std::ranges::out_value_result

namespace std::ranges {
  // (1)
  template<class O, class T>
  struct out_value_result {
    [[no_unique_address]] O out;
    [[no_unique_address]] T value;

    template<class O2, class T2>
      requires convertible_to<const O&, O2> && convertible_to<const T&, T2>
    constexpr operator out_value_result<O2, T2>() const & {
      return {out, value};
    }

    template<class O2, class T2>
      requires convertible_to<O, O2> && convertible_to<T, T2>
    constexpr operator out_value_result<O2, T2>() && {
      return {std::move(out), std::move(value)};
    }
  };

  // (2)
  template< class O, class T >
  using iota_result = out_value_result<O, T>;
}