syntax_data: {"ast_node_type":"other","tokens":[{"end":82,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:         // (for trivial or-patterns), and avoid useless work (for never patterns).
context_before:         // with remaining match pairs, to avoid exponential blowup if possible
context_after:         if let Some(last_candidate) = candidates_to_expand.last_mut() {