skip pointee correctly

Author: BoxyUwU

compiler/rustc_trait_selection/src/error_reporting/infer/nice_region_error/trait_impl_difference.rs

@@ -141,7 +141,10 @@ impl<'tcx> Visitor<'tcx> for TypeParamSpanVisitor<'tcx> {
         match arg.kind {
             hir::TyKind::Ref(_, ref mut_ty) => {
                 // We don't want to suggest looking into borrowing `&T` or `&Self`.
-                hir::intravisit::walk_ty(self, mut_ty.ty);
+                match mut_ty.ty.kind {
+                    hir::TyKind::Infer(()) => (),
+                    _ => hir::intravisit::walk_ambig_ty(self, mut_ty.ty.as_ambig_ty()),
+                }
                 return;
             }
             hir::TyKind::Path(hir::QPath::Resolved(None, path)) => match &path.segments {