syntax_data: {"ast_node_type":"other","tokens":[{"end":71,"kind":"keyword","start":0,"text":"extra_filename:"}]}
source_snippet:     extra_filename: String = (String::new(), parse_string, [UNTRACKED],
context_before:         "emit bitcode in rlibs (default: yes)"),
context_after:         "extra data to put in each output filename"),