Loop over all opaque types instead of looking at just the first one with the same DefId

Author: oli-obk

compiler/rustc_typeck/src/collect/type_of.rs

@@ -542,13 +542,14 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
             }
             // Use borrowck to get the type with unerased regions.
             let concrete_opaque_types = &self.tcx.mir_borrowck(def_id).concrete_opaque_types;
-            if let Some((opaque_type_key, concrete_type)) =
-                concrete_opaque_types.iter().find(|(key, _)| key.def_id == self.def_id)
-            {
-                debug!(
-                    "find_opaque_ty_constraints: found constraint for `{:?}` at `{:?}`: {:?}",
-                    self.def_id, def_id, concrete_type,
-                );
+            debug!(?concrete_opaque_types);
+            for (opaque_type_key, concrete_type) in concrete_opaque_types {
+                if opaque_type_key.def_id != self.def_id {
+                    // Ignore constraints for other opaque types.
+                    continue;
+                }
+
+                debug!(?concrete_type, ?opaque_type_key.substs, "found constraint");
 
                 // FIXME(oli-obk): trace the actual span from inference to improve errors.
                 let span = self.tcx.def_span(def_id);
@@ -613,11 +614,6 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: LocalDefId) -> Ty<'_> {
                 } else {
                     self.found = Some((span, concrete_type));
                 }
-            } else {
-                debug!(
-                    "find_opaque_ty_constraints: no constraint for `{:?}` at `{:?}`",
-                    self.def_id, def_id,
-                );
             }
         }
     }

src/test/ui/type-alias-impl-trait/issue-85113.rs

@@ -12,6 +12,7 @@ trait Output<'a> {}
 impl<'a> Output<'a> for &'a str {}
 
 fn cool_fn<'a>(arg: &'a str) -> OpaqueOutputImpl<'a> {
+    //~^ ERROR: concrete type differs from previous defining opaque type use
     let out: OpaqueOutputImpl<'a> = arg;
     arg
 }

src/test/ui/type-alias-impl-trait/issue-85113.stderr

@@ -10,6 +10,18 @@ note: hidden type `&'<empty> str` captures lifetime smaller than the function bo
 LL | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a;
    |                             ^^^^^^^^^^^^^^^^^^^^
 
+error: concrete type differs from previous defining opaque type use
+  --> $DIR/issue-85113.rs:14:1
+   |
+LL | fn cool_fn<'a>(arg: &'a str) -> OpaqueOutputImpl<'a> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `&'<empty> str`, got `&'a str`
+   |
+note: previous use here
+  --> $DIR/issue-85113.rs:14:1
+   |
+LL | fn cool_fn<'a>(arg: &'a str) -> OpaqueOutputImpl<'a> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error[E0477]: the type `&'<empty> str` does not fulfill the required lifetime
   --> $DIR/issue-85113.rs:5:29
    |
@@ -42,7 +54,7 @@ LL | type OpaqueOutputImpl<'a> = impl Output<'a> + 'a;
    = note: expected `Output<'a>`
               found `Output<'_>`
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
 Some errors have detailed explanations: E0477, E0495, E0700.
 For more information about an error, try `rustc --explain E0477`.