Yes, deliberate denormalization is not a solution. If you need an ADT, use an ADT. However, you can put all the case-by-case data in separate non-ADT structures

Yes, deliberate denormalization is not a solution. If you need an ADT, use an ADT. However, you can put all the case-by-case data in separate non-ADT structures. Then think hard if you really need to "unify" them and only if so make an ADT that simply links to the other structures and contains no additional data. Works well for me. (This is not a hard rule. For example, layouts for disk serialization might be better done as a single union with a discriminator field. In this case we're not optimizing for code but for disk accesses).