[Scala 3] Test with enum-based adts

[TimWSpence]

We just copied the scala 2 adt definitions so we're not currently testing derivation for scala 3 enums

[wahtique]

Hi ! I was looking for a first issue to contribute and this look like a nice one to start :)
To clarify it :

• does this mainly concern the ADTs defined in https://github.com/typelevel/kittens/blob/dotty/core/src/test/scala-3/cats/derived/adtdefns.scala ? My understanding is that they seem to be reused in other tests and are thus the main target for this issue
• should the scala 3 enums replace the scala 2 style ADTs or should we also consider keeping the scala 2 version and duplicating the tests with enum in order to keep ensure compatibility with both styles ?

[joroKr21]

Hey @wahtique thank you for your interest to help!

• So yes this is mostly about the ADTs in the file you linked, but they are not enums, because they were copied from the Scala 2 tests. What we need now is to add tests with Scala 3 enums - they don't have to be exactly the same, but it's probably easier to copy some of them and convert them to enums.
• We should keep the Scala 2 tests because they ensure that we have source compatibility with Scala 2 so it should be relatively easy for people to migrate by just changing the imports.

[TimWSpence]

Hey @wahtique I'm so sorry, I didn't see this and just opened #498. But if you spot gaps in my test coverage and want to add more then that would be brilliant! Thanks so much for wanting to get involved ❤️