interface Inv2<A : Any?, B : Any?> {
}

fun box(): String {
  val x: Inv2<String, Int> = test()
  return "OK"
}

fun <T : Any?, R : Any?> check(x: T, y: R, f: Function1<T, R>): Inv2<T, R> {
  return TODO()
}

fun <X : Any?, Y : Any?> foo(): Function1<X, Y> {
  return TODO()
}

fun test(): Inv2<String, Int> {
  return check<String, Int>(x = "", y = 1, f = foo<String, Int>())
}