From 6438b9eca8fed1972627911121aee5c8b8906a97 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 13 Mar 2025 17:36:33 +0000
Subject: Use {Decodable,Encodable}_NoContext in type_ir

---
 compiler/rustc_macros/src/serialize.rs | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

(limited to 'compiler/rustc_macros/src/serialize.rs')

diff --git a/compiler/rustc_macros/src/serialize.rs b/compiler/rustc_macros/src/serialize.rs
index 2c33a0ac0aa..77b2735064a 100644
--- a/compiler/rustc_macros/src/serialize.rs
+++ b/compiler/rustc_macros/src/serialize.rs
@@ -15,7 +15,7 @@ pub(super) fn type_decodable_derive(
         quote! {}
     };
 
-    s.add_impl_generic(parse_quote! { #decoder_ty: ::rustc_type_ir::codec::TyDecoder #bound });
+    s.add_impl_generic(parse_quote! { #decoder_ty: ::rustc_middle::ty::codec::TyDecoder #bound });
     s.add_bounds(synstructure::AddBounds::Fields);
     s.underscore_const(true);
 
@@ -45,12 +45,12 @@ pub(super) fn decodable_derive(mut s: synstructure::Structure<'_>) -> proc_macro
     decodable_body(s, decoder_ty)
 }
 
-pub(super) fn decodable_generic_derive(
+pub(super) fn decodable_nocontext_derive(
     mut s: synstructure::Structure<'_>,
 ) -> proc_macro2::TokenStream {
     let decoder_ty = quote! { __D };
     s.add_impl_generic(parse_quote! { #decoder_ty: ::rustc_serialize::Decoder });
-    s.add_bounds(synstructure::AddBounds::Generics);
+    s.add_bounds(synstructure::AddBounds::Fields);
     s.underscore_const(true);
 
     decodable_body(s, decoder_ty)
@@ -141,7 +141,7 @@ pub(super) fn type_encodable_derive(
     };
 
     let encoder_ty = quote! { __E };
-    s.add_impl_generic(parse_quote! { #encoder_ty: ::rustc_type_ir::codec::TyEncoder #bound });
+    s.add_impl_generic(parse_quote! { #encoder_ty: ::rustc_middle::ty::codec::TyEncoder #bound });
     s.add_bounds(synstructure::AddBounds::Fields);
     s.underscore_const(true);
 
@@ -171,12 +171,12 @@ pub(super) fn encodable_derive(mut s: synstructure::Structure<'_>) -> proc_macro
     encodable_body(s, encoder_ty, false)
 }
 
-pub(super) fn encodable_generic_derive(
+pub(super) fn encodable_nocontext_derive(
     mut s: synstructure::Structure<'_>,
 ) -> proc_macro2::TokenStream {
     let encoder_ty = quote! { __E };
     s.add_impl_generic(parse_quote! { #encoder_ty: ::rustc_serialize::Encoder });
-    s.add_bounds(synstructure::AddBounds::Generics);
+    s.add_bounds(synstructure::AddBounds::Fields);
     s.underscore_const(true);
 
     encodable_body(s, encoder_ty, false)
-- 
cgit 1.4.1-3-g733a5


From 19c84c8812adb7fa0e7540b5de2541a5995e901a Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Thu, 13 Mar 2025 17:53:36 +0000
Subject: Move codec module back into middle

---
 compiler/rustc_macros/src/serialize.rs             |  26 ++--
 compiler/rustc_metadata/src/rmeta/decoder.rs       |   6 +-
 compiler/rustc_metadata/src/rmeta/encoder.rs       |   4 +-
 .../rustc_middle/src/mir/interpret/allocation.rs   |  11 +-
 .../src/mir/interpret/allocation/init_mask.rs      |  13 +-
 compiler/rustc_middle/src/mir/interpret/mod.rs     |   4 +-
 compiler/rustc_middle/src/mir/mod.rs               |   4 +-
 compiler/rustc_middle/src/query/on_disk_cache.rs   |   6 +-
 compiler/rustc_middle/src/ty/codec.rs              | 155 ++++++++++++---------
 compiler/rustc_middle/src/ty/generic_args.rs       |   4 +-
 compiler/rustc_middle/src/ty/mod.rs                |   5 +-
 compiler/rustc_query_impl/src/plumbing.rs          |   3 +-
 compiler/rustc_type_ir/src/binder.rs               |   4 +-
 compiler/rustc_type_ir/src/codec.rs                |  61 --------
 compiler/rustc_type_ir/src/lib.rs                  |   4 -
 compiler/rustc_type_ir/src/ty_kind.rs              |   6 +-
 16 files changed, 129 insertions(+), 187 deletions(-)
 delete mode 100644 compiler/rustc_type_ir/src/codec.rs

