syntax_data: {"ast_node_type":"variable","tokens":[{"end":89,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let latest_expns = { mem::take(&mut *self.latest_expns.lock()) }.into_iter();
context_before:             #[allow(rustc::potential_query_instability)]
context_after:             let all_expn_data: Vec<_> = HygieneData::with(|data| {