class Foo(var x: Int) {
  
  /**
   * Value of this object is itself
   */
  operator fun getValue(thisRef: Any?, property: KProperty<*>): Foo = this

  /*
   * Perform deep copy on set
   */
  operator fun setValue(thisRef: Any?, property: KProperty<*>, value: Foo) {
    this.x = value.x
  }

}

class ClassWithValueFoo {

  /*
   * Delegation results in value-type-like semantics
   */
  var foo: Foo by Foo(5)

}

fun sample() {
  val test = ClassWithValueFoo()
  test.foo = Foo(10) // deep copy instead of reassignment
}