}

  private interface NullRejectingFromTo<F, T> extends Function<F, T> {
    @Override
    T apply(F from);
  }

  private static class NullRejectingInterfaceDefaultValueChecker extends DefaultValueChecker {

    @SuppressWarnings("unused") // called by NullPointerTester
    @Keep
    public void checkArray(NullRejectingFromTo<String, Integer> f, String s) {
      calledWith(f, s);