"@:using" is not working on interfaces.

[posxposy]

Hello! :)

//using Test.TestTools; //Works
class Test implements ITest {
  static function main() {
        new Test().test();
  }
  
  function new(){}
}

@:using(Test.TestTools) //Not works
interface ITest {}

class TestTools {
    public static inline function test(v:ITest):Void {
        trace("Test!");
    }
}

Error: Test.hx:3: characters 9-24 : Test has no field test
http://try-haxe.mrcdk.com/#7Cd23

Haxe 4. RC1

[Gama11]

At this point I'm wondering, what does @:using work on? :D

[Simn]

This shouldn't work. @:using on a type only has an effect when a field access is made on that type. The compiler doesn't explore all related types to find all possible static extensions.

We will document this accordingly.

[nadako]

I don't know, this looks like a somewhat legit use-case and it looks like it should work. And we don't have to explore anything here, right? We can inherit @:using when processing class heritage.

[Simn]

We can, but I don't think we should because this gets very magical.

I'm inclined to go the opposite way and restrict @:using to enums. That's why I originally added it, and because enums don't have sub-types we don't have to worry about complexity.

[nadako]

restrict @:using to enums

Well, I can live with that. If we error on other types it'll at least look as something actually designed and not randomly (not) working :-) And we can revisit this some time in future.

[posxposy]

I'm inclined to go the opposite way and restrict @:using to enums.

Please, noooo :(
It is very useful for class types too. I'm using it in my project and I really like this feature.

[nadako]

But you can just add your usings to import.hx...

[posxposy]

But you can just add your usings to import.hx...

Yes, but you can do the same for enums... Why do you need @:using then?
It is just good when you have a syntax sugar and different solutions for one problem.
import.hx doing it in a bit implicit way.

[back2dos]

Dunno. When I proposed this, I specifically mentioned interfaces as a use case. And quite frankly, I don't get it: if you can apply the same extensions via using "globally" in import.hx, then what different kind of problem arises when applying them via @:using?

As for "why not just use import.hx":

[Gama11]

#8188