{"ast_node_type":"variable","tokens":[{"end":68,"kind":"keyword","start":0,"text":"let"}]}
    let main_fnsig = tcx.fn_sig(main_def_id).instantiate_identity();
fn check_main_fn_ty(tcx: TyCtxt<'_>, main_def_id: DefId) {
    let main_span = tcx.def_span(main_def_id);