syntax_data: {"ast_node_type":"function","tokens":[{"end":66,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn local_expn_data(&self, expn_id: LocalExpnId) -> &ExpnData {
context_before:     #[inline]
context_after:         self.local_expn_data[expn_id].as_ref().expect("no expansion data for an expansion ID")