1 files changed, 13 insertions, 16 deletions

diff --git a/crates/hir_ty/src/method_resolution.rs b/crates/hir_ty/src/method_resolution.rs
index 7e09a1539..766880b14 100644
--- a/crates/hir_ty/src/method_resolution.rs
+++ b/crates/hir_ty/src/method_resolution.rs
@@ -6,7 +6,11 @@ use std::{iter, sync::Arc};
 
 use arrayvec::ArrayVec;
 use base_db::CrateId;
-use chalk_ir::{cast::Cast, Mutability, UniverseIndex};
+use chalk_ir::{
+    cast::Cast,
+    fold::{Fold, Folder},
+    Fallible, Mutability, UniverseIndex,
+};
 use hir_def::{
     lang_item::LangItemTarget, nameres::DefMap, AssocContainerId, AssocItemId, FunctionId,
     GenericDefId, HasModule, ImplId, Lookup, ModuleId, TraitId,
@@ -21,7 +25,7 @@ use crate::{
     primitive::{self, FloatTy, IntTy, UintTy},
     static_lifetime,
     utils::all_super_traits,
-    AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer, FnSig, ForeignDefId,
+    AdtId, BoundVar, Canonical, CanonicalVarKinds, DebruijnIndex, FnPointer, FnSig, ForeignDefId,
     InEnvironment, Interner, Scalar, Substitution, TraitEnvironment, TraitRefExt, Ty, TyBuilder,
     TyExt, TyKind, TypeWalk,
 };
@@ -757,20 +761,13 @@ pub(crate) fn inherent_impl_substs(
 /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
 /// num_vars_to_keep) by `TyKind::Unknown`.
 fn fallback_bound_vars(s: Substitution, num_vars_to_keep: usize) -> Substitution {
-    s.fold_binders(
-        &mut |ty, binders| {
-            if let TyKind::BoundVar(bound) = ty.kind(&Interner) {
-                if bound.index >= num_vars_to_keep && bound.debruijn >= binders {
-                    TyKind::Error.intern(&Interner)
-                } else {
-                    ty
-                }
-            } else {
-                ty
-            }
-        },
-        DebruijnIndex::INNERMOST,
-    )
+    crate::fold_free_vars(s, |bound, binders| {
+        if bound.index >= num_vars_to_keep && bound.debruijn == DebruijnIndex::INNERMOST {
+            TyKind::Error.intern(&Interner)
+        } else {
+            bound.shifted_in_from(binders).to_ty(&Interner)
+        }
+    })
 }
 
 fn transform_receiver_ty(