(limited to 'compiler/rustc_macros/src/serialize.rs')

diff --git a/compiler/rustc_macros/src/serialize.rs b/compiler/rustc_macros/src/serialize.rs
index 77b2735064a..673e6cd618f 100644
--- a/compiler/rustc_macros/src/serialize.rs
+++ b/compiler/rustc_macros/src/serialize.rs
@@ -6,16 +6,11 @@ use syn::spanned::Spanned;
 pub(super) fn type_decodable_derive(
     mut s: synstructure::Structure<'_>,
 ) -> proc_macro2::TokenStream {
+    if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
+        s.add_impl_generic(parse_quote! { 'tcx });
+    }
     let decoder_ty = quote! { __D };
-    let bound = if s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
-        quote! { <I = ::rustc_middle::ty::TyCtxt<'tcx>> }
-    } else if s.ast().generics.type_params().any(|ty| ty.ident == "I") {
-        quote! { <I = I> }
-    } else {
-        quote! {}
-    };
-
-    s.add_impl_generic(parse_quote! { #decoder_ty: ::rustc_middle::ty::codec::TyDecoder #bound });
+    s.add_impl_generic(parse_quote! { #decoder_ty: ::rustc_middle::ty::codec::TyDecoder<'tcx> });
     s.add_bounds(synstructure::AddBounds::Fields);
     s.underscore_const(true);
 
@@ -132,16 +127,11 @@ fn decode_field(field: &syn::Field) -> proc_macro2::TokenStream {
 pub(super) fn type_encodable_derive(
     mut s: synstructure::Structure<'_>,
 ) -> proc_macro2::TokenStream {
-    let bound = if s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
-        quote! { <I = ::rustc_middle::ty::TyCtxt<'tcx>> }
-    } else if s.ast().generics.type_params().any(|ty| ty.ident == "I") {
-        quote! { <I = I> }
-    } else {
-        quote! {}
-    };
-
     let encoder_ty = quote! { __E };
-    s.add_impl_generic(parse_quote! { #encoder_ty: ::rustc_middle::ty::codec::TyEncoder #bound });
+    if !s.ast().generics.lifetimes().any(|lt| lt.lifetime.ident == "tcx") {
+        s.add_impl_generic(parse_quote! { 'tcx });
+    }
+    s.add_impl_generic(parse_quote! { #encoder_ty: ::rustc_middle::ty::codec::TyEncoder<'tcx> });
     s.add_bounds(synstructure::AddBounds::Fields);
     s.underscore_const(true);
 
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 6ffbebfffd5..e60904eebeb 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -386,13 +386,11 @@ impl<'a, 'tcx> DecodeContext<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> TyDecoder for DecodeContext<'a, 'tcx> {
+impl<'a, 'tcx> TyDecoder<'tcx> for DecodeContext<'a, 'tcx> {
     const CLEAR_CROSS_CRATE: bool = true;
 
-    type I = TyCtxt<'tcx>;
-
     #[inline]
-    fn interner(&self) -> Self::I {
+    fn interner(&self) -> TyCtxt<'tcx> {
         self.tcx()
     }
 
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 57c941976e4..2b9113242aa 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -378,11 +378,9 @@ impl<'a, 'tcx> Encodable<EncodeContext<'a, 'tcx>> for [u8] {
     }
 }
 
-impl<'a, 'tcx> TyEncoder for EncodeContext<'a, 'tcx> {
+impl<'a, 'tcx> TyEncoder<'tcx> for EncodeContext<'a, 'tcx> {
     const CLEAR_CROSS_CRATE: bool = true;
 
-    type I = TyCtxt<'tcx>;
-
     fn position(&self) -> usize {
         self.opaque.position()
     }
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation.rs b/compiler/rustc_middle/src/mir/interpret/allocation.rs
index aed38414ab1..57aafbb26bc 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation.rs
@@ -16,8 +16,7 @@ use rustc_abi::{Align, HasDataLayout, Size};
 use rustc_ast::Mutability;
 use rustc_data_structures::intern::Interned;
 use rustc_macros::HashStable;
-use rustc_serialize::{Decodable, Encodable};
-use rustc_type_ir::{TyDecoder, TyEncoder};
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 
 use super::{
     AllocId, BadBytesAccess, CtfeProvenance, InterpErrorKind, InterpResult, Pointer,
@@ -112,7 +111,7 @@ struct AllocFlags {
     all_zero: bool,
 }
 
-impl<E: TyEncoder> Encodable<E> for AllocFlags {
+impl<E: Encoder> Encodable<E> for AllocFlags {
     fn encode(&self, encoder: &mut E) {
         // Make sure Align::MAX can be stored with the high 2 bits unset.
         const {
@@ -131,7 +130,7 @@ impl<E: TyEncoder> Encodable<E> for AllocFlags {
     }
 }
 
-impl<D: TyDecoder> Decodable<D> for AllocFlags {
+impl<D: Decoder> Decodable<D> for AllocFlags {
     fn decode(decoder: &mut D) -> Self {
         let flags: u8 = Decodable::decode(decoder);
         let align = flags & 0b0011_1111;
@@ -173,7 +172,7 @@ fn all_zero(buf: &[u8]) -> bool {
 }
 
 /// Custom encoder for [`Allocation`] to more efficiently represent the case where all bytes are 0.
-impl<Prov: Provenance, Extra, Bytes, E: TyEncoder> Encodable<E> for Allocation<Prov, Extra, Bytes>
+impl<Prov: Provenance, Extra, Bytes, E: Encoder> Encodable<E> for Allocation<Prov, Extra, Bytes>
 where
     Bytes: AllocBytes,
     ProvenanceMap<Prov>: Encodable<E>,
@@ -193,7 +192,7 @@ where
     }
 }
 
