Rollup merge of rust-lang#111450 - compiler-errors:opaque-ty-key, r=oli-obk

Use `OpaqueTypeKey` in query response

Makes it a bit clearer that at least one of the types being returned from a canonical query is an opaque.

Author: GuillaumeGomez

compiler/rustc_infer/src/infer/canonical/query_response.rs

@@ -153,20 +153,22 @@ impl<'tcx> InferCtxt<'tcx> {
 
     /// Used by the new solver as that one takes the opaque types at the end of a probe
     /// to deal with multiple candidates without having to recompute them.
-    pub fn clone_opaque_types_for_query_response(&self) -> Vec<(Ty<'tcx>, Ty<'tcx>)> {
+    pub fn clone_opaque_types_for_query_response(
+        &self,
+    ) -> Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)> {
         self.inner
             .borrow()
             .opaque_type_storage
             .opaque_types
             .iter()
-            .map(|(k, v)| (self.tcx.mk_opaque(k.def_id.to_def_id(), k.substs), v.hidden_type.ty))
+            .map(|(k, v)| (*k, v.hidden_type.ty))
             .collect()
     }
 
-    fn take_opaque_types_for_query_response(&self) -> Vec<(Ty<'tcx>, Ty<'tcx>)> {
+    fn take_opaque_types_for_query_response(&self) -> Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)> {
         std::mem::take(&mut self.inner.borrow_mut().opaque_type_storage.opaque_types)
             .into_iter()
-            .map(|(k, v)| (self.tcx.mk_opaque(k.def_id.to_def_id(), k.substs), v.hidden_type.ty))
+            .map(|(k, v)| (k, v.hidden_type.ty))
             .collect()
     }
 
@@ -507,8 +509,22 @@ impl<'tcx> InferCtxt<'tcx> {
             let a = substitute_value(self.tcx, &result_subst, a);
             let b = substitute_value(self.tcx, &result_subst, b);
             debug!(?a, ?b, "constrain opaque type");
-            obligations
-                .extend(self.at(cause, param_env).eq(DefineOpaqueTypes::Yes, a, b)?.obligations);
+            // We use equate here instead of, for example, just registering the
+            // opaque type's hidden value directly, because we may be instantiating
+            // a query response that was canonicalized in an InferCtxt that had
+            // a different defining anchor. In that case, we may have inferred
+            // `NonLocalOpaque := LocalOpaque` but can only instantiate it in
+            // the other direction as `LocalOpaque := NonLocalOpaque`. Using eq
+            // here allows us to try both directions (in `InferCtxt::handle_opaque_type`).
+            obligations.extend(
+                self.at(cause, param_env)
+                    .eq(
+                        DefineOpaqueTypes::Yes,
+                        self.tcx.mk_opaque(a.def_id.to_def_id(), a.substs),
+                        b,
+                    )?
+                    .obligations,
+            );
         }
 
         Ok(InferOk { value: result_subst, obligations })

compiler/rustc_middle/src/infer/canonical.rs

@@ -280,7 +280,7 @@ pub struct QueryResponse<'tcx, R> {
     /// should get its hidden type inferred. So we bubble the opaque type
     /// and the type it was compared against upwards and let the query caller
     /// handle it.
-    pub opaque_types: Vec<(Ty<'tcx>, Ty<'tcx>)>,
+    pub opaque_types: Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>,
     pub value: R,
 }
 

compiler/rustc_middle/src/traits/solve.rs

@@ -124,7 +124,7 @@ impl<'tcx> std::ops::Deref for ExternalConstraints<'tcx> {
 pub struct ExternalConstraintsData<'tcx> {
     // FIXME: implement this.
     pub region_constraints: QueryRegionConstraints<'tcx>,
-    pub opaque_types: Vec<(Ty<'tcx>, Ty<'tcx>)>,
+    pub opaque_types: Vec<(ty::OpaqueTypeKey<'tcx>, Ty<'tcx>)>,
 }
 
 // FIXME: Having to clone `region_constraints` for folding feels bad and