add haxe.NoData

[nadako]

This is an unit type extracted from #9111, serving the same purpose as e.g. tink.core.Noise: to be a dummy value in value-places created by type parameters (e.g. Future<NoData>, Signal<NoData> and such).

Sample usage:

var signal = new Signal<NoData>();
signal.dispatch(NoData);

It's implemented as a single-variant enum abstract over Dynamic and is always just a null at run-time which is probably the most lightweight implementation.

I still think that normal Void could work the same way, but looks like that's not going to happen, so let's at least add this one, because it is needed very often and currently everyone has to implement their own thing.

Also I'm not sure if it should or should not be in StdTypes.

[nadako]

I still think that normal Void could work the same way

BTW, one concern that was raised when discussing this was the Void->Void vs (Void)->Void situation. I recendly found out that TypeScript is dealing with this by allowing skipping of void arguments, e.g. the following compiles:

class Signal<T> {
    dispatch(arg:T) {}
}

var signal = new Signal<void>();
signal.dispatch(); // no argument required

I personally don't like it to much though, because it makes arity unclear and I think signal.dispatch(void) is good enough.

[nadako]

Hmm, maybe I'll draft a haxe-evolution proposal about Void unit type...

[nadako]

Hmm, maybe I'll draft a haxe-evolution proposal about Void unit type...

OK, here we go: HaxeFoundation/haxe-evolution#76

[nadako]

I'll close this since we kind of agreed that we could re-use Void for this.