l : int) (u : int) =
-    [%#span25] forall j : int . forall i : int . l <= i /\ i < j /\ j < u  -> index_logic'1 s i <= index_logic'1 s j
+    [%#span21] forall j : int . forall i : int . l <= i /\ i < j /\ j < u  -> index_logic'1 s i <= index_logic'1 s j
   
   predicate sorted'0 [#"../04_binary_search.rs" 15 0 15 30] (s : Seq'0.t_seq uint32) =
-    [%#span26] sorted_range'0 s 0 (len'1 s)
+    [%#span22] sorted_range'0 s 0 (len'1 s)
   
   use prelude.prelude.Intrinsic
   
@@ -301,31 +270,31 @@ module C04BinarySearch_BinarySearch
   use prelude.prelude.Slice
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq uint32) (out : uint32) =
-    [%#span27] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span23] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq uint32) =
-    [%#span28] UIntSize.to_int self < len'1 seq
+    [%#span24] UIntSize.to_int self < len'1 seq
   
   function shallow_model'0 (self : Vec'0.t_vec uint32 (Global'0.t_global)) : Seq'0.t_seq uint32 =
-    [%#span29] shallow_model'1 self
+    [%#span25] shallow_model'1 self
   
-  let rec index'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (index:usize) (return'  (ret:uint32))= {[@expl:precondition] [%#span32] inv'2 index}
-    {[@expl:precondition] [%#span31] inv'0 self}
-    {[@expl:precondition] [%#span30] in_bounds'0 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (index:usize) (return'  (ret:uint32))= {[@expl:precondition] [%#span28] inv'1 index}
+    {[@expl:precondition] [%#span27] inv'0 self}
+    {[@expl:precondition] [%#span26] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:uint32)-> {[%#span34] inv'3 result}
-      {[%#span33] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:uint32)-> {[%#span30] inv'2 result}
+      {[%#span29] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec uint32 (Global'0.t_global)) (ix : int) : uint32 =
-    [%#span35] index_logic'1 (shallow_model'1 self) ix
+    [%#span31] index_logic'1 (shallow_model'1 self) ix
   
   use Core_Result_Result_Type as Result'0
   
-  let rec len'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span36] inv'0 self}
+  let rec len'0 (self:Vec'0.t_vec uint32 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span32] inv'0 self}
     any
-    [ return' (result:usize)-> {[%#span37] UIntSize.to_int result = len'1 (shallow_model'0 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span33] UIntSize.to_int result = len'1 (shallow_model'0 self)} (! return' {result}) ]
     
   
   let rec binary_search (arr:Vec'0.t_vec uint32 (Global'0.t_global)) (elem:uint32) (return'  (ret:Result'0.t_result usize usize))= {[%#s04_binary_search10] sorted'0 (shallow_model'0 arr)}
diff --git a/creusot/tests/should_succeed/vector/05_binary_search_generic.coma b/creusot/tests/should_succeed/vector/05_binary_search_generic.coma
index f33a760868..4f75e00711 100644
--- a/creusot/tests/should_succeed/vector/05_binary_search_generic.coma
+++ b/creusot/tests/should_succeed/vector/05_binary_search_generic.coma
@@ -1,21 +1,6 @@
 
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Cmp_Ordering_Type
   type t_ordering  =
@@ -194,153 +179,141 @@ module C05BinarySearchGeneric_BinarySearch
   
   let%span span17 = "" 0 0 0 0
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span23 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span24 = "../../../../../creusot-contracts/src/logic/ord.rs" 70 14 70 15
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span25 = "../../../../../creusot-contracts/src/logic/ord.rs" 70 23 70 24
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span26 = "../../../../../creusot-contracts/src/logic/ord.rs" 69 14 69 59
   
-  let%span span27 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span27 = "../../../../../creusot-contracts/src/logic/ord.rs" 64 15 64 48
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/ord.rs" 70 14 70 15
+  let%span span28 = "../../../../../creusot-contracts/src/logic/ord.rs" 66 16 66 17
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/ord.rs" 70 23 70 24
+  let%span span29 = "../../../../../creusot-contracts/src/logic/ord.rs" 66 25 66 26
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/ord.rs" 69 14 69 59
+  let%span span30 = "../../../../../creusot-contracts/src/logic/ord.rs" 65 14 65 44
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/ord.rs" 64 15 64 48
+  let%span span31 = "../../../../../creusot-contracts/src/logic/ord.rs" 59 15 59 45
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/ord.rs" 66 16 66 17
+  let%span span32 = "../../../../../creusot-contracts/src/logic/ord.rs" 61 16 61 17
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/ord.rs" 66 25 66 26
+  let%span span33 = "../../../../../creusot-contracts/src/logic/ord.rs" 61 25 61 26
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/ord.rs" 65 14 65 44
+  let%span span34 = "../../../../../creusot-contracts/src/logic/ord.rs" 60 14 60 47
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/ord.rs" 59 15 59 45
+  let%span span35 = "../../../../../creusot-contracts/src/logic/ord.rs" 53 15 53 32
   
-  let%span span36 = "../../../../../creusot-contracts/src/logic/ord.rs" 61 16 61 17
+  let%span span36 = "../../../../../creusot-contracts/src/logic/ord.rs" 54 15 54 32
   
-  let%span span37 = "../../../../../creusot-contracts/src/logic/ord.rs" 61 25 61 26
+  let%span span37 = "../../../../../creusot-contracts/src/logic/ord.rs" 56 13 56 14
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/ord.rs" 60 14 60 47
+  let%span span38 = "../../../../../creusot-contracts/src/logic/ord.rs" 56 22 56 23
   
-  let%span span39 = "../../../../../creusot-contracts/src/logic/ord.rs" 53 15 53 32
+  let%span span39 = "../../../../../creusot-contracts/src/logic/ord.rs" 56 31 56 32
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/ord.rs" 54 15 54 32
+  let%span span40 = "../../../../../creusot-contracts/src/logic/ord.rs" 55 14 55 31
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/ord.rs" 56 13 56 14
+  let%span span41 = "../../../../../creusot-contracts/src/logic/ord.rs" 50 12 50 13
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/ord.rs" 56 22 56 23
+  let%span span42 = "../../../../../creusot-contracts/src/logic/ord.rs" 49 14 49 45
   
-  let%span span43 = "../../../../../creusot-contracts/src/logic/ord.rs" 56 31 56 32
+  let%span span43 = "../../../../../creusot-contracts/src/logic/ord.rs" 46 18 46 19
   
-  let%span span44 = "../../../../../creusot-contracts/src/logic/ord.rs" 55 14 55 31
+  let%span span44 = "../../../../../creusot-contracts/src/logic/ord.rs" 46 27 46 28
   
-  let%span span45 = "../../../../../creusot-contracts/src/logic/ord.rs" 50 12 50 13
+  let%span span45 = "../../../../../creusot-contracts/src/logic/ord.rs" 45 14 45 64
   
-  let%span span46 = "../../../../../creusot-contracts/src/logic/ord.rs" 49 14 49 45
+  let%span span46 = "../../../../../creusot-contracts/src/logic/ord.rs" 36 18 36 19
   
-  let%span span47 = "../../../../../creusot-contracts/src/logic/ord.rs" 46 18 46 19
+  let%span span47 = "../../../../../creusot-contracts/src/logic/ord.rs" 36 27 36 28
   
-  let%span span48 = "../../../../../creusot-contracts/src/logic/ord.rs" 46 27 46 28
+  let%span span48 = "../../../../../creusot-contracts/src/logic/ord.rs" 35 14 35 61
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/ord.rs" 45 14 45 64
+  let%span span49 = "../../../../../creusot-contracts/src/logic/ord.rs" 26 18 26 19
   
-  let%span span50 = "../../../../../creusot-contracts/src/logic/ord.rs" 36 18 36 19
+  let%span span50 = "../../../../../creusot-contracts/src/logic/ord.rs" 26 27 26 28
   
-  let%span span51 = "../../../../../creusot-contracts/src/logic/ord.rs" 36 27 36 28
+  let%span span51 = "../../../../../creusot-contracts/src/logic/ord.rs" 25 14 25 61
   
-  let%span span52 = "../../../../../creusot-contracts/src/logic/ord.rs" 35 14 35 61
+  let%span span52 = "../../../../../creusot-contracts/src/logic/ord.rs" 16 18 16 19
   
-  let%span span53 = "../../../../../creusot-contracts/src/logic/ord.rs" 26 18 26 19
+  let%span span53 = "../../../../../creusot-contracts/src/logic/ord.rs" 16 27 16 28
   
-  let%span span54 = "../../../../../creusot-contracts/src/logic/ord.rs" 26 27 26 28
+  let%span span54 = "../../../../../creusot-contracts/src/logic/ord.rs" 15 14 15 64
   
-  let%span span55 = "../../../../../creusot-contracts/src/logic/ord.rs" 25 14 25 61
+  let%span span55 = "../05_binary_search_generic.rs" 10 4 12 5
   
-  let%span span56 = "../../../../../creusot-contracts/src/logic/ord.rs" 16 18 16 19
+  let%span span56 = "../05_binary_search_generic.rs" 17 4 17 31
   
-  let%span span57 = "../../../../../creusot-contracts/src/logic/ord.rs" 16 27 16 28
+  let%span span57 = "" 0 0 0 0
   
-  let%span span58 = "../../../../../creusot-contracts/src/logic/ord.rs" 15 14 15 64
+  let%span span58 = "" 0 0 0 0
   
-  let%span span59 = "../05_binary_search_generic.rs" 10 4 12 5
+  let%span span59 = "../../../../../creusot-contracts/src/std/cmp.rs" 50 26 50 85
   
-  let%span span60 = "../05_binary_search_generic.rs" 17 4 17 31
+  let%span span60 = "../../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
   let%span span61 = "" 0 0 0 0
   
   let%span span62 = "" 0 0 0 0
   
-  let%span span63 = "../../../../../creusot-contracts/src/std/cmp.rs" 50 26 50 85
+  let%span span63 = "../../../../../creusot-contracts/src/std/cmp.rs" 39 26 39 76
   
-  let%span span64 = "../../../../../creusot-contracts/src/model.rs" 81 8 81 28
+  let%span span64 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span65 = "" 0 0 0 0
+  let%span span65 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span66 = "" 0 0 0 0
+  let%span span66 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span67 = "../../../../../creusot-contracts/src/std/cmp.rs" 39 26 39 76
+  let%span span67 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span68 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span68 = "" 0 0 0 0
   
-  let%span span69 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span69 = "" 0 0 0 0
   
-  let%span span70 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span70 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span71 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span71 = "" 0 0 0 0
   
-  let%span span72 = "" 0 0 0 0
+  let%span span72 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span73 = "" 0 0 0 0
+  let%span span73 = "../../../../../creusot-contracts/src/std/vec.rs" 33 18 33 22
   
-  let%span span74 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span74 = "../../../../../creusot-contracts/src/std/vec.rs" 30 14 30 56
   
-  let%span span75 = "" 0 0 0 0
+  let%span span75 = "../../../../../creusot-contracts/src/std/vec.rs" 31 4 32 53
   
-  let%span span76 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span76 = "" 0 0 0 0
   
-  let%span span77 = "../../../../../creusot-contracts/src/std/vec.rs" 33 18 33 22
+  let%span span77 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
-  let%span span78 = "../../../../../creusot-contracts/src/std/vec.rs" 30 14 30 56
-  
-  let%span span79 = "../../../../../creusot-contracts/src/std/vec.rs" 31 4 32 53
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span80 = "../../../../../creusot-contracts/src/std/vec.rs" 33 4 33 44
+  predicate invariant'6 (self : Seq'0.t_seq t)
   
-  let%span span81 = "" 0 0 0 0
+  predicate inv'6 (_x : Seq'0.t_seq t)
   
-  let%span span82 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  axiom inv'6 : forall x : Seq'0.t_seq t . inv'6 x = true
   
   type deep_model_ty'0
   
-  predicate invariant'7 (self : deep_model_ty'0)
-  
-  predicate inv'7 (_x : deep_model_ty'0)
-  
-  axiom inv'7 : forall x : deep_model_ty'0 . inv'7 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  predicate invariant'5 (self : deep_model_ty'0)
   
-  predicate invariant'6 (self : Seq'0.t_seq deep_model_ty'0)
+  predicate inv'5 (_x : deep_model_ty'0)
   
-  predicate inv'6 (_x : Seq'0.t_seq deep_model_ty'0)
-  
-  axiom inv'6 : forall x : Seq'0.t_seq deep_model_ty'0 . inv'6 x = true
-  
-  predicate inv'3 (_x : Seq'0.t_seq t)
+  axiom inv'5 : forall x : deep_model_ty'0 . inv'5 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -354,51 +327,38 @@ module C05BinarySearchGeneric_BinarySearch
   
   constant max'0 : usize = [%#span17] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq t) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq t . ([%#span18] inv'3 self)  -> ([%#span19] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq t . [%#span18] len'1 self >= 0
   
-  predicate inv'5 (_x : Vec'0.t_vec t (Global'0.t_global))
+  predicate inv'4 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span20] inv'5 self)
-   -> ([%#span22] inv'3 (shallow_model'1 self))
-  && ([%#span21] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'5 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span23] inv'3 (shallow_model'1 self)
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span19] inv'4 self)
+   -> ([%#span20] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
-  axiom inv'5 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'5 x = true
+  predicate invariant'4 (self : Vec'0.t_vec t (Global'0.t_global)) =
+    [%#span21] inv'6 (shallow_model'1 self)
   
-  use seq.Seq
+  axiom inv'4 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'4 x = true
   
   function len'2 (self : Seq'0.t_seq deep_model_ty'0) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq deep_model_ty'0 . ([%#span18] inv'6 self)
-   -> ([%#span19] len'2 self >= 0)
-  
-  constant empty'1 : Seq'0.t_seq deep_model_ty'0 = [%#span24] ()
+  axiom len'2_spec : forall self : Seq'0.t_seq deep_model_ty'0 . [%#span18] len'2 self >= 0
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span26] ()
+  constant empty'1 : Seq'0.t_seq deep_model_ty'0
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span25] len'2 (empty'1 : Seq'0.t_seq deep_model_ty'0) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  predicate invariant'4 (self : usize) =
-    [%#span27] true
+  axiom empty_len'1_spec : forall _1 : () . [%#span22] len'2 (empty'1 : Seq'0.t_seq deep_model_ty'0) = 0
   
-  predicate inv'4 (_x : usize)
+  predicate invariant'3 (self : usize) =
+    [%#span23] true
   
-  axiom inv'4 : forall x : usize . inv'4 x = true
+  predicate inv'3 (_x : usize)
   
-  predicate invariant'3 (self : Seq'0.t_seq t)
-  
-  axiom inv'3 : forall x : Seq'0.t_seq t . inv'3 x = true
+  axiom inv'3 : forall x : usize . inv'3 x = true
   
   predicate invariant'2 (self : t)
   
@@ -412,67 +372,66 @@ module C05BinarySearchGeneric_BinarySearch
   
   function eq_cmp'0 (x : deep_model_ty'0) (y : deep_model_ty'0) : ()
   
-  axiom eq_cmp'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span28] inv'7 x)
-   -> ([%#span29] inv'7 y)  -> ([%#span30] (x = y) = (cmp_log'0 x y = Ordering'0.C_Equal))
+  axiom eq_cmp'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span24] inv'5 x)
+   -> ([%#span25] inv'5 y)  -> ([%#span26] (x = y) = (cmp_log'0 x y = Ordering'0.C_Equal))
   
   function antisym2'0 (x : deep_model_ty'0) (y : deep_model_ty'0) : ()
   
-  axiom antisym2'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span31] cmp_log'0 x y
+  axiom antisym2'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span27] cmp_log'0 x y
   = Ordering'0.C_Greater)
-   -> ([%#span32] inv'7 x)  -> ([%#span33] inv'7 y)  -> ([%#span34] cmp_log'0 y x = Ordering'0.C_Less)
+   -> ([%#span28] inv'5 x)  -> ([%#span29] inv'5 y)  -> ([%#span30] cmp_log'0 y x = Ordering'0.C_Less)
   
   function antisym1'0 (x : deep_model_ty'0) (y : deep_model_ty'0) : ()
   
-  axiom antisym1'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span35] cmp_log'0 x y
+  axiom antisym1'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span31] cmp_log'0 x y
   = Ordering'0.C_Less)
-   -> ([%#span36] inv'7 x)  -> ([%#span37] inv'7 y)  -> ([%#span38] cmp_log'0 y x = Ordering'0.C_Greater)
+   -> ([%#span32] inv'5 x)  -> ([%#span33] inv'5 y)  -> ([%#span34] cmp_log'0 y x = Ordering'0.C_Greater)
   
   function trans'0 (x : deep_model_ty'0) (y : deep_model_ty'0) (z : deep_model_ty'0) (o : Ordering'0.t_ordering) : ()
   
-  axiom trans'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0, z : deep_model_ty'0, o : Ordering'0.t_ordering . ([%#span39] cmp_log'0 x y
+  axiom trans'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0, z : deep_model_ty'0, o : Ordering'0.t_ordering . ([%#span35] cmp_log'0 x y
   = o)
-   -> ([%#span40] cmp_log'0 y z = o)
-   -> ([%#span41] inv'7 x)  -> ([%#span42] inv'7 y)  -> ([%#span43] inv'7 z)  -> ([%#span44] cmp_log'0 x z = o)
+   -> ([%#span36] cmp_log'0 y z = o)
+   -> ([%#span37] inv'5 x)  -> ([%#span38] inv'5 y)  -> ([%#span39] inv'5 z)  -> ([%#span40] cmp_log'0 x z = o)
   
   function refl'0 (x : deep_model_ty'0) : ()
   
-  axiom refl'0_spec : forall x : deep_model_ty'0 . ([%#span45] inv'7 x)
-   -> ([%#span46] cmp_log'0 x x = Ordering'0.C_Equal)
+  axiom refl'0_spec : forall x : deep_model_ty'0 . ([%#span41] inv'5 x)
+   -> ([%#span42] cmp_log'0 x x = Ordering'0.C_Equal)
   
   function gt_log'0 (self : deep_model_ty'0) (o : deep_model_ty'0) : bool
   
   function cmp_gt_log'0 (x : deep_model_ty'0) (y : deep_model_ty'0) : ()
   
-  axiom cmp_gt_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span47] inv'7 x)
-   -> ([%#span48] inv'7 y)  -> ([%#span49] gt_log'0 x y = (cmp_log'0 x y = Ordering'0.C_Greater))
+  axiom cmp_gt_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span43] inv'5 x)
+   -> ([%#span44] inv'5 y)  -> ([%#span45] gt_log'0 x y = (cmp_log'0 x y = Ordering'0.C_Greater))
   
   function ge_log'0 (self : deep_model_ty'0) (o : deep_model_ty'0) : bool
   
   function cmp_ge_log'0 (x : deep_model_ty'0) (y : deep_model_ty'0) : ()
   
-  axiom cmp_ge_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span50] inv'7 x)
-   -> ([%#span51] inv'7 y)  -> ([%#span52] ge_log'0 x y = (cmp_log'0 x y <> Ordering'0.C_Less))
+  axiom cmp_ge_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span46] inv'5 x)
+   -> ([%#span47] inv'5 y)  -> ([%#span48] ge_log'0 x y = (cmp_log'0 x y <> Ordering'0.C_Less))
   
   function lt_log'0 (self : deep_model_ty'0) (o : deep_model_ty'0) : bool
   
   function cmp_lt_log'0 (x : deep_model_ty'0) (y : deep_model_ty'0) : ()
   
-  axiom cmp_lt_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span53] inv'7 x)
-   -> ([%#span54] inv'7 y)  -> ([%#span55] lt_log'0 x y = (cmp_log'0 x y = Ordering'0.C_Less))
+  axiom cmp_lt_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span49] inv'5 x)
+   -> ([%#span50] inv'5 y)  -> ([%#span51] lt_log'0 x y = (cmp_log'0 x y = Ordering'0.C_Less))
   
   function le_log'0 (self : deep_model_ty'0) (o : deep_model_ty'0) : bool
   
   function cmp_le_log'0 (x : deep_model_ty'0) (y : deep_model_ty'0) : ()
   
-  axiom cmp_le_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span56] inv'7 x)
-   -> ([%#span57] inv'7 y)  -> ([%#span58] le_log'0 x y = (cmp_log'0 x y <> Ordering'0.C_Greater))
+  axiom cmp_le_log'0_spec : forall x : deep_model_ty'0, y : deep_model_ty'0 . ([%#span52] inv'5 x)
+   -> ([%#span53] inv'5 y)  -> ([%#span54] le_log'0 x y = (cmp_log'0 x y <> Ordering'0.C_Greater))
   
-  constant empty'0 : Seq'0.t_seq t = [%#span24] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span26] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span25] len'1 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span22] len'1 (empty'0 : Seq'0.t_seq t) = 0
   
   predicate invariant'1 (self : Vec'0.t_vec t (Global'0.t_global))
   
@@ -486,18 +445,16 @@ module C05BinarySearchGeneric_BinarySearch
   
   axiom inv'0 : forall x : t . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq deep_model_ty'0) (x : int) : deep_model_ty'0
+  function index_logic'0 (self : Seq'0.t_seq deep_model_ty'0) (_2 : int) : deep_model_ty'0
   
   predicate sorted_range'0 [#"../05_binary_search_generic.rs" 9 0 9 63] (s : Seq'0.t_seq deep_model_ty'0) (l : int) (u : int)
     
    =
-    [%#span59] forall j : int . forall i : int . l <= i /\ i <= j /\ j < u
+    [%#span55] forall j : int . forall i : int . l <= i /\ i <= j /\ j < u
      -> le_log'0 (index_logic'0 s i) (index_logic'0 s j)
   
   predicate sorted'0 [#"../05_binary_search_generic.rs" 16 0 16 41] (s : Seq'0.t_seq deep_model_ty'0) =
-    [%#span60] sorted_range'0 s 0 (len'2 s)
+    [%#span56] sorted_range'0 s 0 (len'2 s)
   
   use prelude.prelude.Intrinsic
   
@@ -505,20 +462,20 @@ module C05BinarySearchGeneric_BinarySearch
   
   function deep_model'1 (self : t) : deep_model_ty'0
   
-  let rec cmp'0 (self:t) (other:t) (return'  (ret:Ordering'0.t_ordering))= {[@expl:precondition] [%#span62] inv'2 other}
-    {[@expl:precondition] [%#span61] inv'2 self}
+  let rec cmp'0 (self:t) (other:t) (return'  (ret:Ordering'0.t_ordering))= {[@expl:precondition] [%#span58] inv'2 other}
+    {[@expl:precondition] [%#span57] inv'2 self}
     any
-    [ return' (result:Ordering'0.t_ordering)-> {[%#span63] result = cmp_log'0 (deep_model'1 self) (deep_model'1 other)}
+    [ return' (result:Ordering'0.t_ordering)-> {[%#span59] result = cmp_log'0 (deep_model'1 self) (deep_model'1 other)}
       (! return' {result}) ]
     
   
   function deep_model'3 (self : t) : deep_model_ty'0 =
-    [%#span64] deep_model'1 self
+    [%#span60] deep_model'1 self
   
-  let rec gt'0 (self:t) (other:t) (return'  (ret:bool))= {[@expl:precondition] [%#span66] inv'2 other}
-    {[@expl:precondition] [%#span65] inv'2 self}
+  let rec gt'0 (self:t) (other:t) (return'  (ret:bool))= {[@expl:precondition] [%#span62] inv'2 other}
+    {[@expl:precondition] [%#span61] inv'2 self}
     any
-    [ return' (result:bool)-> {[%#span67] result = gt_log'0 (deep_model'3 self) (deep_model'3 other)}
+    [ return' (result:bool)-> {[%#span63] result = gt_log'0 (deep_model'3 self) (deep_model'3 other)}
       (! return' {result}) ]
     
   
@@ -526,41 +483,38 @@ module C05BinarySearchGeneric_BinarySearch
   
   use prelude.prelude.Slice
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'2 (self : Seq'0.t_seq t) (_2 : int) : t
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) (out : t) =
-    [%#span68] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span64] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) =
-    [%#span69] UIntSize.to_int self < len'1 seq
+    [%#span65] UIntSize.to_int self < len'1 seq
   
   function shallow_model'0 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t =
-    [%#span70] shallow_model'1 self
+    [%#span66] shallow_model'1 self
   
-  let rec index'0 (self:Vec'0.t_vec t (Global'0.t_global)) (index:usize) (return'  (ret:t))= {[@expl:precondition] [%#span73] inv'4 index}
-    {[@expl:precondition] [%#span72] inv'1 self}
-    {[@expl:precondition] [%#span71] in_bounds'0 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec t (Global'0.t_global)) (index:usize) (return'  (ret:t))= {[@expl:precondition] [%#span69] inv'3 index}
+    {[@expl:precondition] [%#span68] inv'1 self}
+    {[@expl:precondition] [%#span67] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:t)-> {[%#span75] inv'2 result}
-      {[%#span74] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:t)-> {[%#span71] inv'2 result}
+      {[%#span70] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span76] index_logic'2 (shallow_model'1 self) ix
+    [%#span72] index_logic'2 (shallow_model'1 self) ix
   
   function deep_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq deep_model_ty'0
   
-  axiom deep_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span77] inv'5 self)
-   -> ([%#span80] inv'6 (deep_model'2 self))
-  && ([%#span79] forall i : int . 0 <= i /\ i < len'1 (shallow_model'1 self)
+  axiom deep_model'2_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span73] inv'4 self)
+   -> ([%#span75] forall i : int . 0 <= i /\ i < len'1 (shallow_model'1 self)
    -> index_logic'0 (deep_model'2 self) i = deep_model'1 (index_logic'1 self i))
-  && ([%#span78] len'1 (shallow_model'1 self) = len'2 (deep_model'2 self))
+  && ([%#span74] len'1 (shallow_model'1 self) = len'2 (deep_model'2 self))
   
   function deep_model'0 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq deep_model_ty'0 =
-    [%#span64] deep_model'2 self
+    [%#span60] deep_model'2 self
   
   use Core_Result_Result_Type as Result'0
   
@@ -568,9 +522,9 @@ module C05BinarySearchGeneric_BinarySearch
   
   predicate resolve'0 (self : t)
   
