{"ast_node_type":"impl","tokens":[{"end":89,"kind":"keyword","start":0,"text":"//"}]}
                    // Check whether the impl imposes obligations we have to worry about.
                    xform_ret_ty = ocx.normalize(cause, self.param_env, xform_ret_ty);
                    let impl_def_id = probe.item.container_id(self.tcx);