{"ast_node_type":"other","tokens":[{"end":79,"kind":"keyword","start":0,"text":"($span:expr,"}]}
    ($span:expr, $msg:expr) => {{ throw_span_err!($span, $msg, |diag| diag) }};
macro_rules! throw_span_err {
    ($span:expr, $msg:expr, $f:expr) => {{