-impl<Prov: Provenance, Extra, Bytes, D: TyDecoder> Decodable<D> for Allocation<Prov, Extra, Bytes>
+impl<Prov: Provenance, Extra, Bytes, D: Decoder> Decodable<D> for Allocation<Prov, Extra, Bytes>
 where
     Bytes: AllocBytes,
     ProvenanceMap<Prov>: Decodable<D>,
diff --git a/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
index fea5038e6dd..20492cda4e2 100644
--- a/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
+++ b/compiler/rustc_middle/src/mir/interpret/allocation/init_mask.rs
@@ -5,9 +5,8 @@ use std::ops::Range;
 use std::{hash, iter};
 
 use rustc_abi::Size;
-use rustc_macros::{HashStable, TyDecodable, TyEncodable};
-use rustc_serialize::{Decodable, Encodable};
-use rustc_type_ir::{TyDecoder, TyEncoder};
+use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable};
+use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
 
 use super::AllocRange;
 
@@ -19,13 +18,13 @@ type Block = u64;
 /// possible. Currently, if all the blocks have the same value, then the mask represents either a
 /// fully initialized or fully uninitialized const allocation, so we can only store that single
 /// value.
-#[derive(Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(Clone, Debug, Eq, PartialEq, Encodable_NoContext, Decodable_NoContext, Hash, HashStable)]
 pub struct InitMask {
     blocks: InitMaskBlocks,
     len: Size,
 }
 
-#[derive(Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash, HashStable)]
+#[derive(Clone, Debug, Eq, PartialEq, Encodable_NoContext, Decodable_NoContext, Hash, HashStable)]
 enum InitMaskBlocks {
     Lazy {
         /// Whether the lazy init mask is fully initialized or uninitialized.
@@ -194,7 +193,7 @@ struct InitMaskMaterialized {
 // and also produces more output when the high bits of each `u64` are occupied.
 // Note: There is probably a remaining optimization for masks that do not use an entire
 // `Block`.
-impl<E: TyEncoder> Encodable<E> for InitMaskMaterialized {
+impl<E: Encoder> Encodable<E> for InitMaskMaterialized {
     fn encode(&self, encoder: &mut E) {
         encoder.emit_usize(self.blocks.len());
         for block in &self.blocks {
@@ -204,7 +203,7 @@ impl<E: TyEncoder> Encodable<E> for InitMaskMaterialized {
 }
 
 // This implementation is deliberately not derived, see the matching `Encodable` impl.
-impl<D: TyDecoder> Decodable<D> for InitMaskMaterialized {
+impl<D: Decoder> Decodable<D> for InitMaskMaterialized {
     fn decode(decoder: &mut D) -> Self {
         let num_blocks = decoder.read_usize();
         let mut blocks = Vec::with_capacity(num_blocks);
diff --git a/compiler/rustc_middle/src/mir/interpret/mod.rs b/compiler/rustc_middle/src/mir/interpret/mod.rs
index effedf854e4..c2438af6a1e 100644
--- a/compiler/rustc_middle/src/mir/interpret/mod.rs
+++ b/compiler/rustc_middle/src/mir/interpret/mod.rs
@@ -105,7 +105,7 @@ enum AllocDiscriminant {
     Static,
 }
 
-pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>>(
+pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<'tcx>>(
     encoder: &mut E,
     tcx: TyCtxt<'tcx>,
     alloc_id: AllocId,
@@ -175,7 +175,7 @@ impl<'s> AllocDecodingSession<'s> {
     /// Decodes an `AllocId` in a thread-safe way.
     pub fn decode_alloc_id<'tcx, D>(&self, decoder: &mut D) -> AllocId
     where
-        D: TyDecoder<I = TyCtxt<'tcx>>,
+        D: TyDecoder<'tcx>,
     {
         // Read the index of the allocation.
         let idx = usize::try_from(decoder.read_u32()).unwrap();
diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs
index e6b92440e7b..7090e93549e 100644
--- a/compiler/rustc_middle/src/mir/mod.rs
+++ b/compiler/rustc_middle/src/mir/mod.rs
@@ -790,7 +790,7 @@ impl<T> ClearCrossCrate<T> {
 const TAG_CLEAR_CROSS_CRATE_CLEAR: u8 = 0;
 const TAG_CLEAR_CROSS_CRATE_SET: u8 = 1;
 
