// WITH_STDLIB

/*
 * KOTLIN CODEGEN BOX SPEC TEST (POSITIVE)
 *
 * SPEC VERSION: 0.1-213
 * MAIN LINK: expressions, prefix-expressions, prefix-increment-expression -> paragraph 6 -> sentence 1
 * PRIMARY LINKS: expressions, prefix-expressions, prefix-increment-expression -> paragraph 5 -> sentence 1
 * overloadable-operators -> paragraph 4 -> sentence 1
 * NUMBER: 2
 * DESCRIPTION:
 */


fun box(): String {
    var a = A()
    val res: Any? = ++a
    return if (res is B) "OK"
    else "NOK"
}

open class A() {
    var i = 0

    open operator fun inc(): B {
        var b = B()
        b.i = this.i
        b.i++
        return b
    }

}

class B() : A() {}
