message: [crispy] boxed: Adds ability to box enum types.
diff: @@ -49,7 +49,7 @@ constexpr bool is_boxed = helper::is_boxed<T>::value;
  template <typename T, typename Tag> struct boxed
  {
  static_assert(
  - std::is_integral_v<T> || std::is_floating_point_v<T>,
  + std::is_enum_v<T> || std::is_integral_v<T> || std::is_floating_point_v<T>,
  "Boxing is only useful on integral & floating point types."
  );
  