-impl<E: TyEncoder, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
+impl<'tcx, E: TyEncoder<'tcx>, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
     #[inline]
     fn encode(&self, e: &mut E) {
         if E::CLEAR_CROSS_CRATE {
@@ -806,7 +806,7 @@ impl<E: TyEncoder, T: Encodable<E>> Encodable<E> for ClearCrossCrate<T> {
         }
     }
 }
-impl<D: TyDecoder, T: Decodable<D>> Decodable<D> for ClearCrossCrate<T> {
+impl<'tcx, D: TyDecoder<'tcx>, T: Decodable<D>> Decodable<D> for ClearCrossCrate<T> {
     #[inline]
     fn decode(d: &mut D) -> ClearCrossCrate<T> {
         if D::CLEAR_CROSS_CRATE {
diff --git a/compiler/rustc_middle/src/query/on_disk_cache.rs b/compiler/rustc_middle/src/query/on_disk_cache.rs
index d9035efaf56..e66958dfcb8 100644
--- a/compiler/rustc_middle/src/query/on_disk_cache.rs
+++ b/compiler/rustc_middle/src/query/on_disk_cache.rs
@@ -518,8 +518,7 @@ where
     value
 }
 
-impl<'a, 'tcx> TyDecoder for CacheDecoder<'a, 'tcx> {
-    type I = TyCtxt<'tcx>;
+impl<'a, 'tcx> TyDecoder<'tcx> for CacheDecoder<'a, 'tcx> {
     const CLEAR_CROSS_CRATE: bool = false;
 
     #[inline]
@@ -943,8 +942,7 @@ impl<'a, 'tcx> SpanEncoder for CacheEncoder<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> TyEncoder for CacheEncoder<'a, 'tcx> {
-    type I = TyCtxt<'tcx>;
+impl<'a, 'tcx> TyEncoder<'tcx> for CacheEncoder<'a, 'tcx> {
     const CLEAR_CROSS_CRATE: bool = false;
 
     #[inline]
diff --git a/compiler/rustc_middle/src/ty/codec.rs b/compiler/rustc_middle/src/ty/codec.rs
index fe42a224d9f..74b34afe616 100644
--- a/compiler/rustc_middle/src/ty/codec.rs
+++ b/compiler/rustc_middle/src/ty/codec.rs
@@ -14,9 +14,8 @@ use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::LocalDefId;
 use rustc_serialize::{Decodable, Encodable};
-use rustc_span::Span;
 use rustc_span::source_map::Spanned;
-pub use rustc_type_ir::{TyDecoder, TyEncoder};
+use rustc_span::{Span, SpanDecoder, SpanEncoder};
 
 use crate::arena::ArenaAllocatable;
 use crate::infer::canonical::{CanonicalVarInfo, CanonicalVarInfos};
@@ -31,13 +30,45 @@ use crate::ty::{self, AdtDef, GenericArgsRef, Ty, TyCtxt};
 /// This offset is also chosen so that the first byte is never < 0x80.
 pub const SHORTHAND_OFFSET: usize = 0x80;
 
-pub trait EncodableWithShorthand<E: TyEncoder>: Copy + Eq + Hash {
+pub trait TyEncoder<'tcx>: SpanEncoder {
+    const CLEAR_CROSS_CRATE: bool;
+
+    fn position(&self) -> usize;
+
+    fn type_shorthands(&mut self) -> &mut FxHashMap<Ty<'tcx>, usize>;
+
+    fn predicate_shorthands(&mut self) -> &mut FxHashMap<ty::PredicateKind<'tcx>, usize>;
+
+    fn encode_alloc_id(&mut self, alloc_id: &AllocId);
+}
+
+pub trait TyDecoder<'tcx>: SpanDecoder {
+    const CLEAR_CROSS_CRATE: bool;
+
+    fn interner(&self) -> TyCtxt<'tcx>;
+
+    fn cached_ty_for_shorthand<F>(&mut self, shorthand: usize, or_insert_with: F) -> Ty<'tcx>
+    where
+        F: FnOnce(&mut Self) -> Ty<'tcx>;
+
+    fn with_position<F, R>(&mut self, pos: usize, f: F) -> R
+    where
+        F: FnOnce(&mut Self) -> R;
+
+    fn positioned_at_shorthand(&self) -> bool {
+        (self.peek_byte() & (SHORTHAND_OFFSET as u8)) != 0
+    }
+
+    fn decode_alloc_id(&mut self) -> AllocId;
+}
+
+pub trait EncodableWithShorthand<'tcx, E: TyEncoder<'tcx>>: Copy + Eq + Hash {
     type Variant: Encodable<E>;
     fn variant(&self) -> &Self::Variant;
 }
 
 #[allow(rustc::usage_of_ty_tykind)]
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> EncodableWithShorthand<E> for Ty<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> EncodableWithShorthand<'tcx, E> for Ty<'tcx> {
     type Variant = ty::TyKind<'tcx>;
 
     #[inline]
@@ -46,7 +77,7 @@ impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> EncodableWithShorthand<E> for Ty<'tcx
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> EncodableWithShorthand<E> for ty::PredicateKind<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> EncodableWithShorthand<'tcx, E> for ty::PredicateKind<'tcx> {
     type Variant = ty::PredicateKind<'tcx>;
 
     #[inline]
@@ -65,16 +96,16 @@ impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> EncodableWithShorthand<E> for ty::Pre
 ///
 /// `Decodable` can still be implemented in cases where `Decodable` is required
 /// by a trait bound.
-pub trait RefDecodable<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> {
+pub trait RefDecodable<'tcx, D: TyDecoder<'tcx>> {
     fn decode(d: &mut D) -> &'tcx Self;
 }
 
