c# - Any clean way for generic parent to get type of child?

[cvi]

@Zecc Based on this, I propose the keywords be changed to the following

• fun for a function
• sad for constants/single static assignment values
• ind for variables

[error]

@cvi said in c# - Any clean way for generic parent to get type of child?:

@Zecc Based on this, I propose the keywords be changed to the following

• fun for a function
• sad for constants/single static assignment values
• ind for variables

We can fork the language and call it BiPOLAR.

[dkf]

@cvi said in c# - Any clean way for generic parent to get type of child?:

@Zecc Based on this, I propose the keywords be changed to the following

• fun for a function
• sad for constants/single static assignment values
• ind for variables

That means we can have ‼fun‼ for functors!

[pie_flavor]

@dkf

class Foo
operator fun Foo?.not(): Foo? = this
fun main() {
    val `fun`: Foo? = Foo()
    !!`fun`!!
}

[Gąska]

@pie_flavor doesn't !! have higher precedence than !?

[pie_flavor]

@Gąska does it matter?

[Gąska]

@pie_flavor I'd think so. Why is a method defined on Foo? called on Foo?

[pie_flavor]

@Gąska toString is defined on Any? but is still called on normal objects.

[Gąska]

@pie_flavor what toString?

Edit: are you trying to say that every non-nullable type in Kotlin is automatically a subtype of its respective nullable type?

[pie_flavor]

@Gąska Yes.

[Gąska]

@pie_flavor is this preserved by generics? If so, are other kinds of subtyping preserved by generics?

[pie_flavor]

@Gąska this is Java. Nothing is preserved in generics. Unless you mean "can List<T> be assigned to List<T?>, in which case yes.

[Gąska]

@pie_flavor so generics are covariant. Fucking great. I guess nothing is perfect... Is there some kind of opt-out at least? And please tell me regular inheritance doesn't cause covariance.

[pie_flavor]

@Gąska what are you on about?
interface List<out E> : Collection<E>
As opposed to MutableList<> which is invariant.

[dkf]

@Gąska said in c# - Any clean way for generic parent to get type of child?:

generics are covariant

In Java (with no guarantee about other JVM-based languages), you get to select whether generics are invariant (usual case), covariant or contravariant. (I can never remember which way round extends and super map to those two terms.)

[Gąska]

@pie_flavor said in c# - Any clean way for generic parent to get type of child?:

@Gąska what are you on about?

The same thing as you, except in more words because I'm not a fucking asshole, and more questions than answers because I'm not a fucking expert on Kotlin unlike you.

interface List<out E> : Collection<E>
As opposed to MutableList<> which is invariant.

Okay, so out specifies covariance, and if you omit it, it's invariant, and you can set contravariance for a type parameter too. Dunno why you menthioned Collection though, because if A: B, then MutableList<A>: Collection<B> too.

[pie_flavor]

@Gąska I didn't 'mention' Collection. That's just the definition of List.

[pie_flavor]

@Gąska said in c# - Any clean way for generic parent to get type of child?:

The same thing as you, except in more words because I'm not a fucking asshole, and more questions than answers because I'm not a fucking expert on Kotlin unlike you.