More type annotations

[erwald]

This pull request adds generics to RACMulticastConnection, RACBehaviorSubject and type annotations to RACSignal's +empty and +return methods.

It seems to me that it'd also make sense to add generics to RACChannelTerminal, RACChannel and RACSubject. Thoughts on that?

[erichoracek]

This is great!

Aren't some of these classes private to the implementation to ReactiveObjC? E.g. RACEmptySignal and RACReturnSignal? What is the benefit of making them generic?

Re: RACSubject, as far as I can tell from our usage of the existing generics, it should be possible to make RACSubject generic to its value type since it is a direct subclass of RACSignal. This should work in the same way that NSMutableArray generic element type works with NSArray.

Re: RACChannel/RACChannelTerminal, that should work as well if you want to take a stab at it.

[erwald]

Yes, true, for RACEmptySignal and RACReturnSignal generics are not much use practically; I added it more on theoretical grounds. It makes sense to me semantically that a RACEmptySignal and RACReturnSignal has one associated type just like RACSignal does. But maybe it's just noise. Should I revert those changes?

Meanwhile, it seems the Travis CI build failed, although everything was hunky dory when running the tests locally. I'll have a look at that.

[erichoracek]

That seems reasonable re: the internal types—it doesn't add any overhead to consumers.

[erwald]

All right, so I'll keep it as it is, then.

As for the failing Travis CI build, it seems to be a failure in three tests related to intervals. I don't see how that could possibly be caused by these type changes, and, moreover, the same tests pass locally.

Is it possible that the tests themselves are fickle, or that there are problems with the CI environment?

[erwald]

@erichoracek Possible to merge?