But not for that syntax unfortunately, unless I'm missing it? I use sealed traits and case classes to do the same - the union syntax would be much nicer.

Coming in Dotty/Scala 3.0, along with a slew of other improvements to the language.

Combine that with the proposed new enum syntax and existing sealed trait plus case class/object boilerplate will be gone. Looks pretty great, but we'll have to wait until next year sometime to use it in production.