We may still need opaque version

[hax]

I understand that copying properties extends the use cases of this proposal, allowing it to also serve as a kind of immutable data type. However, from the perspective of key use cases, 'opaque' might make sense. For example, for a class, the state used for differentiation might be private (via private fields). In other programming languages, hashCode/equals methods do not expose these private states externally, yet the current design of 'composite' requires such exposure. I feel this could be an issue. Perhaps we still need an opaque version (maybe as an option?)