Add helper for resolving associated type of trait in infer

1 files changed, 18 insertions, 0 deletions

diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index d16f1eb46..62d5c8803 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -338,6 +338,24 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
         self.table.resolve_ty_shallow(ty)
     }
 
+    fn resolve_associated_type(&mut self, inner_ty: Ty, assoc_ty: Option<TypeAliasId>) -> Ty {
+        match assoc_ty {
+            Some(res_assoc_ty) => {
+                let ty = self.table.new_type_var();
+                let projection = ProjectionPredicate {
+                    ty: ty.clone(),
+                    projection_ty: ProjectionTy {
+                        associated_ty: res_assoc_ty,
+                        parameters: Substs::single(inner_ty),
+                    },
+                };
+                self.obligations.push(Obligation::Projection(projection));
+                self.resolve_ty_as_possible(ty)
+            }
+            None => Ty::Unknown,
+        }
+    }
+
     /// Recurses through the given type, normalizing associated types mentioned
     /// in it by replacing them by type variables and registering obligations to
     /// resolve later. This should be done once for every type we get from some