mp_units::utility::detail::is_value_preserving_v

template<
    typename From,
    typename To>
inline constexpr bool is_value_preserving_v = [] {
  if constexpr (integral<underlying_int_type_t<From>> && integral<underlying_int_type_t<To>>)
    return is_value_preserving_int_v<From, To>;
  else
    return false;
}();