// !DIAGNOSTICS: -UNUSED_PARAMETER -OPT_IN_IS_NOT_ENABLED
// WITH_STDLIB

import kotlin.experimental.ExperimentalTypeInference

@OptIn(ExperimentalTypeInference::class)
class A1<T> {
    fun <BT1> builder1(configure: A2<BT1>.() -> Unit) {}
}

@OptIn(ExperimentalTypeInference::class)
class A2<A2_BT1> {
    fun <BT2> builder2(configure: A3<A2_BT1, BT2>.() -> Unit) {}
}

@OptIn(ExperimentalTypeInference::class)
class A3<A3_BT1, A3_BT2> {
    fun <BT3> builder3(configure: A4<A3_BT1, A3_BT2, BT3>.() -> Unit) {}
}

class A4<A3_BT1, A3_BT2, A3_BT3> {
    fun resolver(x: A3_BT3) {}
}

fun foo(x: A1<String>) {
    x.builder1<String> {
        builder2<String> {
            builder3 {
                resolver("")
            }
            builder3 {
                resolver("")
            }
        }
        builder2<String> {
            builder3 {
                resolver("")
            }
            builder3 {
                resolver("")
            }
        }
    }
}

fun box(): String {
    foo(A1())
    return "OK"
}