syntax_data: {"ast_node_type":"variable","tokens":[{"end":51,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:         if let Some(expn_id) = expn_id.as_local() {
context_before:     fn expn_data(&self, expn_id: ExpnId) -> &ExpnData {
context_after:             self.local_expn_data[expn_id].as_ref().expect("no expansion data for an expansion ID")