Use real opaque type instead of just saying impl Trait

compiler/rustc_borrowck/src/diagnostics/region_errors.rs

@@ -78,6 +78,8 @@ pub(crate) enum RegionErrorKind<'tcx> {
         span: Span,
         /// The hidden type.
         hidden_ty: Ty<'tcx>,
+        /// The opaque type.
+        key: ty::OpaqueTypeKey<'tcx>,
         /// The unexpected region.
         member_region: ty::Region<'tcx>,
     },
@@ -205,14 +207,16 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
                     }
                 }
 
-                RegionErrorKind::UnexpectedHiddenRegion { span, hidden_ty, member_region } => {
+                RegionErrorKind::UnexpectedHiddenRegion { span, hidden_ty, key, member_region } => {
                     let named_ty = self.regioncx.name_regions(self.infcx.tcx, hidden_ty);
+                    let named_key = self.regioncx.name_regions(self.infcx.tcx, key);
                     let named_region = self.regioncx.name_regions(self.infcx.tcx, member_region);
                     self.buffer_error(unexpected_hidden_region_diagnostic(
                         self.infcx.tcx,
                         span,
                         named_ty,
                         named_region,
+                        named_key,
                     ));
                 }
 

compiler/rustc_borrowck/src/member_constraints.rs

@@ -38,6 +38,8 @@ pub(crate) struct NllMemberConstraint<'tcx> {
     /// The hidden type in which `R0` appears. (Used in error reporting.)
     pub(crate) hidden_ty: Ty<'tcx>,
 
+    pub(crate) key: ty::OpaqueTypeKey<'tcx>,
+
     /// The region `R0`.
     pub(crate) member_region_vid: ty::RegionVid,
 
@@ -90,6 +92,7 @@ impl<'tcx> MemberConstraintSet<'tcx, ty::RegionVid> {
             member_region_vid,
             definition_span: m_c.definition_span,
             hidden_ty: m_c.hidden_ty,
+            key: m_c.key,
             start_index,
             end_index,
         });

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -1763,6 +1763,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             errors_buffer.push(RegionErrorKind::UnexpectedHiddenRegion {
                 span: m_c.definition_span,
                 hidden_ty: m_c.hidden_ty,
+                key: m_c.key,
                 member_region,
             });
         }

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -246,7 +246,7 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
         // after producing an error for each of them.
         let definition_ty = instantiated_ty.ty.fold_with(&mut ReverseMapper::new(
             self.tcx,
-            def_id,
+            opaque_type_key,
             map,
             instantiated_ty.ty,
             instantiated_ty.span,
@@ -429,7 +429,7 @@ fn check_opaque_type_parameter_valid(
 struct ReverseMapper<'tcx> {
     tcx: TyCtxt<'tcx>,
 
-    opaque_type_def_id: LocalDefId,
+    key: ty::OpaqueTypeKey<'tcx>,
     map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>>,
     map_missing_regions_to_empty: bool,
 
@@ -443,14 +443,14 @@ struct ReverseMapper<'tcx> {
 impl<'tcx> ReverseMapper<'tcx> {
     fn new(
         tcx: TyCtxt<'tcx>,
-        opaque_type_def_id: LocalDefId,
+        key: ty::OpaqueTypeKey<'tcx>,
         map: FxHashMap<GenericArg<'tcx>, GenericArg<'tcx>>,
         hidden_ty: Ty<'tcx>,
         span: Span,
     ) -> Self {
         Self {
             tcx,
-            opaque_type_def_id,
+            key,
             map,
             map_missing_regions_to_empty: false,
             hidden_ty: Some(hidden_ty),
@@ -504,7 +504,7 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
             }
         }
 
-        let generics = self.tcx().generics_of(self.opaque_type_def_id);
+        let generics = self.tcx().generics_of(self.key.def_id);
         match self.map.get(&r.into()).map(|k| k.unpack()) {
             Some(GenericArgKind::Lifetime(r1)) => r1,
             Some(u) => panic!("region mapped to unexpected kind: {:?}", u),
@@ -513,9 +513,10 @@ impl<'tcx> TypeFolder<'tcx> for ReverseMapper<'tcx> {
                 if let Some(hidden_ty) = self.hidden_ty.take() {
                     unexpected_hidden_region_diagnostic(
                         self.tcx,
-                        self.tcx.def_span(self.opaque_type_def_id),
+                        self.tcx.def_span(self.key.def_id),
                         hidden_ty,
                         r,
+                        self.key,
                     )
                     .emit();
                 }

