why does `foo::class` return `KClass<out String>` instead of `KClass<String>`, and...wha...

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[nanodeath]

why does foo::class return KClass<out String> instead of KClass<String>, and...what are my options if I actually want the latter?

[nanodeath]

I guess I can just cast it for now 🤷‍♂️

[diesieben07]

Because you are getting the actual runtime type of foo. It might be a subtype of the static type (val foo: A = B() where class B : A()) - In case of String that is not possible, but the compiler cannot rely on that (someone might make it open at some point and then you have a problem with separate compilation).

If you want KClass<String> use String::class or something like this.

[nanodeath]

thanks @diesieben07. yeah I think that makes sense -- even though I'm using a generic type parameter, you still don't know (in code, at least) exactly what type it is

[nanodeath]

I guess what I'd need to really solve this is for this line:

fun <T : Component> addComponent(c: T) {

I need some way to guarantee that c is exactly a type T, and not simply a subclass of T. but I don't think there's a way to do that.

[diesieben07]

No there isn't, and that violates a core principle of OOP.

[diesieben07]

If A extends B then it must be okay to pass a A everywhere that expects a B, otherwise A should not extend B.

[nanodeath]

liskov substitution principle right?

[nanodeath]

the class addComponent calls uses T in both in and out positions though, so...

[diesieben07]

I think you need to show more code...

[nanodeath]

can do, in a few hours