syntax_data: {"ast_node_type":"other","tokens":[{"end":62,"kind":"keyword","start":0,"text":"if"}]}
source_snippet:                 if self.serialized_expns.lock().insert(expn) {
context_before:             for (expn, expn_data, expn_hash) in all_expn_data {
context_after:                     encode_expn(encoder, expn, &expn_data, expn_hash);