syntax_data: {"ast_node_type":"function","tokens":[{"end":92,"kind":"keyword","start":0,"text":"pub"}]}
source_snippet:     pub fn opt_param_def_id(self, tcx: TyCtxt<'tcx>, binding_item: DefId) -> Option<DefId> {
context_before:     /// or one of the parent generics. Returns the `DefId` of the parameter definition if so.
context_after:         match self.kind() {