{"ast_node_type":"variable","tokens":[{"end":74,"kind":"keyword","start":0,"text":"let"}]}
            let fn_mut = tcx.require_lang_item(LangItem::FnMut, DUMMY_SP);
        ty::InstanceKind::ClosureOnceShim { call_once: _, track_caller: _ } => {
            let call_mut = tcx