syntax_data: {"ast_node_type":"other","tokens":[{"end":69,"kind":"keyword","start":0,"text":"debug_assert!(_old_id.is_none()"}]}
source_snippet:         debug_assert!(_old_id.is_none() || _old_id == Some(expn_id));
context_before:         let _old_id = hygiene_data.expn_hash_to_expn_id.insert(hash, expn_id);
context_after:     });