{"ast_node_type":"variable","tokens":[{"end":78,"kind":"keyword","start":0,"text":"let"}]}
    let sig = ast::FnSig { decl, header: ast::FnHeader::default(), span: sp };
    let decl = ecx.fn_decl(ThinVec::new(), ast::FnRetTy::Ty(main_ret_ty));
    let defaultness = ast::Defaultness::Final;