AsLocalKey trait

4 files changed, 48 insertions, 313 deletions

diff --git a/compiler/rustc_middle/src/query/keys.rs b/compiler/rustc_middle/src/query/keys.rs
index 2f99a8874c0..f161f61d53e 100644
--- a/compiler/rustc_middle/src/query/keys.rs
+++ b/compiler/rustc_middle/src/query/keys.rs
@@ -26,12 +26,6 @@ pub trait Key: Sized {
     //      r-a issue: <https://github.com/rust-lang/rust-analyzer/issues/13693>
     type CacheSelector;
 
-    type LocalKey;
-
-    /// Given an instance of this key, what crate is it referring to?
-    /// This is used to find the provider.
-    fn as_local_key(&self) -> Option<Self::LocalKey>;
-
     /// In the event that a cycle occurs, if no explicit span has been
     /// given for a query with key `self`, what span should we use?
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span;
@@ -47,14 +41,16 @@ pub trait Key: Sized {
     }
 }
 
+pub trait AsLocalKey: Key {
+    type LocalKey;
+
+    /// Given an instance of this key, what crate is it referring to?
+    /// This is used to find the provider.
+    fn as_local_key(&self) -> Option<Self::LocalKey>;
+}
+
 impl Key for () {
     type CacheSelector = SingleCacheSelector;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -63,26 +59,23 @@ impl Key for () {
 
 impl<'tcx> Key for ty::InstanceDef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        self.def_id().is_local().then(|| *self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
     }
 }
 
-impl<'tcx> Key for ty::Instance<'tcx> {
-    type CacheSelector = DefaultCacheSelector<Self>;
+impl<'tcx> AsLocalKey for ty::InstanceDef<'tcx> {
     type LocalKey = Self;
 
     #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
+    fn as_local_key(&self) -> Option<Self::LocalKey> {
         self.def_id().is_local().then(|| *self)
     }
+}
+
+impl<'tcx> Key for ty::Instance<'tcx> {
+    type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
@@ -91,12 +84,6 @@ impl<'tcx> Key for ty::Instance<'tcx> {
 
 impl<'tcx> Key for mir::interpret::GlobalId<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.instance.default_span(tcx)
@@ -105,12 +92,6 @@ impl<'tcx> Key for mir::interpret::GlobalId<'tcx> {
 
 impl<'tcx> Key for (Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -119,12 +100,6 @@ impl<'tcx> Key for (Ty<'tcx>, Option<ty::PolyExistentialTraitRef<'tcx>>) {
 
 impl<'tcx> Key for mir::interpret::LitToConstInput<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -133,26 +108,23 @@ impl<'tcx> Key for mir::interpret::LitToConstInput<'tcx> {
 
 impl Key for CrateNum {
     type CacheSelector = VecCacheSelector<Self>;
+
+    fn default_span(&self, _: TyCtxt<'_>) -> Span {
+        DUMMY_SP
+    }
+}
+
+impl AsLocalKey for CrateNum {
     type LocalKey = ();
 
     #[inline(always)]
     fn as_local_key(&self) -> Option<Self::LocalKey> {
         (*self == LOCAL_CRATE).then_some(())
     }
-
-    fn default_span(&self, _: TyCtxt<'_>) -> Span {
-        DUMMY_SP
-    }
 }
 
 impl Key for OwnerId {
     type CacheSelector = VecCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.to_def_id().default_span(tcx)
@@ -165,12 +137,6 @@ impl Key for OwnerId {
 
 impl Key for LocalDefId {
     type CacheSelector = VecCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.to_def_id().default_span(tcx)
@@ -183,12 +149,6 @@ impl Key for LocalDefId {
 
 impl Key for DefId {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = LocalDefId;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        self.as_local()
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(*self)
@@ -200,14 +160,17 @@ impl Key for DefId {
     }
 }
 
-impl Key for ty::WithOptConstParam<LocalDefId> {
-    type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
+impl AsLocalKey for DefId {
+    type LocalKey = LocalDefId;
 
