Why does `Foo Bar lt Quax gt ` require `Quax` to be public i

Question

Why does `Foo Bar lt Quax gt ` require `Quax` to be public i e internal not allowed

Dominaezzz · Answer

I think it s because inheritance is public

Casey Brooks · Answer

Is `Foo` public I would guess that the type parameter needs to have the same level of access as the class itself

ursus · Answer

Yes foo is public

ursus · Answer

Inheritance is public I dont get what you mean

Dominaezzz · Answer

In C++ you can have private inheritance Where only the class know it has implemented an interface

ursus · Answer

I dont think thats the issue here issue is the visibility of the generic param and also that its different from java

Dominaezzz · Answer

Inheritance in Kotlin Java is public So anything that has access to `Foo` will see that it inherits `Bar` Since `Bar` has a generic parameter the parameter would have to be visible to anything that has access to `Foo` So if `Foo` is public anything it exposes has to be `public` If something has access to `Foo` it won t know what `Quax` is since it s internal I hope this makes sense

ursus · Answer

I dont think you are correct because package private Quax works in java

Dominaezzz · Answer

And `Foo` can be used outside the package

ursus · Answer

yep

ursus · Answer

works np ``` public class Rah extends Meh lt Ohe gt class Ohe public abstract class Meh lt T gt ```

Dominaezzz · Answer

Yup Sounds like I m wrong Still weird to see Perhaps Kotlin handles generics differently or something

ursus · Answer

yea idk thanks anyways

ursus · Answer

although by the same logic private Ohe should work too but doesnt something is fishy

thanksforallthefish · Answer

< Dominaezzz> you are actually right Roman explains the reason for the choice in Kotlin Java behaves differently here

thanksforallthefish · Answer

though truth be told it looks a bit inconsistent to me Does not compile ``` abstract class Bar lt T gt internal class Quax class Foo Bar lt Quax gt ``` compiles ``` interface Bar lt T gt visibility here does not matter it always compiles internal class Quax class Foo Bar lt Quax gt ```

ursus · Answer

huh really weird

corneil · Answer

When you extend a class you need access to the internals when you implement interface there are no internals you need access to The compiler isn t going to wait for your extended class to access something it can t have access to before complaining so it complains when you try to extend in a way that may cause problems