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -237,12 +237,14 @@ pub fn unexpected_hidden_region_diagnostic<'tcx>(
     span: Span,
     hidden_ty: Ty<'tcx>,
     hidden_region: ty::Region<'tcx>,
+    opaque_ty: ty::OpaqueTypeKey<'tcx>,
 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
+    let opaque_ty = tcx.mk_opaque(opaque_ty.def_id.to_def_id(), opaque_ty.substs);
     let mut err = struct_span_err!(
         tcx.sess,
         span,
         E0700,
-        "hidden type for `impl Trait` captures lifetime that does not appear in bounds",
+        "hidden type for `{opaque_ty}` captures lifetime that does not appear in bounds",
     );
 
     // Explain the region we are capturing.

compiler/rustc_infer/src/infer/mod.rs

@@ -974,14 +974,14 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
     #[instrument(skip(self), level = "debug")]
     pub fn member_constraint(
         &self,
-        opaque_type_def_id: LocalDefId,
+        key: ty::OpaqueTypeKey<'tcx>,
         definition_span: Span,
         hidden_ty: Ty<'tcx>,
         region: ty::Region<'tcx>,
         in_regions: &Lrc<Vec<ty::Region<'tcx>>>,
     ) {
         self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
-            opaque_type_def_id,
+            key,
             definition_span,
             hidden_ty,
             region,

compiler/rustc_infer/src/infer/opaque_types.rs

@@ -394,15 +394,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
         );
 
         concrete_ty.visit_with(&mut ConstrainOpaqueTypeRegionVisitor {
-            op: |r| {
+            op: |r| self.member_constraint(opaque_type_key, span, concrete_ty, r, &choice_regions),
-                self.member_constraint(
-                    opaque_type_key.def_id,
-                    span,
-                    concrete_ty,
-                    r,
-                    &choice_regions,
-                )
-            },
         });
     }
 

compiler/rustc_infer/src/infer/region_constraints/mod.rs

@@ -12,7 +12,6 @@ use rustc_data_structures::intern::Interned;
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::undo_log::UndoLogs;
 use rustc_data_structures::unify as ut;
-use rustc_hir::def_id::LocalDefId;
 use rustc_index::vec::IndexVec;
 use rustc_middle::infer::unify_key::{RegionVidKey, UnifiedRegion};
 use rustc_middle::ty::ReStatic;
@@ -533,7 +532,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
 
     pub fn member_constraint(
         &mut self,
-        opaque_type_def_id: LocalDefId,
+        key: ty::OpaqueTypeKey<'tcx>,
         definition_span: Span,
         hidden_ty: Ty<'tcx>,
         member_region: ty::Region<'tcx>,
@@ -546,7 +545,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> {
         }
 
         self.data.member_constraints.push(MemberConstraint {
-            opaque_type_def_id,
+            key,
             definition_span,
             hidden_ty,
             member_region,

compiler/rustc_middle/src/infer/mod.rs

@@ -2,9 +2,8 @@ pub mod canonical;
 pub mod unify_key;
 
 use crate::ty::Region;
-use crate::ty::Ty;
+use crate::ty::{OpaqueTypeKey, Ty};
 use rustc_data_structures::sync::Lrc;
-use rustc_hir::def_id::LocalDefId;
 use rustc_span::Span;
 
 /// Requires that `region` must be equal to one of the regions in `choice_regions`.
@@ -15,8 +14,9 @@ use rustc_span::Span;
 /// ```
 #[derive(Debug, Clone, HashStable, TypeFoldable, TypeVisitable, Lift)]
 pub struct MemberConstraint<'tcx> {
-    /// The `DefId` of the opaque type causing this constraint: used for error reporting.
+    /// The `DefId` and substs of the opaque type causing this constraint.
-    pub opaque_type_def_id: LocalDefId,
+    /// Used for error reporting.
+    pub key: OpaqueTypeKey<'tcx>,
 
     /// The span where the hidden type was instantiated.
     pub definition_span: Span,

src/test/ui/async-await/multiple-lifetimes/ret-impl-trait-one.stderr

@@ -13,7 +13,7 @@ LL | | }
    |
    = help: consider adding the following bound: `'a: 'b`
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Trait<'a>` captures lifetime that does not appear in bounds
   --> $DIR/ret-impl-trait-one.rs:16:80
    |
 LL |   async fn async_ret_impl_trait1<'a, 'b>(a: &'a u8, b: &'b u8) -> impl Trait<'a> {

