Confusing nullability on subscribe(BiConsumer)

[ZacSweers]

With RxJava 3.1.x's improve nullability annotations and Kotlin 1.5.30's improved recognition of them, I came across an interesting nullability mismatch with the subscribe(BiConsumer) case. In short - the generic T is always assumed non null now, but the nature of this method is that both parameters to the consumer are actually nullable (since only one is guaranteed to be present).

I'm not sure what the right solution is for this off-hand, but raising here for visibility.

[ZacSweers]

For now, I'm explicitly typing these parameters as nullable rather than allowing type inference to assume otherwise

[akarnokd]

Probably the declaration-side override could work:

Disposable subscribe(@NonNull BiConsumer<@Nullable ? super T, @Nullable ? super Throwable> onCallback)

Not sure how to verify it works with Kotlin. Could you create a mockup method with this kind of signature and see if the inference works for you?

[ZacSweers]

Yup I'll give that a try and report back

[ZacSweers]

Confirmed that works with this example

public class Example<@NonNull T> {
  void subscribe(BiConsumer<@Nullable T, @Nullable Throwable> consumer) {

  }
}

[ZacSweers]

I'll make a PR