Fix shifting of binders in FnPointer

 - don't shift in/out for Chalk mapping (we want to have the same
   binders now)
 - do shift in when creating the signature for a closure (though it
   shouldn't matter much)
 - do shift in when lowering a `fn()` type
 - correctly deal with the implied binder in TypeWalk

1 files changed, 4 insertions, 2 deletions

diff --git a/crates/hir_ty/src/infer/expr.rs b/crates/hir_ty/src/infer/expr.rs
index a2a7236a8..ff564106b 100644
--- a/crates/hir_ty/src/infer/expr.rs
+++ b/crates/hir_ty/src/infer/expr.rs
@@ -23,7 +23,7 @@ use crate::{
     traits::{chalk::from_chalk, FnTrait},
     utils::{generics, variant_data, Generics},
     AdtId, Binders, CallableDefId, FnPointer, FnSig, FnSubst, InEnvironment, Interner,
-    ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyKind,
+    ProjectionTyExt, Rawness, Scalar, Substitution, TraitRef, Ty, TyBuilder, TyKind, TypeWalk,
 };
 
 use super::{
@@ -262,7 +262,9 @@ impl<'a> InferenceContext<'a> {
                 let sig_ty = TyKind::Function(FnPointer {
                     num_binders: 0,
                     sig: FnSig { abi: (), safety: chalk_ir::Safety::Safe, variadic: false },
-                    substitution: FnSubst(Substitution::from_iter(&Interner, sig_tys.clone())),
+                    substitution: FnSubst(
+                        Substitution::from_iter(&Interner, sig_tys.clone()).shifted_in(&Interner),
+                    ),
                 })
                 .intern(&Interner);
                 let closure_id = self.db.intern_closure((self.owner, tgt_expr)).into();