std::execution::emplace-from(C++26)

template<callable Fun>
  requires is_nothrow_move_constructible_v<Fun>
struct emplace-from {
  Fun fun;  // exposition only
  using type = call-result-t<Fun>;

  constexpr operator type() && noexcept(nothrow-callable<Fun>) {
    return std::move(fun)();
  }

  constexpr type operator()() && noexcept(nothrow-callable<Fun>) {
    return std::move(fun)();
  }
};