fun <T : Any?> useTX(x: T, fn: Function0<T>): T {
  return fn.invoke()
}

fun testNoNullCheck(xs: Array<String>) {
  useTX<@FlexibleNullability Serializable?>(x = xs, fn = local fun <anonymous>(): @FlexibleNullability Serializable? {
    return string()
  }
) /*~> Unit */
}
