syntax_data: {"ast_node_type":"other","tokens":[{"end":50,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // should actually be emitting JSON blobs.
context_before:         // `--error-format=json`. This means that `--json` is specified we
context_after:         _ if !matches.opt_strs("json").is_empty() => {