{"ast_node_type":"variable","tokens":[{"end":56,"kind":"keyword","start":0,"text":"let"}]}
    let fixture = bench_fixture::numerous_macro_rules();
fn macro_rules_fixtures_tt() -> FxHashMap<String, tt::TopSubtree<Span>> {
    let source_file = ast::SourceFile::parse(&fixture, span::Edition::CURRENT).ok().unwrap();