Description
dart2js is blocked on this issue.
Consider:
class One<R> {}
class AnInterface<X> implements One<int> {}
class ADifferentInterface<Y> extends AnInterface<Y>{}
class TheMixin<Q> implements AnInterface<Q> {}
class Two<T> extends One<int> with TheMixin<T> implements AnInterface<T> {}
class Three<T> extends One<int> with TheMixin<T> implements ADifferentInterface<T> {}
main() {
new Two<double>();
}What we see is that One<int> with TheMixin<T> is abstracted like so
class OneWithTheMixin<U, V> = One<U> with TheMixin<V>;
class Two<T> extends OneWithTheMixin<int, T> ...This breaks on dart2js. dart2js has a constraint that a class cannot implement a type with different parameterizations. (The constraint allows the relationship between Two and One to be expressed as a function, the existence of this function is fundamental to the whole type representation.)
However, the introduced type OneWithTheMixin implements One<U> and One<int>. In particular, the raw type OneWithTheMixin implements One<dynamic> and One<int>.
The simplest for dart2js would be to create a fresh class for each with. This is what the old pipeline does - so it would be an advantage to do the same (we can compare outputs), and then reconsider a version of this abstraction later when we are done with the transition to Kernel.
This issue is blocking our next step, compiling angular apps with dart2js-with-kernel, so it is our highest priority issue with kernel.