Will kotlin ever get proper generics (not the castrated jvm half-assed solution)?

# compiler

[ursus]

Will kotlin ever get proper generics (not the castrated jvm half-assed solution)?

[Youssef Shoaib [MOD]]

I think you can do a lot of it already with inline + reified

[ursus]

reifeid doesn't do anything for class level generic parameters

I still need a
abtract fun fooType() : Class<T> to override in sublasses, don't I?

[AdamW]

https://openjdk.org/projects/valhalla/design-notes/in-defense-of-erasure

[ursus]

I'm sure there were reasons, but state of the matter is that it's lacking compared say to Swift

[ursus]

so I'm wondering if it's even possible to get rid of the java baggage

[eygraber]

Erasure is probably going to be there for a long time, if not always, as long as interop with Java is a thing.

[AdamW]

What are you trying to do, anyway? Do you have a longer snippet?

[ursus]

basically this

class Screen<T> {
	fun createViewModel() {
		val scopes = Scopes.get(T::class) <----
		..
	}
}

[eygraber]

It's not the best but the typical pattern is

inline fun <reified T> Screen() = Screen(T::class.java)

class Screen<T>(private val clazz: Class<T>) ...

[ursus]

I should have given more context

this is android, I cannot have ctor parameters .. well I can but then they need to be serialized etc

[eygraber]

Class is serializable so if the class is Serializable it should be fine. I believe Parcels can hold Serializable, so you should be fine if the class is Parcelable

[ursus]

not sure if it's worth the reflection runtime penalty 😕

[ursus]

is there no way to trick it like this?

class Screen<T> {
    fun foo() {
        
    }

    inline reified <T> whatever() -> KClass<T> {
        T::class
    }
}

[eygraber]

I think that would be a different T, but if you want to specify T when you invoke whatever that would work (but would be brittle)

You might also have to do an unsafe cast

[eygraber]

not sure if it's worth the reflection runtime penalty

You mean Class.forName (if that's what deserialization is using)? Unless this is a critical section you're probably fine. Not even sure how big of a penalty it is.

[Johann Pardanaud]

@AdamW that was a really interesting reading, thanks for sharing!