Jon Pretty

I've written a lesson about some of the more advanced capabilities of enumerations in Scala 3. It's still "beginner level", so I managed to avoid going into detail on variance, but virtually everything else is covered: https://scala.zone/courses/scala-beginner/data/enums2 …

I drifted away from Scala (job wise), but are there no more sealed traits, just enums? The enums with fields seems dangerous

Sealed traits are still there. The new enums add more flexibility, as well as concision, compared to the the old enumerations, so they can be used for many abstract data types now.

The new enumeration syntax should cover the vast majority of ADT definitions that would previously have been implemented with case classes and sealed traits, but they're still implemented that way under the hood.

The type inference in pattern matching GADTs or GADT-like structures is a big change. It was broken now it’s magical.

Good one. I saw Alex, who did the work on this, describe it in a Scala symposium talk in London last year. Some ripper examples.