syntax_data: {"ast_node_type":"other","tokens":[{"end":70,"kind":"keyword","start":0,"text":"opt(Stable,"}]}
source_snippet:         opt(Stable, Multi, "", "emit", &EMIT_HELP, "<TYPE>[=<FILE>]"),
context_before:         opt(Stable, Opt, "", "edition", &EDITION_STRING, EDITION_NAME_LIST),
context_after:         opt(Stable, Multi, "", "print", &PRINT_HELP, "<INFO>[=<FILE>]"),