Hey guys I’m stuck with a kotlin generics problem: How to inherit from same generic interface twice with two different types?

interface A<T> {}

class B: A<Apple> {}

class MyClass: B, A<Orange> {}

Kotlin gave me an error: Type parameter T of ‘A’ has inconsistent values: Apple, Orange

Simple answer: you can't.

And it's not just a Kotlin generics problem, it's a JVM generics problem due to type erasure – https://en.wikipedia.org/wiki/Generics_in_Java#Problems_with_type_erasure

@Jay Because of type erasure, you can only implement an interface once with the same type parameter

got it, Thx!

I thought you could do something like

class MyClass<T> : B, A<T> where T : Apple, T : Orange

if Apple and Orange were interfaces, but it gives an error. Anyone know what the problem is with that?

@marstran Because you want it to be an

A<Apple>

and an

A<Apple and Orange>

at the same time which is not possible due to type erasure (of course in this case it's just redundant so you can just get rid of B)