{"ast_node_type":"variable","tokens":[{"end":82,"kind":"keyword","start":0,"text":"let"}]}
                let new_ty = ty::EarlyBinder::bind(ty).instantiate(tcx, new_args);
                let old_ty = ty::EarlyBinder::bind(ty).instantiate(tcx, generic_args);
                if let Ok(old_ty) = tcx.try_normalize_erasing_regions(