     #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
+    fn as_local_key(&self) -> Option<Self::LocalKey> {
+        self.as_local()
     }
+}
+
+impl Key for ty::WithOptConstParam<LocalDefId> {
+    type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.did.default_span(tcx)
@@ -216,12 +179,6 @@ impl Key for ty::WithOptConstParam<LocalDefId> {
 
 impl Key for SimplifiedType {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -230,12 +187,6 @@ impl Key for SimplifiedType {
 
 impl Key for (DefId, DefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = (LocalDefId, DefId);
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        Some((self.0.as_local()?, self.1))
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
@@ -244,12 +195,6 @@ impl Key for (DefId, DefId) {
 
 impl<'tcx> Key for (ty::Instance<'tcx>, LocalDefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
@@ -258,12 +203,6 @@ impl<'tcx> Key for (ty::Instance<'tcx>, LocalDefId) {
 
 impl Key for (DefId, LocalDefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = (LocalDefId, LocalDefId);
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        Some((self.0.as_local()?, self.1))
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
@@ -272,12 +211,6 @@ impl Key for (DefId, LocalDefId) {
 
 impl Key for (LocalDefId, DefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
@@ -286,12 +219,6 @@ impl Key for (LocalDefId, DefId) {
 
 impl Key for (LocalDefId, LocalDefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
@@ -300,11 +227,6 @@ impl Key for (LocalDefId, LocalDefId) {
 
 impl Key for (DefId, Option<Ident>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = (LocalDefId, Option<Ident>);
-
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        Some((self.0.as_local()?, self.1))
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.0)
@@ -318,11 +240,6 @@ impl Key for (DefId, Option<Ident>) {
 
 impl Key for (LocalDefId, LocalDefId, Ident) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
@@ -331,40 +248,40 @@ impl Key for (LocalDefId, LocalDefId, Ident) {
 
 impl Key for (CrateNum, DefId) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = DefId;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        (self.0 == LOCAL_CRATE).then_some(self.1)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.1.default_span(tcx)
     }
 }
 
-impl Key for (CrateNum, SimplifiedType) {
-    type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = SimplifiedType;
+impl AsLocalKey for (CrateNum, DefId) {
+    type LocalKey = DefId;
 
     #[inline(always)]
     fn as_local_key(&self) -> Option<Self::LocalKey> {
-        (self.0 == LOCAL_CRATE).then_some(self.1)
+        (self.0 == LOCAL_CRATE).then(|| self.1)
     }
+}
+
+impl Key for (CrateNum, SimplifiedType) {
+    type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
     }
 }
 
-impl Key for (DefId, SimplifiedType) {
-    type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = (LocalDefId, SimplifiedType);
+impl AsLocalKey for (CrateNum, SimplifiedType) {
+    type LocalKey = SimplifiedType;
 
     #[inline(always)]
     fn as_local_key(&self) -> Option<Self::LocalKey> {
-        Some((self.0.as_local()?, self.1))
+        (self.0 == LOCAL_CRATE).then(|| self.1)
     }
+}
+
+impl Key for (DefId, SimplifiedType) {
+    type CacheSelector = DefaultCacheSelector<Self>;
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
@@ -373,12 +290,6 @@ impl Key for (DefId, SimplifiedType) {
 
 impl<'tcx> Key for SubstsRef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -387,12 +298,6 @@ impl<'tcx> Key for SubstsRef<'tcx> {
 
 impl<'tcx> Key for (DefId, SubstsRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = (LocalDefId, SubstsRef<'tcx>);
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        Some((self.0.as_local()?, self.1))
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
@@ -401,12 +306,6 @@ impl<'tcx> Key for (DefId, SubstsRef<'tcx>) {
 
 impl<'tcx> Key for (ty::UnevaluatedConst<'tcx>, ty::UnevaluatedConst<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        self.0.def.is_local().then_some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         (self.0).def.did.default_span(tcx)
@@ -415,12 +314,6 @@ impl<'tcx> Key for (ty::UnevaluatedConst<'tcx>, ty::UnevaluatedConst<'tcx>) {
 
 impl<'tcx> Key for (LocalDefId, DefId, SubstsRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
@@ -429,12 +322,6 @@ impl<'tcx> Key for (LocalDefId, DefId, SubstsRef<'tcx>) {
 
 impl<'tcx> Key for (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        self.1.def_id().is_local().then_some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.1.def_id())
@@ -443,12 +330,6 @@ impl<'tcx> Key for (ty::ParamEnv<'tcx>, ty::PolyTraitRef<'tcx>) {
 
 impl<'tcx> Key for (ty::Const<'tcx>, mir::Field) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -457,12 +338,6 @@ impl<'tcx> Key for (ty::Const<'tcx>, mir::Field) {
 
