@staticInterop and generics

[Zekfad]

If there any good way to make a @staticInterop class generic until extension types lands in stable?

I see only 2 methods with current dart:

1. Give up on @staticInterop, making class via dynamic interop would make it possible to add generics.
   But this gives following disadvantages:
   • Possible collision with existing classes of dart:html with @Native annotation will crash the thing: [dart2js] Iterator is confused with NodeIterator #53532
   • Opting out of future wasm support.
2. Make a wrapper object which would enforce type:
   • You have to make wrapper methods/getters to substitute class, and such wrapper will likely be instantiated on every call. Extension types (Implement Extension Type Feature #52684) will likely make this a less hustle.
   • Error prone due to dynamic going everywhere in underlying layer.

In my actual use case (I'm developing fetch_client and fetch_api) both methods is inconvenient:
With first we have still not fixed #53532 (which I presume requires a single line change in @Native annotation), this causing Zekfad/fetch_client#9
With second it's requires a workaround for generics: Zekfad/fetch_api#3

Also as a related question, will views/extension types be able to passed as @staticInterop external members, or we would still be required to make a wrapper methods?

[srujzs]

You should be able to use generics in @staticInterop in 3.2 now that we've re-enabled external extension instance members to be able to use type parameters. We've previously disallowed this due to some worries with dart2wasm JS interop lowerings, but that's not an issue. Ultimately, this a static guarantee of course, as the generics are never reified since these objects are external to the Dart runtime.

Once extension types comes along, that should be even easier to write as you note. I'd avoid creating an expensive wrapper type and either use @staticInterop or an extension type for JS interop objects.

Extension types will be allowed to use external extension members just like @staticInterop. With dart:js_interop the erasure will be more obvious, where you can declare the representation type using one of the JS types declared in that library. There is no need for an actual wrapper - this should be a zero-cost wrapper.

[srujzs]

I'm going to go ahead and close this issue as the original question is resolved (I believe).