-  let rec len'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span81] inv'1 self}
+  let rec len'0 (self:Vec'0.t_vec t (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span76] inv'1 self}
     any
-    [ return' (result:usize)-> {[%#span82] UIntSize.to_int result = len'1 (shallow_model'0 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span77] UIntSize.to_int result = len'1 (shallow_model'0 self)} (! return' {result}) ]
     
   
   let rec binary_search (arr:Vec'0.t_vec t (Global'0.t_global)) (elem:t) (return'  (ret:Result'0.t_result usize usize))= {[%#s05_binary_search_generic13] inv'0 elem}
diff --git a/creusot/tests/should_succeed/vector/06_knights_tour.coma b/creusot/tests/should_succeed/vector/06_knights_tour.coma
index 666f5de186..74c73a8a66 100644
--- a/creusot/tests/should_succeed/vector/06_knights_tour.coma
+++ b/creusot/tests/should_succeed/vector/06_knights_tour.coma
@@ -271,22 +271,7 @@ module C06KnightsTour_Board_Type
       end
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module CreusotContracts_Snapshot_Snapshot_Type
   type t_snapshot 't
@@ -379,35 +364,27 @@ module C06KnightsTour_Impl1_New_Closure3
   
   let%span span3 = "" 0 0 0 0
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span9 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span13 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
-  
-  let%span span14 = "" 0 0 0 0
+  let%span span10 = "" 0 0 0 0
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 174 22 174 41
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
+  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 175 12 175 78
   
-  let%span span17 = "" 0 0 0 0
+  let%span span13 = "" 0 0 0 0
   
-  let%span span18 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span14 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
   use prelude.prelude.UIntSize
   
@@ -430,24 +407,19 @@ module C06KnightsTour_Impl1_New_Closure3
   
   constant max'0 : usize = [%#span3] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq usize) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq usize . ([%#span4] inv'2 self)  -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq usize . [%#span4] len'0 self >= 0
   
   predicate inv'1 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span6] inv'1 self)
-   -> ([%#span8] inv'2 (shallow_model'0 self))
-  && ([%#span7] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span5] inv'1 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span9] inv'2 (shallow_model'0 self)
+    [%#span7] inv'2 (shallow_model'0 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'1 x = true
   
@@ -458,12 +430,11 @@ module C06KnightsTour_Impl1_New_Closure3
   
   axiom inv'0 : forall x : usize . inv'0 x = true
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span10] ()
+  constant empty'0 : Seq'0.t_seq usize
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span12] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span11] len'0 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq usize) = 0
   
   use prelude.prelude.Int16
   
@@ -484,23 +455,21 @@ module C06KnightsTour_Impl1_New_Closure3
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec usize (Global'0.t_global)) (ix : int) : usize =
-    [%#span13] index_logic'1 (shallow_model'0 self) ix
+    [%#span9] index_logic'1 (shallow_model'0 self) ix
   
-  let rec from_elem'0 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span14] inv'0 elem}
+  let rec from_elem'0 (elem:usize) (n:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span10] inv'0 elem}
     any
-    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span17] inv'1 result}
-      {[%#span16] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
-      {[%#span15] len'0 (shallow_model'0 result) = UIntSize.to_int n}
+    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span13] inv'1 result}
+      {[%#span12] forall i : int . 0 <= i /\ i < UIntSize.to_int n  -> index_logic'0 result i = elem}
+      {[%#span11] len'0 (shallow_model'0 result) = UIntSize.to_int n}
       (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed Closure'0.c06knightstour_impl1_new_closure3) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   let rec c06knightstour_impl1_new_closure3 (_1:borrowed Closure'0.c06knightstour_impl1_new_closure3) (_2:usize) (_3:Snapshot'0.t_snapshot (Seq'0.t_seq usize)) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= (! bb0
     [ bb0 = s0
@@ -536,190 +505,161 @@ module C06KnightsTour_Impl1_New
   
   let%span s06_knights_tour3 = "../06_knights_tour.rs" 39 14 39 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span9 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
-  
-  let%span span10 = "" 0 0 0 0
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span4 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span7 = "" 0 0 0 0
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span20 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span21 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span11 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 47 15 47 50
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 23 50 27
+  let%span span13 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 48 14 48 35
+  let%span span14 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 49 4 49 87
+  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 42 15 42 50
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 50 4 50 52
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 43 14 43 35
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 44 4 44 87
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span18 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 37 8 49 9
+  let%span span19 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 28 15 28 32
+  let%span span20 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 37 8 49 9
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 29 15 29 32
+  let%span span21 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 28 15 28 32
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 22 31 23
+  let%span span22 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 29 15 29 32
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 31 31 33
+  let%span span23 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 22 31 23
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 52 31 53
+  let%span span24 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 52 31 53
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 61 31 63
+  let%span span25 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 82 31 83
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 31 82 31 83
+  let%span span26 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 30 14 30 42
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 30 14 30 42
+  let%span span27 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 24 21 24 25
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 24 21 24 25
+  let%span span28 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 23 14 23 45
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 23 14 23 45
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span32 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 112 8 116 9
   
-  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 112 8 116 9
+  let%span span34 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 135 8 142 9
   
-  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 24 121 28
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 135 8 142 9
+  let%span span36 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 33 121 37
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 24 121 28
+  let%span span37 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 120 4 120 83
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 33 121 37
+  let%span span38 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 121 42 121 50
+  let%span span39 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 120 4 120 83
+  let%span span40 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 148 8 153 9
   
-  let%span span51 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span41 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span53 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 148 8 153 9
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span54 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span55 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span45 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span46 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span47 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span58 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span48 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span49 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
   
-  let%span span60 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span50 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
   
-  let%span span61 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span51 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
   
-  let%span span62 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span52 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
   
-  let%span span63 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span53 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
   
-  let%span span64 = "../../../../../creusot-contracts/src/std/iter.rs" 38 15 38 32
+  let%span span54 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
   
-  let%span span65 = "../../../../../creusot-contracts/src/std/iter.rs" 39 15 39 32
+  let%span span55 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
   
-  let%span span66 = "../../../../../creusot-contracts/src/std/iter.rs" 41 22 41 23
+  let%span span56 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
   
-  let%span span67 = "../../../../../creusot-contracts/src/std/iter.rs" 41 31 41 33
+  let%span span57 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span68 = "../../../../../creusot-contracts/src/std/iter.rs" 41 52 41 53
+  let%span span58 = "../06_knights_tour.rs" 31 8 35 9
   
-  let%span span69 = "../../../../../creusot-contracts/src/std/iter.rs" 41 61 41 63
+  let%span span59 = "../../../../../creusot-contracts/src/std/vec.rs" 275 20 275 32
   
-  let%span span70 = "../../../../../creusot-contracts/src/std/iter.rs" 41 82 41 83
+  let%span span60 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 15 8 18 9
   
-  let%span span71 = "../../../../../creusot-contracts/src/std/iter.rs" 40 14 40 42
+  let%span span61 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span72 = "../../../../../creusot-contracts/src/std/iter.rs" 35 21 35 25
+  let%span span62 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 56 4 56 27
   
-  let%span span73 = "../../../../../creusot-contracts/src/std/iter.rs" 34 14 34 45
+  let%span span63 = "" 0 0 0 0
   
-  let%span span74 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span64 = "../../../../../creusot-contracts/src/std/iter.rs" 136 16 137 83
   
-  let%span span75 = "../06_knights_tour.rs" 31 8 35 9
+  let%span span65 = "" 0 0 0 0
   
-  let%span span76 = "../../../../../creusot-contracts/src/std/vec.rs" 275 20 275 32
+  let%span span66 = "../../../../../creusot-contracts/src/std/iter.rs" 43 4 43 141
   
-  let%span span77 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 15 8 18 9
+  let%span span67 = "../../../../../creusot-contracts/src/std/iter.rs" 44 15 44 51
   
-  let%span span78 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span68 = "../../../../../creusot-contracts/src/std/iter.rs" 45 15 45 70
   
-  let%span span79 = "../../../../../creusot-contracts/src/std/iter/map_inv.rs" 56 4 56 27
+  let%span span69 = "../../../../../creusot-contracts/src/std/iter.rs" 47 21 47 25
   
-  let%span span80 = "" 0 0 0 0
+  let%span span70 = "../../../../../creusot-contracts/src/std/iter.rs" 47 27 47 31
   
-  let%span span81 = "../../../../../creusot-contracts/src/std/iter.rs" 136 16 137 83
+  let%span span71 = "../../../../../creusot-contracts/src/std/iter.rs" 46 14 46 88
   
-  let%span span82 = "" 0 0 0 0
+  let%span span72 = "../../../../../creusot-contracts/src/std/iter.rs" 47 4 50 61
   
-  let%span span83 = "../../../../../creusot-contracts/src/std/iter.rs" 43 4 43 141
+  use Alloc_Alloc_Global_Type as Global'0
   
-  let%span span84 = "../../../../../creusot-contracts/src/std/iter.rs" 44 15 44 51
+  use prelude.prelude.UIntSize
   
-  let%span span85 = "../../../../../creusot-contracts/src/std/iter.rs" 45 15 45 70
+  use Alloc_Vec_Vec_Type as Vec'0
   
-  let%span span86 = "../../../../../creusot-contracts/src/std/iter.rs" 47 21 47 25
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span87 = "../../../../../creusot-contracts/src/std/iter.rs" 47 27 47 31
+  predicate invariant'10 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span4] true
   
-  let%span span88 = "../../../../../creusot-contracts/src/std/iter.rs" 46 14 46 88
+  predicate inv'10 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   
-  let%span span89 = "../../../../../creusot-contracts/src/std/iter.rs" 47 4 50 61
+  axiom inv'10 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'10 x = true
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use Alloc_Alloc_Global_Type as Global'0
-  
-  use prelude.prelude.UIntSize
-  
-  use Alloc_Vec_Vec_Type as Vec'0
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Int16
@@ -728,124 +668,99 @@ module C06KnightsTour_Impl1_New
   
   use prelude.prelude.Borrow
   
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
-  predicate inv'11 (_x : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3))
-  
   function len'2 (self : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3)) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3) . ([%#span4] inv'11 self)
-   -> ([%#span5] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3) . [%#span5] len'2 self
+  >= 0
   
-  constant empty'2 : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3) = [%#span6] ()
+  constant empty'2 : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3)
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span7] len'2 (empty'2 : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3))
+  axiom empty_len'2_spec : forall _1 : () . [%#span6] len'2 (empty'2 : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3))
   = 0
   
-  predicate invariant'11 (self : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3)) =
-    [%#span9] true
-  
-  axiom inv'11 : forall x : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3) . inv'11 x = true
-  
-  predicate invariant'10 (self : borrowed Closure'0.c06knightstour_impl1_new_closure3) =
-    [%#span9] true
+  predicate invariant'9 (self : borrowed Closure'0.c06knightstour_impl1_new_closure3) =
+    [%#span4] true
   
-  predicate inv'10 (_x : borrowed Closure'0.c06knightstour_impl1_new_closure3)
+  predicate inv'9 (_x : borrowed Closure'0.c06knightstour_impl1_new_closure3)
   
-  axiom inv'10 : forall x : borrowed Closure'0.c06knightstour_impl1_new_closure3 . inv'10 x = true
+  axiom inv'9 : forall x : borrowed Closure'0.c06knightstour_impl1_new_closure3 . inv'9 x = true
   
-  predicate inv'7 (_x : Seq'0.t_seq usize)
+  predicate inv'6 (_x : Seq'0.t_seq usize)
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
-  
-  use seq.Seq
+  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span4] inv'7 self)  -> ([%#span5] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span5] len'1 self >= 0
   
-  predicate inv'9 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'8 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span11] inv'9 self)
-   -> ([%#span13] inv'7 (shallow_model'1 self))
-  && ([%#span12] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'8 self)
+   -> ([%#span9] len'1 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'9 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span14] inv'7 (shallow_model'1 self)
+  predicate invariant'8 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span10] inv'6 (shallow_model'1 self)
   
-  axiom inv'9 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'9 x = true
+  axiom inv'8 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'8 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
-  predicate invariant'8 (self : borrowed (Range'0.t_range usize)) =
-    [%#span9] true
-  
-  predicate inv'8 (_x : borrowed (Range'0.t_range usize))
-  
-  axiom inv'8 : forall x : borrowed (Range'0.t_range usize) . inv'8 x = true
+  predicate invariant'7 (self : borrowed (Range'0.t_range usize)) =
+    [%#span4] true
   
-  predicate invariant'7 (self : Seq'0.t_seq usize) =
-    [%#span9] true
+  predicate inv'7 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'7 : forall x : Seq'0.t_seq usize . inv'7 x = true
+  axiom inv'7 : forall x : borrowed (Range'0.t_range usize) . inv'7 x = true
   
-  use seq.Seq
+  predicate invariant'6 (self : Seq'0.t_seq usize) =
+    [%#span4] true
   
-  predicate inv'4 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom inv'6 : forall x : Seq'0.t_seq usize . inv'6 x = true
   
   function len'0 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span4] inv'4 self)
-   -> ([%#span5] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . [%#span5] len'0 self >= 0
   
-  constant empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) = [%#span6] ()
+  constant empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span7] len'0 (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom empty_len'1_spec : forall _1 : () . [%#span6] len'0 (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   = 0
   
-  predicate inv'6 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
+  predicate inv'5 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span11] inv'6 self)
-   -> ([%#span13] inv'4 (shallow_model'0 self))
-  && ([%#span12] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span8] inv'5 self)
+   -> ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'6 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span14] inv'4 (shallow_model'0 self)
+  predicate invariant'5 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
+    [%#span10] inv'10 (shallow_model'0 self)
   
-  axiom inv'6 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'6 x = true
+  axiom inv'5 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'5 x = true
   
   use CreusotContracts_Std1_Iter_MapInv_MapInv_Type as MapInv'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (x : int) : Vec'0.t_vec usize (Global'0.t_global)
+  function index_logic'3 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (_2 : int) : Vec'0.t_vec usize (Global'0.t_global)
     
   
   function concat'1 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (other : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)), other : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span15] inv'4 self)
-   -> ([%#span16] inv'4 other)
-   -> ([%#span19] inv'4 (concat'1 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'0 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)), other : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span12] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'1 self other)
    -> index_logic'3 (concat'1 self other) i
   = (if i < len'0 self then index_logic'3 self i else index_logic'3 other (i - len'0 self)))
-  && ([%#span17] len'0 (concat'1 self other) = len'0 self + len'0 other)
+  && ([%#span11] len'0 (concat'1 self other) = len'0 self + len'0 other)
   
   predicate inv'3 (_x : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3)
   
@@ -873,40 +788,28 @@ module C06KnightsTour_Impl1_New
   
   function new'0 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'0_spec : forall x : Seq'0.t_seq usize . ([%#span20] inv'7 x)  -> ([%#span21] deref'0 (new'0 x) = x)
-  
-  use prelude.seq_ext.SeqExt
+  axiom new'0_spec : forall x : Seq'0.t_seq usize . ([%#span13] inv'6 x)  -> ([%#span14] deref'0 (new'0 x) = x)
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function subsequence'0 (self : Seq'0.t_seq usize) (n : int) (m : int) : Seq'0.t_seq usize
   
-  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#span22] 0 <= n
+  axiom subsequence'0_spec : forall self : Seq'0.t_seq usize, n : int, m : int . ([%#span15] 0 <= n
   /\ n <= m /\ m <= len'1 self)
-   -> ([%#span23] inv'7 self)
-   -> ([%#span26] inv'7 (subsequence'0 self n m))
-  && ([%#span25] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
+   -> ([%#span17] forall i : int . 0 <= i /\ i < len'1 (subsequence'0 self n m)
    -> index_logic'1 (subsequence'0 self n m) i = index_logic'1 self (n + i))
-  && ([%#span24] len'1 (subsequence'0 self n m) = m - n)
-  
-  use seq.Seq
+  && ([%#span16] len'1 (subsequence'0 self n m) = m - n)
   
-  function index_logic'2 (self : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3)) (x : int) : borrowed Closure'0.c06knightstour_impl1_new_closure3
+  function index_logic'2 (self : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3)) (_2 : int) : borrowed Closure'0.c06knightstour_impl1_new_closure3
     
   
-  use seq.Seq
-  
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span15] inv'7 self)
-   -> ([%#span16] inv'7 other)
-   -> ([%#span19] inv'7 (concat'0 self other))
-  && ([%#span18] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span12] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span17] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span11] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   function inner'0 (self : Snapshot'0.t_snapshot (Seq'0.t_seq usize)) : Seq'0.t_seq usize
   
@@ -915,12 +818,12 @@ module C06KnightsTour_Impl1_New
   use prelude.prelude.Int
   
   function deep_model'0 (self : usize) : int =
-    [%#span27] UIntSize.to_int self
+    [%#span18] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span28] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span19] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'1 visited > 0
@@ -933,14 +836,12 @@ module C06KnightsTour_Impl1_New
   predicate produces'1 [@inline:trivial] (self : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) (visited : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (succ : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3)
     
    =
-    [%#span29] unnest'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self) (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func succ)
-    /\ (exists s : Seq'0.t_seq usize . inv'7 s
-    /\ len'1 s = len'0 visited
+    [%#span20] unnest'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self) (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func succ)
+    /\ (exists s : Seq'0.t_seq usize . len'1 s = len'0 visited
     /\ produces'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter self) s (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter succ)
     /\ inner'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced succ)
     = concat'0 (deref'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced self)) s
-    /\ (exists fs : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3) . inv'11 fs
-    /\ len'2 fs = len'0 visited
+    /\ (exists fs : Seq'0.t_seq (borrowed Closure'0.c06knightstour_impl1_new_closure3) . len'2 fs = len'0 visited
     /\ (forall i : int . 1 <= i /\ i < len'2 fs  ->  ^ index_logic'2 fs (i - 1) =  * index_logic'2 fs i)
     /\ (if len'0 visited = 0 then
       CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self
@@ -957,92 +858,80 @@ module C06KnightsTour_Impl1_New
   function produces_trans'2 (a : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) (ab : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (b : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) (bc : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (c : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) : ()
     
   
-  axiom produces_trans'2_spec : forall a : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3, ab : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)), b : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3, bc : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)), c : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3 . ([%#span30] produces'1 a ab b)
-   -> ([%#span31] produces'1 b bc c)
-   -> ([%#span32] inv'3 a)
-   -> ([%#span33] inv'4 ab)
-   -> ([%#span34] inv'3 b)
-   -> ([%#span35] inv'4 bc)  -> ([%#span36] inv'3 c)  -> ([%#span37] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'2_spec : forall a : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3, ab : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)), b : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3, bc : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)), c : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3 . ([%#span21] produces'1 a ab b)
+   -> ([%#span22] produces'1 b bc c)
+   -> ([%#span23] inv'3 a)
+   -> ([%#span24] inv'3 b)  -> ([%#span25] inv'3 c)  -> ([%#span26] produces'1 a (concat'1 ab bc) c)
   
   function produces_refl'2 (self : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) : ()
     
   
-  axiom produces_refl'2_spec : forall self : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3 . ([%#span38] inv'3 self)
-   -> ([%#span39] produces'1 self (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) self)
+  axiom produces_refl'2_spec : forall self : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3 . ([%#span27] inv'3 self)
+   -> ([%#span28] produces'1 self (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) self)
   
-  predicate invariant'5 (self : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3))
+  predicate invariant'4 (self : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3))
     
    =
-    [%#span9] true
+    [%#span4] true
   
-  predicate inv'5 (_x : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3))
+  predicate inv'4 (_x : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3))
     
   
-  axiom inv'5 : forall x : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) . inv'5 x
+  axiom inv'4 : forall x : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) . inv'4 x
   = (inv'3 ( * x) /\ inv'3 ( ^ x))
   
-  predicate invariant'4 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span9] true
-  
-  axiom inv'4 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'4 x = true
-  
-  use seq.Seq
-  
   predicate inv'1 (_x : usize)
   
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span40] inv'1 v)
-   -> ([%#span43] inv'7 (singleton'0 v))
-  && ([%#span42] index_logic'1 (singleton'0 v) 0 = v) && ([%#span41] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span29] inv'1 v)
+   -> ([%#span31] index_logic'1 (singleton'0 v) 0 = v) && ([%#span30] len'1 (singleton'0 v) = 1)
   
   predicate inv'0 (_x : Range'0.t_range usize)
   
   predicate next_precondition'0 (iter : Range'0.t_range usize) (func : Closure'0.c06knightstour_impl1_new_closure3) (produced : Seq'0.t_seq usize)
     
    =
-    [%#span44] forall i : Range'0.t_range usize . forall e : usize . inv'0 i
+    [%#span32] forall i : Range'0.t_range usize . forall e : usize . inv'0 i
      -> inv'1 e  -> produces'0 iter (singleton'0 e) i  -> precondition'0 func (e, new'0 produced)
   
   function push'0 [@inline:trivial] (self : Seq'0.t_seq usize) (v : usize) : Seq'0.t_seq usize =
-    [%#span45] concat'0 self (singleton'0 v)
+    [%#span33] concat'0 self (singleton'0 v)
   
   predicate preservation'0 (iter : Range'0.t_range usize) (func : Closure'0.c06knightstour_impl1_new_closure3) =
-    [%#span46] forall i : Range'0.t_range usize . forall b : Vec'0.t_vec usize (Global'0.t_global) . forall f : borrowed Closure'0.c06knightstour_impl1_new_closure3 . forall e2 : usize . forall e1 : usize . forall s : Seq'0.t_seq usize . inv'0 i
-     -> inv'9 b
-     -> inv'10 f
+    [%#span34] forall i : Range'0.t_range usize . forall b : Vec'0.t_vec usize (Global'0.t_global) . forall f : borrowed Closure'0.c06knightstour_impl1_new_closure3 . forall e2 : usize . forall e1 : usize . forall s : Seq'0.t_seq usize . inv'0 i
+     -> inv'8 b
+     -> inv'9 f
      -> inv'1 e2
      -> inv'1 e1
-     -> inv'7 s
      -> unnest'0 func ( * f)
      -> produces'0 iter (push'0 (push'0 s e1) e2) i
      -> precondition'0 ( * f) (e1, new'0 s)
      -> postcondition_mut'0 f (e1, new'0 s) b  -> precondition'0 ( ^ f) (e2, new'0 (push'0 s e1))
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span6] ()
+  constant empty'0 : Seq'0.t_seq usize
   
   predicate inv'2 (_x : Closure'0.c06knightstour_impl1_new_closure3)
   
   predicate preservation_inv'0 (iter : Range'0.t_range usize) (func : Closure'0.c06knightstour_impl1_new_closure3) (produced : Seq'0.t_seq usize)
     
   
-  axiom preservation_inv'0_spec : forall iter : Range'0.t_range usize, func : Closure'0.c06knightstour_impl1_new_closure3, produced : Seq'0.t_seq usize . ([%#span47] inv'0 iter)
-   -> ([%#span48] inv'2 func)
-   -> ([%#span49] inv'7 produced)
-   -> ([%#span50] produced = (empty'0 : Seq'0.t_seq usize)
+  axiom preservation_inv'0_spec : forall iter : Range'0.t_range usize, func : Closure'0.c06knightstour_impl1_new_closure3, produced : Seq'0.t_seq usize . ([%#span35] inv'0 iter)
+   -> ([%#span36] inv'2 func)
+   -> ([%#span37] produced = (empty'0 : Seq'0.t_seq usize)
    -> preservation_inv'0 iter func produced = preservation'0 iter func)
   
   predicate resolve'3 (self : borrowed (Range'0.t_range usize)) =
-    [%#span51]  ^ self =  * self
+    [%#span38]  ^ self =  * self
   
   predicate completed'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span52] resolve'3 self
+    [%#span39] resolve'3 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
   predicate reinitialize'0 (_1 : ()) =
-    [%#span53] forall func : Closure'0.c06knightstour_impl1_new_closure3 . forall iter : borrowed (Range'0.t_range usize) . inv'2 func
-     -> inv'8 iter
+    [%#span40] forall func : Closure'0.c06knightstour_impl1_new_closure3 . forall iter : borrowed (Range'0.t_range usize) . inv'2 func
+     -> inv'7 iter
      -> completed'1 iter
      -> next_precondition'0 ( ^ iter) func (empty'0 : Seq'0.t_seq usize) /\ preservation'0 ( ^ iter) func
   
@@ -1056,66 +945,61 @@ module C06KnightsTour_Impl1_New
     end)
   
   predicate invariant'2 (self : Closure'0.c06knightstour_impl1_new_closure3) =
-    [%#span9] true
+    [%#span4] true
   
   axiom inv'2 : forall x : Closure'0.c06knightstour_impl1_new_closure3 . inv'2 x = true
   
   function produces_trans'1 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span54] produces'0 a ab b)
-   -> ([%#span55] produces'0 b bc c)
-   -> ([%#span56] inv'0 a)
-   -> ([%#span57] inv'7 ab)
-   -> ([%#span58] inv'0 b)
-   -> ([%#span59] inv'7 bc)  -> ([%#span60] inv'0 c)  -> ([%#span61] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span41] produces'0 a ab b)
+   -> ([%#span42] produces'0 b bc c)
+   -> ([%#span43] inv'0 a)
+   -> ([%#span44] inv'0 b)  -> ([%#span45] inv'0 c)  -> ([%#span46] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'1 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span62] inv'0 self)
-   -> ([%#span63] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span47] inv'0 self)
+   -> ([%#span48] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span8] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'1 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'1 (empty'0 : Seq'0.t_seq usize) = 0
   
   predicate invariant'1 (self : usize) =
-    [%#span9] true
+    [%#span4] true
   
   axiom inv'1 : forall x : usize . inv'1 x = true
   
   predicate invariant'0 (self : Range'0.t_range usize) =
-    [%#span9] true
+    [%#span4] true
   
   axiom inv'0 : forall x : Range'0.t_range usize . inv'0 x = true
   
   function produces_trans'0 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span64] produces'0 a ab b)
-   -> ([%#span65] produces'0 b bc c)
-   -> ([%#span66] inv'0 a)
-   -> ([%#span67] inv'7 ab)
-   -> ([%#span68] inv'0 b)
-   -> ([%#span69] inv'7 bc)  -> ([%#span70] inv'0 c)  -> ([%#span71] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span49] produces'0 a ab b)
+   -> ([%#span50] produces'0 b bc c)
+   -> ([%#span51] inv'0 a)
+   -> ([%#span52] inv'0 b)  -> ([%#span53] inv'0 c)  -> ([%#span54] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span72] inv'0 self)
-   -> ([%#span73] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span55] inv'0 self)
+   -> ([%#span56] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (ix : int) : Vec'0.t_vec usize (Global'0.t_global)
     
