syntax_data: {"ast_node_type":"function","tokens":[{"end":56,"kind":"keyword","start":0,"text":"fn"}]}
source_snippet:     fn encode_def_index(&mut self, def_index: DefIndex);
context_before:     fn encode_crate_num(&mut self, crate_num: CrateNum);
context_after:     fn encode_def_id(&mut self, def_id: DefId);