Drive by: handle references in same_type_modulo_infer

Author: estebank

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -333,6 +333,9 @@ pub fn same_type_modulo_infer<'tcx>(a: Ty<'tcx>, b: Ty<'tcx>) -> bool {
         )
         | (&ty::Infer(ty::InferTy::TyVar(_)), _)
         | (_, &ty::Infer(ty::InferTy::TyVar(_))) => true,
+        (&ty::Ref(reg_a, ty_a, mut_a), &ty::Ref(reg_b, ty_b, mut_b)) => {
+            reg_a == reg_b && mut_a == mut_b && same_type_modulo_infer(ty_a, ty_b)
+        }
         _ => a == b,
     }
 }