gistfile1.kt

class Foo<out T>() {
  var value : T? = null
}

fun main(args : Array<String>) {
  val a : Foo<Int> = Foo<Int>()
  a.value = 5
  
  val b : Foo<Number> = a
  b.value = 2.0
  
  println(a.value) // 2.0
}