kotlinExtensions.kt

fun Int?.toString() {
  return "42"
}

fun Any?.toString() {
  if (this == null) return "null"
  return toString()
}

fun main(args : Array<String>) {
  val x = null
  println(x.toString()) // prints "42" (even though it is not defined as Int?)
  val y : String? = null
  println(y.toString()) // prints "null"
}