import kotlin.contracts.*

@OptIn(ExperimentalContracts::class)
fun bar(x: () -> Unit) {
    contract {
        callsInPlace(x, InvocationKind.EXACTLY_ONCE)
    }

    x.invoke()
}

@OptIn(ExperimentalContracts::class)
fun foo(x: () -> Unit, y: () -> Unit, z: () -> Unit) {
    contract {
        callsInPlace(x, InvocationKind.EXACTLY_ONCE)
        callsInPlace(y, InvocationKind.AT_MOST_ONCE)
        callsInPlace(z, InvocationKind.EXACTLY_ONCE)
    }

    x.invoke()

    if (true) {
        y()
    }

    bar(z)
}
