syntax_data: {"ast_node_type":"other","tokens":[{"end":66,"kind":"keyword","start":0,"text":"MacroExpansion(_)"}]}
source_snippet:             MacroExpansion(_) => write!(fmt, "<macro expansion>"),
context_before:             CfgSpec(_) => write!(fmt, "<cfgspec>"),
context_after:             Anon(_) => write!(fmt, "<anon>"),