in include/unifex/indexed_for.hpp [154:162]
auto connect(Receiver&& receiver) && {
return unifex::connect(
std::forward<Predecessor>(pred_),
_ifor::receiver_t<Policy, Range, Func, Receiver>{
(Func &&) func_,
(Policy &&) policy_,
(Range &&) range_,
(Receiver &&) receiver});
}