syntax_data: {"ast_node_type":"other","tokens":[{"end":92,"kind":"keyword","start":0,"text":"assert!(old_expn_data.is_none(),"}]}
source_snippet:             assert!(old_expn_data.is_none(), "expansion data is reset for an expansion ID");
context_before:             let old_expn_data = &mut data.local_expn_data[self];
context_after:             *old_expn_data = Some(expn_data);