    =
-    [%#span74] index_logic'3 (shallow_model'0 self) ix
+    [%#span57] index_logic'3 (shallow_model'0 self) ix
   
   use C06KnightsTour_Board_Type as C06KnightsTour_Board_Type
   
   use C06KnightsTour_Board_Type as Board'0
   
   predicate wf'0 [#"../06_knights_tour.rs" 30 4 30 23] (self : Board'0.t_board) =
-    [%#span75] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
+    [%#span58] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
     /\ len'0 (shallow_model'0 (C06KnightsTour_Board_Type.board_field self))
     = UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ (forall i : int . 0 <= i /\ i < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
@@ -1127,12 +1011,12 @@ module C06KnightsTour_Impl1_New
   predicate from_iter_post'0 (prod : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (res : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
     
    =
-    [%#span76] prod = shallow_model'0 res
+    [%#span59] prod = shallow_model'0 res
   
   predicate completed'0 (self : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3))
     
    =
-    [%#span77] deref'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced ( ^ self))
+    [%#span60] deref'0 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_produced ( ^ self))
     = (empty'0 : Seq'0.t_seq usize)
     /\ completed'1 (Borrow.borrow_logic (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter ( * self)) (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter ( ^ self)) (Borrow.inherit_id (Borrow.get_id self) 1))
     /\ CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func ( * self)
@@ -1142,32 +1026,31 @@ module C06KnightsTour_Impl1_New
     true
   
   predicate resolve'1 (self : Range'0.t_range usize) =
-    [%#span78] true
+    [%#span61] true
   
   predicate resolve'0 (self : MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3)
     
    =
-    [%#span79] resolve'1 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter self)
+    [%#span62] resolve'1 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_iter self)
     /\ resolve'2 (CreusotContracts_Std1_Iter_MapInv_MapInv_Type.mapinv_func self)
   
-  let rec collect'0 (self:MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) (return'  (ret:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))= {[@expl:precondition] [%#span80] inv'3 self}
+  let rec collect'0 (self:MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) (return'  (ret:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)))= {[@expl:precondition] [%#span63] inv'3 self}
     any
-    [ return' (result:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))-> {[%#span82] inv'6 result}
-      {[%#span81] exists prod : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . exists done' : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) . inv'4 prod
-      /\ inv'5 done'
+    [ return' (result:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))-> {[%#span65] inv'5 result}
+      {[%#span64] exists prod : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . exists done' : borrowed (MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3) . inv'4 done'
       /\ resolve'0 ( ^ done') /\ completed'0 done' /\ produces'1 self prod ( * done') /\ from_iter_post'0 prod result}
       (! return' {result}) ]
     
   
-  let rec map_inv'0 (self:Range'0.t_range usize) (func:Closure'0.c06knightstour_impl1_new_closure3) (return'  (ret:MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3))= {[@expl:precondition] [%#span87] inv'2 func}
-    {[@expl:precondition] [%#span86] inv'0 self}
-    {[@expl:precondition] [%#span85] preservation'0 self func}
-    {[@expl:precondition] [%#span84] reinitialize'0 ()}
-    {[@expl:precondition] [%#span83] forall i2 : Range'0.t_range usize . forall e : usize . inv'0 i2
+  let rec map_inv'0 (self:Range'0.t_range usize) (func:Closure'0.c06knightstour_impl1_new_closure3) (return'  (ret:MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3))= {[@expl:precondition] [%#span70] inv'2 func}
+    {[@expl:precondition] [%#span69] inv'0 self}
+    {[@expl:precondition] [%#span68] preservation'0 self func}
+    {[@expl:precondition] [%#span67] reinitialize'0 ()}
+    {[@expl:precondition] [%#span66] forall i2 : Range'0.t_range usize . forall e : usize . inv'0 i2
      -> inv'1 e  -> produces'0 self (singleton'0 e) i2  -> precondition'0 func (e, new'0 (empty'0 : Seq'0.t_seq usize))}
     any
-    [ return' (result:MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3)-> {[%#span89] inv'3 result}
-      {[%#span88] result = MapInv'0.C_MapInv self func (new'0 (empty'0 : Seq'0.t_seq usize))}
+    [ return' (result:MapInv'0.t_mapinv (Range'0.t_range usize) usize Closure'0.c06knightstour_impl1_new_closure3)-> {[%#span72] inv'3 result}
+      {[%#span71] result = MapInv'0.C_MapInv self func (new'0 (empty'0 : Seq'0.t_seq usize))}
       (! return' {result}) ]
     
   
@@ -1229,45 +1112,37 @@ module C06KnightsTour_Impl1_Available
   
   let%span span7 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span17 = "../06_knights_tour.rs" 63 12 63 75
+  let%span span13 = "../06_knights_tour.rs" 63 12 63 75
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span14 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span19 = "../06_knights_tour.rs" 31 8 35 9
+  let%span span15 = "../06_knights_tour.rs" 31 8 35 9
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span17 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span22 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span18 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span24 = "" 0 0 0 0
+  let%span span20 = "" 0 0 0 0
   
-  let%span span25 = "" 0 0 0 0
+  let%span span21 = "" 0 0 0 0
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span27 = "" 0 0 0 0
+  let%span span23 = "" 0 0 0 0
   
   use prelude.prelude.UIntSize
   
@@ -1284,74 +1159,63 @@ module C06KnightsTour_Impl1_Available
   
   use Alloc_Vec_Vec_Type as Vec'0
   
+  predicate invariant'6 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span6] true
+  
+  predicate inv'6 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  
+  axiom inv'6 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'6 x = true
+  
   use prelude.prelude.UIntSize
   
   use prelude.prelude.Int
   
   constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span8] inv'7 self)  -> ([%#span9] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span8] len'1 self >= 0
   
-  predicate inv'6 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'5 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span10] inv'6 self)
-   -> ([%#span12] inv'7 (shallow_model'3 self))
-  && ([%#span11] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'6 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span13] inv'7 (shallow_model'3 self)
-  
-  axiom inv'6 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'6 x = true
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span9] inv'5 self)
+   -> ([%#span10] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'5 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span6] true
-  
-  predicate inv'5 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
-  
-  axiom inv'5 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'5 x = true
+  predicate invariant'5 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span11] inv'7 (shallow_model'3 self)
   
-  use seq.Seq
+  axiom inv'5 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'5 x = true
   
   function len'0 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span8] inv'5 self)
-   -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . [%#span8] len'0 self >= 0
   
   predicate inv'4 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span10] inv'4 self)
-   -> ([%#span12] inv'5 (shallow_model'2 self))
-  && ([%#span11] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span9] inv'4 self)
+   -> ([%#span10] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'4 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span13] inv'5 (shallow_model'2 self)
+    [%#span11] inv'6 (shallow_model'2 self)
   
   axiom inv'4 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'4 x = true
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span14] ()
+  constant empty'1 : Seq'0.t_seq usize
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span16] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span15] len'1 (empty'1 : Seq'0.t_seq usize) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span12] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
-  constant empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) = [%#span14] ()
+  constant empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span16] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'0 (empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom empty_len'0_spec : forall _1 : () . [%#span12] len'0 (empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   = 0
   
   predicate invariant'3 (self : usize) =
@@ -1393,25 +1257,23 @@ module C06KnightsTour_Impl1_Available
   use C06KnightsTour_Board_Type as Board'0
   
   predicate in_bounds'0 [#"../06_knights_tour.rs" 61 4 61 40] (self : Board'0.t_board) (p : Point'0.t_point) =
-    [%#span17] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
+    [%#span13] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (x : int) : Vec'0.t_vec usize (Global'0.t_global)
+  function index_logic'1 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (_2 : int) : Vec'0.t_vec usize (Global'0.t_global)
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (ix : int) : Vec'0.t_vec usize (Global'0.t_global)
     
    =
-    [%#span18] index_logic'1 (shallow_model'2 self) ix
+    [%#span14] index_logic'1 (shallow_model'2 self) ix
   
   predicate wf'0 [#"../06_knights_tour.rs" 30 4 30 23] (self : Board'0.t_board) =
-    [%#span19] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
+    [%#span15] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
     /\ len'0 (shallow_model'2 (C06KnightsTour_Board_Type.board_field self))
     = UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ (forall i : int . 0 <= i /\ i < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
@@ -1424,47 +1286,45 @@ module C06KnightsTour_Impl1_Available
   
   use prelude.prelude.Borrow
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span20] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span16] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'2 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span21] UIntSize.to_int self < len'1 seq
+    [%#span17] UIntSize.to_int self < len'1 seq
   
   function shallow_model'1 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize =
-    [%#span22] shallow_model'3 self
+    [%#span18] shallow_model'3 self
   
-  let rec index'1 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span25] inv'1 index}
-    {[@expl:precondition] [%#span24] inv'2 self}
-    {[@expl:precondition] [%#span23] in_bounds'2 index (shallow_model'1 self)}
+  let rec index'1 (self:Vec'0.t_vec usize (Global'0.t_global)) (index:usize) (return'  (ret:usize))= {[@expl:precondition] [%#span21] inv'1 index}
+    {[@expl:precondition] [%#span20] inv'2 self}
+    {[@expl:precondition] [%#span19] in_bounds'2 index (shallow_model'1 self)}
     any
-    [ return' (result:usize)-> {[%#span27] inv'3 result}
-      {[%#span26] has_value'1 index (shallow_model'1 self) result}
+    [ return' (result:usize)-> {[%#span23] inv'3 result}
+      {[%#span22] has_value'1 index (shallow_model'1 self) result}
       (! return' {result}) ]
     
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (out : Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span20] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span16] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span21] UIntSize.to_int self < len'0 seq
+    [%#span17] UIntSize.to_int self < len'0 seq
   
   function shallow_model'0 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span22] shallow_model'2 self
+    [%#span18] shallow_model'2 self
   
-  let rec index'0 (self:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (index:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span25] inv'1 index}
-    {[@expl:precondition] [%#span24] inv'0 self}
-    {[@expl:precondition] [%#span23] in_bounds'1 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (index:usize) (return'  (ret:Vec'0.t_vec usize (Global'0.t_global)))= {[@expl:precondition] [%#span21] inv'1 index}
+    {[@expl:precondition] [%#span20] inv'0 self}
+    {[@expl:precondition] [%#span19] in_bounds'1 index (shallow_model'0 self)}
     any
-    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span27] inv'2 result}
-      {[%#span26] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:Vec'0.t_vec usize (Global'0.t_global))-> {[%#span23] inv'2 result}
+      {[%#span22] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
@@ -1629,125 +1489,105 @@ module C06KnightsTour_Impl1_CountDegree
   
   let%span span11 = "" 0 0 0 0
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span17 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
-  
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
-  
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
-  
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
-  
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
-  
-  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
+  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 268 31 268 33
+  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/vec.rs" 268 52 268 54
+  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
+  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
+  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
+  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
+  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
+  let%span span28 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
+  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
   
-  let%span span39 = "../06_knights_tour.rs" 63 12 63 75
+  let%span span30 = "../06_knights_tour.rs" 63 12 63 75
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span31 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span41 = "../06_knights_tour.rs" 31 8 35 9
+  let%span span32 = "../06_knights_tour.rs" 31 8 35 9
   
-  let%span span42 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span33 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span43 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
+  let%span span34 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/vec.rs" 239 8 239 85
+  let%span span35 = "../../../../../creusot-contracts/src/std/vec.rs" 239 8 239 85
   
-  let%span span45 = "../06_knights_tour.rs" 50 15 50 24
+  let%span span36 = "../06_knights_tour.rs" 50 15 50 24
   
-  let%span span46 = "../06_knights_tour.rs" 51 4 51 44
+  let%span span37 = "../06_knights_tour.rs" 51 4 51 44
   
-  let%span span47 = "../06_knights_tour.rs" 12 15 12 52
+  let%span span38 = "../06_knights_tour.rs" 12 15 12 52
   
-  let%span span48 = "../06_knights_tour.rs" 13 15 13 52
+  let%span span39 = "../06_knights_tour.rs" 13 15 13 52
   
-  let%span span49 = "../06_knights_tour.rs" 14 15 14 46
+  let%span span40 = "../06_knights_tour.rs" 14 15 14 46
   
-  let%span span50 = "../06_knights_tour.rs" 15 15 15 46
+  let%span span41 = "../06_knights_tour.rs" 15 15 15 46
   
-  let%span span51 = "../06_knights_tour.rs" 16 14 16 41
+  let%span span42 = "../06_knights_tour.rs" 16 14 16 41
   
-  let%span span52 = "../06_knights_tour.rs" 17 14 17 41
+  let%span span43 = "../06_knights_tour.rs" 17 14 17 41
   
-  let%span span53 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span44 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span54 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span45 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span55 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span46 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span56 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span47 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span57 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span48 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span58 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span49 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
+  let%span span50 = "" 0 0 0 0
   
-  let%span span60 = "" 0 0 0 0
+  let%span span51 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span61 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span52 = "" 0 0 0 0
   
-  let%span span62 = "" 0 0 0 0
+  let%span span53 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span63 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span54 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span64 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span55 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
   
-  let%span span65 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
+  let%span span56 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
   
-  let%span span66 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
+  let%span span57 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span67 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span58 = "" 0 0 0 0
   
-  let%span span68 = "" 0 0 0 0
+  let%span span59 = "" 0 0 0 0
   
-  let%span span69 = "" 0 0 0 0
+  let%span span60 = "../06_knights_tour.rs" 93 10 93 28
   
-  let%span span70 = "../06_knights_tour.rs" 93 10 93 28
-  
-  let%span span71 = "../06_knights_tour.rs" 94 0 94 130
+  let%span span61 = "../06_knights_tour.rs" 94 0 94 130
   
   use prelude.prelude.UIntSize
   
@@ -1764,74 +1604,63 @@ module C06KnightsTour_Impl1_CountDegree
   
   use Alloc_Vec_Vec_Type as Vec'0
   
+  predicate invariant'8 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span10] true
+  
+  predicate inv'8 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  
+  axiom inv'8 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'8 x = true
+  
   use prelude.prelude.UIntSize
   
   use prelude.prelude.Int
   
   constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'2 (self : Seq'0.t_seq usize) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq usize . ([%#span12] inv'9 self)  -> ([%#span13] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq usize . [%#span12] len'2 self >= 0
   
-  predicate inv'8 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'7 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span14] inv'8 self)
-   -> ([%#span16] inv'9 (shallow_model'3 self))
-  && ([%#span15] len'2 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span13] inv'7 self)
+   -> ([%#span14] len'2 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'8 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span17] inv'9 (shallow_model'3 self)
+  predicate invariant'7 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span15] inv'9 (shallow_model'3 self)
   
-  axiom inv'8 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'8 x = true
-  
-  predicate invariant'7 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span10] true
-  
-  predicate inv'7 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
-  
-  axiom inv'7 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'7 x = true
-  
-  use seq.Seq
+  axiom inv'7 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'7 x = true
   
   function len'1 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span12] inv'7 self)
-   -> ([%#span13] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . [%#span12] len'1 self >= 0
   
   predicate inv'6 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span14] inv'6 self)
-   -> ([%#span16] inv'7 (shallow_model'2 self))
-  && ([%#span15] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span13] inv'6 self)
+   -> ([%#span14] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'6 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span17] inv'7 (shallow_model'2 self)
+    [%#span15] inv'8 (shallow_model'2 self)
   
   axiom inv'6 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'6 x = true
   
-  constant empty'2 : Seq'0.t_seq usize = [%#span18] ()
+  constant empty'2 : Seq'0.t_seq usize
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span20] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span19] len'2 (empty'2 : Seq'0.t_seq usize) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span16] len'2 (empty'2 : Seq'0.t_seq usize) = 0
   
-  constant empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) = [%#span18] ()
+  constant empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span20] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span19] len'1 (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom empty_len'1_spec : forall _1 : () . [%#span16] len'1 (empty'1 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   = 0
   
   use prelude.prelude.IntSize
@@ -1870,41 +1699,33 @@ module C06KnightsTour_Impl1_CountDegree
   
   axiom inv'2 : forall x : Seq'0.t_seq (isize, isize) . inv'2 x = true
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq (isize, isize)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (isize, isize) . ([%#span12] inv'2 self)  -> ([%#span13] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (isize, isize) . [%#span12] len'0 self >= 0
   
   predicate inv'1 (_x : Vec'0.t_vec (isize, isize) (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) : Seq'0.t_seq (isize, isize)
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec (isize, isize) (Global'0.t_global) . ([%#span14] inv'1 self)
-   -> ([%#span16] inv'2 (shallow_model'0 self))
-  && ([%#span15] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec (isize, isize) (Global'0.t_global) . ([%#span13] inv'1 self)
+   -> ([%#span14] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'1 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) =
-    [%#span17] inv'2 (shallow_model'0 self)
+    [%#span15] inv'2 (shallow_model'0 self)
   
   axiom inv'1 : forall x : Vec'0.t_vec (isize, isize) (Global'0.t_global) . inv'1 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (isize, isize)) (x : int) : (isize, isize)
+  function index_logic'1 (self : Seq'0.t_seq (isize, isize)) (_2 : int) : (isize, isize)
   
   function concat'0 (self : Seq'0.t_seq (isize, isize)) (other : Seq'0.t_seq (isize, isize)) : Seq'0.t_seq (isize, isize)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (isize, isize), other : Seq'0.t_seq (isize, isize) . ([%#span21] inv'2 self)
-   -> ([%#span22] inv'2 other)
-   -> ([%#span25] inv'2 (concat'0 self other))
-  && ([%#span24] forall i : int . 0 <= i /\ i < len'0 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (isize, isize), other : Seq'0.t_seq (isize, isize) . ([%#span18] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'0 self then index_logic'1 self i else index_logic'1 other (i - len'0 self)))
-  && ([%#span23] len'0 (concat'0 self other) = len'0 self + len'0 other)
+  && ([%#span17] len'0 (concat'0 self other) = len'0 self + len'0 other)
   
   predicate inv'0 (_x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
   
@@ -1914,37 +1735,34 @@ module C06KnightsTour_Impl1_CountDegree
   predicate produces'0 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) (visited : Seq'0.t_seq (isize, isize)) (rhs : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
     
    =
-    [%#span26] shallow_model'1 self = concat'0 visited (shallow_model'1 rhs)
+    [%#span19] shallow_model'1 self = concat'0 visited (shallow_model'1 rhs)
   
   function produces_trans'0 (a : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) (ab : Seq'0.t_seq (isize, isize)) (b : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) (bc : Seq'0.t_seq (isize, isize)) (c : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) : ()
     
    =
-    [%#span35] ()
+    [%#span26] ()
   
-  axiom produces_trans'0_spec : forall a : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), ab : Seq'0.t_seq (isize, isize), b : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), bc : Seq'0.t_seq (isize, isize), c : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span27] produces'0 a ab b)
-   -> ([%#span28] produces'0 b bc c)
-   -> ([%#span29] inv'0 a)
-   -> ([%#span30] inv'2 ab)
-   -> ([%#span31] inv'0 b)
-   -> ([%#span32] inv'2 bc)  -> ([%#span33] inv'0 c)  -> ([%#span34] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), ab : Seq'0.t_seq (isize, isize), b : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), bc : Seq'0.t_seq (isize, isize), c : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span20] produces'0 a ab b)
+   -> ([%#span21] produces'0 b bc c)
+   -> ([%#span22] inv'0 a)
+   -> ([%#span23] inv'0 b)  -> ([%#span24] inv'0 c)  -> ([%#span25] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq (isize, isize) = [%#span18] ()
+  constant empty'0 : Seq'0.t_seq (isize, isize)
   
   function produces_refl'0 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) : () =
-    [%#span38] ()
+    [%#span29] ()
   
-  axiom produces_refl'0_spec : forall self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span36] inv'0 self)
-   -> ([%#span37] produces'0 self (empty'0 : Seq'0.t_seq (isize, isize)) self)
+  axiom produces_refl'0_spec : forall self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span27] inv'0 self)
+   -> ([%#span28] produces'0 self (empty'0 : Seq'0.t_seq (isize, isize)) self)
   
   predicate invariant'0 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) =
     [%#span10] true
   
   axiom inv'0 : forall x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span20] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span19] len'0 (empty'0 : Seq'0.t_seq (isize, isize)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span16] len'0 (empty'0 : Seq'0.t_seq (isize, isize)) = 0
   
   use C06KnightsTour_Point_Type as C06KnightsTour_Point_Type
   
@@ -1957,25 +1775,23 @@ module C06KnightsTour_Impl1_CountDegree
   use C06KnightsTour_Board_Type as Board'0
   
   predicate in_bounds'0 [#"../06_knights_tour.rs" 61 4 61 40] (self : Board'0.t_board) (p : Point'0.t_point) =
-    [%#span39] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
+    [%#span30] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
   
-  use seq.Seq
-  
-  function index_logic'3 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (x : int) : Vec'0.t_vec usize (Global'0.t_global)
+  function index_logic'3 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (_2 : int) : Vec'0.t_vec usize (Global'0.t_global)
     
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (ix : int) : Vec'0.t_vec usize (Global'0.t_global)
     
    =
-    [%#span40] index_logic'3 (shallow_model'2 self) ix
+    [%#span31] index_logic'3 (shallow_model'2 self) ix
   
   predicate wf'0 [#"../06_knights_tour.rs" 30 4 30 23] (self : Board'0.t_board) =
-    [%#span41] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
+    [%#span32] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
     /\ len'1 (shallow_model'2 (C06KnightsTour_Board_Type.board_field self))
     = UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ (forall i : int . 0 <= i /\ i < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
@@ -1987,58 +1803,55 @@ module C06KnightsTour_Impl1_CountDegree
   use prelude.prelude.Intrinsic
   
   predicate resolve'3 (self : isize) =
-    [%#span42] true
+    [%#span33] true
   
   predicate resolve'1 (self : (isize, isize)) =
-    [%#span43] resolve'3 (let (a, _) = self in a) /\ resolve'3 (let (_, a) = self in a)
+    [%#span34] resolve'3 (let (a, _) = self in a) /\ resolve'3 (let (_, a) = self in a)
   
   predicate resolve'2 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) =
-    [%#span44] forall i : int . 0 <= i /\ i < len'0 (shallow_model'1 self)
+    [%#span35] forall i : int . 0 <= i /\ i < len'0 (shallow_model'1 self)
      -> resolve'1 (index_logic'1 (shallow_model'1 self) i)
   
-  let rec available'0 (self:Board'0.t_board) (p:Point'0.t_point) (return'  (ret:bool))= {[@expl:precondition] [%#span45] wf'0 self}
-    any [ return' (result:bool)-> {[%#span46] result  -> in_bounds'0 self p} (! return' {result}) ] 
+  let rec available'0 (self:Board'0.t_board) (p:Point'0.t_point) (return'  (ret:bool))= {[@expl:precondition] [%#span36] wf'0 self}
+    any [ return' (result:bool)-> {[%#span37] result  -> in_bounds'0 self p} (! return' {result}) ] 
   
-  let rec mov'0 (self:Point'0.t_point) (p:(isize, isize)) (return'  (ret:Point'0.t_point))= {[@expl:precondition] [%#span50] - 10000
+  let rec mov'0 (self:Point'0.t_point) (p:(isize, isize)) (return'  (ret:Point'0.t_point))= {[@expl:precondition] [%#span41] - 10000
     <= IntSize.to_int (let (_, a) = p in a)
     /\ IntSize.to_int (let (_, a) = p in a) <= 10000}
-    {[@expl:precondition] [%#span49] - 10000 <= IntSize.to_int (let (a, _) = p in a)
+    {[@expl:precondition] [%#span40] - 10000 <= IntSize.to_int (let (a, _) = p in a)
     /\ IntSize.to_int (let (a, _) = p in a) <= 10000}
-    {[@expl:precondition] [%#span48] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y self)
+    {[@expl:precondition] [%#span39] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y self)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_y self) <= 10000}
-    {[@expl:precondition] [%#span47] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x self)
+    {[@expl:precondition] [%#span38] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x self)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_x self) <= 10000}
     any
-    [ return' (result:Point'0.t_point)-> {[%#span52] IntSize.to_int (C06KnightsTour_Point_Type.point_y result)
+    [ return' (result:Point'0.t_point)-> {[%#span43] IntSize.to_int (C06KnightsTour_Point_Type.point_y result)
       = IntSize.to_int (C06KnightsTour_Point_Type.point_y self) + IntSize.to_int (let (_, a) = p in a)}
-      {[%#span51] IntSize.to_int (C06KnightsTour_Point_Type.point_x result)
+      {[%#span42] IntSize.to_int (C06KnightsTour_Point_Type.point_x result)
       = IntSize.to_int (C06KnightsTour_Point_Type.point_x self) + IntSize.to_int (let (a, _) = p in a)}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'0 (v : (isize, isize)) : Seq'0.t_seq (isize, isize)
   
-  axiom singleton'0_spec : forall v : (isize, isize) . ([%#span53] inv'5 v)
-   -> ([%#span56] inv'2 (singleton'0 v))
-  && ([%#span55] index_logic'1 (singleton'0 v) 0 = v) && ([%#span54] len'0 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (isize, isize) . ([%#span44] inv'5 v)
+   -> ([%#span46] index_logic'1 (singleton'0 v) 0 = v) && ([%#span45] len'0 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) =
-    [%#span57]  ^ self =  * self
+    [%#span47]  ^ self =  * self
   
   function shallow_model'4 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) : Seq'0.t_seq (isize, isize)
     
    =
-    [%#span58] shallow_model'1 ( * self)
+    [%#span48] shallow_model'1 ( * self)
   
   predicate completed'0 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) =
-    [%#span59] resolve'0 self /\ shallow_model'4 self = (empty'0 : Seq'0.t_seq (isize, isize))
+    [%#span49] resolve'0 self /\ shallow_model'4 self = (empty'0 : Seq'0.t_seq (isize, isize))
   