 /// Encode the given value or a previously cached shorthand.
 pub fn encode_with_shorthand<'tcx, E, T, M>(encoder: &mut E, value: &T, cache: M)
 where
-    E: TyEncoder<I = TyCtxt<'tcx>>,
+    E: TyEncoder<'tcx>,
     M: for<'b> Fn(&'b mut E) -> &'b mut FxHashMap<T, usize>,
-    T: EncodableWithShorthand<E>,
+    T: EncodableWithShorthand<'tcx, E>,
     // The discriminant and shorthand must have the same size.
     T::Variant: DiscriminantKind<Discriminant = isize>,
 {
@@ -108,13 +139,13 @@ where
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for Ty<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for Ty<'tcx> {
     fn encode(&self, e: &mut E) {
         encode_with_shorthand(e, self, TyEncoder::type_shorthands);
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Predicate<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Predicate<'tcx> {
     fn encode(&self, e: &mut E) {
         let kind = self.kind();
         kind.bound_vars().encode(e);
@@ -122,76 +153,72 @@ impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Predicate<'tcx>
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Clause<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Clause<'tcx> {
     fn encode(&self, e: &mut E) {
         self.as_predicate().encode(e);
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Region<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Region<'tcx> {
     fn encode(&self, e: &mut E) {
         self.kind().encode(e);
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Const<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Const<'tcx> {
     fn encode(&self, e: &mut E) {
         self.0.0.encode(e);
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::Pattern<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Pattern<'tcx> {
     fn encode(&self, e: &mut E) {
         self.0.0.encode(e);
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::ValTree<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::ValTree<'tcx> {
     fn encode(&self, e: &mut E) {
         self.0.0.encode(e);
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ConstAllocation<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ConstAllocation<'tcx> {
     fn encode(&self, e: &mut E) {
         self.inner().encode(e)
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for AdtDef<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for AdtDef<'tcx> {
     fn encode(&self, e: &mut E) {
         self.0.0.encode(e)
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for AllocId {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for AllocId {
     fn encode(&self, e: &mut E) {
         e.encode_alloc_id(self)
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for CtfeProvenance {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for CtfeProvenance {
     fn encode(&self, e: &mut E) {
         self.into_parts().encode(e);
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for ty::ParamEnv<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::ParamEnv<'tcx> {
     fn encode(&self, e: &mut E) {
         self.caller_bounds().encode(e);
     }
 }
 
 #[inline]
-fn decode_arena_allocable<
-    'tcx,
-    D: TyDecoder<I = TyCtxt<'tcx>>,
-    T: ArenaAllocatable<'tcx> + Decodable<D>,
->(
+fn decode_arena_allocable<'tcx, D: TyDecoder<'tcx>, T: ArenaAllocatable<'tcx> + Decodable<D>>(
     decoder: &mut D,
 ) -> &'tcx T
 where
-    D: TyDecoder,
+    D: TyDecoder<'tcx>,
 {
     decoder.interner().arena.alloc(Decodable::decode(decoder))
 }
@@ -199,18 +226,18 @@ where
 #[inline]
 fn decode_arena_allocable_slice<
     'tcx,
-    D: TyDecoder<I = TyCtxt<'tcx>>,
+    D: TyDecoder<'tcx>,
     T: ArenaAllocatable<'tcx> + Decodable<D>,
 >(
     decoder: &mut D,
 ) -> &'tcx [T]
 where
-    D: TyDecoder,
+    D: TyDecoder<'tcx>,
 {
     decoder.interner().arena.alloc_from_iter(<Vec<T> as Decodable<D>>::decode(decoder))
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for Ty<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for Ty<'tcx> {
     #[allow(rustc::usage_of_ty_tykind)]
     fn decode(decoder: &mut D) -> Ty<'tcx> {
         // Handle shorthands first, if we have a usize > 0x80.
@@ -229,7 +256,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for Ty<'tcx> {
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Predicate<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Predicate<'tcx> {
     fn decode(decoder: &mut D) -> ty::Predicate<'tcx> {
         let bound_vars = Decodable::decode(decoder);
         // Handle shorthands first, if we have a usize > 0x80.
@@ -249,14 +276,14 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Predicate<'tcx>
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Clause<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Clause<'tcx> {
     fn decode(decoder: &mut D) -> ty::Clause<'tcx> {
         let pred: ty::Predicate<'tcx> = Decodable::decode(decoder);
         pred.expect_clause()
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for GenericArgsRef<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for GenericArgsRef<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let len = decoder.read_usize();
         let tcx = decoder.interner();
@@ -266,7 +293,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for GenericArgsRef<'tcx>
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for mir::Place<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for mir::Place<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let local: mir::Local = Decodable::decode(decoder);
         let len = decoder.read_usize();
@@ -277,13 +304,13 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for mir::Place<'tcx> {
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Region<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Region<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         ty::Region::new_from_kind(decoder.interner(), Decodable::decode(decoder))
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for CanonicalVarInfos<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for CanonicalVarInfos<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let len = decoder.read_usize();
         decoder.interner().mk_canonical_var_infos_from_iter(
@@ -292,26 +319,26 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for CanonicalVarInfos<'t
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for AllocId {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for AllocId {
     fn decode(decoder: &mut D) -> Self {
         decoder.decode_alloc_id()
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for CtfeProvenance {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for CtfeProvenance {
     fn decode(decoder: &mut D) -> Self {
         let parts = Decodable::decode(decoder);
         CtfeProvenance::from_parts(parts)
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::SymbolName<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::SymbolName<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         ty::SymbolName::new(decoder.interner(), decoder.read_str())
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::ParamEnv<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::ParamEnv<'tcx> {
     fn decode(d: &mut D) -> Self {
         let caller_bounds = Decodable::decode(d);
         ty::ParamEnv::new(caller_bounds)
@@ -320,7 +347,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::ParamEnv<'tcx> {
 
