pub(crate) fn closure_trait_ref_and_return_type<'tcx>( tcx: TyCtxt<'tcx>, fn_trait_def_id: DefId, self_ty: Ty<'tcx>, sig: PolyFnSig<'tcx>, tuple_arguments: TupleArgumentsFlag, ) -> Binder<'tcx, (TraitRef<'tcx>, Ty<'tcx>)>