-  let rec next'0 (self:borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) (return'  (ret:Option'0.t_option (isize, isize)))= {[@expl:precondition] [%#span60] inv'3 self}
+  let rec next'0 (self:borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) (return'  (ret:Option'0.t_option (isize, isize)))= {[@expl:precondition] [%#span50] inv'3 self}
     any
-    [ return' (result:Option'0.t_option (isize, isize))-> {[%#span62] inv'4 result}
-      {[%#span61] match result with
+    [ return' (result:Option'0.t_option (isize, isize))-> {[%#span52] inv'4 result}
+      {[%#span51] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -2057,42 +1870,42 @@ module C06KnightsTour_Impl1_CountDegree
   
   function new'1 (x : Seq'0.t_seq (isize, isize)) : Snapshot'0.t_snapshot (Seq'0.t_seq (isize, isize))
   
-  axiom new'1_spec : forall x : Seq'0.t_seq (isize, isize) . ([%#span63] inv'2 x)  -> ([%#span64] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq (isize, isize) . ([%#span53] inv'2 x)  -> ([%#span54] deref'0 (new'1 x) = x)
   
   function new'0 (x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) : Snapshot'0.t_snapshot (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
     
   
-  axiom new'0_spec : forall x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span63] inv'0 x)
-   -> ([%#span64] deref'1 (new'0 x) = x)
+  axiom new'0_spec : forall x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span53] inv'0 x)
+   -> ([%#span54] deref'1 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) (res : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
     
    =
-    [%#span65] shallow_model'0 self = shallow_model'1 res
+    [%#span55] shallow_model'0 self = shallow_model'1 res
   
   predicate into_iter_pre'0 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) =
-    [%#span66] true
+    [%#span56] true
   
-  let rec into_iter'0 (self:Vec'0.t_vec (isize, isize) (Global'0.t_global)) (return'  (ret:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)))= {[@expl:precondition] [%#span68] inv'1 self}
-    {[@expl:precondition] [%#span67] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Vec'0.t_vec (isize, isize) (Global'0.t_global)) (return'  (ret:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)))= {[@expl:precondition] [%#span58] inv'1 self}
+    {[@expl:precondition] [%#span57] into_iter_pre'0 self}
     any
-    [ return' (result:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))-> {[%#span69] inv'0 result}
-      {[%#span67] into_iter_post'0 self result}
+    [ return' (result:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))-> {[%#span59] inv'0 result}
+      {[%#span57] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) (ix : int) : (isize, isize)
     
    =
-    [%#span40] index_logic'1 (shallow_model'0 self) ix
+    [%#span31] index_logic'1 (shallow_model'0 self) ix
   
   let rec moves'0 (_1:()) (return'  (ret:Vec'0.t_vec (isize, isize) (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec (isize, isize) (Global'0.t_global))-> {[%#span71] forall i : int . 0 <= i /\ i < 8
+    [ return' (result:Vec'0.t_vec (isize, isize) (Global'0.t_global))-> {[%#span61] forall i : int . 0 <= i /\ i < 8
        -> - 2 <= IntSize.to_int (let (a, _) = index_logic'0 result i in a)
       /\ IntSize.to_int (let (a, _) = index_logic'0 result i in a) <= 2
       /\ - 2 <= IntSize.to_int (let (_, a) = index_logic'0 result i in a)
       /\ IntSize.to_int (let (_, a) = index_logic'0 result i in a) <= 2}
-      {[%#span70] len'0 (shallow_model'0 result) = 8}
+      {[%#span60] len'0 (shallow_model'0 result) = 8}
       (! return' {result}) ]
     
   
@@ -2214,55 +2027,47 @@ module C06KnightsTour_Impl1_Set
   
   let%span span5 = "" 0 0 0 0
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
-  
-  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span15 = "../06_knights_tour.rs" 63 12 63 75
+  let%span span11 = "../06_knights_tour.rs" 63 12 63 75
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span12 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span17 = "../06_knights_tour.rs" 31 8 35 9
+  let%span span13 = "../06_knights_tour.rs" 31 8 35 9
   
-  let%span span18 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span14 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
+  let%span span15 = "../../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span17 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span22 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span18 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span24 = "" 0 0 0 0
+  let%span span20 = "" 0 0 0 0
   
-  let%span span25 = "" 0 0 0 0
+  let%span span21 = "" 0 0 0 0
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
+  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
+  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
+  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span30 = "" 0 0 0 0
+  let%span span26 = "" 0 0 0 0
   
   use prelude.prelude.UIntSize
   
@@ -2279,58 +2084,49 @@ module C06KnightsTour_Impl1_Set
   
   use Alloc_Vec_Vec_Type as Vec'0
   
+  predicate invariant'6 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span4] true
+  
+  predicate inv'6 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  
+  axiom inv'6 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'6 x = true
+  
   use prelude.prelude.UIntSize
   
   use prelude.prelude.Int
   
   constant max'0 : usize = [%#span5] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span6] inv'7 self)  -> ([%#span7] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span6] len'1 self >= 0
   
-  predicate inv'6 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'5 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'3_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span8] inv'6 self)
-   -> ([%#span10] inv'7 (shallow_model'3 self))
-  && ([%#span9] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'6 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span11] inv'7 (shallow_model'3 self)
-  
-  axiom inv'6 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'6 x = true
-  
-  predicate invariant'5 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span4] true
-  
-  predicate inv'5 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom shallow_model'3_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span7] inv'5 self)
+   -> ([%#span8] len'1 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
-  axiom inv'5 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'5 x = true
+  predicate invariant'5 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span9] inv'7 (shallow_model'3 self)
   
-  use seq.Seq
+  axiom inv'5 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'5 x = true
   
   function len'0 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span6] inv'5 self)
-   -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . [%#span6] len'0 self >= 0
   
   predicate inv'4 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span8] inv'4 self)
-   -> ([%#span10] inv'5 (shallow_model'1 self))
-  && ([%#span9] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span7] inv'4 self)
+   -> ([%#span8] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'4 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span11] inv'5 (shallow_model'1 self)
+    [%#span9] inv'6 (shallow_model'1 self)
   
   axiom inv'4 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'4 x = true
   
@@ -2343,12 +2139,11 @@ module C06KnightsTour_Impl1_Set
   
   axiom inv'3 : forall x : borrowed usize . inv'3 x = true
   
-  constant empty'1 : Seq'0.t_seq usize = [%#span12] ()
+  constant empty'1 : Seq'0.t_seq usize
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span14] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span13] len'1 (empty'1 : Seq'0.t_seq usize) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span10] len'1 (empty'1 : Seq'0.t_seq usize) = 0
   
   predicate invariant'2 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
     [%#span4] true
@@ -2357,12 +2152,11 @@ module C06KnightsTour_Impl1_Set
   
   axiom inv'2 : forall x : borrowed (Vec'0.t_vec usize (Global'0.t_global)) . inv'2 x = true
   
-  constant empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) = [%#span12] ()
+  constant empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span14] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span13] len'0 (empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom empty_len'0_spec : forall _1 : () . [%#span10] len'0 (empty'0 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   = 0
   
   predicate invariant'1 (self : usize) =
@@ -2391,25 +2185,23 @@ module C06KnightsTour_Impl1_Set
   use C06KnightsTour_Board_Type as Board'0
   
   predicate in_bounds'0 [#"../06_knights_tour.rs" 61 4 61 40] (self : Board'0.t_board) (p : Point'0.t_point) =
-    [%#span15] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
+    [%#span11] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (x : int) : Vec'0.t_vec usize (Global'0.t_global)
+  function index_logic'1 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (_2 : int) : Vec'0.t_vec usize (Global'0.t_global)
     
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (ix : int) : Vec'0.t_vec usize (Global'0.t_global)
     
    =
-    [%#span16] index_logic'1 (shallow_model'1 self) ix
+    [%#span12] index_logic'1 (shallow_model'1 self) ix
   
   predicate wf'0 [#"../06_knights_tour.rs" 30 4 30 23] (self : Board'0.t_board) =
-    [%#span17] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
+    [%#span13] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
     /\ len'0 (shallow_model'1 (C06KnightsTour_Board_Type.board_field self))
     = UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ (forall i : int . 0 <= i /\ i < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
@@ -2419,73 +2211,71 @@ module C06KnightsTour_Impl1_Set
   use prelude.prelude.Intrinsic
   
   predicate resolve'2 (self : borrowed (Board'0.t_board)) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   predicate resolve'1 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   predicate resolve'0 (self : borrowed usize) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
   use prelude.prelude.Slice
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'2 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   predicate resolve_elswhere'1 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq usize) (fin : Seq'0.t_seq usize) =
-    [%#span19] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
+    [%#span15] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'1 old'
      -> index_logic'2 old' i = index_logic'2 fin i
   
   predicate has_value'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) (out : usize) =
-    [%#span20] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span16] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'2 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq usize) =
-    [%#span21] UIntSize.to_int self < len'1 seq
+    [%#span17] UIntSize.to_int self < len'1 seq
   
   function shallow_model'2 (self : borrowed (Vec'0.t_vec usize (Global'0.t_global))) : Seq'0.t_seq usize =
-    [%#span22] shallow_model'3 ( * self)
+    [%#span18] shallow_model'3 ( * self)
   
-  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span25] inv'1 index}
-    {[@expl:precondition] [%#span24] inv'2 self}
-    {[@expl:precondition] [%#span23] in_bounds'2 index (shallow_model'2 self)}
+  let rec index_mut'1 (self:borrowed (Vec'0.t_vec usize (Global'0.t_global))) (index:usize) (return'  (ret:borrowed usize))= {[@expl:precondition] [%#span21] inv'1 index}
+    {[@expl:precondition] [%#span20] inv'2 self}
+    {[@expl:precondition] [%#span19] in_bounds'2 index (shallow_model'2 self)}
     any
-    [ return' (result:borrowed usize)-> {[%#span30] inv'3 result}
-      {[%#span29] len'1 (shallow_model'3 ( ^ self)) = len'1 (shallow_model'2 self)}
-      {[%#span28] resolve_elswhere'1 index (shallow_model'2 self) (shallow_model'3 ( ^ self))}
-      {[%#span27] has_value'1 index (shallow_model'3 ( ^ self)) ( ^ result)}
-      {[%#span26] has_value'1 index (shallow_model'2 self) ( * result)}
+    [ return' (result:borrowed usize)-> {[%#span26] inv'3 result}
+      {[%#span25] len'1 (shallow_model'3 ( ^ self)) = len'1 (shallow_model'2 self)}
+      {[%#span24] resolve_elswhere'1 index (shallow_model'2 self) (shallow_model'3 ( ^ self))}
+      {[%#span23] has_value'1 index (shallow_model'3 ( ^ self)) ( ^ result)}
+      {[%#span22] has_value'1 index (shallow_model'2 self) ( * result)}
       (! return' {result}) ]
     
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (fin : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
     
    =
-    [%#span19] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
+    [%#span15] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
      -> index_logic'1 old' i = index_logic'1 fin i
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (out : Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span20] index_logic'1 seq (UIntSize.to_int self) = out
+    [%#span16] index_logic'1 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'1 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span21] UIntSize.to_int self < len'0 seq
+    [%#span17] UIntSize.to_int self < len'0 seq
   
   function shallow_model'0 (self : borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
    =
-    [%#span22] shallow_model'1 ( * self)
+    [%#span18] shallow_model'1 ( * self)
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (Vec'0.t_vec usize (Global'0.t_global))))= {[@expl:precondition] [%#span25] inv'1 index}
-    {[@expl:precondition] [%#span24] inv'0 self}
-    {[@expl:precondition] [%#span23] in_bounds'1 index (shallow_model'0 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))) (index:usize) (return'  (ret:borrowed (Vec'0.t_vec usize (Global'0.t_global))))= {[@expl:precondition] [%#span21] inv'1 index}
+    {[@expl:precondition] [%#span20] inv'0 self}
+    {[@expl:precondition] [%#span19] in_bounds'1 index (shallow_model'0 self)}
     any
-    [ return' (result:borrowed (Vec'0.t_vec usize (Global'0.t_global)))-> {[%#span30] inv'2 result}
-      {[%#span29] len'0 (shallow_model'1 ( ^ self)) = len'0 (shallow_model'0 self)}
-      {[%#span28] resolve_elswhere'0 index (shallow_model'0 self) (shallow_model'1 ( ^ self))}
-      {[%#span27] has_value'0 index (shallow_model'1 ( ^ self)) ( ^ result)}
-      {[%#span26] has_value'0 index (shallow_model'0 self) ( * result)}
+    [ return' (result:borrowed (Vec'0.t_vec usize (Global'0.t_global)))-> {[%#span26] inv'2 result}
+      {[%#span25] len'0 (shallow_model'1 ( ^ self)) = len'0 (shallow_model'0 self)}
+      {[%#span24] resolve_elswhere'0 index (shallow_model'0 self) (shallow_model'1 ( ^ self))}
+      {[%#span23] has_value'0 index (shallow_model'1 ( ^ self)) ( ^ result)}
+      {[%#span22] has_value'0 index (shallow_model'0 self) ( * result)}
       (! return' {result}) ]
     
   
@@ -2592,118 +2382,99 @@ module C06KnightsTour_Min
   
   let%span span7 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
-  
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
-  
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
-  
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
-  
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span15 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
-  
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
-  
-  let%span span18 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span19 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span12 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span20 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span13 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span14 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
+  let%span span15 = "../../../../../creusot-contracts/src/std/slice.rs" 18 21 18 25
   
-  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
+  let%span span16 = "../../../../../creusot-contracts/src/std/slice.rs" 17 14 17 41
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 18 4 18 50
+  let%span span17 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/ops.rs" 43 8 43 31
+  let%span span18 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span26 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span19 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 76 19 76 23
+  let%span span20 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 74 14 74 41
+  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 75 4 75 82
+  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/slice.rs" 76 4 76 35
+  let%span span23 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/slice.rs" 384 12 384 66
+  let%span span24 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/slice.rs" 395 15 395 32
+  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/slice.rs" 396 15 396 32
+  let%span span26 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 398 31 398 33
+  let%span span27 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/slice.rs" 398 61 398 63
+  let%span span28 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/slice.rs" 397 14 397 42
+  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/slice.rs" 393 4 393 10
+  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/slice.rs" 390 14 390 45
+  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/slice.rs" 388 4 388 10
+  let%span span32 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span40 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span33 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span34 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span35 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span43 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span36 = "" 0 0 0 0
   
-  let%span span44 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span37 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span45 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span38 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/slice.rs" 377 20 377 61
+  let%span span39 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span40 = "../../../../../creusot-contracts/src/std/vec.rs" 205 20 205 34
   
-  let%span span48 = "" 0 0 0 0
+  let%span span41 = "../../../../../creusot-contracts/src/std/vec.rs" 199 20 199 24
   
-  let%span span49 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span50 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span43 = "" 0 0 0 0
   
-  let%span span51 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  use C06KnightsTour_Point_Type as Point'0
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/vec.rs" 205 20 205 34
+  use prelude.prelude.UIntSize
   
-  let%span span53 = "../../../../../creusot-contracts/src/std/vec.rs" 199 20 199 24
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span54 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  predicate invariant'8 (self : Seq'0.t_seq (usize, Point'0.t_point)) =
+    [%#span6] true
   
-  let%span span55 = "" 0 0 0 0
+  predicate inv'8 (_x : Seq'0.t_seq (usize, Point'0.t_point))
   
-  use C06KnightsTour_Point_Type as Point'0
-  
-  use prelude.prelude.UIntSize
+  axiom inv'8 : forall x : Seq'0.t_seq (usize, Point'0.t_point) . inv'8 x = true
   
   use prelude.prelude.Slice
   
-  predicate invariant'8 (self : slice (usize, Point'0.t_point)) =
+  predicate invariant'7 (self : slice (usize, Point'0.t_point)) =
     [%#span6] true
   
-  predicate inv'8 (_x : slice (usize, Point'0.t_point))
+  predicate inv'7 (_x : slice (usize, Point'0.t_point))
   
-  axiom inv'8 : forall x : slice (usize, Point'0.t_point) . inv'8 x = true
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
-  
-  predicate inv'3 (_x : Seq'0.t_seq (usize, Point'0.t_point))
+  axiom inv'7 : forall x : slice (usize, Point'0.t_point) . inv'7 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -2715,56 +2486,45 @@ module C06KnightsTour_Min
   
   constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq (usize, Point'0.t_point)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span8] inv'3 self)
-   -> ([%#span9] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point) . [%#span8] len'0 self >= 0
   
-  predicate inv'7 (_x : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))
+  predicate inv'6 (_x : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) : Seq'0.t_seq (usize, Point'0.t_point)
     
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global) . ([%#span10] inv'7 self)
-   -> ([%#span12] inv'3 (shallow_model'2 self))
-  && ([%#span11] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global) . ([%#span9] inv'6 self)
+   -> ([%#span10] len'0 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'7 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) =
-    [%#span13] inv'3 (shallow_model'2 self)
+  predicate invariant'6 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) =
+    [%#span11] inv'8 (shallow_model'2 self)
   
-  axiom inv'7 : forall x : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global) . inv'7 x = true
+  axiom inv'6 : forall x : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global) . inv'6 x = true
   
-  predicate invariant'6 (self : slice (usize, Point'0.t_point)) =
+  predicate invariant'5 (self : slice (usize, Point'0.t_point)) =
     [%#span6] true
   
-  predicate inv'6 (_x : slice (usize, Point'0.t_point))
+  predicate inv'5 (_x : slice (usize, Point'0.t_point))
   
-  axiom inv'6 : forall x : slice (usize, Point'0.t_point) . inv'6 x = true
+  axiom inv'5 : forall x : slice (usize, Point'0.t_point) . inv'5 x = true
   
-  predicate invariant'5 (self : (usize, Point'0.t_point)) =
+  predicate invariant'4 (self : (usize, Point'0.t_point)) =
     [%#span6] true
   
-  predicate inv'5 (_x : (usize, Point'0.t_point))
+  predicate inv'4 (_x : (usize, Point'0.t_point))
   
-  axiom inv'5 : forall x : (usize, Point'0.t_point) . inv'5 x = true
+  axiom inv'4 : forall x : (usize, Point'0.t_point) . inv'4 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'4 (self : Option'0.t_option (usize, Point'0.t_point)) =
+  predicate invariant'3 (self : Option'0.t_option (usize, Point'0.t_point)) =
     [%#span6] true
   
-  predicate inv'4 (_x : Option'0.t_option (usize, Point'0.t_point))
-  
-  axiom inv'4 : forall x : Option'0.t_option (usize, Point'0.t_point) . inv'4 x = true
+  predicate inv'3 (_x : Option'0.t_option (usize, Point'0.t_point))
   
-  predicate invariant'3 (self : Seq'0.t_seq (usize, Point'0.t_point)) =
-    [%#span6] true
-  
-  axiom inv'3 : forall x : Seq'0.t_seq (usize, Point'0.t_point) . inv'3 x = true
+  axiom inv'3 : forall x : Option'0.t_option (usize, Point'0.t_point) . inv'3 x = true
   
   predicate invariant'2 (self : Seq'0.t_seq (usize, Point'0.t_point)) =
     [%#span6] true
@@ -2780,88 +2540,74 @@ module C06KnightsTour_Min
   
   axiom inv'1 : forall x : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global) . inv'1 x = true
   
-  constant empty'1 : Seq'0.t_seq (usize, Point'0.t_point) = [%#span14] ()
+  constant empty'1 : Seq'0.t_seq (usize, Point'0.t_point)
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span16] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span15] len'0 (empty'1 : Seq'0.t_seq (usize, Point'0.t_point)) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span12] len'0 (empty'1 : Seq'0.t_seq (usize, Point'0.t_point)) = 0
   
   use prelude.prelude.Borrow
   
   use Core_Slice_Iter_Iter_Type as Iter'0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq (usize, Point'0.t_point)) (x : int) : (usize, Point'0.t_point)
-  
-  use seq.Seq
+  function index_logic'2 (self : Seq'0.t_seq (usize, Point'0.t_point)) (_2 : int) : (usize, Point'0.t_point)
   
   function len'1 (self : Seq'0.t_seq (usize, Point'0.t_point)) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span8] inv'2 self)
-   -> ([%#span9] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point) . [%#span8] len'1 self >= 0
   
   function concat'0 (self : Seq'0.t_seq (usize, Point'0.t_point)) (other : Seq'0.t_seq (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point)
     
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point), other : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span17] inv'2 self)
-   -> ([%#span18] inv'2 other)
-   -> ([%#span21] inv'2 (concat'0 self other))
-  && ([%#span20] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point), other : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span14] forall i : int . 0
+  <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'2 (concat'0 self other) i
   = (if i < len'1 self then index_logic'2 self i else index_logic'2 other (i - len'1 self)))
-  && ([%#span19] len'1 (concat'0 self other) = len'1 self + len'1 other)
-  
-  use seq.Seq
+  && ([%#span13] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
-  function index_logic'1 (self : Seq'0.t_seq (usize, Point'0.t_point)) (x : int) : (usize, Point'0.t_point)
+  function index_logic'1 (self : Seq'0.t_seq (usize, Point'0.t_point)) (_2 : int) : (usize, Point'0.t_point)
   
   function shallow_model'5 (self : slice (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point)
   
-  axiom shallow_model'5_spec : forall self : slice (usize, Point'0.t_point) . ([%#span22] inv'8 self)
-   -> ([%#span24] inv'3 (shallow_model'5 self))
-  && ([%#span23] len'0 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'5_spec : forall self : slice (usize, Point'0.t_point) . ([%#span15] inv'7 self)
+   -> ([%#span16] len'0 (shallow_model'5 self) <= UIntSize.to_int (max'0 : usize))
   
   function index_logic'3 [@inline:trivial] (self : slice (usize, Point'0.t_point)) (ix : int) : (usize, Point'0.t_point)
    =
-    [%#span25] index_logic'1 (shallow_model'5 self) ix
+    [%#span17] index_logic'1 (shallow_model'5 self) ix
   
   function shallow_model'3 (self : slice (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point) =
-    [%#span26] shallow_model'5 self
+    [%#span18] shallow_model'5 self
   
   function to_ref_seq'0 (self : slice (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point)
   
-  axiom to_ref_seq'0_spec : forall self : slice (usize, Point'0.t_point) . ([%#span27] inv'6 self)
-   -> ([%#span30] inv'2 (to_ref_seq'0 self))
-  && ([%#span29] forall i : int . 0 <= i /\ i < len'1 (to_ref_seq'0 self)
+  axiom to_ref_seq'0_spec : forall self : slice (usize, Point'0.t_point) . ([%#span19] inv'5 self)
+   -> ([%#span21] forall i : int . 0 <= i /\ i < len'1 (to_ref_seq'0 self)
    -> index_logic'2 (to_ref_seq'0 self) i = index_logic'3 self i)
-  && ([%#span28] len'1 (to_ref_seq'0 self) = len'0 (shallow_model'3 self))
+  && ([%#span20] len'1 (to_ref_seq'0 self) = len'0 (shallow_model'3 self))
   
   function shallow_model'1 (self : Iter'0.t_iter (usize, Point'0.t_point)) : slice (usize, Point'0.t_point)
   
   predicate produces'0 (self : Iter'0.t_iter (usize, Point'0.t_point)) (visited : Seq'0.t_seq (usize, Point'0.t_point)) (tl : Iter'0.t_iter (usize, Point'0.t_point))
     
    =
-    [%#span31] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
+    [%#span22] to_ref_seq'0 (shallow_model'1 self) = concat'0 visited (to_ref_seq'0 (shallow_model'1 tl))
   
   function produces_trans'0 (a : Iter'0.t_iter (usize, Point'0.t_point)) (ab : Seq'0.t_seq (usize, Point'0.t_point)) (b : Iter'0.t_iter (usize, Point'0.t_point)) (bc : Seq'0.t_seq (usize, Point'0.t_point)) (c : Iter'0.t_iter (usize, Point'0.t_point)) : ()
     
    =
-    [%#span37] ()
+    [%#span26] ()
   
-  axiom produces_trans'0_spec : forall a : Iter'0.t_iter (usize, Point'0.t_point), ab : Seq'0.t_seq (usize, Point'0.t_point), b : Iter'0.t_iter (usize, Point'0.t_point), bc : Seq'0.t_seq (usize, Point'0.t_point), c : Iter'0.t_iter (usize, Point'0.t_point) . ([%#span32] produces'0 a ab b)
-   -> ([%#span33] produces'0 b bc c)
-   -> ([%#span34] inv'2 ab)  -> ([%#span35] inv'2 bc)  -> ([%#span36] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Iter'0.t_iter (usize, Point'0.t_point), ab : Seq'0.t_seq (usize, Point'0.t_point), b : Iter'0.t_iter (usize, Point'0.t_point), bc : Seq'0.t_seq (usize, Point'0.t_point), c : Iter'0.t_iter (usize, Point'0.t_point) . ([%#span23] produces'0 a ab b)
+   -> ([%#span24] produces'0 b bc c)  -> ([%#span25] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq (usize, Point'0.t_point) = [%#span14] ()
+  constant empty'0 : Seq'0.t_seq (usize, Point'0.t_point)
   
   function produces_refl'0 (self : Iter'0.t_iter (usize, Point'0.t_point)) : () =
-    [%#span39] ()
+    [%#span28] ()
   
-  axiom produces_refl'0_spec : forall self : Iter'0.t_iter (usize, Point'0.t_point) . [%#span38] produces'0 self (empty'0 : Seq'0.t_seq (usize, Point'0.t_point)) self
+  axiom produces_refl'0_spec : forall self : Iter'0.t_iter (usize, Point'0.t_point) . [%#span27] produces'0 self (empty'0 : Seq'0.t_seq (usize, Point'0.t_point)) self
   
   predicate invariant'0 (self : Iter'0.t_iter (usize, Point'0.t_point)) =
     [%#span6] true
@@ -2870,36 +2616,32 @@ module C06KnightsTour_Min
   
   axiom inv'0 : forall x : Iter'0.t_iter (usize, Point'0.t_point) . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span16] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span15] len'1 (empty'0 : Seq'0.t_seq (usize, Point'0.t_point)) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span12] len'1 (empty'0 : Seq'0.t_seq (usize, Point'0.t_point)) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
   use prelude.prelude.Intrinsic
   
-  use seq.Seq
-  
   function singleton'0 (v : (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point)
   
