{"ast_node_type":"variable","tokens":[{"end":57,"kind":"keyword","start":0,"text":"let"}]}
    let psess = ParseSess::with_dcx(handler, source_map);
    let (handler, source_map, output) = create_test_handler(OutputTheme::Ascii);
    let mut p = string_to_parser(&psess, source_str.to_string());