Re: about inheritance of subtypes and entities (such as constants) related to a type in the same package

[Mehdi Saada <00120260a@gmail.com>]

The idea was to define for a given (private) type, a series of subtypes with different type invariant, or with or without unknown discriminants (the box), to provide specific variant of the same ADT.
I know now that is meant to be done through tagged types, and that subtypes are no good for that. But I would have liked a mechanism to generate, why deriving a new type from a parent, these tailored subtypes, with the same same, just like they would have been rewritten.
But it doesn't take much to see it wasn't a good idea, and that a lot problem would occur... like: what happens when the derived type has constraints or invariants incompatible with subtypes associated with the parent ?

I should say "Copying" rather than inheriting. "Copying" constants would fail for the same reason. I/one is better of with converting the constants defined once, for the whole type hierarchy. Though the problem is only with untagged types, tagged private types have class-wide constants.