message: [crispy] boxed: improves cast_from(*) to also accept boxed types as input.
diff: @@ -82,6 +82,9 @@ template <typename T, typename Tag> struct boxed
  template <typename Source>
  constexpr static boxed<T, Tag> cast_from(Source _value)
  {
  + if constexpr (is_boxed<Source>)
  + return boxed<T, Tag>{static_cast<T>(_value.value)};
  + else
  return boxed<T, Tag>(static_cast<T>(_value));
  }
  };
  