1 files changed, 16 insertions, 1 deletions
diff --git a/compiler/rustc_trait_selection/src/solve/weak_types.rs b/compiler/rustc_trait_selection/src/solve/weak_types.rs
index b095b54c5..54de32cf6 100644
--- a/compiler/rustc_trait_selection/src/solve/weak_types.rs
+++ b/compiler/rustc_trait_selection/src/solve/weak_types.rs
@@ -1,3 +1,8 @@
+//! Computes a normalizes-to (projection) goal for inherent associated types,
+//! `#![feature(lazy_type_alias)]` and `#![feature(type_alias_impl_trait)]`.
+//!
+//! Since a weak alias is not ambiguous, this just computes the `type_of` of
+//! the alias and registers the where-clauses of the type alias.
 use rustc_middle::traits::solve::{Certainty, Goal, QueryResult};
 use rustc_middle::ty;
 
@@ -12,8 +17,18 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
         let weak_ty = goal.predicate.projection_ty;
         let expected = goal.predicate.term.ty().expect("no such thing as a const alias");
 
-        let actual = tcx.type_of(weak_ty.def_id).subst(tcx, weak_ty.substs);
+        let actual = tcx.type_of(weak_ty.def_id).instantiate(tcx, weak_ty.args);
         self.eq(goal.param_env, expected, actual)?;
+
+        // Check where clauses
+        self.add_goals(
+            tcx.predicates_of(weak_ty.def_id)
+                .instantiate(tcx, weak_ty.args)
+                .predicates
+                .into_iter()
+                .map(|pred| goal.with(tcx, pred)),
+        );
+
         self.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
     }
 }