-  axiom singleton'0_spec : forall v : (usize, Point'0.t_point) . ([%#span40] inv'5 v)
-   -> ([%#span43] inv'2 (singleton'0 v))
-  && ([%#span42] index_logic'2 (singleton'0 v) 0 = v) && ([%#span41] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : (usize, Point'0.t_point) . ([%#span29] inv'4 v)
+   -> ([%#span31] index_logic'2 (singleton'0 v) 0 = v) && ([%#span30] len'1 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Iter'0.t_iter (usize, Point'0.t_point))) =
-    [%#span44]  ^ self =  * self
+    [%#span32]  ^ self =  * self
   
   function shallow_model'4 (self : borrowed (Iter'0.t_iter (usize, Point'0.t_point))) : slice (usize, Point'0.t_point) =
-    [%#span45] shallow_model'1 ( * self)
+    [%#span33] shallow_model'1 ( * self)
   
   predicate completed'0 (self : borrowed (Iter'0.t_iter (usize, Point'0.t_point))) =
-    [%#span46] resolve'0 self
+    [%#span34] resolve'0 self
     /\ shallow_model'5 (shallow_model'4 self) = (empty'1 : Seq'0.t_seq (usize, Point'0.t_point))
   
   let rec next'0 (self:borrowed (Iter'0.t_iter (usize, Point'0.t_point))) (return'  (ret:Option'0.t_option (usize, Point'0.t_point)))= any
-    [ return' (result:Option'0.t_option (usize, Point'0.t_point))-> {[%#span48] inv'4 result}
-      {[%#span47] match result with
+    [ return' (result:Option'0.t_option (usize, Point'0.t_point))-> {[%#span36] inv'3 result}
+      {[%#span35] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -2909,12 +2651,12 @@ module C06KnightsTour_Min
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) (ix : int) : (usize, Point'0.t_point)
     
    =
-    [%#span49] index_logic'1 (shallow_model'2 self) ix
+    [%#span37] index_logic'1 (shallow_model'2 self) ix
   
   function shallow_model'0 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) : Seq'0.t_seq (usize, Point'0.t_point)
     
    =
-    [%#span26] shallow_model'2 self
+    [%#span18] shallow_model'2 self
   
   function deref'1 (self : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, Point'0.t_point))) : Seq'0.t_seq (usize, Point'0.t_point)
     
@@ -2931,27 +2673,27 @@ module C06KnightsTour_Min
   function new'1 (x : Seq'0.t_seq (usize, Point'0.t_point)) : Snapshot'0.t_snapshot (Seq'0.t_seq (usize, Point'0.t_point))
     
   
-  axiom new'1_spec : forall x : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span50] inv'2 x)
-   -> ([%#span51] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span38] inv'2 x)
+   -> ([%#span39] deref'1 (new'1 x) = x)
   
   function new'0 (x : Iter'0.t_iter (usize, Point'0.t_point)) : Snapshot'0.t_snapshot (Iter'0.t_iter (usize, Point'0.t_point))
     
   
-  axiom new'0_spec : forall x : Iter'0.t_iter (usize, Point'0.t_point) . ([%#span50] inv'0 x)
-   -> ([%#span51] deref'0 (new'0 x) = x)
+  axiom new'0_spec : forall x : Iter'0.t_iter (usize, Point'0.t_point) . ([%#span38] inv'0 x)
+   -> ([%#span39] deref'0 (new'0 x) = x)
   
   predicate into_iter_post'0 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) (res : Iter'0.t_iter (usize, Point'0.t_point))
     
    =
-    [%#span52] shallow_model'0 self = shallow_model'3 (shallow_model'1 res)
+    [%#span40] shallow_model'0 self = shallow_model'3 (shallow_model'1 res)
   
   predicate into_iter_pre'0 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) =
-    [%#span53] true
+    [%#span41] true
   
-  let rec into_iter'0 (self:Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) (return'  (ret:Iter'0.t_iter (usize, Point'0.t_point)))= {[@expl:precondition] [%#span55] inv'1 self}
-    {[@expl:precondition] [%#span54] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) (return'  (ret:Iter'0.t_iter (usize, Point'0.t_point)))= {[@expl:precondition] [%#span43] inv'1 self}
+    {[@expl:precondition] [%#span42] into_iter_pre'0 self}
     any
-    [ return' (result:Iter'0.t_iter (usize, Point'0.t_point))-> {[%#span54] into_iter_post'0 self result}
+    [ return' (result:Iter'0.t_iter (usize, Point'0.t_point))-> {[%#span42] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
@@ -3125,359 +2867,320 @@ module C06KnightsTour_KnightsTour
   
   let%span s06_knights_tour19 = "../06_knights_tour.rs" 135 11 135 19
   
-  let%span span20 = "" 0 0 0 0
+  let%span span20 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span21 = "" 0 0 0 0
   
-  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span25 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span27 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span28 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span29 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
   
-  let%span span30 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
   
-  let%span span31 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
   
-  let%span span32 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span32 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
   
-  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
   
-  let%span span34 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span34 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
   
-  let%span span35 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span35 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/vec.rs" 254 12 254 41
+  let%span span36 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/vec.rs" 265 15 265 32
+  let%span span37 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
   
-  let%span span38 = "../../../../../creusot-contracts/src/std/vec.rs" 266 15 266 32
+  let%span span38 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/vec.rs" 268 22 268 23
+  let%span span39 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/vec.rs" 268 31 268 33
+  let%span span40 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span41 = "../../../../../creusot-contracts/src/std/vec.rs" 268 43 268 44
+  let%span span41 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span42 = "../../../../../creusot-contracts/src/std/vec.rs" 268 52 268 54
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/vec.rs" 268 64 268 65
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/vec.rs" 267 14 267 42
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/vec.rs" 263 4 263 10
+  let%span span45 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/vec.rs" 261 21 261 25
+  let%span span46 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/vec.rs" 260 14 260 45
+  let%span span47 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/vec.rs" 258 4 258 10
+  let%span span48 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span49 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span50 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
   
-  let%span span51 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span51 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span52 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span53 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span53 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
   
-  let%span span54 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span54 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span55 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span55 = "../06_knights_tour.rs" 109 0 110 62
   
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span56 = "../../../../../creusot-contracts/src/std/vec.rs" 239 8 239 85
   
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span57 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span58 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span58 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span59 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span60 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span60 = "../../../../../creusot-contracts/src/logic/seq2.rs" 98 8 98 39
   
-  let%span span61 = "../../../../../creusot-contracts/src/resolve.rs" 46 8 46 12
+  let%span span61 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span62 = "../../../../../creusot-contracts/src/resolve.rs" 17 8 17 60
+  let%span span62 = "" 0 0 0 0
   
-  let%span span63 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span63 = "" 0 0 0 0
   
-  let%span span64 = "../../../../../creusot-contracts/src/std/vec.rs" 51 8 51 85
+  let%span span64 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
   
-  let%span span65 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span65 = "../06_knights_tour.rs" 63 12 63 75
   
-  let%span span66 = "../06_knights_tour.rs" 109 0 110 62
+  let%span span66 = "../06_knights_tour.rs" 31 8 35 9
   
-  let%span span67 = "../../../../../creusot-contracts/src/std/vec.rs" 239 8 239 85
+  let%span span67 = "../06_knights_tour.rs" 68 15 68 24
   
-  let%span span68 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span68 = "../06_knights_tour.rs" 69 15 69 32
   
-  let%span span69 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span69 = "../06_knights_tour.rs" 50 15 50 24
   
-  let%span span70 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span70 = "../06_knights_tour.rs" 51 4 51 44
   
-  let%span span71 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span71 = "../06_knights_tour.rs" 12 15 12 52
   
-  let%span span72 = "../../../../../creusot-contracts/src/logic/seq2.rs" 99 8 99 39
+  let%span span72 = "../06_knights_tour.rs" 13 15 13 52
   
-  let%span span73 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span73 = "../06_knights_tour.rs" 14 15 14 46
   
-  let%span span74 = "" 0 0 0 0
+  let%span span74 = "../06_knights_tour.rs" 15 15 15 46
   
-  let%span span75 = "" 0 0 0 0
+  let%span span75 = "../06_knights_tour.rs" 16 14 16 41
   
-  let%span span76 = "../../../../../creusot-contracts/src/std/vec.rs" 82 26 82 51
+  let%span span76 = "../06_knights_tour.rs" 17 14 17 41
   
-  let%span span77 = "../06_knights_tour.rs" 63 12 63 75
+  let%span span77 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span78 = "../06_knights_tour.rs" 31 8 35 9
+  let%span span78 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
   
-  let%span span79 = "../06_knights_tour.rs" 68 15 68 24
+  let%span span79 = "" 0 0 0 0
   
-  let%span span80 = "../06_knights_tour.rs" 69 15 69 32
+  let%span span80 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
-  let%span span81 = "../06_knights_tour.rs" 50 15 50 24
+  let%span span81 = "" 0 0 0 0
   
-  let%span span82 = "../06_knights_tour.rs" 51 4 51 44
+  let%span span82 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span83 = "../06_knights_tour.rs" 12 15 12 52
+  let%span span83 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span84 = "../06_knights_tour.rs" 13 15 13 52
+  let%span span84 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
   
-  let%span span85 = "../06_knights_tour.rs" 14 15 14 46
+  let%span span85 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
   
-  let%span span86 = "../06_knights_tour.rs" 15 15 15 46
+  let%span span86 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span87 = "../06_knights_tour.rs" 16 14 16 41
+  let%span span87 = "" 0 0 0 0
   
-  let%span span88 = "../06_knights_tour.rs" 17 14 17 41
+  let%span span88 = "" 0 0 0 0
   
-  let%span span89 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span89 = "../06_knights_tour.rs" 93 10 93 28
   
-  let%span span90 = "../../../../../creusot-contracts/src/std/vec.rs" 247 20 247 57
+  let%span span90 = "../06_knights_tour.rs" 94 0 94 130
   
-  let%span span91 = "" 0 0 0 0
+  let%span span91 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
   
-  let%span span92 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span92 = "" 0 0 0 0
   
-  let%span span93 = "" 0 0 0 0
+  let%span span93 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span94 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span94 = "" 0 0 0 0
   
-  let%span span95 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span95 = "" 0 0 0 0
   
-  let%span span96 = "../../../../../creusot-contracts/src/std/vec.rs" 191 20 191 33
+  let%span span96 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span97 = "../../../../../creusot-contracts/src/std/vec.rs" 185 20 185 24
+  let%span span97 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span98 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span98 = "" 0 0 0 0
   
   let%span span99 = "" 0 0 0 0
   
-  let%span span100 = "" 0 0 0 0
+  let%span span100 = "../06_knights_tour.rs" 129 11 129 22
   
-  let%span span101 = "../06_knights_tour.rs" 93 10 93 28
+  let%span span101 = "../06_knights_tour.rs" 130 10 130 30
   
-  let%span span102 = "../06_knights_tour.rs" 94 0 94 130
+  let%span span102 = "../06_knights_tour.rs" 128 0 128 8
   
-  let%span span103 = "../../../../../creusot-contracts/src/std/vec.rs" 69 26 69 44
+  let%span span103 = "../06_knights_tour.rs" 83 15 83 24
   
-  let%span span104 = "" 0 0 0 0
+  let%span span104 = "../06_knights_tour.rs" 84 15 84 32
   
-  let%span span105 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span105 = "../06_knights_tour.rs" 85 14 85 26
   
-  let%span span106 = "" 0 0 0 0
+  let%span span106 = "../06_knights_tour.rs" 86 14 86 42
   
-  let%span span107 = "" 0 0 0 0
+  let%span span107 = "../06_knights_tour.rs" 37 15 37 28
   
-  let%span span108 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
+  let%span span108 = "../06_knights_tour.rs" 38 14 38 33
   
-  let%span span109 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
+  let%span span109 = "../06_knights_tour.rs" 39 14 39 25
   
-  let%span span110 = "" 0 0 0 0
-  
-  let%span span111 = "" 0 0 0 0
-  
-  let%span span112 = "../06_knights_tour.rs" 129 11 129 22
+  use Alloc_Alloc_Global_Type as Global'0
   
-  let%span span113 = "../06_knights_tour.rs" 130 10 130 30
+  use prelude.prelude.UIntSize
   
-  let%span span114 = "../06_knights_tour.rs" 128 0 128 8
+  use Alloc_Vec_Vec_Type as Vec'0
   
-  let%span span115 = "../06_knights_tour.rs" 83 15 83 24
+  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  let%span span116 = "../06_knights_tour.rs" 84 15 84 32
+  predicate invariant'18 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
+    [%#span20] true
   
-  let%span span117 = "../06_knights_tour.rs" 85 14 85 26
+  predicate inv'18 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   
-  let%span span118 = "../06_knights_tour.rs" 86 14 86 42
+  axiom inv'18 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'18 x = true
   
-  let%span span119 = "../06_knights_tour.rs" 37 15 37 28
+  use C06KnightsTour_Point_Type as Point'0
   
-  let%span span120 = "../06_knights_tour.rs" 38 14 38 33
+  predicate invariant'17 (self : Seq'0.t_seq (usize, Point'0.t_point)) =
+    [%#span20] true
   
-  let%span span121 = "../06_knights_tour.rs" 39 14 39 25
+  predicate inv'17 (_x : Seq'0.t_seq (usize, Point'0.t_point))
   
-  use prelude.prelude.UIntSize
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
+  axiom inv'17 : forall x : Seq'0.t_seq (usize, Point'0.t_point) . inv'17 x = true
   
   predicate inv'3 (_x : Seq'0.t_seq usize)
   
-  use Alloc_Alloc_Global_Type as Global'0
-  
-  use Alloc_Vec_Vec_Type as Vec'0
-  
   use prelude.prelude.UIntSize
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span20] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span21] (18446744073709551615 : usize)
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span21] inv'3 self)  -> ([%#span22] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span22] len'1 self >= 0
   
-  predicate inv'18 (_x : Vec'0.t_vec usize (Global'0.t_global))
+  predicate inv'16 (_x : Vec'0.t_vec usize (Global'0.t_global))
   
   function shallow_model'2 (self : Vec'0.t_vec usize (Global'0.t_global)) : Seq'0.t_seq usize
   
-  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span23] inv'18 self)
-   -> ([%#span25] inv'3 (shallow_model'2 self))
-  && ([%#span24] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'18 (self : Vec'0.t_vec usize (Global'0.t_global)) =
-    [%#span26] inv'3 (shallow_model'2 self)
-  
-  axiom inv'18 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'18 x = true
-  
-  predicate invariant'17 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) =
-    [%#span27] true
+  axiom shallow_model'2_spec : forall self : Vec'0.t_vec usize (Global'0.t_global) . ([%#span23] inv'16 self)
+   -> ([%#span24] len'1 (shallow_model'2 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate inv'17 (_x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  predicate invariant'16 (self : Vec'0.t_vec usize (Global'0.t_global)) =
+    [%#span25] inv'3 (shallow_model'2 self)
   
-  axiom inv'17 : forall x : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . inv'17 x = true
-  
-  use seq.Seq
+  axiom inv'16 : forall x : Vec'0.t_vec usize (Global'0.t_global) . inv'16 x = true
   
   function len'2 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . ([%#span21] inv'17 self)
-   -> ([%#span22] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) . [%#span22] len'2 self >= 0
   
-  predicate inv'16 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
+  predicate inv'15 (_x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
     
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span23] inv'16 self)
-   -> ([%#span25] inv'17 (shallow_model'1 self))
-  && ([%#span24] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
-  
-  predicate invariant'16 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
-    [%#span26] inv'17 (shallow_model'1 self)
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . ([%#span23] inv'15 self)
+   -> ([%#span24] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
-  axiom inv'16 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'16 x = true
+  predicate invariant'15 (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) =
+    [%#span25] inv'18 (shallow_model'1 self)
   
-  use C06KnightsTour_Point_Type as Point'0
+  axiom inv'15 : forall x : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global) . inv'15 x = true
   
-  predicate invariant'15 (self : (usize, Point'0.t_point)) =
-    [%#span27] true
+  predicate invariant'14 (self : (usize, Point'0.t_point)) =
+    [%#span20] true
   
-  predicate inv'15 (_x : (usize, Point'0.t_point))
+  predicate inv'14 (_x : (usize, Point'0.t_point))
   
-  axiom inv'15 : forall x : (usize, Point'0.t_point) . inv'15 x = true
+  axiom inv'14 : forall x : (usize, Point'0.t_point) . inv'14 x = true
   
   use prelude.prelude.Borrow
   
-  predicate invariant'14 (self : borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))) =
-    [%#span27] true
+  predicate invariant'13 (self : borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))) =
+    [%#span20] true
   
-  predicate inv'14 (_x : borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)))
+  predicate inv'13 (_x : borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)))
   
-  axiom inv'14 : forall x : borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) . inv'14 x = true
+  axiom inv'13 : forall x : borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) . inv'13 x = true
   
   use prelude.prelude.IntSize
   
-  predicate invariant'13 (self : (isize, isize)) =
-    [%#span27] true
+  predicate invariant'12 (self : (isize, isize)) =
+    [%#span20] true
   
-  predicate inv'13 (_x : (isize, isize))
+  predicate inv'12 (_x : (isize, isize))
   
-  axiom inv'13 : forall x : (isize, isize) . inv'13 x = true
+  axiom inv'12 : forall x : (isize, isize) . inv'12 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'12 (self : Option'0.t_option (isize, isize)) =
-    [%#span27] true
+  predicate invariant'11 (self : Option'0.t_option (isize, isize)) =
+    [%#span20] true
   
-  predicate inv'12 (_x : Option'0.t_option (isize, isize))
+  predicate inv'11 (_x : Option'0.t_option (isize, isize))
   
-  axiom inv'12 : forall x : Option'0.t_option (isize, isize) . inv'12 x = true
+  axiom inv'11 : forall x : Option'0.t_option (isize, isize) . inv'11 x = true
   
   use Alloc_Vec_IntoIter_IntoIter_Type as IntoIter'0
   
-  predicate invariant'11 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) =
-    [%#span27] true
-  
-  predicate inv'11 (_x : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)))
+  predicate invariant'10 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) =
+    [%#span20] true
   
-  axiom inv'11 : forall x : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) . inv'11 x = true
+  predicate inv'10 (_x : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)))
   
-  predicate invariant'10 (self : Seq'0.t_seq (usize, Point'0.t_point)) =
-    [%#span27] true
-  
-  predicate inv'10 (_x : Seq'0.t_seq (usize, Point'0.t_point))
-  
-  axiom inv'10 : forall x : Seq'0.t_seq (usize, Point'0.t_point) . inv'10 x = true
+  axiom inv'10 : forall x : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) . inv'10 x = true
   
   predicate invariant'9 (self : Seq'0.t_seq (isize, isize)) =
-    [%#span27] true
+    [%#span20] true
   
   predicate inv'9 (_x : Seq'0.t_seq (isize, isize))
   
   axiom inv'9 : forall x : Seq'0.t_seq (isize, isize) . inv'9 x = true
   
-  use seq.Seq
-  
   function len'3 (self : Seq'0.t_seq (isize, isize)) : int
   
-  axiom len'3_spec : forall self : Seq'0.t_seq (isize, isize) . ([%#span21] inv'9 self)  -> ([%#span22] len'3 self >= 0)
+  axiom len'3_spec : forall self : Seq'0.t_seq (isize, isize) . [%#span22] len'3 self >= 0
   
   predicate inv'8 (_x : Vec'0.t_vec (isize, isize) (Global'0.t_global))
   
   function shallow_model'3 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) : Seq'0.t_seq (isize, isize)
   
   axiom shallow_model'3_spec : forall self : Vec'0.t_vec (isize, isize) (Global'0.t_global) . ([%#span23] inv'8 self)
-   -> ([%#span25] inv'9 (shallow_model'3 self))
-  && ([%#span24] len'3 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
+   -> ([%#span24] len'3 (shallow_model'3 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'8 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) =
-    [%#span26] inv'9 (shallow_model'3 self)
+    [%#span25] inv'9 (shallow_model'3 self)
   
   axiom inv'8 : forall x : Vec'0.t_vec (isize, isize) (Global'0.t_global) . inv'8 x = true
   
-  use seq.Seq
-  
   function len'0 (self : Seq'0.t_seq (usize, Point'0.t_point)) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span21] inv'10 self)
-   -> ([%#span22] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point) . [%#span22] len'0 self >= 0
   
   predicate inv'7 (_x : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))
   
@@ -3485,23 +3188,22 @@ module C06KnightsTour_KnightsTour
     
   
   axiom shallow_model'0_spec : forall self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global) . ([%#span23] inv'7 self)
-   -> ([%#span25] inv'10 (shallow_model'0 self))
-  && ([%#span24] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+   -> ([%#span24] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'7 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) =
-    [%#span26] inv'10 (shallow_model'0 self)
+    [%#span25] inv'17 (shallow_model'0 self)
   
   axiom inv'7 : forall x : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global) . inv'7 x = true
   
   predicate invariant'6 (self : usize) =
-    [%#span27] true
+    [%#span20] true
   
   predicate inv'6 (_x : usize)
   
   axiom inv'6 : forall x : usize . inv'6 x = true
   
   predicate invariant'5 (self : Option'0.t_option usize) =
-    [%#span27] true
+    [%#span20] true
   
   predicate inv'5 (_x : Option'0.t_option usize)
   
@@ -3510,55 +3212,48 @@ module C06KnightsTour_KnightsTour
   use Core_Ops_Range_Range_Type as Range'0
   
   predicate invariant'4 (self : borrowed (Range'0.t_range usize)) =
-    [%#span27] true
+    [%#span20] true
   
   predicate inv'4 (_x : borrowed (Range'0.t_range usize))
   
   axiom inv'4 : forall x : borrowed (Range'0.t_range usize) . inv'4 x = true
   
-  constant empty'3 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)) = [%#span28] ()
+  constant empty'3 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))
   
-  function empty_len'3 (_1 : ()) : () =
-    [%#span30] ()
+  function empty_len'3 (_1 : ()) : ()
   
-  axiom empty_len'3_spec : forall _1 : () . [%#span29] len'2 (empty'3 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
+  axiom empty_len'3_spec : forall _1 : () . [%#span26] len'2 (empty'3 : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global)))
   = 0
   
   predicate invariant'3 (self : Seq'0.t_seq usize) =
-    [%#span27] true
+    [%#span20] true
   
   axiom inv'3 : forall x : Seq'0.t_seq usize . inv'3 x = true
   
   predicate invariant'2 (self : ()) =
-    [%#span27] true
+    [%#span20] true
   
   predicate inv'2 (_x : ())
   
   axiom inv'2 : forall x : () . inv'2 x = true
   
-  constant empty'2 : Seq'0.t_seq (usize, Point'0.t_point) = [%#span28] ()
+  constant empty'2 : Seq'0.t_seq (usize, Point'0.t_point)
   
-  function empty_len'2 (_1 : ()) : () =
-    [%#span30] ()
+  function empty_len'2 (_1 : ()) : ()
   
-  axiom empty_len'2_spec : forall _1 : () . [%#span29] len'0 (empty'2 : Seq'0.t_seq (usize, Point'0.t_point)) = 0
+  axiom empty_len'2_spec : forall _1 : () . [%#span26] len'0 (empty'2 : Seq'0.t_seq (usize, Point'0.t_point)) = 0
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'5 (self : Seq'0.t_seq (isize, isize)) (x : int) : (isize, isize)
+  function index_logic'5 (self : Seq'0.t_seq (isize, isize)) (_2 : int) : (isize, isize)
   
   function concat'1 (self : Seq'0.t_seq (isize, isize)) (other : Seq'0.t_seq (isize, isize)) : Seq'0.t_seq (isize, isize)
     
   
-  axiom concat'1_spec : forall self : Seq'0.t_seq (isize, isize), other : Seq'0.t_seq (isize, isize) . ([%#span31] inv'9 self)
-   -> ([%#span32] inv'9 other)
-   -> ([%#span35] inv'9 (concat'1 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'3 (concat'1 self other)
+  axiom concat'1_spec : forall self : Seq'0.t_seq (isize, isize), other : Seq'0.t_seq (isize, isize) . ([%#span28] forall i : int . 0
+  <= i
+  /\ i < len'3 (concat'1 self other)
    -> index_logic'5 (concat'1 self other) i
   = (if i < len'3 self then index_logic'5 self i else index_logic'5 other (i - len'3 self)))
-  && ([%#span33] len'3 (concat'1 self other) = len'3 self + len'3 other)
+  && ([%#span27] len'3 (concat'1 self other) = len'3 self + len'3 other)
   
   predicate inv'1 (_x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
   
@@ -3568,65 +3263,56 @@ module C06KnightsTour_KnightsTour
   predicate produces'1 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) (visited : Seq'0.t_seq (isize, isize)) (rhs : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
     
    =
-    [%#span36] shallow_model'4 self = concat'1 visited (shallow_model'4 rhs)
+    [%#span29] shallow_model'4 self = concat'1 visited (shallow_model'4 rhs)
   
   function produces_trans'1 (a : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) (ab : Seq'0.t_seq (isize, isize)) (b : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) (bc : Seq'0.t_seq (isize, isize)) (c : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) : ()
     
    =
-    [%#span45] ()
+    [%#span36] ()
   
-  axiom produces_trans'1_spec : forall a : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), ab : Seq'0.t_seq (isize, isize), b : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), bc : Seq'0.t_seq (isize, isize), c : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span37] produces'1 a ab b)
-   -> ([%#span38] produces'1 b bc c)
-   -> ([%#span39] inv'1 a)
-   -> ([%#span40] inv'9 ab)
-   -> ([%#span41] inv'1 b)
-   -> ([%#span42] inv'9 bc)  -> ([%#span43] inv'1 c)  -> ([%#span44] produces'1 a (concat'1 ab bc) c)
+  axiom produces_trans'1_spec : forall a : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), ab : Seq'0.t_seq (isize, isize), b : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global), bc : Seq'0.t_seq (isize, isize), c : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span30] produces'1 a ab b)
+   -> ([%#span31] produces'1 b bc c)
+   -> ([%#span32] inv'1 a)
+   -> ([%#span33] inv'1 b)  -> ([%#span34] inv'1 c)  -> ([%#span35] produces'1 a (concat'1 ab bc) c)
   
-  constant empty'1 : Seq'0.t_seq (isize, isize) = [%#span28] ()
+  constant empty'1 : Seq'0.t_seq (isize, isize)
   
   function produces_refl'1 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) : () =
-    [%#span48] ()
+    [%#span39] ()
   
