Add context accessor to all encoders and decoders

crates/musli-core/src/de/as_decoder.rs

@@ -5,7 +5,7 @@ use super::Decoder;
 /// Trait that allows a type to be repeatedly coerced into a decoder.
 pub trait AsDecoder {
     /// Context associated with the decoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// The decoder we reborrow as.
     type Decoder<'this>: Decoder<
         'this,

crates/musli-core/src/de/decoder.rs

@@ -24,7 +24,7 @@ pub enum TryFastDecode<T, D> {
 #[must_use = "Decoders must be consumed through one of its decode_* methods"]
 pub trait Decoder<'de>: Sized {
     /// Context associated with the decoder.
-    type Cx: ?Sized + Context<Error = Self::Error, Mode = Self::Mode>;
+    type Cx: Context<Error = Self::Error, Mode = Self::Mode>;
     /// Error associated with decoding.
     type Error;
     /// Mode associated with decoding.
@@ -55,10 +55,11 @@ pub trait Decoder<'de>: Sized {
     #[doc(hidden)]
     type __UseMusliDecoderAttributeMacro;
 
-    /// Perform an operation while accessing the context.
+    /// Access the context associated with the decoder.
     fn cx(&self) -> Self::Cx;
 
     /// Construct an decoder with a different context.
+    #[inline]
     fn with_context<U>(self, cx: U) -> Result<Self::WithContext<U>, <Self::Cx as Context>::Error>
     where
         U: Context,

crates/musli-core/src/de/entries_decoder.rs

@@ -12,7 +12,7 @@ use super::{Decoder, SizeHint};
 #[must_use = "Must call end_entries to complete decoding"]
 pub trait EntriesDecoder<'de> {
     /// Context associated with the decoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// The decoder to use for a tuple field index.
     type DecodeEntryKey<'this>: Decoder<
         'de,
@@ -32,6 +32,9 @@ pub trait EntriesDecoder<'de> {
     where
         Self: 'this;
 
+    /// Access the context associated with the decoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Get a size hint for the size of the map being decoded.
     #[inline]
     fn size_hint(&self) -> SizeHint {

crates/musli-core/src/de/entry_decoder.rs

@@ -5,7 +5,7 @@ use super::{Decoder, SizeHint};
 /// Trait governing how to decode a map entry.
 pub trait EntryDecoder<'de> {
     /// Context associated with the decoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// The decoder to use for a tuple field index.
     type DecodeKey<'this>: Decoder<
         'de,
@@ -23,6 +23,9 @@ pub trait EntryDecoder<'de> {
         Mode = <Self::Cx as Context>::Mode,
     >;
 
+    /// Access the context associated with the decoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Get a size hint for the size of the map being decoded.
     #[inline]
     fn size_hint(&self) -> SizeHint {

crates/musli-core/src/de/map_decoder.rs

@@ -5,7 +5,7 @@ use super::{Decode, Decoder, EntriesDecoder, EntryDecoder, SizeHint};
 /// Trait governing how to decode a sequence of pairs.
 pub trait MapDecoder<'de> {
     /// Context associated with the decoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// The decoder to use for a key.
     type DecodeEntry<'this>: EntryDecoder<'de, Cx = Self::Cx>
     where
@@ -15,6 +15,9 @@ pub trait MapDecoder<'de> {
     where
         Self: 'this;
 
+    /// Access the context associated with the decoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Get a size hint of known remaining elements.
     #[inline]
     fn size_hint(&self) -> SizeHint {

crates/musli-core/src/de/sequence_decoder.rs

@@ -5,7 +5,7 @@ use super::{Decode, Decoder, SizeHint};
 /// Trait governing how to decode a sequence.
 pub trait SequenceDecoder<'de> {
     /// Context associated with the decoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// The decoder for individual items.
     type DecodeNext<'this>: Decoder<
         'de,
@@ -16,6 +16,9 @@ pub trait SequenceDecoder<'de> {
     where
         Self: 'this;
 
