syntax_data: {"ast_node_type":"variable","tokens":[{"end":77,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:                         let param = generics.type_param(*param_ty, self.tcx);
context_before:                         let generics = self.tcx.generics_of(def_id);
context_after:                         let span = self.tcx.def_span(param.def_id);