 impl<'tcx> Key for mir::interpret::ConstAlloc<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -471,12 +346,6 @@ impl<'tcx> Key for mir::interpret::ConstAlloc<'tcx> {
 
 impl<'tcx> Key for ty::PolyTraitRef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        self.def_id().is_local().then_some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
@@ -485,12 +354,6 @@ impl<'tcx> Key for ty::PolyTraitRef<'tcx> {
 
 impl<'tcx> Key for ty::PolyExistentialTraitRef<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        self.def_id().is_local().then_some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.def_id())
@@ -499,12 +362,6 @@ impl<'tcx> Key for ty::PolyExistentialTraitRef<'tcx> {
 
 impl<'tcx> Key for (ty::PolyTraitRef<'tcx>, ty::PolyTraitRef<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        self.0.def_id().is_local().then_some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.def_span(self.0.def_id())
@@ -513,12 +370,6 @@ impl<'tcx> Key for (ty::PolyTraitRef<'tcx>, ty::PolyTraitRef<'tcx>) {
 
 impl<'tcx> Key for GenericArg<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -527,12 +378,6 @@ impl<'tcx> Key for GenericArg<'tcx> {
 
 impl<'tcx> Key for mir::ConstantKind<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -541,12 +386,6 @@ impl<'tcx> Key for mir::ConstantKind<'tcx> {
 
 impl<'tcx> Key for ty::Const<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -555,12 +394,6 @@ impl<'tcx> Key for ty::Const<'tcx> {
 
 impl<'tcx> Key for Ty<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -576,12 +409,6 @@ impl<'tcx> Key for Ty<'tcx> {
 
 impl<'tcx> Key for TyAndLayout<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -590,12 +417,6 @@ impl<'tcx> Key for TyAndLayout<'tcx> {
 
 impl<'tcx> Key for (Ty<'tcx>, Ty<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -604,12 +425,6 @@ impl<'tcx> Key for (Ty<'tcx>, Ty<'tcx>) {
 
 impl<'tcx> Key for &'tcx ty::List<ty::Predicate<'tcx>> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -618,12 +433,6 @@ impl<'tcx> Key for &'tcx ty::List<ty::Predicate<'tcx>> {
 
 impl<'tcx> Key for ty::ParamEnv<'tcx> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -632,11 +441,6 @@ impl<'tcx> Key for ty::ParamEnv<'tcx> {
 
 impl<'tcx, T: Key> Key for ty::ParamEnvAnd<'tcx, T> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = ty::ParamEnvAnd<'tcx, T::LocalKey>;
-
-    fn as_local_key(&self) -> Option<Self::LocalKey> {
-        self.value.as_local_key().map(|value| ty::ParamEnvAnd { param_env: self.param_env, value })
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.value.default_span(tcx)
@@ -645,12 +449,6 @@ impl<'tcx, T: Key> Key for ty::ParamEnvAnd<'tcx, T> {
 
 impl Key for Symbol {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -659,12 +457,6 @@ impl Key for Symbol {
 
 impl Key for Option<Symbol> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -675,12 +467,6 @@ impl Key for Option<Symbol> {
 /// are not tied to any crate in particular.
 impl<'tcx, T: Clone> Key for Canonical<'tcx, T> {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(self.clone())
-    }
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -689,12 +475,6 @@ impl<'tcx, T: Clone> Key for Canonical<'tcx, T> {
 
 impl Key for (Symbol, u32, u32) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -703,12 +483,6 @@ impl Key for (Symbol, u32, u32) {
 
 impl<'tcx> Key for (DefId, Ty<'tcx>, SubstsRef<'tcx>, ty::ParamEnv<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -717,12 +491,6 @@ impl<'tcx> Key for (DefId, Ty<'tcx>, SubstsRef<'tcx>, ty::ParamEnv<'tcx>) {
 
 impl<'tcx> Key for (ty::Predicate<'tcx>, traits::WellFormedLoc) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _tcx: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -731,12 +499,6 @@ impl<'tcx> Key for (ty::Predicate<'tcx>, traits::WellFormedLoc) {
 
 impl<'tcx> Key for (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -745,12 +507,6 @@ impl<'tcx> Key for (ty::PolyFnSig<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
 
 impl<'tcx> Key for (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         self.0.default_span(tcx)
@@ -759,12 +515,6 @@ impl<'tcx> Key for (ty::Instance<'tcx>, &'tcx ty::List<Ty<'tcx>>) {
 
