Support Scala 3 Union Types

[lvitaly]

It looks like Scala 3 Union Types could replace Shapeless Coproduct. But in practice, usage of the Union Type leads to an error like this.

[error] -- [E172] Type Error:
[error] 17 |        implicit override lazy val s5: Serde[PushMessageCommand] = Avro4sSerde(client)
[error]    |                                                                                      ^
[error]    |No given instance of type com.sksamuel.avro4s.Encoder[model.SendPushMessage |
[error]    |  model.MarkIsRead] was found.
[error]    |I found:
[error]    |
[error]    |    com.sksamuel.avro4s.Encoder.autoDerived[
[error]    |        model.SendPushMessage |
[error]    |          model.MarkIsRead
[error]    |    ](
[error]    |      /* missing */
[error]    |        summon[
[error]    |          deriving.Mirror.Of[
[error]    |            model.SendPushMessage |
[error]    |              model.MarkIsRead
[error]    |          ]
[error]    |        ]
[error]    |    )
[error]    |
[error]    |But Failed to synthesize an instance of type deriving.Mirror.Of[
[error]    |  model.SendPushMessage |
[error]    |    model.MarkIsRead
[error]    |]:
[error]    |	* type `model.SendPushMessage |
[error]    |  model.MarkIsRead` is not a generic product because its subpart `model.SendPushMessage |
[error]    |  model.MarkIsRead` is a top-level union type.
[error]    |	* type `model.SendPushMessage |
[error]    |  model.MarkIsRead` is not a generic sum because its subpart `model.SendPushMessage |
[error]    |  model.MarkIsRead` is a top-level union type..
[error]    |----------------------------------------------------------------------------
[error]    |Inline stack trace
[error]    |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[error]    |This location contains code that was inlined from impl.scala:86
[error]    |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[error]    |This location contains code that was inlined from impl.scala:86
[error]    |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[error]    |This location contains code that was inlined from impl.scala:86
[error]    |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[error]    |This location contains code that was inlined from impl.scala:86
[error]    |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[error]    |This location contains code that was inlined from impl.scala:86
[error]    |- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
[error]    |This location contains code that was inlined from impl.scala:86
[error]     ----------------------------------------------------------------------------

Scala 3.3.1
avro4s 5.0.7

What do you think about the possibility of supporting Union Types?

[ticofab]

I'm interested in this one too. Thanks for any updates 🙏