syntax_data: {"ast_node_type":"other","tokens":[{"end":38,"kind":"keyword","start":0,"text":"//"}]}
source_snippet:     // comp. uses to identify a DefId.
context_before:     // This information is safe to access, since it's hashed as part of the DefPathHash, which incr.
context_after:     fn def_key(&self, def: DefId) -> DefKey;