Trying to have enums backed by an

IntBuffer

, I'm writing an extension function for an Enum, where its companion object extends a specific interface. But if I cast, the compiler says the cast can never succeed.. why?

fun <E> Enum<E>.bind() where E : Enum<E>, E : A = (Enum.Companion as B).buffers[ordinal].bind() // this cast can never succeed

Also don’t you need to put the return type of the function before the where clause?

this fails

Enum.Companion as B

Because that refers to the companion of the

Enum

class, not the companion of the receiver

oh I see I misread that

is there a way ro retrieve the receiver companion?

There is no way in the type system to specify "a class that has a companion object" (let alone of a specific type)

A decent compromise is to replace

Enum<E>

with an interface that can return it's "companion object". Won't be type safe but .... it works 😅.

Or change

bind

to accept a

B

@Dominaezzz problem is that then the buffers would be static per interface. I need to have them per enum. Because I'd like to have the possibility to have multiple enums (extending the same interface) backing each different objects

From the interface you decide what object you want to return,

can you elaborate @Dominaezzz?

That gist has several problems with generics

GlBufE

can have a method that returns an instance of

GlBufEco

.

yeah yeah, it's just a draft

Sorry, I only meant I don't understand what each placeholder is supposed to do as the generics don't line up. But I'd go with @Dominaezzz's suggestion if it makes sense (you'd probably have to change the function to

fun <E> E.bind(...

instead of

Enum<E>.bind(...

)

Tiny upgrade,

T : Enum<T>

.

Wouldn't that make

bind

infinitely recursive?

Oh nvm. I just had another look at the signature of

bind

.

@Ruckus interesting if I write:

fun <T> T.bind(target: BufferTarget) where T : Enum<T>, T : GlBufE = T.buffers[ordinal].bind(target)

I get:

Error:(182, 70) Kotlin: Type parameter 'T' cannot have or inherit a companion object, so it cannot be on the left hand side of dot

Nvm