-  axiom produces_refl'1_spec : forall self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span46] inv'1 self)
-   -> ([%#span47] produces'1 self (empty'1 : Seq'0.t_seq (isize, isize)) self)
+  axiom produces_refl'1_spec : forall self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span37] inv'1 self)
+   -> ([%#span38] produces'1 self (empty'1 : Seq'0.t_seq (isize, isize)) self)
   
   predicate invariant'1 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) =
-    [%#span27] true
+    [%#span20] true
   
   axiom inv'1 : forall x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . inv'1 x = true
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span30] ()
-  
-  axiom empty_len'1_spec : forall _1 : () . [%#span29] len'3 (empty'1 : Seq'0.t_seq (isize, isize)) = 0
+  function empty_len'1 (_1 : ()) : ()
   
-  use seq.Seq
+  axiom empty_len'1_spec : forall _1 : () . [%#span26] len'3 (empty'1 : Seq'0.t_seq (isize, isize)) = 0
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq usize) (x : int) : usize
+  function index_logic'1 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span31] inv'3 self)
-   -> ([%#span32] inv'3 other)
-   -> ([%#span35] inv'3 (concat'0 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span28] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'1 (concat'0 self other) i
   = (if i < len'1 self then index_logic'1 self i else index_logic'1 other (i - len'1 self)))
-  && ([%#span33] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span27] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'0 (_x : Range'0.t_range usize)
   
   use prelude.prelude.Int
   
   function deep_model'0 (self : usize) : int =
-    [%#span49] UIntSize.to_int self
+    [%#span40] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'0 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span50] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span41] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'1 visited > 0
@@ -3639,29 +3325,26 @@ module C06KnightsTour_KnightsTour
   function produces_trans'0 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span51] produces'0 a ab b)
-   -> ([%#span52] produces'0 b bc c)
-   -> ([%#span53] inv'0 a)
-   -> ([%#span54] inv'3 ab)
-   -> ([%#span55] inv'0 b)
-   -> ([%#span56] inv'3 bc)  -> ([%#span57] inv'0 c)  -> ([%#span58] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span42] produces'0 a ab b)
+   -> ([%#span43] produces'0 b bc c)
+   -> ([%#span44] inv'0 a)
+   -> ([%#span45] inv'0 b)  -> ([%#span46] inv'0 c)  -> ([%#span47] produces'0 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span28] ()
+  constant empty'0 : Seq'0.t_seq usize
   
   function produces_refl'0 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span59] inv'0 self)
-   -> ([%#span60] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'0_spec : forall self : Range'0.t_range usize . ([%#span48] inv'0 self)
+   -> ([%#span49] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
   
   predicate invariant'0 (self : Range'0.t_range usize) =
-    [%#span27] true
+    [%#span20] true
   
   axiom inv'0 : forall x : Range'0.t_range usize . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span30] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span29] len'1 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span26] len'1 (empty'0 : Seq'0.t_seq usize) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
@@ -3670,82 +3353,74 @@ module C06KnightsTour_KnightsTour
   use C06KnightsTour_Board_Type as Board'0
   
   predicate resolve'8 (self : Point'0.t_point) =
-    [%#span61] true
+    [%#span50] true
   
   predicate resolve'7 (self : usize) =
-    [%#span61] true
+    [%#span50] true
   
   predicate resolve'6 (self : (usize, Point'0.t_point)) =
-    [%#span62] resolve'7 (let (a, _) = self in a) /\ resolve'8 (let (_, a) = self in a)
-  
-  use seq.Seq
+    [%#span51] resolve'7 (let (a, _) = self in a) /\ resolve'8 (let (_, a) = self in a)
   
-  function index_logic'4 (self : Seq'0.t_seq (usize, Point'0.t_point)) (x : int) : (usize, Point'0.t_point)
+  function index_logic'4 (self : Seq'0.t_seq (usize, Point'0.t_point)) (_2 : int) : (usize, Point'0.t_point)
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) (ix : int) : (usize, Point'0.t_point)
     
    =
-    [%#span63] index_logic'4 (shallow_model'0 self) ix
+    [%#span52] index_logic'4 (shallow_model'0 self) ix
   
   predicate resolve'4 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) =
-    [%#span64] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'6 (index_logic'0 self i)
+    [%#span53] forall i : int . 0 <= i /\ i < len'0 (shallow_model'0 self)  -> resolve'6 (index_logic'0 self i)
   
   function shallow_model'6 (self : Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) : Seq'0.t_seq (usize, Point'0.t_point)
     
    =
-    [%#span65] shallow_model'0 self
+    [%#span54] shallow_model'0 self
   
   let rec min'0 (v:Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)) (return'  (ret:Option'0.t_option (usize, Point'0.t_point)))= any
-    [ return' (result:Option'0.t_option (usize, Point'0.t_point))-> {[%#span66] forall r : (usize, Point'0.t_point) . result
+    [ return' (result:Option'0.t_option (usize, Point'0.t_point))-> {[%#span55] forall r : (usize, Point'0.t_point) . result
       = Option'0.C_Some r  -> (exists i : int . 0 <= i /\ i < len'0 (shallow_model'6 v) /\ index_logic'0 v i = r)}
       (! return' {result}) ]
     
   
   predicate resolve'5 (self : isize) =
-    [%#span61] true
+    [%#span50] true
   
   predicate resolve'2 (self : (isize, isize)) =
-    [%#span62] resolve'5 (let (a, _) = self in a) /\ resolve'5 (let (_, a) = self in a)
+    [%#span51] resolve'5 (let (a, _) = self in a) /\ resolve'5 (let (_, a) = self in a)
   
   predicate resolve'3 (self : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) =
-    [%#span67] forall i : int . 0 <= i /\ i < len'3 (shallow_model'4 self)
+    [%#span56] forall i : int . 0 <= i /\ i < len'3 (shallow_model'4 self)
      -> resolve'2 (index_logic'5 (shallow_model'4 self) i)
   
-  use seq.Seq
-  
   function concat'2 (self : Seq'0.t_seq (usize, Point'0.t_point)) (other : Seq'0.t_seq (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point)
     
   
-  axiom concat'2_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point), other : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span31] inv'10 self)
-   -> ([%#span32] inv'10 other)
-   -> ([%#span35] inv'10 (concat'2 self other))
-  && ([%#span34] forall i : int . 0 <= i /\ i < len'0 (concat'2 self other)
+  axiom concat'2_spec : forall self : Seq'0.t_seq (usize, Point'0.t_point), other : Seq'0.t_seq (usize, Point'0.t_point) . ([%#span28] forall i : int . 0
+  <= i
+  /\ i < len'0 (concat'2 self other)
    -> index_logic'4 (concat'2 self other) i
   = (if i < len'0 self then index_logic'4 self i else index_logic'4 other (i - len'0 self)))
-  && ([%#span33] len'0 (concat'2 self other) = len'0 self + len'0 other)
-  
-  use seq.Seq
+  && ([%#span27] len'0 (concat'2 self other) = len'0 self + len'0 other)
   
   function singleton'2 (v : (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point)
   
-  axiom singleton'2_spec : forall v : (usize, Point'0.t_point) . ([%#span68] inv'15 v)
-   -> ([%#span71] inv'10 (singleton'2 v))
-  && ([%#span70] index_logic'4 (singleton'2 v) 0 = v) && ([%#span69] len'0 (singleton'2 v) = 1)
+  axiom singleton'2_spec : forall v : (usize, Point'0.t_point) . ([%#span57] inv'14 v)
+   -> ([%#span59] index_logic'4 (singleton'2 v) 0 = v) && ([%#span58] len'0 (singleton'2 v) = 1)
   
   function push'1 [@inline:trivial] (self : Seq'0.t_seq (usize, Point'0.t_point)) (v : (usize, Point'0.t_point)) : Seq'0.t_seq (usize, Point'0.t_point)
     
    =
-    [%#span72] concat'2 self (singleton'2 v)
+    [%#span60] concat'2 self (singleton'2 v)
   
   function shallow_model'5 (self : borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))) : Seq'0.t_seq (usize, Point'0.t_point)
     
    =
-    [%#span73] shallow_model'0 ( * self)
+    [%#span61] shallow_model'0 ( * self)
   
-  let rec push'0 (self:borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))) (value:(usize, Point'0.t_point)) (return'  (ret:()))= {[@expl:precondition] [%#span75] inv'15 value}
-    {[@expl:precondition] [%#span74] inv'14 self}
+  let rec push'0 (self:borrowed (Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))) (value:(usize, Point'0.t_point)) (return'  (ret:()))= {[@expl:precondition] [%#span63] inv'14 value}
+    {[@expl:precondition] [%#span62] inv'13 self}
     any
-    [ return' (result:())-> {[%#span76] shallow_model'0 ( ^ self) = push'1 (shallow_model'5 self) value}
+    [ return' (result:())-> {[%#span64] shallow_model'0 ( ^ self) = push'1 (shallow_model'5 self) value}
       (! return' {result}) ]
     
   
@@ -3756,78 +3431,73 @@ module C06KnightsTour_KnightsTour
   use prelude.prelude.IntSize
   
   predicate in_bounds'0 [#"../06_knights_tour.rs" 61 4 61 40] (self : Board'0.t_board) (p : Point'0.t_point) =
-    [%#span77] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
+    [%#span65] 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_x p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ 0 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_y p)
     < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
   
-  use seq.Seq
-  
-  function index_logic'6 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (x : int) : Vec'0.t_vec usize (Global'0.t_global)
+  function index_logic'6 (self : Seq'0.t_seq (Vec'0.t_vec usize (Global'0.t_global))) (_2 : int) : Vec'0.t_vec usize (Global'0.t_global)
     
   
   function index_logic'2 [@inline:trivial] (self : Vec'0.t_vec (Vec'0.t_vec usize (Global'0.t_global)) (Global'0.t_global)) (ix : int) : Vec'0.t_vec usize (Global'0.t_global)
     
    =
-    [%#span63] index_logic'6 (shallow_model'1 self) ix
+    [%#span52] index_logic'6 (shallow_model'1 self) ix
   
   predicate wf'0 [#"../06_knights_tour.rs" 30 4 30 23] (self : Board'0.t_board) =
-    [%#span78] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
+    [%#span66] UIntSize.to_int (C06KnightsTour_Board_Type.board_size self) <= 1000
     /\ len'2 (shallow_model'1 (C06KnightsTour_Board_Type.board_field self))
     = UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
     /\ (forall i : int . 0 <= i /\ i < UIntSize.to_int (C06KnightsTour_Board_Type.board_size self)
      -> len'1 (shallow_model'2 (index_logic'2 (C06KnightsTour_Board_Type.board_field self) i))
     = UIntSize.to_int (C06KnightsTour_Board_Type.board_size self))
   
-  let rec count_degree'0 (self:Board'0.t_board) (p:Point'0.t_point) (return'  (ret:usize))= {[@expl:precondition] [%#span80] in_bounds'0 self p}
-    {[@expl:precondition] [%#span79] wf'0 self}
+  let rec count_degree'0 (self:Board'0.t_board) (p:Point'0.t_point) (return'  (ret:usize))= {[@expl:precondition] [%#span68] in_bounds'0 self p}
+    {[@expl:precondition] [%#span67] wf'0 self}
     any [ return' (result:usize)-> (! return' {result}) ] 
   
-  let rec available'0 (self:Board'0.t_board) (p:Point'0.t_point) (return'  (ret:bool))= {[@expl:precondition] [%#span81] wf'0 self}
-    any [ return' (result:bool)-> {[%#span82] result  -> in_bounds'0 self p} (! return' {result}) ] 
+  let rec available'0 (self:Board'0.t_board) (p:Point'0.t_point) (return'  (ret:bool))= {[@expl:precondition] [%#span69] wf'0 self}
+    any [ return' (result:bool)-> {[%#span70] result  -> in_bounds'0 self p} (! return' {result}) ] 
   
-  let rec mov'0 (self:Point'0.t_point) (p:(isize, isize)) (return'  (ret:Point'0.t_point))= {[@expl:precondition] [%#span86] - 10000
+  let rec mov'0 (self:Point'0.t_point) (p:(isize, isize)) (return'  (ret:Point'0.t_point))= {[@expl:precondition] [%#span74] - 10000
     <= IntSize.to_int (let (_, a) = p in a)
     /\ IntSize.to_int (let (_, a) = p in a) <= 10000}
-    {[@expl:precondition] [%#span85] - 10000 <= IntSize.to_int (let (a, _) = p in a)
+    {[@expl:precondition] [%#span73] - 10000 <= IntSize.to_int (let (a, _) = p in a)
     /\ IntSize.to_int (let (a, _) = p in a) <= 10000}
-    {[@expl:precondition] [%#span84] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y self)
+    {[@expl:precondition] [%#span72] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_y self)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_y self) <= 10000}
-    {[@expl:precondition] [%#span83] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x self)
+    {[@expl:precondition] [%#span71] - 10000 <= IntSize.to_int (C06KnightsTour_Point_Type.point_x self)
     /\ IntSize.to_int (C06KnightsTour_Point_Type.point_x self) <= 10000}
     any
-    [ return' (result:Point'0.t_point)-> {[%#span88] IntSize.to_int (C06KnightsTour_Point_Type.point_y result)
+    [ return' (result:Point'0.t_point)-> {[%#span76] IntSize.to_int (C06KnightsTour_Point_Type.point_y result)
       = IntSize.to_int (C06KnightsTour_Point_Type.point_y self) + IntSize.to_int (let (_, a) = p in a)}
-      {[%#span87] IntSize.to_int (C06KnightsTour_Point_Type.point_x result)
+      {[%#span75] IntSize.to_int (C06KnightsTour_Point_Type.point_x result)
       = IntSize.to_int (C06KnightsTour_Point_Type.point_x self) + IntSize.to_int (let (a, _) = p in a)}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'1 (v : (isize, isize)) : Seq'0.t_seq (isize, isize)
   
-  axiom singleton'1_spec : forall v : (isize, isize) . ([%#span68] inv'13 v)
-   -> ([%#span71] inv'9 (singleton'1 v))
-  && ([%#span70] index_logic'5 (singleton'1 v) 0 = v) && ([%#span69] len'3 (singleton'1 v) = 1)
+  axiom singleton'1_spec : forall v : (isize, isize) . ([%#span57] inv'12 v)
+   -> ([%#span59] index_logic'5 (singleton'1 v) 0 = v) && ([%#span58] len'3 (singleton'1 v) = 1)
   
   predicate resolve'1 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) =
-    [%#span89]  ^ self =  * self
+    [%#span77]  ^ self =  * self
   
   function shallow_model'7 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) : Seq'0.t_seq (isize, isize)
     
    =
-    [%#span73] shallow_model'4 ( * self)
+    [%#span61] shallow_model'4 ( * self)
   
   predicate completed'1 (self : borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) =
-    [%#span90] resolve'1 self /\ shallow_model'7 self = (empty'1 : Seq'0.t_seq (isize, isize))
+    [%#span78] resolve'1 self /\ shallow_model'7 self = (empty'1 : Seq'0.t_seq (isize, isize))
   
-  let rec next'1 (self:borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) (return'  (ret:Option'0.t_option (isize, isize)))= {[@expl:precondition] [%#span91] inv'11 self}
+  let rec next'1 (self:borrowed (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))) (return'  (ret:Option'0.t_option (isize, isize)))= {[@expl:precondition] [%#span79] inv'10 self}
     any
-    [ return' (result:Option'0.t_option (isize, isize))-> {[%#span93] inv'12 result}
-      {[%#span92] match result with
+    [ return' (result:Option'0.t_option (isize, isize))-> {[%#span81] inv'11 result}
+      {[%#span80] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'1 v) ( ^ self)
         end}
@@ -3846,71 +3516,68 @@ module C06KnightsTour_KnightsTour
   
   function new'6 (x : Seq'0.t_seq (isize, isize)) : Snapshot'0.t_snapshot (Seq'0.t_seq (isize, isize))
   
-  axiom new'6_spec : forall x : Seq'0.t_seq (isize, isize) . ([%#span94] inv'9 x)  -> ([%#span95] deref'4 (new'6 x) = x)
+  axiom new'6_spec : forall x : Seq'0.t_seq (isize, isize) . ([%#span82] inv'9 x)  -> ([%#span83] deref'4 (new'6 x) = x)
   
   function new'5 (x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)) : Snapshot'0.t_snapshot (IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
     
   
-  axiom new'5_spec : forall x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span94] inv'1 x)
-   -> ([%#span95] deref'3 (new'5 x) = x)
+  axiom new'5_spec : forall x : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global) . ([%#span82] inv'1 x)
+   -> ([%#span83] deref'3 (new'5 x) = x)
   
   predicate into_iter_post'1 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) (res : IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))
     
    =
-    [%#span96] shallow_model'3 self = shallow_model'4 res
+    [%#span84] shallow_model'3 self = shallow_model'4 res
   
   predicate into_iter_pre'1 (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) =
-    [%#span97] true
+    [%#span85] true
   
-  let rec into_iter'1 (self:Vec'0.t_vec (isize, isize) (Global'0.t_global)) (return'  (ret:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)))= {[@expl:precondition] [%#span99] inv'8 self}
-    {[@expl:precondition] [%#span98] into_iter_pre'1 self}
+  let rec into_iter'1 (self:Vec'0.t_vec (isize, isize) (Global'0.t_global)) (return'  (ret:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global)))= {[@expl:precondition] [%#span87] inv'8 self}
+    {[@expl:precondition] [%#span86] into_iter_pre'1 self}
     any
-    [ return' (result:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))-> {[%#span100] inv'1 result}
-      {[%#span98] into_iter_post'1 self result}
+    [ return' (result:IntoIter'0.t_intoiter (isize, isize) (Global'0.t_global))-> {[%#span88] inv'1 result}
+      {[%#span86] into_iter_post'1 self result}
       (! return' {result}) ]
     
   
   function index_logic'3 [@inline:trivial] (self : Vec'0.t_vec (isize, isize) (Global'0.t_global)) (ix : int) : (isize, isize)
     
    =
-    [%#span63] index_logic'5 (shallow_model'3 self) ix
+    [%#span52] index_logic'5 (shallow_model'3 self) ix
   
   let rec moves'0 (_1:()) (return'  (ret:Vec'0.t_vec (isize, isize) (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec (isize, isize) (Global'0.t_global))-> {[%#span102] forall i : int . 0 <= i /\ i < 8
+    [ return' (result:Vec'0.t_vec (isize, isize) (Global'0.t_global))-> {[%#span90] forall i : int . 0 <= i /\ i < 8
        -> - 2 <= IntSize.to_int (let (a, _) = index_logic'3 result i in a)
       /\ IntSize.to_int (let (a, _) = index_logic'3 result i in a) <= 2
       /\ - 2 <= IntSize.to_int (let (_, a) = index_logic'3 result i in a)
       /\ IntSize.to_int (let (_, a) = index_logic'3 result i in a) <= 2}
-      {[%#span101] len'3 (shallow_model'3 result) = 8}
+      {[%#span89] len'3 (shallow_model'3 result) = 8}
       (! return' {result}) ]
     
   
   let rec new'4 (_1:()) (return'  (ret:Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global)))= any
-    [ return' (result:Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))-> {[%#span104] inv'7 result}
-      {[%#span103] len'0 (shallow_model'0 result) = 0}
+    [ return' (result:Vec'0.t_vec (usize, Point'0.t_point) (Global'0.t_global))-> {[%#span92] inv'7 result}
+      {[%#span91] len'0 (shallow_model'0 result) = 0}
       (! return' {result}) ]
     
   
-  use seq.Seq
-  
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span68] inv'6 v)
-   -> ([%#span71] inv'3 (singleton'0 v))
-  && ([%#span70] index_logic'1 (singleton'0 v) 0 = v) && ([%#span69] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span57] inv'6 v)
+   -> ([%#span59] index_logic'1 (singleton'0 v) 0 = v) && ([%#span58] len'1 (singleton'0 v) = 1)
   
   predicate resolve'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span89]  ^ self =  * self
+    [%#span77]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (Range'0.t_range usize)) =
-    [%#span105] resolve'0 self
+    [%#span93] resolve'0 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span106] inv'4 self}
+  let rec next'0 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span94] inv'4 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span107] inv'5 result}
-      {[%#span92] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span95] inv'5 result}
+      {[%#span80] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -3927,23 +3594,23 @@ module C06KnightsTour_KnightsTour
   
   function new'3 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'3_spec : forall x : Seq'0.t_seq usize . ([%#span94] inv'3 x)  -> ([%#span95] deref'2 (new'3 x) = x)
+  axiom new'3_spec : forall x : Seq'0.t_seq usize . ([%#span82] inv'3 x)  -> ([%#span83] deref'2 (new'3 x) = x)
   
   function new'2 (x : Range'0.t_range usize) : Snapshot'0.t_snapshot (Range'0.t_range usize)
   
-  axiom new'2_spec : forall x : Range'0.t_range usize . ([%#span94] inv'0 x)  -> ([%#span95] deref'1 (new'2 x) = x)
+  axiom new'2_spec : forall x : Range'0.t_range usize . ([%#span82] inv'0 x)  -> ([%#span83] deref'1 (new'2 x) = x)
   
   predicate into_iter_post'0 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span108] self = res
+    [%#span96] self = res
   
   predicate into_iter_pre'0 (self : Range'0.t_range usize) =
-    [%#span109] true
+    [%#span97] true
   
-  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span110] inv'0 self}
-    {[@expl:precondition] [%#span98] into_iter_pre'0 self}
+  let rec into_iter'0 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span98] inv'0 self}
+    {[@expl:precondition] [%#span86] into_iter_pre'0 self}
     any
-    [ return' (result:Range'0.t_range usize)-> {[%#span111] inv'0 result}
-      {[%#span98] into_iter_post'0 self result}
+    [ return' (result:Range'0.t_range usize)-> {[%#span99] inv'0 result}
+      {[%#span86] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
@@ -3951,28 +3618,28 @@ module C06KnightsTour_KnightsTour
   
   function new'1 (x : ()) : Snapshot'0.t_snapshot ()
   
-  axiom new'1_spec : forall x : () . ([%#span94] inv'2 x)  -> ([%#span95] deref'0 (new'1 x) = x)
+  axiom new'1_spec : forall x : () . ([%#span82] inv'2 x)  -> ([%#span83] deref'0 (new'1 x) = x)
   
   function dumb_nonlinear_arith'0 [#"../06_knights_tour.rs" 131 0 131 33] (a : usize) : () =
-    [%#span114] ()
+    [%#span102] ()
   
-  axiom dumb_nonlinear_arith'0_spec : forall a : usize . ([%#span112] UIntSize.to_int a <= 1000)
-   -> ([%#span113] UIntSize.to_int a * UIntSize.to_int a <= 1000000)
+  axiom dumb_nonlinear_arith'0_spec : forall a : usize . ([%#span100] UIntSize.to_int a <= 1000)
+   -> ([%#span101] UIntSize.to_int a * UIntSize.to_int a <= 1000000)
   
-  let rec set'0 (self:borrowed (Board'0.t_board)) (p:Point'0.t_point) (v:usize) (return'  (ret:()))= {[@expl:precondition] [%#span116] in_bounds'0 ( * self) p}
-    {[@expl:precondition] [%#span115] wf'0 ( * self)}
+  let rec set'0 (self:borrowed (Board'0.t_board)) (p:Point'0.t_point) (v:usize) (return'  (ret:()))= {[@expl:precondition] [%#span104] in_bounds'0 ( * self) p}
+    {[@expl:precondition] [%#span103] wf'0 ( * self)}
     any
-    [ return' (result:())-> {[%#span118] C06KnightsTour_Board_Type.board_size ( ^ self)
+    [ return' (result:())-> {[%#span106] C06KnightsTour_Board_Type.board_size ( ^ self)
       = C06KnightsTour_Board_Type.board_size ( * self)}
-      {[%#span117] wf'0 ( ^ self)}
+      {[%#span105] wf'0 ( ^ self)}
       (! return' {result}) ]
     
   
-  let rec new'0 (size:usize) (return'  (ret:Board'0.t_board))= {[@expl:precondition] [%#span119] UIntSize.to_int size
+  let rec new'0 (size:usize) (return'  (ret:Board'0.t_board))= {[@expl:precondition] [%#span107] UIntSize.to_int size
     <= 1000}
     any
-    [ return' (result:Board'0.t_board)-> {[%#span121] wf'0 result}
-      {[%#span120] C06KnightsTour_Board_Type.board_size result = size}
+    [ return' (result:Board'0.t_board)-> {[%#span109] wf'0 result}
+      {[%#span108] C06KnightsTour_Board_Type.board_size result = size}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/vector/07_read_write.coma b/creusot/tests/should_succeed/vector/07_read_write.coma
index 1eb997237e..9b2b09bbaf 100644
--- a/creusot/tests/should_succeed/vector/07_read_write.coma
+++ b/creusot/tests/should_succeed/vector/07_read_write.coma
@@ -101,22 +101,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C07ReadWrite_ReadWrite
   type t
@@ -131,71 +116,63 @@ module C07ReadWrite_ReadWrite
   
   let%span span4 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span7 = "" 0 0 0 0
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span10 = "" 0 0 0 0
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span11 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span12 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span13 = "../../../../../creusot-contracts/src/model.rs" 81 8 81 28
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span14 = "" 0 0 0 0
   
-  let%span span15 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span15 = "" 0 0 0 0
   
-  let%span span16 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span16 = "../../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
   
-  let%span span17 = "../../../../../creusot-contracts/src/model.rs" 81 8 81 28
+  let%span span17 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span18 = "" 0 0 0 0
+  let%span span18 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span19 = "" 0 0 0 0
+  let%span span19 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/cmp.rs" 11 26 11 75
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span21 = "" 0 0 0 0
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span22 = "" 0 0 0 0
   
-  let%span span23 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span23 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span24 = "" 0 0 0 0
   
-  let%span span25 = "" 0 0 0 0
+  let%span span25 = "../../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
   
-  let%span span26 = "" 0 0 0 0
+  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
   
-  let%span span27 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span27 = "" 0 0 0 0
   
   let%span span28 = "" 0 0 0 0
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/slice.rs" 114 8 114 96
-  
-  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 146 27 146 46
+  let%span span29 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
   
-  let%span span31 = "" 0 0 0 0
+  let%span span30 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
   
-  let%span span32 = "" 0 0 0 0
+  let%span span31 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/vec.rs" 147 26 147 54
+  let%span span32 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/vec.rs" 148 26 148 57
-  
-  let%span span35 = "../../../../../creusot-contracts/src/std/vec.rs" 149 26 149 62
-  
-  let%span span36 = "../../../../../creusot-contracts/src/std/vec.rs" 150 26 150 55
-  
-  let%span span37 = "" 0 0 0 0
+  let%span span33 = "" 0 0 0 0
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
@@ -226,20 +203,15 @@ module C07ReadWrite_ReadWrite
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span5] inv'7 self)  -> ([%#span6] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span5] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span7] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span9] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span8] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span6] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use prelude.prelude.Borrow
   