src/test/ui/impl-trait/hidden-lifetimes.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Swap` captures lifetime that does not appear in bounds
   --> $DIR/hidden-lifetimes.rs:29:5
    |
 LL | fn hide_ref<'a, 'b, T: 'static>(x: &'a mut &'b T) -> impl Swap + 'a {
@@ -11,7 +11,7 @@ help: to declare that the `impl Trait` captures `'b`, you can add an explicit `'
 LL | fn hide_ref<'a, 'b, T: 'static>(x: &'a mut &'b T) -> impl Swap + 'a + 'b {
    |                                                                     ++++
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Swap` captures lifetime that does not appear in bounds
   --> $DIR/hidden-lifetimes.rs:46:5
    |
 LL | fn hide_rc_refcell<'a, 'b: 'a, T: 'static>(x: Rc<RefCell<&'b T>>) -> impl Swap + 'a {

src/test/ui/impl-trait/multiple-lifetimes/error-handling-2.rs

@@ -20,7 +20,7 @@ fn foo<'a: 'b, 'b, 'c>(x: &'static i32, mut y: &'a i32) -> E<'b, 'c> {
         let _: &'b i32 = *u.0;
     }
     u.0
-    //~^ ERROR hidden type for `impl Trait` captures lifetime that does not appear in bounds
+    //~^ ERROR hidden type for `E<'b, 'c>` captures lifetime that does not appear in bounds
 }
 
 fn main() {}

src/test/ui/impl-trait/multiple-lifetimes/error-handling-2.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `E<'b, 'c>` captures lifetime that does not appear in bounds
   --> $DIR/error-handling-2.rs:22:5
    |
 LL | fn foo<'a: 'b, 'b, 'c>(x: &'static i32, mut y: &'a i32) -> E<'b, 'c> {

src/test/ui/impl-trait/multiple-lifetimes/ordinary-bounds-unrelated.rs

@@ -26,7 +26,7 @@ where
     // 'a in ['d, 'e]
     // ```
     if condition() { a } else { b }
-    //~^ ERROR hidden type for `impl Trait` captures lifetime that does not appear in bounds
+    //~^ ERROR hidden type for `impl Trait<'d, 'e>` captures lifetime that does not appear in bounds
 }
 
 fn condition() -> bool {

src/test/ui/impl-trait/multiple-lifetimes/ordinary-bounds-unrelated.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Trait<'d, 'e>` captures lifetime that does not appear in bounds
   --> $DIR/ordinary-bounds-unrelated.rs:28:33
    |
 LL | fn upper_bounds<'a, 'b, 'c, 'd, 'e>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'d, 'e>

src/test/ui/impl-trait/multiple-lifetimes/ordinary-bounds-unsuited.rs

@@ -29,7 +29,7 @@ fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b>
     //
     // We are forced to pick that '0 = 'e, because only 'e is outlived by *both* 'a and 'b.
     if condition() { a } else { b }
-    //~^ ERROR hidden type for `impl Trait` captures lifetime that does not appear in bounds
+    //~^ ERROR hidden type for `impl Trait<'a, 'b>` captures lifetime that does not appear in bounds
 }
 
 fn condition() -> bool {

src/test/ui/impl-trait/multiple-lifetimes/ordinary-bounds-unsuited.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Trait<'a, 'b>` captures lifetime that does not appear in bounds
   --> $DIR/ordinary-bounds-unsuited.rs:31:33
    |
 LL | fn upper_bounds<'a, 'b>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'a, 'b>

src/test/ui/impl-trait/must_outlive_least_region_or_bound.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Copy` captures lifetime that does not appear in bounds
   --> $DIR/must_outlive_least_region_or_bound.rs:3:35
    |
 LL | fn elided(x: &i32) -> impl Copy { x }
@@ -11,7 +11,7 @@ help: to declare that the `impl Trait` captures `'_`, you can add an explicit `'
 LL | fn elided(x: &i32) -> impl Copy + '_ { x }
    |                                 ++++
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Copy` captures lifetime that does not appear in bounds
   --> $DIR/must_outlive_least_region_or_bound.rs:6:44
    |
 LL | fn explicit<'a>(x: &'a i32) -> impl Copy { x }
@@ -96,7 +96,7 @@ help: alternatively, add an explicit `'static` bound to this reference
 LL | fn with_bound<'a>(x: &'static i32) -> impl LifetimeTrait<'a> + 'static { x }
    |                      ~~~~~~~~~~~~
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Fn(&'a u32)` captures lifetime that does not appear in bounds
   --> $DIR/must_outlive_least_region_or_bound.rs:38:5
    |
 LL | fn move_lifetime_into_fn<'a, 'b>(x: &'a u32, y: &'b u32) -> impl Fn(&'a u32) {

