{"ast_node_type":"variable","tokens":[{"end":44,"kind":"keyword","start":0,"text":"let"}]}
        let return_ty = main_fnsig.output();
    if let Some(term_did) = tcx.lang_items().termination() {
        let return_ty_span = main_fn_return_type_span(tcx, main_def_id).unwrap_or(main_span);