syntax_data: {"ast_node_type":"other","tokens":[{"end":54,"kind":"keyword","start":0,"text":"_"}]}
source_snippet:         _ if !matches.opt_strs("json").is_empty() => {
context_before:         // should actually be emitting JSON blobs.
context_after:             early_dcx.early_fatal("using `--json` requires also using `--error-format=json`");