syntax_data: {"ast_node_type":"variable","tokens":[{"end":64,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let expn_id = hygiene_data.local_expn_data.next_index();
context_before:     HygieneData::with(|hygiene_data| {
context_after:         hygiene_data.local_expn_data.push(Some(data));