Compilation error if Promise.NEVER is in condition and preceding the data

[serjek]

Consider the following:

function tryGetData():Promise<Data> return shouldHalt ? Promise.NEVER : data;

it will give compilation error unless Promise.NEVER is put after the data or data is wrapped to Promise.resolve. Note that function already has type hint, but it does not help the compiler to cast the Promise.NEVER properly.

[serjek]

checked with haxe 4.1.2 and 4.1.3

[serjek]

Apparently same applies to Promise.NOISE as well.

[back2dos]

Hmm, after the changes to NEVER this seems to work fine.

[serjek]

still repro:

final p = function():Promise<Int> return Promise.resolve(42);
p().next(v -> if (v == 42) Promise.NEVER else "okay").handle(function(o) trace(o));

String should be tink.core.Promise<tink.core.Never> And yes it will compile just fine if string comes first in condition.

[serjek]

But this time wrapping string to Promise.resolve does not help ;(

[kevinresol]

I reverted the change due to #158

[serjek]

Note, now this works with haxe 4.1.5 but does repro with 4.2.2

[kevinresol]

Current workaround is to explicitly type-hint the NEVER value:

final promise = if (v == 42) (Promise.NEVER:Promise<String>) else "okay";

[back2dos]

As @nadako suggested, we should probably add static public function never<X>():Promise<X> to Promise and advertise that instead.

[back2dos]

The suggestions from the above comment was actually implemented a while ago.