{"ast_node_type":"other","tokens":[{"end":50,"kind":"keyword","start":0,"text":"predicate:"}]}
        predicate: ty::PolySubtypePredicate<'tcx>,
        param_env: ty::ParamEnv<'tcx>,
    ) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {