Abstracts, implicit casts and externs

[Żabojad]

I'm having the following issue with abstracts implicit casting + extern EitherType : http://try.haxe.org/#44f74

Using abstract implicit casting in an extern method signature in fine. But if I use EitherType, it's not anymore...

Is that a bug or a known limitation?

[Żabojad]

OK, that probably because haxe.extern. EitherType is already an abstract and we thus fall into this limitation:

http://haxe.org/manual/types-abstract-implicit-casts.html

While the individual casts from A to B and from B to C are allowed, a transitive cast from A to C is not. This is to avoid ambiguous cast-paths and retain a simple selection algorithm.

Could there be a metadata to deactivate this limitation? ^^ 

[Żabojad]

Would there be a macro way to allow the casting of A => B => C ?

[Żabojad]

I'm far from being a macro champion but I believe that would be feasible:

Can I attach some macro logic to an extern method definition so that every time it's used, it that would add an intermediate call to perform the conversion from A to B and from B to C ?

Something like:

extern class ExTest {
    @:build(myMacro.convert)

    static function test2(v : haxe.extern.EitherType<MyAbstractInt,SomethingElse>) : Void;

}

and MyMacro.convert would actually just wrap with, or add inline the conversion:

var arg : MyAbstractInt = T2;

ExTest.test2(arg);

Full example still available there : http://try.haxe.org/#44f74