// WITH_STDLIB
// IGNORE_BACKEND_K2: ANY

/*
 * KOTLIN CODEGEN BOX SPEC TEST (NEGATIVE)
 *
 * SPEC VERSION: 0.1-488
 * MAIN LINK: overload-resolution, building-the-overload-candidate-set-ocs, operator-call -> paragraph 1 -> sentence 2
 * SECONDARY LINKS: statements, assignments, operator-assignments -> paragraph 2 -> sentence 1
 * statements, assignments, operator-assignments -> paragraph 2 -> sentence 2
 * statements, assignments, operator-assignments -> paragraph 2 -> sentence 3
 * NUMBER: 3
 * DESCRIPTION: nullable receiver
 * EXCEPTION: compiletime
 */

fun box(): String {
    val a: A? = A(B())
    val c: C? = C()

    a?.b += c
    if (f3 && !f1 && !f2 && !f4) {
        f3 = false
        a?.b.plusAssign(c)
        if (f3 && !f1 && !f2 && !f4)
            return "OK"
    }
    return "NOK"
}

class A(val b: B)

var f1 = false
var f2 = false
var f3 = false
var f4 = false

class B {
    operator fun plusAssign(c: C) {
        f1 = true
        print("1")
    }

    operator fun plus(c: C): C {
        f2 = true
        print("2")
        return c
    }
}

operator fun B.plusAssign(c: C) {
    f3 = true
    print("3")
}

operator fun B.plusAssign(c: Any) {
    f4 = true
    print("4")
}


class C