enum branches can extend any class

[Blaisorblade]

Noticed by accident that enum cases might extend the wrong enum. That is, Z below is accepted and should probably be rejected. I also confirmed that Z indeed extends Expr and not Var.

object GADTs2 {
  enum Var[G, A] {
    case Z[A, G] extends Expr[(A, G), A]
  }
  enum Expr[G, A] {
    case Lit[G](n: Int) extends Expr[G, Int]
        // case S[A, G](x:
  }
}

[bishabosha]

Actually you can extend anything at all

[bishabosha]

class Foo

enum Var[G, A] with
  case Z[A, G]() extends Foo

val isVar = Var.Z().isInstanceOf[Var[?,?]] // false
val isEnum = Var.Z().isInstanceOf[scala.Enum] // false