pub 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,
fn_host_effect: Const<'tcx>
) -> Binder<'tcx, (TraitRef<'tcx>, Ty<'tcx>)>