syntax_data: {"ast_node_type":"other","tokens":[{"end":78,"kind":"keyword","start":0,"text":"FnDef(d,"}]}
source_snippet:             FnDef(d, s) => f.debug_tuple("FnDef").field(d).field(&s).finish(),
context_before:             Ref(r, t, m) => write!(f, "&{:?} {}{:?}", r, m.prefix_str(), t),
context_after:             FnPtr(sig_tys, hdr) => write!(f, "{:?}", sig_tys.with(*hdr)),