syntax_data: {"ast_node_type":"variable","tokens":[{"end":62,"kind":"keyword","start":0,"text":"let"}]}
source_snippet:             let opt_variances = tcx.variances_of(item_def_id);
context_before:             let tcx = self.cx();
context_after:             relate_args_with_variances(self, item_def_id, opt_variances, a_arg, b_arg, false)