 macro_rules! impl_decodable_via_ref {
     ($($t:ty,)+) => {
-        $(impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for $t {
+        $(impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for $t {
             fn decode(decoder: &mut D) -> Self {
                 RefDecodable::decode(decoder)
             }
@@ -328,7 +355,7 @@ macro_rules! impl_decodable_via_ref {
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<Ty<'tcx>> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
         decoder
@@ -337,7 +364,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<Ty
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D>
     for ty::List<ty::PolyExistentialPredicate<'tcx>>
 {
     fn decode(decoder: &mut D) -> &'tcx Self {
@@ -348,38 +375,38 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Const<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Const<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         let kind: ty::ConstKind<'tcx> = Decodable::decode(decoder);
         decoder.interner().mk_ct_from_kind(kind)
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::Pattern<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Pattern<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         decoder.interner().mk_pat(Decodable::decode(decoder))
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ty::ValTree<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::ValTree<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         decoder.interner().intern_valtree(Decodable::decode(decoder))
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for ConstAllocation<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ConstAllocation<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         decoder.interner().mk_const_alloc(Decodable::decode(decoder))
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for AdtDef<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for AdtDef<'tcx> {
     fn decode(decoder: &mut D) -> Self {
         decoder.interner().mk_adt_def_from_data(Decodable::decode(decoder))
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [(ty::Clause<'tcx>, Span)] {
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [(ty::Clause<'tcx>, Span)] {
     fn decode(decoder: &mut D) -> &'tcx Self {
         decoder
             .interner()
@@ -388,9 +415,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [(ty::Claus
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
-    for [(ty::PolyTraitRef<'tcx>, Span)]
-{
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [(ty::PolyTraitRef<'tcx>, Span)] {
     fn decode(decoder: &mut D) -> &'tcx Self {
         decoder
             .interner()
@@ -399,7 +424,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [Spanned<MonoItem<'tcx>>] {
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [Spanned<MonoItem<'tcx>>] {
     fn decode(decoder: &mut D) -> &'tcx Self {
         decoder
             .interner()
@@ -408,9 +433,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [Spanned<Mo
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
-    for ty::List<ty::BoundVariableKind>
-{
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<ty::BoundVariableKind> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
         decoder.interner().mk_bound_variable_kinds_from_iter(
@@ -419,7 +442,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty::Const<'tcx>> {
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<ty::Const<'tcx>> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
         decoder.interner().mk_const_list_from_iter(
@@ -428,7 +451,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<ty
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D>
     for ty::ListWithCachedTypeInfo<ty::Clause<'tcx>>
 {
     fn decode(decoder: &mut D) -> &'tcx Self {
@@ -439,7 +462,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<FieldIdx> {
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<FieldIdx> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
         decoder
@@ -448,7 +471,7 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<Fi
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<LocalDefId> {
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<LocalDefId> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
         decoder.interner().mk_local_def_ids_from_iter(
@@ -457,15 +480,13 @@ impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for ty::List<Lo
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for &'tcx ty::List<LocalDefId> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for &'tcx ty::List<LocalDefId> {
     fn decode(d: &mut D) -> Self {
         RefDecodable::decode(d)
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D>
-    for ty::List<(VariantIdx, FieldIdx)>
-{
+impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for ty::List<(VariantIdx, FieldIdx)> {
     fn decode(decoder: &mut D) -> &'tcx Self {
         let len = decoder.read_usize();
         decoder.interner().mk_offset_of_from_iter(
@@ -503,14 +524,14 @@ macro_rules! impl_arena_allocatable_decoder {
     ([]$args:tt) => {};
     ([decode $(, $attrs:ident)*]
      [$name:ident: $ty:ty]) => {
-        impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for $ty {
+        impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for $ty {
             #[inline]
             fn decode(decoder: &mut D) -> &'tcx Self {
                 decode_arena_allocable(decoder)
             }
         }
 
-        impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [$ty] {
+        impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [$ty] {
             #[inline]
             fn decode(decoder: &mut D) -> &'tcx Self {
                 decode_arena_allocable_slice(decoder)
@@ -532,14 +553,14 @@ arena_types!(impl_arena_allocatable_decoders);
 
 macro_rules! impl_arena_copy_decoder {
     (<$tcx:tt> $($ty:ty,)*) => {
-        $(impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for $ty {
+        $(impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for $ty {
             #[inline]
             fn decode(decoder: &mut D) -> &'tcx Self {
                 decoder.interner().arena.alloc(Decodable::decode(decoder))
             }
         }
 