src/test/ui/impl-trait/region-escape-via-bound.rs

@@ -15,7 +15,7 @@ fn foo<'x, 'y>(x: Cell<&'x u32>) -> impl Trait<'y>
 where 'x: 'y
 {
     x
-    //~^ ERROR hidden type for `impl Trait` captures lifetime that does not appear in bounds [E0700]
+    //~^ ERROR hidden type for `impl Trait<'y>` captures lifetime that does not appear in bounds [E0700]
 }
 
 fn main() { }

src/test/ui/impl-trait/region-escape-via-bound.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Trait<'y>` captures lifetime that does not appear in bounds
   --> $DIR/region-escape-via-bound.rs:17:5
    |
 LL | fn foo<'x, 'y>(x: Cell<&'x u32>) -> impl Trait<'y>

src/test/ui/impl-trait/static-return-lifetime-infered.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Iterator<Item = u32>` captures lifetime that does not appear in bounds
   --> $DIR/static-return-lifetime-infered.rs:7:9
    |
 LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> {
@@ -11,7 +11,7 @@ help: to declare that the `impl Trait` captures `'_`, you can add an explicit `'
 LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> + '_ {
    |                                                           ++++
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Iterator<Item = u32>` captures lifetime that does not appear in bounds
   --> $DIR/static-return-lifetime-infered.rs:7:9
    |
 LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> {
@@ -24,7 +24,7 @@ help: to declare that the `impl Trait` captures `'_`, you can add an explicit `'
 LL |     fn iter_values_anon(&self) -> impl Iterator<Item=u32> + '_ {
    |                                                           ++++
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Iterator<Item = u32>` captures lifetime that does not appear in bounds
   --> $DIR/static-return-lifetime-infered.rs:12:9
    |
 LL |     fn iter_values<'a>(&'a self) -> impl Iterator<Item=u32> {
@@ -37,7 +37,7 @@ help: to declare that the `impl Trait` captures `'a`, you can add an explicit `'
 LL |     fn iter_values<'a>(&'a self) -> impl Iterator<Item=u32> + 'a {
    |                                                             ++++
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Iterator<Item = u32>` captures lifetime that does not appear in bounds
   --> $DIR/static-return-lifetime-infered.rs:12:9
    |
 LL |     fn iter_values<'a>(&'a self) -> impl Iterator<Item=u32> {

src/test/ui/nll/issue-73159-rpit-static.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Iterator<Item = u8>` captures lifetime that does not appear in bounds
   --> $DIR/issue-73159-rpit-static.rs:8:9
    |
 LL | impl<'a> Foo<'a> {

src/test/ui/nll/ty-outlives/impl-trait-captures.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `Opaque(DefId(0:11 ~ impl_trait_captures[1afc]::foo::{opaque#0}), [ReStatic, T, ReEarlyBound(0, 'a)])` captures lifetime that does not appear in bounds
   --> $DIR/impl-trait-captures.rs:11:5
    |
 LL | fn foo<'a, T>(x: &T) -> impl Foo<'a> {

src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait-async.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Clone` captures lifetime that does not appear in bounds
   --> $DIR/arbitrary_self_types_pin_lifetime_impl_trait-async.rs:8:48
    |
 LL |     async fn f(self: Pin<&Self>) -> impl Clone { self }

src/test/ui/self/arbitrary_self_types_pin_lifetime_impl_trait.stderr

@@ -1,4 +1,4 @@
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl Clone` captures lifetime that does not appear in bounds
   --> $DIR/arbitrary_self_types_pin_lifetime_impl_trait.rs:6:44
    |
 LL |     fn f(self: Pin<&Self>) -> impl Clone { self }

src/test/ui/suggestions/lifetimes/missing-lifetimes-in-signature.rs

@@ -17,7 +17,7 @@ where
     G: Get<T>,
 {
     move || {
-        //~^ ERROR hidden type for `impl Trait` captures lifetime
+        //~^ ERROR hidden type for `impl FnOnce()` captures lifetime
         *dest = g.get();
     }
 }

src/test/ui/suggestions/lifetimes/missing-lifetimes-in-signature.stderr

@@ -6,7 +6,7 @@ LL | fn baz<G: 'a, T>(g: G, dest: &mut T) -> impl FnOnce() + '_
    |        |
    |        help: consider introducing lifetime `'a` here: `'a,`
 
-error[E0700]: hidden type for `impl Trait` captures lifetime that does not appear in bounds
+error[E0700]: hidden type for `impl FnOnce()` captures lifetime that does not appear in bounds
   --> $DIR/missing-lifetimes-in-signature.rs:19:5
    |
 LL |   fn foo<G, T>(g: G, dest: &mut T) -> impl FnOnce()