+    /// Access the context associated with the decoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Get a size hint of known remaining elements.
     #[inline]
     fn size_hint(&self) -> SizeHint {

crates/musli-core/src/de/variant_decoder.rs

@@ -5,7 +5,7 @@ use super::Decoder;
 /// Trait governing how to decode a variant.
 pub trait VariantDecoder<'de> {
     /// Context associated with the decoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// The decoder to use for the variant tag.
     type DecodeTag<'this>: Decoder<
         'de,
@@ -25,6 +25,9 @@ pub trait VariantDecoder<'de> {
     where
         Self: 'this;
 
+    /// Access the context associated with the decoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Return the decoder for the first value in the pair.
     ///
     /// If this is a map the first value would be the key of the map, if this is

crates/musli-core/src/de/visitor.rs

@@ -200,23 +200,23 @@ where
 
     /// Indicates that the visited type is a sequence.
     #[inline]
-    fn visit_sequence<D>(self, cx: C, decoder: &mut D) -> Result<Self::Ok, C::Error>
+    fn visit_sequence<D>(self, decoder: &mut D) -> Result<Self::Ok, C::Error>
     where
         D: ?Sized + SequenceDecoder<'de, Cx = C>,
     {
-        Err(cx.message(expecting::unsupported_type(
+        Err(decoder.cx().message(expecting::unsupported_type(
             &expecting::SequenceWith(decoder.size_hint()),
             ExpectingWrapper::new(&self),
         )))
     }
 
     /// Indicates that the visited type is a map.
     #[inline]
-    fn visit_map<D>(self, cx: C, decoder: &mut D) -> Result<Self::Ok, <D::Cx as Context>::Error>
+    fn visit_map<D>(self, decoder: &mut D) -> Result<Self::Ok, <D::Cx as Context>::Error>
     where
         D: ?Sized + MapDecoder<'de, Cx = C>,
     {
-        Err(cx.message(expecting::unsupported_type(
+        Err(decoder.cx().message(expecting::unsupported_type(
             &expecting::MapWith(decoder.size_hint()),
             ExpectingWrapper::new(&self),
         )))
@@ -242,11 +242,11 @@ where
 
     /// Indicates that the visited type is a variant.
     #[inline]
-    fn visit_variant<D>(self, cx: C, _: &mut D) -> Result<Self::Ok, C::Error>
+    fn visit_variant<D>(self, decoder: &mut D) -> Result<Self::Ok, C::Error>
     where
         D: VariantDecoder<'de, Cx = C>,
     {
-        Err(cx.message(expecting::unsupported_type(
+        Err(decoder.cx().message(expecting::unsupported_type(
             &expecting::Variant,
             ExpectingWrapper::new(&self),
         )))

crates/musli-core/src/en/encoder.rs

@@ -24,7 +24,7 @@ where
 #[must_use = "Encoders must be consumed through one of its encode_* methods"]
 pub trait Encoder: Sized {
     /// Context associated with the encoder.
-    type Cx: ?Sized + Context<Error = Self::Error, Mode = Self::Mode>;
+    type Cx: Context<Error = Self::Error, Mode = Self::Mode>;
     /// The type returned by the encoder. For [Encode] implementations ensures
     /// that they are used correctly, since only functions returned by the
     /// [Encoder] is capable of returning this value.
@@ -60,7 +60,7 @@ pub trait Encoder: Sized {
     #[doc(hidden)]
     type __UseMusliEncoderAttributeMacro;
 
-    /// Perform an operation while accessing the context.
+    /// Access the context associated with the encoder.
     fn cx(&self) -> Self::Cx;
 
     /// Construct an encoder with a different context.

crates/musli-core/src/en/entries_encoder.rs

@@ -11,7 +11,7 @@ use super::{Encode, Encoder};
 /// format might be degraded.
 pub trait EntriesEncoder {
     /// Context associated with the encoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// Result type of the encoder.
     type Ok;
     /// The encoder returned when advancing the map encoder to encode the key.
@@ -33,6 +33,9 @@ pub trait EntriesEncoder {
     where
         Self: 'this;
 
