syntax_data: {"ast_node_type":"other","tokens":[{"end":65,"kind":"keyword","start":0,"text":"proc_macro_backtrace:"}]}
source_snippet:     proc_macro_backtrace: bool = (false, parse_bool, [UNTRACKED],
context_before:         "print layout information for each type encountered (default: no)"),
context_after:          "show backtraces for panics during proc-macro execution (default: no)"),