Invariant default type for enums in Scala 3

Question

Scala 3 now has an improved way to define ADTs. A syntactic sugar that removes all the hassle of doing them with the usual sealed trait way.

So I'll explain my question with an example

enum Adt[+A]{
    case Option1
    case Option2
}

In this case Option1 and Option2 are of type Adt[Nothing], because the type parameter A is covariant.

If the enum were contravariant, they would be of type Adt[Any].

But what if it is invariant?

Answer 1

In Dotty 0.27.0-RC1, this is an error:

scala> enum Adt[A]{
     |     case Option1
     |     case Option2
     | }
2 |    case Option1
  |    ^^^^^^^^^^^^
  |    cannot determine type argument for enum parent class Adt,
  |    type parameter type A is non variant
3 |    case Option2
  |    ^^^^^^^^^^^^
  |    cannot determine type argument for enum parent class Adt,
  |    type parameter type A is non variant