Fix #2467

The stand-alone `unify` requires that the type doesn't contain any type
variables. So we can't share the code here for now (without more refactoring)...

2 files changed, 14 insertions, 3 deletions

diff --git a/crates/ra_hir_ty/src/infer/path.rs b/crates/ra_hir_ty/src/infer/path.rs
index b0024c6e1..37db005ea 100644
--- a/crates/ra_hir_ty/src/infer/path.rs
+++ b/crates/ra_hir_ty/src/infer/path.rs
@@ -1,5 +1,7 @@
 //! Path expression resolution.
 
+use std::iter;
+
 use hir_def::{
     path::{Path, PathKind, PathSegment},
     resolver::{ResolveValueResult, Resolver, TypeNs, ValueNs},
@@ -207,7 +209,16 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 };
                 let substs = match container {
                     ContainerId::ImplId(impl_id) => {
-                        method_resolution::inherent_impl_substs(self.db, impl_id, &ty)
+                        let impl_substs = Substs::build_for_def(self.db, impl_id)
+                            .fill(iter::repeat_with(|| self.table.new_type_var()))
+                            .build();
+                        let impl_self_ty = self.db.impl_self_ty(impl_id).subst(&impl_substs);
+                        let substs = Substs::build_for_def(self.db, item)
+                            .use_parent_substs(&impl_substs)
+                            .fill_with_params()
+                            .build();
+                        self.unify(&impl_self_ty, &ty);
+                        Some(substs)
                     }
                     ContainerId::TraitId(trait_) => {
                         // we're picking this method
diff --git a/crates/ra_hir_ty/src/infer/unify.rs b/crates/ra_hir_ty/src/infer/unify.rs
index 8ed2a6090..fe05642ae 100644
--- a/crates/ra_hir_ty/src/infer/unify.rs
+++ b/crates/ra_hir_ty/src/infer/unify.rs
@@ -167,12 +167,12 @@ impl<T> Canonicalized<T> {
     }
 }
 
-pub fn unify(ty1: Canonical<&Ty>, ty2: &Ty) -> Option<Substs> {
+pub fn unify(ty1: &Canonical<Ty>, ty2: &Canonical<Ty>) -> Option<Substs> {
     let mut table = InferenceTable::new();
     let vars =
         Substs::builder(ty1.num_vars).fill(std::iter::repeat_with(|| table.new_type_var())).build();
     let ty_with_vars = ty1.value.clone().subst_bound_vars(&vars);
-    if !table.unify(&ty_with_vars, ty2) {
+    if !table.unify(&ty_with_vars, &ty2.value) {
         return None;
     }
     Some(