 impl<'tcx> Key for (Ty<'tcx>, ty::ValTree<'tcx>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
@@ -773,12 +523,6 @@ impl<'tcx> Key for (Ty<'tcx>, ty::ValTree<'tcx>) {
 
 impl Key for HirId {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
-
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, tcx: TyCtxt<'_>) -> Span {
         tcx.hir().span(*self)
@@ -792,13 +536,8 @@ impl Key for HirId {
 
 impl<'tcx> Key for (ValidityRequirement, ty::ParamEnvAnd<'tcx, Ty<'tcx>>) {
     type CacheSelector = DefaultCacheSelector<Self>;
-    type LocalKey = Self;
 
     // Just forward to `Ty<'tcx>`
-    #[inline(always)]
-    fn as_local_key(&self) -> Option<Self> {
-        Some(*self)
-    }
 
     fn default_span(&self, _: TyCtxt<'_>) -> Span {
         DUMMY_SP
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index 13f6779bd4f..f5cbfd6623e 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -8,7 +8,7 @@ use crate::ty::{self, print::describe_as_module, TyCtxt};
 use rustc_span::def_id::LOCAL_CRATE;
 
 mod keys;
-pub use keys::Key;
+pub use keys::{AsLocalKey, Key};
 
 // Each of these queries corresponds to a function pointer field in the
 // `Providers` struct for requesting a value of that type, and a method
@@ -796,7 +796,6 @@ rustc_queries! {
     query associated_type_for_impl_trait_in_trait(opaque_ty_def_id: LocalDefId) -> LocalDefId {
         desc { |tcx| "creates the associated item corresponding to the opaque type `{}`", tcx.def_path_str(opaque_ty_def_id.to_def_id()) }
         cache_on_disk_if { true }
-        separate_provide_extern
     }
 
     /// Given an `impl_id`, return the trait it implements.
diff --git a/compiler/rustc_middle/src/ty/query.rs b/compiler/rustc_middle/src/ty/query.rs
index 3cf28408f69..2771d713c42 100644
--- a/compiler/rustc_middle/src/ty/query.rs
+++ b/compiler/rustc_middle/src/ty/query.rs
@@ -17,7 +17,7 @@ use crate::mir::interpret::{
 };
 use crate::mir::interpret::{LitToConstError, LitToConstInput};
 use crate::mir::mono::CodegenUnit;
-use crate::query::Key;
+use crate::query::{AsLocalKey, Key};
 use crate::thir;
 use crate::traits::query::{
     CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal,
@@ -233,7 +233,7 @@ macro_rules! define_callbacks {
         pub mod query_keys_local {
             use super::*;
 
-            $(pub type $name<'tcx> = <$($K)* as Key>::LocalKey;)*
+            $(pub type $name<'tcx> = <$($K)* as AsLocalKey>::LocalKey;)*
         }
         #[allow(nonstandard_style, unused_lifetimes)]
         pub mod query_values {
@@ -416,17 +416,14 @@ macro_rules! define_callbacks {
 
         impl Default for Providers {
             fn default() -> Self {
-                use crate::query::Key;
-
                 Providers {
                     $($name: |_, key| bug!(
-                        "`tcx.{}({:?})` is not supported for {} crate;\n\
+                        "`tcx.{}({:?})` is not supported for this key;\n\
                         hint: Queries can be either made to the local crate, or the external crate. \
                         This error means you tried to use it for one that's not supported.\n\
                         If that's not the case, {} was likely never assigned to a provider function.\n",
                         stringify!($name),
                         key,
-                        if key.as_local_key().is_some() { "local" } else { "external" },
                         stringify!($name),
                     ),)*
                 }
diff --git a/compiler/rustc_query_impl/src/lib.rs b/compiler/rustc_query_impl/src/lib.rs
index 035bfe978f2..4cd94237061 100644
--- a/compiler/rustc_query_impl/src/lib.rs
+++ b/compiler/rustc_query_impl/src/lib.rs
@@ -20,7 +20,7 @@ extern crate rustc_middle;
 use rustc_data_structures::sync::AtomicU64;
 use rustc_middle::arena::Arena;
 use rustc_middle::dep_graph::{self, DepKindStruct};
-use rustc_middle::query::Key;
+use rustc_middle::query::AsLocalKey;
 use rustc_middle::ty::query::{
     query_keys, query_provided, query_provided_to_value, query_storage, query_values,
 };