-        impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> RefDecodable<'tcx, D> for [$ty] {
+        impl<'tcx, D: TyDecoder<'tcx>> RefDecodable<'tcx, D> for [$ty] {
             #[inline]
             fn decode(decoder: &mut D) -> &'tcx Self {
                 decoder.interner().arena.alloc_from_iter(<Vec<_> as Decodable<D>>::decode(decoder))
diff --git a/compiler/rustc_middle/src/ty/generic_args.rs b/compiler/rustc_middle/src/ty/generic_args.rs
index 795ea2a1ea6..e87859a55ed 100644
--- a/compiler/rustc_middle/src/ty/generic_args.rs
+++ b/compiler/rustc_middle/src/ty/generic_args.rs
@@ -334,13 +334,13 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for GenericArg<'tcx> {
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for GenericArg<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for GenericArg<'tcx> {
     fn encode(&self, e: &mut E) {
         self.unpack().encode(e)
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for GenericArg<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for GenericArg<'tcx> {
     fn decode(d: &mut D) -> GenericArg<'tcx> {
         GenericArgKind::decode(d).pack()
     }
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index fd36c1f0085..29949f8b3e3 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -105,6 +105,7 @@ use crate::middle::privacy::EffectiveVisibilities;
 use crate::mir::{Body, CoroutineLayout};
 use crate::query::{IntoQueryParam, Providers};
 use crate::ty;
+use crate::ty::codec::{TyDecoder, TyEncoder};
 pub use crate::ty::diagnostics::*;
 use crate::ty::fast_reject::SimplifiedType;
 use crate::ty::util::Discr;
@@ -549,13 +550,13 @@ impl<'tcx> TypeVisitable<TyCtxt<'tcx>> for Term<'tcx> {
     }
 }
 
-impl<'tcx, E: TyEncoder<I = TyCtxt<'tcx>>> Encodable<E> for Term<'tcx> {
+impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for Term<'tcx> {
     fn encode(&self, e: &mut E) {
         self.unpack().encode(e)
     }
 }
 
