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kotlinlang

hey!
I have an Interface MyInt and its implementation MyIntImp. I'm trying to define a custom annotation(\@MyAnnotation) which accepts one argument of type Class&lt;MyInt&gt;.
When I'm trying to use the annotation like this \@MyAnnotation(MyIntImp::class it gives me an error that it expects Class&lt;MyInt&gt; and not Class&lt;MyIntImp&gt;

what am i missing here?

`Class<T>` is invariant in its type parameter, so by default `Class<MyIntImp>` is not a subtype of `Class<MyInt>` even if `MyIntImp` is a subtype of `MyInt`.

You probably want `Class<out MyInt>` (with the `out` modifier) in your annotation declaration, not just `Class<MyInt>`. You can learn more about generics and variance here:
<https://kotlinlang.org/docs/generics.html>

hey again <@UBXMWAA69>!
will it work if MyInt is parameterzied? MyInt&lt;T&gt;

You will have the same problem transitively :slightly_smiling_face: Does `MyInt` have an `in` or `out` modifier on its own type parameter? Because that is what decides whether the subtyping relationship between `MyInt&lt;T&gt;` and `MyInt&lt;U&gt;` depends on the subtyping relationship between `T` and `U`.

Oh wait, but if we stick to the specific `Class<T>` example, you might have an issue. `Class<MyInt<A>>` doesn't really carry any meaning in itself, because the `Class` instance of a generic class/interface doesn't care about the type parameter.