{"ast_node_type":"other","tokens":[{"end":17,"kind":"keyword","start":0,"text":"macro_rules!"}]}
macro_rules! m2 {
// `_ => ou` overlaps with `$a:expr => $b:ident` but rustc matches it under `_ => $c:expr`.
    ($($a:expr => $b:ident)* _ => $c:expr) => { ok!(); }