-impl<'tcx, D: TyDecoder<I = TyCtxt<'tcx>>> Decodable<D> for Term<'tcx> {
+impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for Term<'tcx> {
     fn decode(d: &mut D) -> Self {
         let res: TermKind<'tcx> = Decodable::decode(d);
         res.pack()
diff --git a/compiler/rustc_query_impl/src/plumbing.rs b/compiler/rustc_query_impl/src/plumbing.rs
index f98d6421307..fa31ef5eeb0 100644
--- a/compiler/rustc_query_impl/src/plumbing.rs
+++ b/compiler/rustc_query_impl/src/plumbing.rs
@@ -19,9 +19,10 @@ use rustc_middle::query::Key;
 use rustc_middle::query::on_disk_cache::{
     AbsoluteBytePos, CacheDecoder, CacheEncoder, EncodedDepNodeIndex,
 };
+use rustc_middle::ty::codec::TyEncoder;
 use rustc_middle::ty::print::with_reduced_queries;
 use rustc_middle::ty::tls::{self, ImplicitCtxt};
-use rustc_middle::ty::{self, TyCtxt, TyEncoder};
+use rustc_middle::ty::{self, TyCtxt};
 use rustc_query_system::dep_graph::{DepNodeParams, HasDepContext};
 use rustc_query_system::ich::StableHashingContext;
 use rustc_query_system::query::{
diff --git a/compiler/rustc_type_ir/src/binder.rs b/compiler/rustc_type_ir/src/binder.rs
index 65d2614f44e..c8b71074de7 100644
--- a/compiler/rustc_type_ir/src/binder.rs
+++ b/compiler/rustc_type_ir/src/binder.rs
@@ -57,7 +57,7 @@ where
 macro_rules! impl_binder_encode_decode {
     ($($t:ty),+ $(,)?) => {
         $(
-            impl<I: Interner, E: crate::TyEncoder<I = I>> rustc_serialize::Encodable<E> for ty::Binder<I, $t>
+            impl<I: Interner, E: rustc_serialize::Encoder> rustc_serialize::Encodable<E> for ty::Binder<I, $t>
             where
                 $t: rustc_serialize::Encodable<E>,
                 I::BoundVarKinds: rustc_serialize::Encodable<E>,
@@ -67,7 +67,7 @@ macro_rules! impl_binder_encode_decode {
                     self.as_ref().skip_binder().encode(e);
                 }
             }
-            impl<I: Interner, D: crate::TyDecoder<I = I>> rustc_serialize::Decodable<D> for ty::Binder<I, $t>
+            impl<I: Interner, D: rustc_serialize::Decoder> rustc_serialize::Decodable<D> for ty::Binder<I, $t>
             where
                 $t: TypeVisitable<I> + rustc_serialize::Decodable<D>,
                 I::BoundVarKinds: rustc_serialize::Decodable<D>,
diff --git a/compiler/rustc_type_ir/src/codec.rs b/compiler/rustc_type_ir/src/codec.rs
deleted file mode 100644
index a1cffe3ca5a..00000000000
--- a/compiler/rustc_type_ir/src/codec.rs
+++ /dev/null
@@ -1,61 +0,0 @@
-use rustc_data_structures::fx::FxHashMap;
-use rustc_span::{SpanDecoder, SpanEncoder};
-
-use crate::{Interner, PredicateKind};
-
-/// The shorthand encoding uses an enum's variant index `usize`
-/// and is offset by this value so it never matches a real variant.
-/// This offset is also chosen so that the first byte is never < 0x80.
-pub const SHORTHAND_OFFSET: usize = 0x80;
-
-/// Trait for decoding to a reference.
-///
-/// This is a separate trait from `Decodable` so that we can implement it for
-/// upstream types, such as `FxHashSet`.
-///
-/// The `Decodable_NoContext` derive macro will use this trait for fields that are
-/// references (and don't use a type alias to hide that).
-///
-/// `Decodable` can still be implemented in cases where `Decodable` is required
-/// by a trait bound.
-pub trait RefDecodable<'tcx, D: TyDecoder> {
-    fn decode(d: &mut D) -> &'tcx Self;
-}
-
-pub trait TyEncoder: SpanEncoder {
-    type I: Interner;
-    const CLEAR_CROSS_CRATE: bool;
-
-    fn position(&self) -> usize;
-
-    fn type_shorthands(&mut self) -> &mut FxHashMap<<Self::I as Interner>::Ty, usize>;
-
-    fn predicate_shorthands(&mut self) -> &mut FxHashMap<PredicateKind<Self::I>, usize>;
-
-    fn encode_alloc_id(&mut self, alloc_id: &<Self::I as Interner>::AllocId);
-}
-
-pub trait TyDecoder: SpanDecoder {
-    type I: Interner;
-    const CLEAR_CROSS_CRATE: bool;
-
-    fn interner(&self) -> Self::I;
-
-    fn cached_ty_for_shorthand<F>(
-        &mut self,
-        shorthand: usize,
-        or_insert_with: F,
-    ) -> <Self::I as Interner>::Ty
-    where
-        F: FnOnce(&mut Self) -> <Self::I as Interner>::Ty;
-
-    fn with_position<F, R>(&mut self, pos: usize, f: F) -> R
-    where
-        F: FnOnce(&mut Self) -> R;
-
-    fn positioned_at_shorthand(&self) -> bool {
-        (self.peek_byte() & (SHORTHAND_OFFSET as u8)) != 0
-    }
-
-    fn decode_alloc_id(&mut self) -> <Self::I as Interner>::AllocId;
-}
diff --git a/compiler/rustc_type_ir/src/lib.rs b/compiler/rustc_type_ir/src/lib.rs
index 5e02bf29319..62912189509 100644
--- a/compiler/rustc_type_ir/src/lib.rs
+++ b/compiler/rustc_type_ir/src/lib.rs
@@ -17,8 +17,6 @@ use std::hash::Hash;
 use rustc_macros::{Decodable, Encodable, HashStable_NoContext};
 
 // These modules are `pub` since they are not glob-imported.
-#[cfg(feature = "nightly")]
-pub mod codec;
 pub mod data_structures;
 pub mod elaborate;
 pub mod error;
@@ -61,8 +59,6 @@ pub use TyKind::*;
 pub use Variance::*;
 pub use binder::*;
 pub use canonical::*;
-#[cfg(feature = "nightly")]
-pub use codec::*;
 pub use const_kind::*;
 pub use flags::*;
 pub use fold::*;
diff --git a/compiler/rustc_type_ir/src/ty_kind.rs b/compiler/rustc_type_ir/src/ty_kind.rs
index af423153587..9bea4482b55 100644
--- a/compiler/rustc_type_ir/src/ty_kind.rs
+++ b/compiler/rustc_type_ir/src/ty_kind.rs
@@ -1037,7 +1037,8 @@ impl<I: Interner> Deref for UnsafeBinderInner<I> {
 }
 
 #[cfg(feature = "nightly")]
-impl<I: Interner, E: crate::TyEncoder<I = I>> rustc_serialize::Encodable<E> for UnsafeBinderInner<I>
+impl<I: Interner, E: rustc_serialize::Encoder> rustc_serialize::Encodable<E>
+    for UnsafeBinderInner<I>
 where
     I::Ty: rustc_serialize::Encodable<E>,
     I::BoundVarKinds: rustc_serialize::Encodable<E>,
@@ -1049,7 +1050,8 @@ where
 }
 
 #[cfg(feature = "nightly")]
-impl<I: Interner, D: crate::TyDecoder<I = I>> rustc_serialize::Decodable<D> for UnsafeBinderInner<I>
+impl<I: Interner, D: rustc_serialize::Decoder> rustc_serialize::Decodable<D>
+    for UnsafeBinderInner<I>
 where
     I::Ty: TypeVisitable<I> + rustc_serialize::Decodable<D>,
     I::BoundVarKinds: rustc_serialize::Decodable<D>,
-- 
cgit 1.4.1-3-g733a5