@@ -269,84 +241,81 @@ module C07ReadWrite_ReadWrite
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span10] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span11] inv'0 self)
-   -> ([%#span13] inv'7 (shallow_model'1 self))
-  && ([%#span12] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span8] inv'0 self)
+   -> ([%#span9] len'0 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span14] inv'7 (shallow_model'1 self)
+    [%#span10] inv'7 (shallow_model'1 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
   function shallow_model'0 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span15] shallow_model'1 ( * self)
+    [%#span11] shallow_model'1 ( * self)
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'3 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span16]  ^ self =  * self
+    [%#span12]  ^ self =  * self
   
   type deep_model_ty'0
   
   function deep_model'1 (self : t) : deep_model_ty'0
   
   function deep_model'0 (self : t) : deep_model_ty'0 =
-    [%#span17] deep_model'1 self
+    [%#span13] deep_model'1 self
   
-  let rec eq'0 (self:t) (other:t) (return'  (ret:bool))= {[@expl:precondition] [%#span19] inv'3 other}
-    {[@expl:precondition] [%#span18] inv'3 self}
-    any [ return' (result:bool)-> {[%#span20] result = (deep_model'0 self = deep_model'0 other)} (! return' {result}) ] 
+  let rec eq'0 (self:t) (other:t) (return'  (ret:bool))= {[@expl:precondition] [%#span15] inv'3 other}
+    {[@expl:precondition] [%#span14] inv'3 self}
+    any [ return' (result:bool)-> {[%#span16] result = (deep_model'0 self = deep_model'0 other)} (! return' {result}) ] 
   
   predicate resolve'2 (self : t)
   
   use prelude.prelude.Slice
   
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'0 (self : Seq'0.t_seq t) (_2 : int) : t
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) (out : t) =
-    [%#span21] index_logic'0 seq (UIntSize.to_int self) = out
+    [%#span17] index_logic'0 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq t) =
-    [%#span22] UIntSize.to_int self < len'0 seq
+    [%#span18] UIntSize.to_int self < len'0 seq
   
   function shallow_model'2 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t =
-    [%#span23] shallow_model'1 self
+    [%#span19] shallow_model'1 self
   
-  let rec index'0 (self:Vec'0.t_vec t (Global'0.t_global)) (index:usize) (return'  (ret:t))= {[@expl:precondition] [%#span26] inv'5 index}
-    {[@expl:precondition] [%#span25] inv'6 self}
-    {[@expl:precondition] [%#span24] in_bounds'0 index (shallow_model'2 self)}
+  let rec index'0 (self:Vec'0.t_vec t (Global'0.t_global)) (index:usize) (return'  (ret:t))= {[@expl:precondition] [%#span22] inv'5 index}
+    {[@expl:precondition] [%#span21] inv'6 self}
+    {[@expl:precondition] [%#span20] in_bounds'0 index (shallow_model'2 self)}
     any
-    [ return' (result:t)-> {[%#span28] inv'3 result}
-      {[%#span27] has_value'0 index (shallow_model'2 self) result}
+    [ return' (result:t)-> {[%#span24] inv'3 result}
+      {[%#span23] has_value'0 index (shallow_model'2 self) result}
       (! return' {result}) ]
     
   
   predicate resolve'1 (self : borrowed t) =
-    [%#span16]  ^ self =  * self
+    [%#span12]  ^ self =  * self
   
   predicate resolve'0 (self : t)
   
   predicate resolve_elswhere'0 [@inline:trivial] (self : usize) (old' : Seq'0.t_seq t) (fin : Seq'0.t_seq t) =
-    [%#span29] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
+    [%#span25] forall i : int . 0 <= i /\ i <> UIntSize.to_int self /\ i < len'0 old'
      -> index_logic'0 old' i = index_logic'0 fin i
   
-  let rec index_mut'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:usize) (return'  (ret:borrowed t))= {[@expl:precondition] [%#span32] inv'5 index}
-    {[@expl:precondition] [%#span31] inv'4 self}
-    {[@expl:precondition] [%#span30] in_bounds'0 index (shallow_model'0 self)}
+  let rec index_mut'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (index:usize) (return'  (ret:borrowed t))= {[@expl:precondition] [%#span28] inv'5 index}
+    {[@expl:precondition] [%#span27] inv'4 self}
+    {[@expl:precondition] [%#span26] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:borrowed t)-> {[%#span37] inv'2 result}
-      {[%#span36] len'0 (shallow_model'1 ( ^ self)) = len'0 (shallow_model'0 self)}
-      {[%#span35] resolve_elswhere'0 index (shallow_model'0 self) (shallow_model'1 ( ^ self))}
-      {[%#span34] has_value'0 index (shallow_model'1 ( ^ self)) ( ^ result)}
-      {[%#span33] has_value'0 index (shallow_model'0 self) ( * result)}
+    [ return' (result:borrowed t)-> {[%#span33] inv'2 result}
+      {[%#span32] len'0 (shallow_model'1 ( ^ self)) = len'0 (shallow_model'0 self)}
+      {[%#span31] resolve_elswhere'0 index (shallow_model'0 self) (shallow_model'1 ( ^ self))}
+      {[%#span30] has_value'0 index (shallow_model'1 ( ^ self)) ( ^ result)}
+      {[%#span29] has_value'0 index (shallow_model'0 self) ( * result)}
       (! return' {result}) ]
     
   
diff --git a/creusot/tests/should_succeed/vector/08_haystack.coma b/creusot/tests/should_succeed/vector/08_haystack.coma
index 544b91acd1..248f10f490 100644
--- a/creusot/tests/should_succeed/vector/08_haystack.coma
+++ b/creusot/tests/should_succeed/vector/08_haystack.coma
@@ -101,22 +101,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module Core_Ops_Range_RangeInclusive_Type
   type t_rangeinclusive 'idx =
@@ -221,177 +206,158 @@ module C08Haystack_Search
   
   let%span s08_haystack14 = "../08_haystack.rs" 20 0 20 139
   
-  let%span span15 = "" 0 0 0 0
+  let%span span15 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span16 = "" 0 0 0 0
   
-  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span17 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
   let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
   let%span span19 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span21 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span21 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
   
-  let%span span22 = "../../../../../creusot-contracts/src/invariant.rs" 8 8 8 12
+  let%span span22 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
   
-  let%span span23 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 18 107 22
+  let%span span23 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
   
-  let%span span24 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 24 107 29
+  let%span span24 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
   
-  let%span span25 = "../../../../../creusot-contracts/src/logic/seq2.rs" 104 14 104 54
+  let%span span25 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
   
-  let%span span26 = "../../../../../creusot-contracts/src/logic/seq2.rs" 105 4 106 62
+  let%span span26 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
   
-  let%span span27 = "../../../../../creusot-contracts/src/logic/seq2.rs" 107 4 107 44
+  let%span span27 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
   
-  let%span span28 = "../../../../../creusot-contracts/src/std/num.rs" 22 16 22 35
+  let%span span28 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
   
-  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 21 8 27 9
+  let%span span29 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
   
-  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 37 15 37 32
+  let%span span30 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
   
-  let%span span31 = "../../../../../creusot-contracts/src/std/iter/range.rs" 38 15 38 32
+  let%span span31 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
   
-  let%span span32 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 22 40 23
+  let%span span32 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
   
-  let%span span33 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 31 40 33
+  let%span span33 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span34 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 52 40 53
+  let%span span34 = "../../../../../creusot-contracts/src/std/ops.rs" 207 20 207 24
   
-  let%span span35 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 61 40 63
+  let%span span35 = "../../../../../creusot-contracts/src/std/ops.rs" 206 4 206 88
   
-  let%span span36 = "../../../../../creusot-contracts/src/std/iter/range.rs" 40 82 40 83
+  let%span span36 = "../../../../../creusot-contracts/src/std/iter/range.rs" 46 62 46 63
   
-  let%span span37 = "../../../../../creusot-contracts/src/std/iter/range.rs" 39 14 39 42
+  let%span span37 = "../../../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
   
-  let%span span38 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span38 = "../../../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
   
-  let%span span39 = "../../../../../creusot-contracts/src/std/iter/range.rs" 33 21 33 25
+  let%span span39 = "../../../../../creusot-contracts/src/std/iter/range.rs" 65 8 71 9
   
-  let%span span40 = "../../../../../creusot-contracts/src/std/iter/range.rs" 32 14 32 45
+  let%span span40 = "../../../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
   
-  let%span span41 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span41 = "../../../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
   
-  let%span span42 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span42 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 22 84 23
   
-  let%span span43 = "../../../../../creusot-contracts/src/std/ops.rs" 207 20 207 24
+  let%span span43 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 52 84 53
   
-  let%span span44 = "../../../../../creusot-contracts/src/std/ops.rs" 206 4 206 88
+  let%span span44 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 82 84 83
   
-  let%span span45 = "../../../../../creusot-contracts/src/std/iter/range.rs" 46 62 46 63
+  let%span span45 = "../../../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
   
-  let%span span46 = "../../../../../creusot-contracts/src/std/iter/range.rs" 45 10 45 43
+  let%span span46 = "../../../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
   
-  let%span span47 = "../../../../../creusot-contracts/src/std/iter/range.rs" 47 4 50 5
+  let%span span47 = "../../../../../creusot-contracts/src/std/iter/range.rs" 77 21 77 25
   
-  let%span span48 = "../../../../../creusot-contracts/src/std/iter/range.rs" 65 8 71 9
+  let%span span48 = "../../../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
   
-  let%span span49 = "../../../../../creusot-contracts/src/std/iter/range.rs" 81 15 81 32
+  let%span span49 = "../../../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
   
-  let%span span50 = "../../../../../creusot-contracts/src/std/iter/range.rs" 82 15 82 32
+  let%span span50 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
   
-  let%span span51 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 22 84 23
+  let%span span51 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
   
-  let%span span52 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 31 84 33
+  let%span span52 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
   
-  let%span span53 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 52 84 53
+  let%span span53 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
   
-  let%span span54 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 61 84 63
+  let%span span54 = "" 0 0 0 0
   
-  let%span span55 = "../../../../../creusot-contracts/src/std/iter/range.rs" 84 82 84 83
+  let%span span55 = "" 0 0 0 0
   
-  let%span span56 = "../../../../../creusot-contracts/src/std/iter/range.rs" 83 14 83 42
+  let%span span56 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
   
-  let%span span57 = "../../../../../creusot-contracts/src/std/iter/range.rs" 79 4 79 10
+  let%span span57 = "" 0 0 0 0
   
-  let%span span58 = "../../../../../creusot-contracts/src/std/iter/range.rs" 77 21 77 25
+  let%span span58 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span59 = "../../../../../creusot-contracts/src/std/iter/range.rs" 76 14 76 45
+  let%span span59 = "../../../../../creusot-contracts/src/logic/seq2.rs" 54 21 54 22
   
-  let%span span60 = "../../../../../creusot-contracts/src/std/iter/range.rs" 74 4 74 10
+  let%span span60 = "../../../../../creusot-contracts/src/logic/seq2.rs" 52 14 52 31
   
-  let%span span61 = "../../../../../creusot-contracts/src/std/slice.rs" 107 20 107 37
+  let%span span61 = "../../../../../creusot-contracts/src/logic/seq2.rs" 53 14 53 28
   
-  let%span span62 = "../../../../../creusot-contracts/src/std/slice.rs" 100 20 100 37
+  let%span span62 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
   
-  let%span span63 = "../../../../../creusot-contracts/src/model.rs" 90 8 90 31
+  let%span span63 = "" 0 0 0 0
   
-  let%span span64 = "../../../../../creusot-contracts/src/std/vec.rs" 156 27 156 46
+  let%span span64 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
   
   let%span span65 = "" 0 0 0 0
   
-  let%span span66 = "" 0 0 0 0
+  let%span span66 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
   
-  let%span span67 = "../../../../../creusot-contracts/src/std/vec.rs" 157 26 157 54
+  let%span span67 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
   
-  let%span span68 = "" 0 0 0 0
+  let%span span68 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
   
-  let%span span69 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span69 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
   
-  let%span span70 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 21 58 22
+  let%span span70 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
   
-  let%span span71 = "../../../../../creusot-contracts/src/logic/seq2.rs" 56 14 56 31
+  let%span span71 = "" 0 0 0 0
   
-  let%span span72 = "../../../../../creusot-contracts/src/logic/seq2.rs" 57 14 57 28
+  let%span span72 = "" 0 0 0 0
   
-  let%span span73 = "../../../../../creusot-contracts/src/logic/seq2.rs" 58 4 58 34
+  let%span span73 = "../../../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
   
-  let%span span74 = "../../../../../creusot-contracts/src/std/iter/range.rs" 14 12 14 78
+  let%span span74 = "" 0 0 0 0
   
   let%span span75 = "" 0 0 0 0
   
-  let%span span76 = "../../../../../creusot-contracts/src/std/iter.rs" 95 26 98 17
+  let%span span76 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span77 = "" 0 0 0 0
+  let%span span77 = "../08_haystack.rs" 8 4 12 5
   
-  let%span span78 = "../../../../../creusot-contracts/src/snapshot.rs" 45 15 45 16
+  let%span span78 = "" 0 0 0 0
   
-  let%span span79 = "../../../../../creusot-contracts/src/snapshot.rs" 43 14 43 28
+  let%span span79 = "" 0 0 0 0
   
-  let%span span80 = "../../../../../creusot-contracts/src/std/iter.rs" 80 8 80 19
+  let%span span80 = "../../../../../creusot-contracts/src/std/ops.rs" 220 26 220 53
   
-  let%span span81 = "../../../../../creusot-contracts/src/std/iter.rs" 74 20 74 24
+  let%span span81 = "../../../../../creusot-contracts/src/std/ops.rs" 221 26 221 49
   
-  let%span span82 = "../../../../../creusot-contracts/src/std/iter.rs" 89 0 175 1
+  let%span span82 = "../../../../../creusot-contracts/src/std/ops.rs" 222 16 222 93
   
   let%span span83 = "" 0 0 0 0
   
   let%span span84 = "" 0 0 0 0
   
-  let%span span85 = "../../../../../creusot-contracts/src/std/iter/range.rs" 58 12 58 57
-  
-  let%span span86 = "" 0 0 0 0
-  
-  let%span span87 = "" 0 0 0 0
-  
-  let%span span88 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
-  
-  let%span span89 = "../08_haystack.rs" 8 4 12 5
-  
-  let%span span90 = "" 0 0 0 0
-  
-  let%span span91 = "" 0 0 0 0
-  
-  let%span span92 = "../../../../../creusot-contracts/src/std/ops.rs" 220 26 220 53
-  
-  let%span span93 = "../../../../../creusot-contracts/src/std/ops.rs" 221 26 221 49
-  
-  let%span span94 = "../../../../../creusot-contracts/src/std/ops.rs" 222 16 222 93
-  
-  let%span span95 = "" 0 0 0 0
-  
-  let%span span96 = "" 0 0 0 0
-  
-  let%span span97 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
+  let%span span85 = "../../../../../creusot-contracts/src/std/vec.rs" 78 26 78 48
   
   use prelude.prelude.UInt8
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
-  predicate inv'5 (_x : Seq'0.t_seq uint8)
+  predicate invariant'10 (self : Seq'0.t_seq uint8) =
+    [%#span15] true
+  
+  predicate inv'10 (_x : Seq'0.t_seq uint8)
+  
+  axiom inv'10 : forall x : Seq'0.t_seq uint8 . inv'10 x = true
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -403,124 +369,106 @@ module C08Haystack_Search
   
   use prelude.prelude.Int
   
-  constant max'0 : usize = [%#span15] (18446744073709551615 : usize)
-  
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
+  constant max'0 : usize = [%#span16] (18446744073709551615 : usize)
   
   function len'2 (self : Seq'0.t_seq uint8) : int
   
-  axiom len'2_spec : forall self : Seq'0.t_seq uint8 . ([%#span16] inv'5 self)  -> ([%#span17] len'2 self >= 0)
+  axiom len'2_spec : forall self : Seq'0.t_seq uint8 . [%#span17] len'2 self >= 0
   
-  predicate inv'10 (_x : Vec'0.t_vec uint8 (Global'0.t_global))
+  predicate inv'9 (_x : Vec'0.t_vec uint8 (Global'0.t_global))
   
   function shallow_model'1 (self : Vec'0.t_vec uint8 (Global'0.t_global)) : Seq'0.t_seq uint8
   
-  axiom shallow_model'1_spec : forall self : Vec'0.t_vec uint8 (Global'0.t_global) . ([%#span18] inv'10 self)
-   -> ([%#span20] inv'5 (shallow_model'1 self))
-  && ([%#span19] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'1_spec : forall self : Vec'0.t_vec uint8 (Global'0.t_global) . ([%#span18] inv'9 self)
+   -> ([%#span19] len'2 (shallow_model'1 self) <= UIntSize.to_int (max'0 : usize))
   
-  predicate invariant'10 (self : Vec'0.t_vec uint8 (Global'0.t_global)) =
-    [%#span21] inv'5 (shallow_model'1 self)
+  predicate invariant'9 (self : Vec'0.t_vec uint8 (Global'0.t_global)) =
+    [%#span20] inv'10 (shallow_model'1 self)
   
-  axiom inv'10 : forall x : Vec'0.t_vec uint8 (Global'0.t_global) . inv'10 x = true
+  axiom inv'9 : forall x : Vec'0.t_vec uint8 (Global'0.t_global) . inv'9 x = true
   
-  predicate invariant'9 (self : uint8) =
-    [%#span22] true
+  predicate invariant'8 (self : uint8) =
+    [%#span15] true
   
-  predicate inv'9 (_x : uint8)
+  predicate inv'8 (_x : uint8)
   
-  axiom inv'9 : forall x : uint8 . inv'9 x = true
+  axiom inv'8 : forall x : uint8 . inv'8 x = true
   
   use Core_Ops_Range_Range_Type as Range'0
   
   use prelude.prelude.Borrow
   
-  predicate invariant'8 (self : borrowed (Range'0.t_range usize)) =
-    [%#span22] true
+  predicate invariant'7 (self : borrowed (Range'0.t_range usize)) =
+    [%#span15] true
   
-  predicate inv'8 (_x : borrowed (Range'0.t_range usize))
+  predicate inv'7 (_x : borrowed (Range'0.t_range usize))
   
-  axiom inv'8 : forall x : borrowed (Range'0.t_range usize) . inv'8 x = true
+  axiom inv'7 : forall x : borrowed (Range'0.t_range usize) . inv'7 x = true
   
   use Core_Option_Option_Type as Option'0
   
-  predicate invariant'7 (self : Option'0.t_option usize) =
-    [%#span22] true
+  predicate invariant'6 (self : Option'0.t_option usize) =
+    [%#span15] true
   
-  predicate inv'7 (_x : Option'0.t_option usize)
+  predicate inv'6 (_x : Option'0.t_option usize)
   
-  axiom inv'7 : forall x : Option'0.t_option usize . inv'7 x = true
+  axiom inv'6 : forall x : Option'0.t_option usize . inv'6 x = true
   
   use Core_Ops_Range_RangeInclusive_Type as RangeInclusive'0
   
-  predicate invariant'6 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
-    [%#span22] true
+  predicate invariant'5 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
+    [%#span15] true
   
-  predicate inv'6 (_x : borrowed (RangeInclusive'0.t_rangeinclusive usize))
+  predicate inv'5 (_x : borrowed (RangeInclusive'0.t_rangeinclusive usize))
   
-  axiom inv'6 : forall x : borrowed (RangeInclusive'0.t_rangeinclusive usize) . inv'6 x = true
-  
-  predicate invariant'5 (self : Seq'0.t_seq uint8) =
-    [%#span22] true
-  
-  axiom inv'5 : forall x : Seq'0.t_seq uint8 . inv'5 x = true
+  axiom inv'5 : forall x : borrowed (RangeInclusive'0.t_rangeinclusive usize) . inv'5 x = true
   
   predicate invariant'4 (self : Seq'0.t_seq usize) =
-    [%#span22] true
+    [%#span15] true
   
   predicate inv'4 (_x : Seq'0.t_seq usize)
   
   axiom inv'4 : forall x : Seq'0.t_seq usize . inv'4 x = true
   
   predicate invariant'3 (self : usize) =
-    [%#span22] true
+    [%#span15] true
   
   predicate inv'3 (_x : usize)
   
   axiom inv'3 : forall x : usize . inv'3 x = true
   
   predicate invariant'2 (self : Vec'0.t_vec uint8 (Global'0.t_global)) =
-    [%#span22] true
+    [%#span15] true
   
   predicate inv'2 (_x : Vec'0.t_vec uint8 (Global'0.t_global))
   
   axiom inv'2 : forall x : Vec'0.t_vec uint8 (Global'0.t_global) . inv'2 x = true
   
-  use seq.Seq
-  
-  use seq.Seq
-  
-  function index_logic'0 (self : Seq'0.t_seq usize) (x : int) : usize
-  
-  use seq.Seq
+  function index_logic'0 (self : Seq'0.t_seq usize) (_2 : int) : usize
   
   function len'1 (self : Seq'0.t_seq usize) : int
   
-  axiom len'1_spec : forall self : Seq'0.t_seq usize . ([%#span16] inv'4 self)  -> ([%#span17] len'1 self >= 0)
+  axiom len'1_spec : forall self : Seq'0.t_seq usize . [%#span17] len'1 self >= 0
   
   function concat'0 (self : Seq'0.t_seq usize) (other : Seq'0.t_seq usize) : Seq'0.t_seq usize
   
-  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span23] inv'4 self)
-   -> ([%#span24] inv'4 other)
-   -> ([%#span27] inv'4 (concat'0 self other))
-  && ([%#span26] forall i : int . 0 <= i /\ i < len'1 (concat'0 self other)
+  axiom concat'0_spec : forall self : Seq'0.t_seq usize, other : Seq'0.t_seq usize . ([%#span22] forall i : int . 0 <= i
+  /\ i < len'1 (concat'0 self other)
    -> index_logic'0 (concat'0 self other) i
   = (if i < len'1 self then index_logic'0 self i else index_logic'0 other (i - len'1 self)))
-  && ([%#span25] len'1 (concat'0 self other) = len'1 self + len'1 other)
+  && ([%#span21] len'1 (concat'0 self other) = len'1 self + len'1 other)
   
   predicate inv'1 (_x : Range'0.t_range usize)
   
   use prelude.prelude.Int
   
   function deep_model'0 (self : usize) : int =
-    [%#span28] UIntSize.to_int self
+    [%#span23] UIntSize.to_int self
   
   use Core_Ops_Range_Range_Type as Core_Ops_Range_Range_Type
   
   predicate produces'1 (self : Range'0.t_range usize) (visited : Seq'0.t_seq usize) (o : Range'0.t_range usize) =
-    [%#span29] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
+    [%#span24] Core_Ops_Range_Range_Type.range_end self = Core_Ops_Range_Range_Type.range_end o
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start self)
     <= deep_model'0 (Core_Ops_Range_Range_Type.range_start o)
     /\ (len'1 visited > 0
@@ -533,31 +481,28 @@ module C08Haystack_Search
   function produces_trans'1 (a : Range'0.t_range usize) (ab : Seq'0.t_seq usize) (b : Range'0.t_range usize) (bc : Seq'0.t_seq usize) (c : Range'0.t_range usize) : ()
     
   
-  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span30] produces'1 a ab b)
-   -> ([%#span31] produces'1 b bc c)
-   -> ([%#span32] inv'1 a)
-   -> ([%#span33] inv'4 ab)
-   -> ([%#span34] inv'1 b)
-   -> ([%#span35] inv'4 bc)  -> ([%#span36] inv'1 c)  -> ([%#span37] produces'1 a (concat'0 ab bc) c)
+  axiom produces_trans'1_spec : forall a : Range'0.t_range usize, ab : Seq'0.t_seq usize, b : Range'0.t_range usize, bc : Seq'0.t_seq usize, c : Range'0.t_range usize . ([%#span25] produces'1 a ab b)
+   -> ([%#span26] produces'1 b bc c)
+   -> ([%#span27] inv'1 a)
+   -> ([%#span28] inv'1 b)  -> ([%#span29] inv'1 c)  -> ([%#span30] produces'1 a (concat'0 ab bc) c)
   
-  constant empty'0 : Seq'0.t_seq usize = [%#span38] ()
+  constant empty'0 : Seq'0.t_seq usize
   
   function produces_refl'1 (self : Range'0.t_range usize) : ()
   
-  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span39] inv'1 self)
-   -> ([%#span40] produces'1 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'1_spec : forall self : Range'0.t_range usize . ([%#span31] inv'1 self)
+   -> ([%#span32] produces'1 self (empty'0 : Seq'0.t_seq usize) self)
   
   predicate invariant'1 (self : Range'0.t_range usize) =
-    [%#span22] true
+    [%#span15] true
   
   axiom inv'1 : forall x : Range'0.t_range usize . inv'1 x = true
   
-  constant empty'1 : Seq'0.t_seq uint8 = [%#span38] ()
+  constant empty'1 : Seq'0.t_seq uint8
   
-  function empty_len'1 (_1 : ()) : () =
-    [%#span42] ()
+  function empty_len'1 (_1 : ()) : ()
   
-  axiom empty_len'1_spec : forall _1 : () . [%#span41] len'2 (empty'1 : Seq'0.t_seq uint8) = 0
+  axiom empty_len'1_spec : forall _1 : () . [%#span33] len'2 (empty'1 : Seq'0.t_seq uint8) = 0
   
   predicate inv'0 (_x : RangeInclusive'0.t_rangeinclusive usize)
   
@@ -569,19 +514,19 @@ module C08Haystack_Search
   
   function is_empty_log'0 (self : RangeInclusive'0.t_rangeinclusive usize) : bool
   
-  axiom is_empty_log'0_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span43] inv'0 self)
-   -> ([%#span44] not is_empty_log'0 self  -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self))
+  axiom is_empty_log'0_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span34] inv'0 self)
+   -> ([%#span35] not is_empty_log'0 self  -> deep_model'0 (start_log'0 self) <= deep_model'0 (end_log'0 self))
   
   function range_inclusive_len'0 (r : RangeInclusive'0.t_rangeinclusive usize) : int =
-    [%#span47] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
+    [%#span38] if is_empty_log'0 r then 0 else deep_model'0 (end_log'0 r) - deep_model'0 (start_log'0 r) + 1
   
