syntax_data: {"ast_node_type":"other","tokens":[{"end":53,"kind":"keyword","start":0,"text":"data.local_expn_hashes[self]"}]}
source_snippet:             data.local_expn_hashes[self] = expn_hash;
context_before:             debug_assert_eq!(data.local_expn_hashes[self].0, Fingerprint::ZERO);
context_after:             let _old_id = data.expn_hash_to_expn_id.insert(expn_hash, self.to_expn_id());