[Scala 3] Roadmap to Scala 3 release

[TimWSpence]

Required:

• Always require Or instances for givens
• implicit keyword in scala 3 tests
• Wildcard import derivation not working
• Derive ShowPretty
• Test derivation for enums
• Make instances Serializable

Optional/under discussion:

• Derivation for deeply nested types
• Extra Covariant and Invariant instances
• Stack safety of derived instances
• Sequence support
• Derive ConsK

[joroKr21]

IMO stack safety and sequence support are not blocking. One of the issues with stack safety (at least the way it was done with Eval in Scala 2) is that it comes at a cost even when you don't need it. And in theory it could apply to any nested derivation, not just Functor and Foldable.

[TimWSpence]

IMO stack safety and sequence support are not blocking. One of the issues with stack safety (at least the way it was done with Eval in Scala 2) is that it comes at a cost even when you don't need it. And in theory it could apply to any nested derivation, not just Functor and Foldable.

Yeah definitely. Woops, I meant to update that ticket to say that it isn't an exhaustive list of derivations that aren't stacksafe 🤦 One option I was considering is if we offered a separate semiauto.stackSafeFunctor that goes through Eval? (So no auto or derives syntax) I think that would work but I guess we'd effectively be maintaining two derivations per typeclass which would suck

[joroKr21]

Yeah it's not great to maintain two derivations. Also a derivation based on Eval is complex because we have to duplicate all method signatures and match on the runtime type of the type class.

[joroKr21]

I will close this now that 3.0 is out. We can tackle the remaining issues independently.