-  axiom range_inclusive_len'0_spec : forall r : RangeInclusive'0.t_rangeinclusive usize . ([%#span45] inv'0 r)
-   -> ([%#span46] is_empty_log'0 r = (range_inclusive_len'0 r = 0))
+  axiom range_inclusive_len'0_spec : forall r : RangeInclusive'0.t_rangeinclusive usize . ([%#span36] inv'0 r)
+   -> ([%#span37] is_empty_log'0 r = (range_inclusive_len'0 r = 0))
   
   predicate produces'0 (self : RangeInclusive'0.t_rangeinclusive usize) (visited : Seq'0.t_seq usize) (o : RangeInclusive'0.t_rangeinclusive usize)
     
    =
-    [%#span48] len'1 visited = range_inclusive_len'0 self - range_inclusive_len'0 o
+    [%#span39] len'1 visited = range_inclusive_len'0 self - range_inclusive_len'0 o
     /\ (is_empty_log'0 self  -> is_empty_log'0 o)
     /\ (is_empty_log'0 o \/ end_log'0 self = end_log'0 o)
     /\ (forall i : int . 0 <= i /\ i < len'1 visited
@@ -590,30 +535,27 @@ module C08Haystack_Search
   function produces_trans'0 (a : RangeInclusive'0.t_rangeinclusive usize) (ab : Seq'0.t_seq usize) (b : RangeInclusive'0.t_rangeinclusive usize) (bc : Seq'0.t_seq usize) (c : RangeInclusive'0.t_rangeinclusive usize) : ()
     
    =
-    [%#span57] ()
+    [%#span46] ()
   
-  axiom produces_trans'0_spec : forall a : RangeInclusive'0.t_rangeinclusive usize, ab : Seq'0.t_seq usize, b : RangeInclusive'0.t_rangeinclusive usize, bc : Seq'0.t_seq usize, c : RangeInclusive'0.t_rangeinclusive usize . ([%#span49] produces'0 a ab b)
-   -> ([%#span50] produces'0 b bc c)
-   -> ([%#span51] inv'0 a)
-   -> ([%#span52] inv'4 ab)
-   -> ([%#span53] inv'0 b)
-   -> ([%#span54] inv'4 bc)  -> ([%#span55] inv'0 c)  -> ([%#span56] produces'0 a (concat'0 ab bc) c)
+  axiom produces_trans'0_spec : forall a : RangeInclusive'0.t_rangeinclusive usize, ab : Seq'0.t_seq usize, b : RangeInclusive'0.t_rangeinclusive usize, bc : Seq'0.t_seq usize, c : RangeInclusive'0.t_rangeinclusive usize . ([%#span40] produces'0 a ab b)
+   -> ([%#span41] produces'0 b bc c)
+   -> ([%#span42] inv'0 a)
+   -> ([%#span43] inv'0 b)  -> ([%#span44] inv'0 c)  -> ([%#span45] produces'0 a (concat'0 ab bc) c)
   
   function produces_refl'0 (self : RangeInclusive'0.t_rangeinclusive usize) : () =
-    [%#span60] ()
+    [%#span49] ()
   
-  axiom produces_refl'0_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span58] inv'0 self)
-   -> ([%#span59] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
+  axiom produces_refl'0_spec : forall self : RangeInclusive'0.t_rangeinclusive usize . ([%#span47] inv'0 self)
+   -> ([%#span48] produces'0 self (empty'0 : Seq'0.t_seq usize) self)
   
   predicate invariant'0 (self : RangeInclusive'0.t_rangeinclusive usize) =
-    [%#span22] true
+    [%#span15] true
   
   axiom inv'0 : forall x : RangeInclusive'0.t_rangeinclusive usize . inv'0 x = true
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span42] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span41] len'1 (empty'0 : Seq'0.t_seq usize) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span33] len'1 (empty'0 : Seq'0.t_seq usize) = 0
   
   use CreusotContracts_Snapshot_Snapshot_Type as Snapshot'0
   
@@ -621,48 +563,43 @@ module C08Haystack_Search
   
   use prelude.prelude.Slice
   
-  use seq.Seq
-  
-  function index_logic'2 (self : Seq'0.t_seq uint8) (x : int) : uint8
+  function index_logic'2 (self : Seq'0.t_seq uint8) (_2 : int) : uint8
   
   predicate has_value'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq uint8) (out : uint8) =
-    [%#span61] index_logic'2 seq (UIntSize.to_int self) = out
+    [%#span50] index_logic'2 seq (UIntSize.to_int self) = out
   
   predicate in_bounds'0 [@inline:trivial] (self : usize) (seq : Seq'0.t_seq uint8) =
-    [%#span62] UIntSize.to_int self < len'2 seq
+    [%#span51] UIntSize.to_int self < len'2 seq
   
   function shallow_model'0 (self : Vec'0.t_vec uint8 (Global'0.t_global)) : Seq'0.t_seq uint8 =
-    [%#span63] shallow_model'1 self
+    [%#span52] shallow_model'1 self
   
-  let rec index'0 (self:Vec'0.t_vec uint8 (Global'0.t_global)) (index:usize) (return'  (ret:uint8))= {[@expl:precondition] [%#span66] inv'3 index}
-    {[@expl:precondition] [%#span65] inv'2 self}
-    {[@expl:precondition] [%#span64] in_bounds'0 index (shallow_model'0 self)}
+  let rec index'0 (self:Vec'0.t_vec uint8 (Global'0.t_global)) (index:usize) (return'  (ret:uint8))= {[@expl:precondition] [%#span55] inv'3 index}
+    {[@expl:precondition] [%#span54] inv'2 self}
+    {[@expl:precondition] [%#span53] in_bounds'0 index (shallow_model'0 self)}
     any
-    [ return' (result:uint8)-> {[%#span68] inv'9 result}
-      {[%#span67] has_value'0 index (shallow_model'0 self) result}
+    [ return' (result:uint8)-> {[%#span57] inv'8 result}
+      {[%#span56] has_value'0 index (shallow_model'0 self) result}
       (! return' {result}) ]
     
   
   predicate resolve'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span69]  ^ self =  * self
-  
-  use seq.Seq
+    [%#span58]  ^ self =  * self
   
   function singleton'0 (v : usize) : Seq'0.t_seq usize
   
-  axiom singleton'0_spec : forall v : usize . ([%#span70] inv'3 v)
-   -> ([%#span73] inv'4 (singleton'0 v))
-  && ([%#span72] index_logic'0 (singleton'0 v) 0 = v) && ([%#span71] len'1 (singleton'0 v) = 1)
+  axiom singleton'0_spec : forall v : usize . ([%#span59] inv'3 v)
+   -> ([%#span61] index_logic'0 (singleton'0 v) 0 = v) && ([%#span60] len'1 (singleton'0 v) = 1)
   
   predicate completed'1 (self : borrowed (Range'0.t_range usize)) =
-    [%#span74] resolve'1 self
+    [%#span62] resolve'1 self
     /\ deep_model'0 (Core_Ops_Range_Range_Type.range_start ( * self))
     >= deep_model'0 (Core_Ops_Range_Range_Type.range_end ( * self))
   
-  let rec next'1 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span75] inv'8 self}
+  let rec next'1 (self:borrowed (Range'0.t_range usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span63] inv'7 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span77] inv'7 result}
-      {[%#span76] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span65] inv'6 result}
+      {[%#span64] match result with
         | Option'0.C_None -> completed'1 self
         | Option'0.C_Some v -> produces'1 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -675,32 +612,32 @@ module C08Haystack_Search
   
   function new'3 (x : Range'0.t_range usize) : Snapshot'0.t_snapshot (Range'0.t_range usize)
   
-  axiom new'3_spec : forall x : Range'0.t_range usize . ([%#span78] inv'1 x)  -> ([%#span79] deref'2 (new'3 x) = x)
+  axiom new'3_spec : forall x : Range'0.t_range usize . ([%#span66] inv'1 x)  -> ([%#span67] deref'2 (new'3 x) = x)
   
   predicate into_iter_post'1 (self : Range'0.t_range usize) (res : Range'0.t_range usize) =
-    [%#span80] self = res
+    [%#span68] self = res
   
   predicate into_iter_pre'1 (self : Range'0.t_range usize) =
-    [%#span81] true
+    [%#span69] true
   
-  let rec into_iter'1 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span83] inv'1 self}
-    {[@expl:precondition] [%#span82] into_iter_pre'1 self}
+  let rec into_iter'1 (self:Range'0.t_range usize) (return'  (ret:Range'0.t_range usize))= {[@expl:precondition] [%#span71] inv'1 self}
+    {[@expl:precondition] [%#span70] into_iter_pre'1 self}
     any
-    [ return' (result:Range'0.t_range usize)-> {[%#span84] inv'1 result}
-      {[%#span82] into_iter_post'1 self result}
+    [ return' (result:Range'0.t_range usize)-> {[%#span72] inv'1 result}
+      {[%#span70] into_iter_post'1 self result}
       (! return' {result}) ]
     
   
   predicate resolve'0 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
-    [%#span69]  ^ self =  * self
+    [%#span58]  ^ self =  * self
   
   predicate completed'0 (self : borrowed (RangeInclusive'0.t_rangeinclusive usize)) =
-    [%#span85] is_empty_log'0 ( * self) /\ is_empty_log'0 ( ^ self)
+    [%#span73] is_empty_log'0 ( * self) /\ is_empty_log'0 ( ^ self)
   
-  let rec next'0 (self:borrowed (RangeInclusive'0.t_rangeinclusive usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span86] inv'6 self}
+  let rec next'0 (self:borrowed (RangeInclusive'0.t_rangeinclusive usize)) (return'  (ret:Option'0.t_option usize))= {[@expl:precondition] [%#span74] inv'5 self}
     any
-    [ return' (result:Option'0.t_option usize)-> {[%#span87] inv'7 result}
-      {[%#span76] match result with
+    [ return' (result:Option'0.t_option usize)-> {[%#span75] inv'6 result}
+      {[%#span64] match result with
         | Option'0.C_None -> completed'0 self
         | Option'0.C_Some v -> produces'0 ( * self) (singleton'0 v) ( ^ self)
         end}
@@ -708,12 +645,12 @@ module C08Haystack_Search
     
   
   function index_logic'1 [@inline:trivial] (self : Vec'0.t_vec uint8 (Global'0.t_global)) (ix : int) : uint8 =
-    [%#span88] index_logic'2 (shallow_model'1 self) ix
+    [%#span76] index_logic'2 (shallow_model'1 self) ix
   
   predicate match_at'0 [#"../08_haystack.rs" 7 0 7 77] (needle : Vec'0.t_vec uint8 (Global'0.t_global)) (haystack : Vec'0.t_vec uint8 (Global'0.t_global)) (pos : int) (len : int)
     
    =
-    [%#span89] len <= len'2 (shallow_model'0 needle)
+    [%#span77] len <= len'2 (shallow_model'0 needle)
     /\ pos <= len'2 (shallow_model'0 haystack) - len
     /\ (forall i : int . 0 <= i /\ i < len  -> index_logic'1 needle i = index_logic'1 haystack (pos + i))
   
@@ -729,43 +666,43 @@ module C08Haystack_Search
   
   function new'2 (x : Seq'0.t_seq usize) : Snapshot'0.t_snapshot (Seq'0.t_seq usize)
   
-  axiom new'2_spec : forall x : Seq'0.t_seq usize . ([%#span78] inv'4 x)  -> ([%#span79] deref'0 (new'2 x) = x)
+  axiom new'2_spec : forall x : Seq'0.t_seq usize . ([%#span66] inv'4 x)  -> ([%#span67] deref'0 (new'2 x) = x)
   
   function new'1 (x : RangeInclusive'0.t_rangeinclusive usize) : Snapshot'0.t_snapshot (RangeInclusive'0.t_rangeinclusive usize)
     
   
-  axiom new'1_spec : forall x : RangeInclusive'0.t_rangeinclusive usize . ([%#span78] inv'0 x)
-   -> ([%#span79] deref'1 (new'1 x) = x)
+  axiom new'1_spec : forall x : RangeInclusive'0.t_rangeinclusive usize . ([%#span66] inv'0 x)
+   -> ([%#span67] deref'1 (new'1 x) = x)
   
   predicate into_iter_post'0 (self : RangeInclusive'0.t_rangeinclusive usize) (res : RangeInclusive'0.t_rangeinclusive usize)
     
    =
-    [%#span80] self = res
+    [%#span68] self = res
   
   predicate into_iter_pre'0 (self : RangeInclusive'0.t_rangeinclusive usize) =
-    [%#span81] true
+    [%#span69] true
   
-  let rec into_iter'0 (self:RangeInclusive'0.t_rangeinclusive usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span83] inv'0 self}
-    {[@expl:precondition] [%#span82] into_iter_pre'0 self}
+  let rec into_iter'0 (self:RangeInclusive'0.t_rangeinclusive usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span71] inv'0 self}
+    {[@expl:precondition] [%#span70] into_iter_pre'0 self}
     any
-    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span84] inv'0 result}
-      {[%#span82] into_iter_post'0 self result}
+    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span72] inv'0 result}
+      {[%#span70] into_iter_post'0 self result}
       (! return' {result}) ]
     
   
-  let rec new'0 (start:usize) (end':usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span91] inv'3 end'}
-    {[@expl:precondition] [%#span90] inv'3 start}
+  let rec new'0 (start:usize) (end':usize) (return'  (ret:RangeInclusive'0.t_rangeinclusive usize))= {[@expl:precondition] [%#span79] inv'3 end'}
+    {[@expl:precondition] [%#span78] inv'3 start}
     any
-    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span95] inv'0 result}
-      {[%#span94] deep_model'0 start <= deep_model'0 end'  -> not is_empty_log'0 result}
-      {[%#span93] end_log'0 result = end'}
-      {[%#span92] start_log'0 result = start}
+    [ return' (result:RangeInclusive'0.t_rangeinclusive usize)-> {[%#span83] inv'0 result}
+      {[%#span82] deep_model'0 start <= deep_model'0 end'  -> not is_empty_log'0 result}
+      {[%#span81] end_log'0 result = end'}
+      {[%#span80] start_log'0 result = start}
       (! return' {result}) ]
     
   
-  let rec len'0 (self:Vec'0.t_vec uint8 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span96] inv'2 self}
+  let rec len'0 (self:Vec'0.t_vec uint8 (Global'0.t_global)) (return'  (ret:usize))= {[@expl:precondition] [%#span84] inv'2 self}
     any
-    [ return' (result:usize)-> {[%#span97] UIntSize.to_int result = len'2 (shallow_model'0 self)} (! return' {result}) ]
+    [ return' (result:usize)-> {[%#span85] UIntSize.to_int result = len'2 (shallow_model'0 self)} (! return' {result}) ]
     
   
   let rec search (needle:Vec'0.t_vec uint8 (Global'0.t_global)) (haystack:Vec'0.t_vec uint8 (Global'0.t_global)) (return'  (ret:usize))= {[%#s08_haystack11] len'2 (shallow_model'0 needle)
diff --git a/creusot/tests/should_succeed/vector/09_capacity.coma b/creusot/tests/should_succeed/vector/09_capacity.coma
index aa68d9c222..278c886575 100644
--- a/creusot/tests/should_succeed/vector/09_capacity.coma
+++ b/creusot/tests/should_succeed/vector/09_capacity.coma
@@ -101,22 +101,7 @@ module Alloc_Alloc_Global_Type
     
 end
 module CreusotContracts_Logic_Seq2_Seq_Type
-  use seq.Seq
-  
-  type t_seq 't =
-    | C_Seq (Seq.seq 't)
-  
-  function any_l (_ : 'b) : 'a
-  
-  let rec t_seq < 't > (input:t_seq 't) (ret  (field_0:Seq.seq 't))= any
-    [ good (field_0:Seq.seq 't)-> {C_Seq field_0 = input} (! ret {field_0})
-    | bad (field_0:Seq.seq 't)-> {C_Seq field_0 <> input} {false} any ]
-    
-  
-  function seq_0 [@inline:trivial] (self : t_seq 't) : Seq.seq 't =
-    match self with
-      | C_Seq a -> a
-      end
+  type t_seq 't
 end
 module C09Capacity_ChangeCapacity
   type t
@@ -133,47 +118,39 @@ module C09Capacity_ChangeCapacity
   
   let%span s09_capacity5 = "../09_capacity.rs" 5 0 5 69
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
+  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span7 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span8 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span8 = "" 0 0 0 0
   
-  let%span span9 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span10 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span11 = "" 0 0 0 0
+  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span12 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span12 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
   
-  let%span span13 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span13 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
   
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span14 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span15 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
+  let%span span15 = "" 0 0 0 0
   
-  let%span span16 = "../../../../../creusot-contracts/src/logic/ops.rs" 20 8 20 31
+  let%span span16 = "../../../../../creusot-contracts/src/std/vec.rs" 125 26 125 43
   
-  let%span span17 = "../../../../../creusot-contracts/src/model.rs" 108 8 108 31
+  let%span span17 = "" 0 0 0 0
   
-  let%span span18 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
+  let%span span18 = "../../../../../creusot-contracts/src/std/vec.rs" 121 26 121 43
   
   let%span span19 = "" 0 0 0 0
   
-  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 125 26 125 43
+  let%span span20 = "../../../../../creusot-contracts/src/std/vec.rs" 117 26 117 43
   
   let%span span21 = "" 0 0 0 0
   
-  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 121 26 121 43
-  
-  let%span span23 = "" 0 0 0 0
-  
-  let%span span24 = "../../../../../creusot-contracts/src/std/vec.rs" 117 26 117 43
-  
-  let%span span25 = "" 0 0 0 0
-  
-  let%span span26 = "../../../../../creusot-contracts/src/std/vec.rs" 113 26 113 43
+  let%span span22 = "../../../../../creusot-contracts/src/std/vec.rs" 113 26 113 43
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
@@ -185,20 +162,15 @@ module C09Capacity_ChangeCapacity
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span6] inv'2 self)  -> ([%#span7] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span6] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span8] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span10] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span9] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span7] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -216,47 +188,44 @@ module C09Capacity_ChangeCapacity
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span11] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span8] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span12] inv'0 self)
-   -> ([%#span14] inv'2 (shallow_model'0 self))
-  && ([%#span13] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span9] inv'0 self)
+   -> ([%#span10] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span15] inv'2 (shallow_model'0 self)
+    [%#span11] inv'2 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
-  use seq.Seq
-  
-  function index_logic'1 (self : Seq'0.t_seq t) (x : int) : t
+  function index_logic'1 (self : Seq'0.t_seq t) (_2 : int) : t
   
   function index_logic'0 [@inline:trivial] (self : Vec'0.t_vec t (Global'0.t_global)) (ix : int) : t =
-    [%#span16] index_logic'1 (shallow_model'0 self) ix
+    [%#span12] index_logic'1 (shallow_model'0 self) ix
   
   function shallow_model'1 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) : Seq'0.t_seq t =
-    [%#span17] shallow_model'0 ( * self)
+    [%#span13] shallow_model'0 ( * self)
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span18]  ^ self =  * self
+    [%#span14]  ^ self =  * self
   
-  let rec shrink_to'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (min_capacity:usize) (return'  (ret:()))= {[@expl:precondition] [%#span19] inv'1 self}
-    any [ return' (result:())-> {[%#span20] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
+  let rec shrink_to'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (min_capacity:usize) (return'  (ret:()))= {[@expl:precondition] [%#span15] inv'1 self}
+    any [ return' (result:())-> {[%#span16] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
   
-  let rec shrink_to_fit'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (return'  (ret:()))= {[@expl:precondition] [%#span21] inv'1 self}
-    any [ return' (result:())-> {[%#span22] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
+  let rec shrink_to_fit'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (return'  (ret:()))= {[@expl:precondition] [%#span17] inv'1 self}
+    any [ return' (result:())-> {[%#span18] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
   
-  let rec reserve_exact'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (additional:usize) (return'  (ret:()))= {[@expl:precondition] [%#span23] inv'1 self}
-    any [ return' (result:())-> {[%#span24] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
+  let rec reserve_exact'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (additional:usize) (return'  (ret:()))= {[@expl:precondition] [%#span19] inv'1 self}
+    any [ return' (result:())-> {[%#span20] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
   
-  let rec reserve'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (additional:usize) (return'  (ret:()))= {[@expl:precondition] [%#span25] inv'1 self}
-    any [ return' (result:())-> {[%#span26] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
+  let rec reserve'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (additional:usize) (return'  (ret:()))= {[@expl:precondition] [%#span21] inv'1 self}
+    any [ return' (result:())-> {[%#span22] shallow_model'0 ( ^ self) = shallow_model'1 self} (! return' {result}) ] 
   
   let rec change_capacity (v:borrowed (Vec'0.t_vec t (Global'0.t_global))) (return'  (ret:()))= {[%#s09_capacity3] inv'1 v}
     (! bb0
@@ -326,31 +295,23 @@ module C09Capacity_ClearVec
   
   let%span s09_capacity1 = "../09_capacity.rs" 13 10 13 26
   
-  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 72 15 72 19
-  
-  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 71 14 71 25
+  let%span span2 = "../../../../../creusot-contracts/src/logic/seq2.rs" 68 14 68 25
   
-  let%span span4 = "../../../../../creusot-contracts/src/logic/seq2.rs" 19 4 19 25
+  let%span span3 = "../../../../../creusot-contracts/src/logic/seq2.rs" 16 14 16 36
   
-  let%span span5 = "../../../../../creusot-contracts/src/logic/seq2.rs" 23 14 23 36
+  let%span span4 = "" 0 0 0 0
   
-  let%span span6 = "../../../../../creusot-contracts/src/logic/seq2.rs" 21 4 21 10
+  let%span span5 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
   
-  let%span span7 = "" 0 0 0 0
+  let%span span6 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
   
-  let%span span8 = "../../../../../creusot-contracts/src/std/vec.rs" 19 21 19 25
+  let%span span7 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
   
-  let%span span9 = "../../../../../creusot-contracts/src/std/vec.rs" 18 14 18 41
+  let%span span8 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
   
-  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 19 4 19 36
+  let%span span9 = "" 0 0 0 0
   
-  let%span span11 = "../../../../../creusot-contracts/src/std/vec.rs" 60 20 60 41
-  
-  let%span span12 = "../../../../../creusot-contracts/src/resolve.rs" 26 20 26 34
-  
-  let%span span13 = "" 0 0 0 0
-  
-  let%span span14 = "../../../../../creusot-contracts/src/std/vec.rs" 129 26 129 45
+  let%span span10 = "../../../../../creusot-contracts/src/std/vec.rs" 129 26 129 45
   
   use CreusotContracts_Logic_Seq2_Seq_Type as Seq'0
   
@@ -362,20 +323,15 @@ module C09Capacity_ClearVec
   
   use prelude.prelude.Int
   
-  use seq.Seq
-  
-  use CreusotContracts_Logic_Seq2_Seq_Type as CreusotContracts_Logic_Seq2_Seq_Type
-  
   function len'0 (self : Seq'0.t_seq t) : int
   
-  axiom len'0_spec : forall self : Seq'0.t_seq t . ([%#span2] inv'2 self)  -> ([%#span3] len'0 self >= 0)
+  axiom len'0_spec : forall self : Seq'0.t_seq t . [%#span2] len'0 self >= 0
   
-  constant empty'0 : Seq'0.t_seq t = [%#span4] ()
+  constant empty'0 : Seq'0.t_seq t
   
-  function empty_len'0 (_1 : ()) : () =
-    [%#span6] ()
+  function empty_len'0 (_1 : ()) : ()
   
-  axiom empty_len'0_spec : forall _1 : () . [%#span5] len'0 (empty'0 : Seq'0.t_seq t) = 0
+  axiom empty_len'0_spec : forall _1 : () . [%#span3] len'0 (empty'0 : Seq'0.t_seq t) = 0
   
   use Alloc_Alloc_Global_Type as Global'0
   
@@ -393,28 +349,27 @@ module C09Capacity_ClearVec
   
   use prelude.prelude.UIntSize
   
-  constant max'0 : usize = [%#span7] (18446744073709551615 : usize)
+  constant max'0 : usize = [%#span4] (18446744073709551615 : usize)
   
   predicate inv'0 (_x : Vec'0.t_vec t (Global'0.t_global))
   
   function shallow_model'0 (self : Vec'0.t_vec t (Global'0.t_global)) : Seq'0.t_seq t
   
-  axiom shallow_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span8] inv'0 self)
-   -> ([%#span10] inv'2 (shallow_model'0 self))
-  && ([%#span9] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
+  axiom shallow_model'0_spec : forall self : Vec'0.t_vec t (Global'0.t_global) . ([%#span5] inv'0 self)
+   -> ([%#span6] len'0 (shallow_model'0 self) <= UIntSize.to_int (max'0 : usize))
   
   predicate invariant'0 (self : Vec'0.t_vec t (Global'0.t_global)) =
-    [%#span11] inv'2 (shallow_model'0 self)
+    [%#span7] inv'2 (shallow_model'0 self)
   
   axiom inv'0 : forall x : Vec'0.t_vec t (Global'0.t_global) . inv'0 x = true
   
   use prelude.prelude.Intrinsic
   
   predicate resolve'0 (self : borrowed (Vec'0.t_vec t (Global'0.t_global))) =
-    [%#span12]  ^ self =  * self
+    [%#span8]  ^ self =  * self
   
-  let rec clear'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (return'  (ret:()))= {[@expl:precondition] [%#span13] inv'1 self}
-    any [ return' (result:())-> {[%#span14] len'0 (shallow_model'0 ( ^ self)) = 0} (! return' {result}) ] 
+  let rec clear'0 (self:borrowed (Vec'0.t_vec t (Global'0.t_global))) (return'  (ret:()))= {[@expl:precondition] [%#span9] inv'1 self}
+    any [ return' (result:())-> {[%#span10] len'0 (shallow_model'0 ( ^ self)) = 0} (! return' {result}) ] 
   
   let rec clear_vec (v:borrowed (Vec'0.t_vec t (Global'0.t_global))) (return'  (ret:()))= {[%#s09_capacity0] inv'1 v}
     (! bb0