clonetest.scala

trait Cloneable[T <: Cloneable[_]] {
  def clone(): T
}

class A(var a: Int) extends Cloneable[A] {
  def clone(): A = new A(a)
}

class B(aa: Int, var b: Int) extends A(aa) with Cloneable[B] {
  def clone(): B = new B(a, b)
}

/*
/home/james/proj/sblast/src/main/scala/clonetest.scala:9: illegal inheritance;
 self-type B does not conform to Cloneable[B]'s selftype Cloneable[B]
class B(aa: Int, var b: Int) extends A(aa) with Cloneable[B] {
                                                ^
one error found
*/