[flow] Fix handling for react element shorthand

Summary:
Instead of special-casing when we enter a render type we should directly handle TypeAppTs to account for the component syntax shorthand.

Changelog: [internal]

Reviewed By: SamChou19815

Differential Revision: D52094619

fbshipit-source-id: eec1690e01d5b35db42cb96ddb9f357388da2b00

src/typing/ty_normalizer.ml

@@ -802,10 +802,6 @@ module Make (I : INPUT) : S = struct
         | _ -> type_app ~env type_ (Some targs))
       | DefT (r, InstanceT { super; inst; _ }) -> instance_t ~env r super inst
       | DefT (_, ClassT t) -> class_t ~env t
-      | DefT (reason, ReactAbstractComponentT { component_kind = Nominal (_, name); _ })
-        when Env.(env.under_render_type) ->
-        let symbol = Reason_utils.component_symbol env name reason in
-        return (Ty.Generic (symbol, Ty.ComponentKind, None))
       | DefT (_, ReactAbstractComponentT { config; instance; renders; component_kind = _ }) ->
         let%bind config = type__ ~env config in
         let%bind instance = type__ ~env instance in
@@ -824,9 +820,7 @@ module Make (I : INPUT) : S = struct
         in
         return (Ty.Generic (symbol, Ty.ComponentKind, None))
       | DefT (_, RendersT (StructuralRenders { renders_variant; renders_structural_type })) ->
-        let%bind ty =
-          type_ctor ~env:(Env.set_under_render_type true env) ~cont renders_structural_type
-        in
+        let%bind ty = type_ctor ~env ~cont renders_structural_type in
         let variant =
           match renders_variant with
           | T.RendersNormal -> Ty.RendersNormal
@@ -1337,7 +1331,15 @@ module Make (I : INPUT) : S = struct
         | DefT (_, TypeT (_, DefT (r, InstanceT { inst; _ })))
         | DefT (_, ClassT (DefT (r, InstanceT { inst; _ }))) ->
           instance_app ~env r inst tparams targs
-        | DefT (r, TypeT (kind, _)) -> type_t_app ~env r kind tparams targs
+        | DefT (r, TypeT (kind, t)) ->
+          (match (t, targs) with
+          | (OpaqueT (_, opaque_type), Some (component :: _))
+            when Some opaque_type.Type.opaque_id
+                 = Flow_js_utils.builtin_react_element_opaque_id (Env.get_cx env) ->
+            (match Lookahead.peek (Env.get_cx env) component with
+            | Lookahead.LowerBounds [t] -> react_element_shorthand ~env r opaque_type targs t
+            | _ -> type_t_app ~env r kind tparams targs)
+          | _ -> type_t_app ~env r kind tparams targs)
         | DefT
             ( r,
               ReactAbstractComponentT
@@ -1408,6 +1410,17 @@ module Make (I : INPUT) : S = struct
           | [] -> Ty.Bot (Ty.NoLowerWithUpper Ty.NoUpper)
           | t :: ts -> Ty.mk_union ~from_bounds:true (t, ts))
 
+    and react_element_shorthand ~env opaque_reason opaque_type targs t =
+      match t with
+      | T.(DefT (reason, ReactAbstractComponentT { component_kind = Nominal (_, name); _ })) ->
+        let symbol = Reason_utils.component_symbol env name reason in
+        return (Ty.Generic (symbol, Ty.ComponentKind, None))
+      | _ ->
+        let name = opaque_type.Type.opaque_name in
+        let opaque_symbol = symbol_from_reason env opaque_reason (Reason.OrdinaryName name) in
+        let%bind targs = optMapM (type__ ~env) targs in
+        return (generic_talias opaque_symbol targs)
+
     and opaque_t ~env reason opaque_type =
       let name = opaque_type.Type.opaque_name in
       let opaque_symbol = symbol_from_reason env reason (Reason.OrdinaryName name) in
@@ -1766,12 +1779,7 @@ module Make (I : INPUT) : S = struct
           }
         | _ -> env
       in
-      let arg_env =
-        match d with
-        | T.ReactPromoteRendersRepresentation _ -> Env.set_under_render_type true env
-        | _ -> env
-      in
-      let%bind ty = type__ ~env:arg_env t in
+      let%bind ty = type__ ~env t in
       match d with
       | T.ReactDRO _ -> return ty
       | T.NonMaybeType -> return (Ty.Utility (Ty.NonMaybeType ty))

src/typing/ty_normalizer_env.ml

@@ -179,7 +179,6 @@ type t = {
      or a unique ID of the type alias to make this distinction, but at the moment
      keeping this information around introduces a small space regression. *)
   under_type_alias: SymbolSet.t;
-  under_render_type: bool;
   (* Detect recursive types *)
   seen_tvar_ids: ISet.t;
   seen_eval_ids: Type.EvalIdSet.t;
@@ -194,7 +193,6 @@ let init ~options ~genv ~tparams_rev ~imported_names =
     infer_tparams = [];
     imported_names;
     under_type_alias = SymbolSet.empty;
-    under_render_type = false;
     seen_tvar_ids = ISet.empty;
     seen_eval_ids = Type.EvalIdSet.empty;
   }
@@ -223,6 +221,4 @@ let add_typeparam env typeparam = { env with tparams_rev = typeparam :: env.tpar
 
 let set_type_alias name e = { e with under_type_alias = SymbolSet.add name e.under_type_alias }
 
-let set_under_render_type b e = { e with under_render_type = b }
-
 let seen_type_alias name e = SymbolSet.mem name e.under_type_alias

tests/type_at_pos_reactscript/render_types.js

@@ -20,3 +20,7 @@ type StarRenders = renders* Foo;
 
 type RendersElement = renders React$Element<typeof Foo>;
 //   ^
+
+component Poly<T>() { return null }
+type PolyElement = renders Poly<number>;
+//   ^

tests/type_at_pos_reactscript/type_at_pos_reactscript.exp

@@ -88,9 +88,14 @@ render_types.js:18:6,18:16
 
 render_types.js:21:6
 Flags:
-type RendersElement = renders React$Element<Foo>
+type RendersElement = renders Foo
 render_types.js:21:6,21:19
 
+render_types.js:25:6
+Flags:
+type PolyElement = renders Poly<number>
+render_types.js:25:6,25:16
+
 render_types.js:8:7 = {
   "types":{
     "unevaluated":{