mergeMap/flatMap and Java 8 type inference

@adelnizamutdinov I don’t see a new issue created, so wanted to pick it up here.

You said this:

mergeMap is almost unusable with Java 8 type inference Always have to extend Observable::just and Observable::empty to anonymous classes

Can you elaborate?

[benjchristensen]

I’m considering this “as good as it can get” then since our flatMap matches the Stream interface definition:

<R> Observable<R> flatMap(Func1<? super T, ? extends Observable<? extends R>> func)

Thanks @akarnokd for the insight.

[akarnokd]

Java 6 and 7 developers would need the full covariance in the parameter types and only Java 8 non-Eclipse developers have to do workarounds such as above. Besides, the Stream.flatMap has full covariance in its signature:

<R> Stream<R> flatMap(Function<? super T,? extends Stream<? extends R>> mapper)

So it is either lambda workarounds for Java 8 devs or unchecked casting for Java 6/7 to bypass the lack of variance.