{"ast_node_type":"other","tokens":[{"end":39,"kind":"keyword","start":0,"text":"Err(_)"}]}
                            Err(_) => {
                            Ok(ok) => return Ok(self.register_infer_ok_obligations(ok)),
                                (Some(prev_ty.fn_sig(self.tcx)), Some(new_ty.fn_sig(self.tcx)))