Auto merge of #86118 - spastorino:tait-soundness-bug, r=nikomatsakis

Create different inference variables for different defining uses of TAITs

Fixes #73481

r? `@nikomatsakis`
cc `@oli-obk`

3 files changed, 13 insertions, 15 deletions

diff --git a/compiler/rustc_middle/src/mir/query.rs b/compiler/rustc_middle/src/mir/query.rs
index 0edb79fdbc8..4fb737f463a 100644
--- a/compiler/rustc_middle/src/mir/query.rs
+++ b/compiler/rustc_middle/src/mir/query.rs
@@ -2,13 +2,14 @@
 
 use crate::mir::{abstract_const, Body, Promoted};
 use crate::ty::{self, Ty, TyCtxt};
-use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
+use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::ErrorReported;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_index::bit_set::BitMatrix;
 use rustc_index::vec::IndexVec;
+use rustc_middle::ty::OpaqueTypeKey;
 use rustc_span::Span;
 use rustc_target::abi::VariantIdx;
 use smallvec::SmallVec;
@@ -210,7 +211,7 @@ pub struct BorrowCheckResult<'tcx> {
     /// All the opaque types that are restricted to concrete types
     /// by this function. Unlike the value in `TypeckResults`, this has
     /// unerased regions.
-    pub concrete_opaque_types: FxHashMap<DefId, ty::ResolvedOpaqueTy<'tcx>>,
+    pub concrete_opaque_types: VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>>,
     pub closure_requirements: Option<ClosureRegionRequirements<'tcx>>,
     pub used_mut_upvars: SmallVec<[Field; 8]>,
 }
diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs
index 047b95f116e..62d1bc7eb6d 100644
--- a/compiler/rustc_middle/src/ty/context.rs
+++ b/compiler/rustc_middle/src/ty/context.rs
@@ -34,6 +34,7 @@ use rustc_data_structures::sharded::{IntoPointer, ShardedHashMap};
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::steal::Steal;
 use rustc_data_structures::sync::{self, Lock, Lrc, WorkerLocal};
+use rustc_data_structures::vec_map::VecMap;
 use rustc_errors::ErrorReported;
 use rustc_hir as hir;
 use rustc_hir::def::{DefKind, Res};
@@ -47,6 +48,7 @@ use rustc_hir::{
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_macros::HashStable;
 use rustc_middle::mir::FakeReadCause;
+use rustc_middle::ty::OpaqueTypeKey;
 use rustc_serialize::opaque::{FileEncodeResult, FileEncoder};
 use rustc_session::config::{BorrowckMode, CrateType, OutputFilenames};
 use rustc_session::lint::{Level, Lint};
@@ -286,17 +288,6 @@ impl<'a, V> LocalTableInContextMut<'a, V> {
     }
 }
 
-/// All information necessary to validate and reveal an `impl Trait`.
-#[derive(TyEncodable, TyDecodable, Debug, HashStable)]
-pub struct ResolvedOpaqueTy<'tcx> {
-    /// The revealed type as seen by this function.
-    pub concrete_type: Ty<'tcx>,
-    /// Generic parameters on the opaque type as passed by this function.
-    /// For `type Foo<A, B> = impl Bar<A, B>; fn foo<T, U>() -> Foo<T, U> { .. }`
-    /// this is `[T, U]`, not `[A, B]`.
-    pub substs: SubstsRef<'tcx>,
-}
-
 /// Whenever a value may be live across a generator yield, the type of that value winds up in the
 /// `GeneratorInteriorTypeCause` struct. This struct adds additional information about such
 /// captured types that can be useful for diagnostics. In particular, it stores the span that
@@ -424,7 +415,7 @@ pub struct TypeckResults<'tcx> {
 
     /// All the opaque types that are restricted to concrete types
     /// by this function.
-    pub concrete_opaque_types: FxHashMap<DefId, ResolvedOpaqueTy<'tcx>>,
+    pub concrete_opaque_types: VecMap<OpaqueTypeKey<'tcx>, Ty<'tcx>>,
 
     /// Tracks the minimum captures required for a closure;
     /// see `MinCaptureInformationMap` for more details.
diff --git a/compiler/rustc_middle/src/ty/mod.rs b/compiler/rustc_middle/src/ty/mod.rs
index b58c92b8415..227aa8dc284 100644
--- a/compiler/rustc_middle/src/ty/mod.rs
+++ b/compiler/rustc_middle/src/ty/mod.rs
@@ -58,7 +58,7 @@ pub use self::consts::{Const, ConstInt, ConstKind, InferConst, ScalarInt, Uneval
 pub use self::context::{
     tls, CanonicalUserType, CanonicalUserTypeAnnotation, CanonicalUserTypeAnnotations,
     CtxtInterners, DelaySpanBugEmitted, FreeRegionInfo, GeneratorInteriorTypeCause, GlobalCtxt,
-    Lift, ResolvedOpaqueTy, TyCtxt, TypeckResults, UserType, UserTypeAnnotationIndex,
+    Lift, TyCtxt, TypeckResults, UserType, UserTypeAnnotationIndex,
 };
 pub use self::instance::{Instance, InstanceDef};
 pub use self::list::List;
@@ -835,6 +835,12 @@ impl<'tcx> InstantiatedPredicates<'tcx> {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
+pub struct OpaqueTypeKey<'tcx> {
+    pub def_id: DefId,
+    pub substs: SubstsRef<'tcx>,
+}
+
 rustc_index::newtype_index! {
     /// "Universes" are used during type- and trait-checking in the
     /// presence of `for<..>` binders to control what sets of names are