clonetest.scala

trait Cloneable[+T <: AnyRef] extends AnyRef {
  def create(): T
  override def clone(): T = create()
}

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

class B(aa: Int, var b: Int) extends A(aa) with Cloneable[B] {
  override def create(): B = new B(a, b)
}
// i can make polymorphic methods by using a typebound of T <: Cloneable[T] now,
// but if i use a bound of A or B or A with Cloneable[T] or B with Cloneable[T] it fails, which is suboptimal
//

// scala> class Bip[T <: A with Cloneable[A]](x: T)
// defined class Bip
// 
// scala> new Bip(new A(5)) 
// res0: Bip[A] = Bip@4d22366e
// 
// scala> class Bip[T <: B with Cloneable[B]](x: T)
// defined class Bip
// 
// scala> new Bip(new A(5))
// <console>:7: error: inferred type arguments [A] do not conform to class Bip's type parameter bounds [T <: B with Cloneable[B]]
//        new Bip(new A(5))
//        ^
// 
// scala> new Bip(new B(5, 10))
// res2: Bip[B] = Bip@2448b7f
//