syntax_data: {"ast_node_type":"variable","tokens":[{"end":28,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:         let mut mark = None;
context_before:     pub fn normalize_to_macros_2_0_and_adjust(&mut self, expn_id: ExpnId) -> Option<ExpnId> {
context_after:         *self = self.map_ctxt(|mut ctxt| {