+    /// Access the context associated with the encoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Return the encoder for the key in the entry.
     #[must_use = "Encoders must be consumed"]
     fn encode_entry_key(

crates/musli-core/src/en/entry_encoder.rs

@@ -5,7 +5,7 @@ use super::{Encode, Encoder};
 /// Trait governing how to encode a map entry.
 pub trait EntryEncoder {
     /// Context associated with the encoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// Result type of the encoder.
     type Ok;
     /// The encoder returned when advancing the map encoder to encode the key.
@@ -27,6 +27,9 @@ pub trait EntryEncoder {
     where
         Self: 'this;
 
+    /// Access the context associated with the encoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Return the encoder for the key in the entry.
     #[must_use = "Encoders must be consumed"]
     fn encode_key(&mut self) -> Result<Self::EncodeKey<'_>, <Self::Cx as Context>::Error>;

crates/musli-core/src/en/map_encoder.rs

@@ -5,14 +5,17 @@ use super::{Encode, EntryEncoder};
 /// Encoder for a map.
 pub trait MapEncoder {
     /// Context associated with the encoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// Result type of the encoder.
     type Ok;
     /// Encode the next pair.
     type EncodeEntry<'this>: EntryEncoder<Cx = Self::Cx, Ok = Self::Ok>
     where
         Self: 'this;
 
+    /// Access the context associated with the encoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Encode the next pair.
     #[must_use = "Encoders must be consumed"]
     fn encode_entry(&mut self) -> Result<Self::EncodeEntry<'_>, <Self::Cx as Context>::Error>;

crates/musli-core/src/en/variant_encoder.rs

@@ -6,7 +6,7 @@ use super::{Encode, Encoder};
 #[must_use = "Must call end_variant to finish encoding"]
 pub trait VariantEncoder {
     /// Context associated with the encoder.
-    type Cx: ?Sized + Context;
+    type Cx: Context;
     /// Result type of the encoder.
     type Ok;
     /// The encoder returned when advancing the map encoder to encode the key.
@@ -28,6 +28,9 @@ pub trait VariantEncoder {
     where
         Self: 'this;
 
+    /// Access the context associated with the encoder.
+    fn cx(&self) -> Self::Cx;
+
     /// Return the encoder for the first element in the variant.
     #[must_use = "Encoders must be consumed"]
     fn encode_tag(&mut self) -> Result<Self::EncodeTag<'_>, <Self::Cx as Context>::Error>;

crates/musli-core/src/lib.rs

@@ -174,7 +174,7 @@ pub use musli_macros::decoder;
 /// #[musli_core::visitor(crate = musli_core)]
 /// impl<'de, C> Visitor<'de, C> for AnyVisitor
 /// where
-///     C: ?Sized + Context,
+///     C: Context,
 /// {
 ///     type Ok = ();
 ///

crates/musli-core/src/never.rs

@@ -192,6 +192,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn decode_entry_key(&mut self) -> Result<Option<Self::DecodeEntryKey<'_>>, C::Error> {
         match self._never {}
@@ -222,6 +227,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn decode_tag(&mut self) -> Result<Self::DecodeTag<'_>, C::Error> {
         match self._never {}
@@ -247,6 +257,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn size_hint(&self) -> SizeHint {
         match self._never {}
@@ -276,6 +291,11 @@ where
         Self: 'this;
     type DecodeValue = Self;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn decode_key(&mut self) -> Result<Self::DecodeKey<'_>, C::Error> {
         match self._never {}
@@ -297,6 +317,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn decode_next(&mut self) -> Result<Self::DecodeNext<'_>, C::Error> {
         match self._never {}
@@ -410,6 +435,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn encode_entry(&mut self) -> Result<Self::EncodeEntry<'_>, C::Error> {
         match self._never {}
@@ -436,6 +466,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn encode_key(&mut self) -> Result<Self::EncodeKey<'_>, C::Error> {
         match self._never {}
@@ -468,6 +503,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn encode_entry_key(&mut self) -> Result<Self::EncodeEntryKey<'_>, C::Error> {
         match self._never {}
@@ -500,6 +540,11 @@ where
     where
         Self: 'this;
 
+    #[inline]
+    fn cx(&self) -> Self::Cx {
+        match self._never {}
+    }
+
     #[inline]
     fn encode_tag(&mut self) -> Result<Self::EncodeTag<'_>, C::Error> {
         match self._never {}