I don't think it will affect opaque types implementation at all, since they exist only in compile time. As for value classes - Valhalla is a reason (Scala's) v

I don't think it will affect opaque types implementation at all, since they exist only in compile time. As for value classes - Valhalla is a reason (Scala's) value classes weren't removed from Scala 3 (in favor of opaque types), since they seem to be a good candidate to be implemented using Valhalla's classes.