in include/unifex/let_error.hpp [231:240]
explicit type(Source&& source, Func2&& func, Receiver2&& dest) noexcept(
std::is_nothrow_constructible_v<Receiver, Receiver2&&>&&
std::is_nothrow_constructible_v<Func, Func2&&>&&
is_nothrow_connectable_v<Source, source_receiver>)
: func_((Func2 &&) func)
, receiver_((Receiver2 &&) dest) {
unifex::activate_union_member_with(sourceOp_, [&] {
return unifex::connect((Source &&) source, source_receiver{this});
});
}