Hey there, I have a weird generics issue where the...

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[Saharath Kleips]

Hey there, I have a weird generics issue where the order of the where clause produces some weird behavior on what the type of box ends up being when combined with a star projection (Baz<*>):

interface Foo {
    fun isFoo(): Boolean
}
interface Bar{
    fun isBar(): Boolean
}
interface Baz<T> where T : Foo, T : Bar {
    val box: T
}
val baz: Baz<*> = TODO()
baz.box.isFoo() // OK where T : Foo, T : Bar -- NOT OK where T : Bar, T : Foo
baz.box.isBar() // NOT OK where T : Foo, T : Bar -- OK where T : Bar, T : Foo

Is this somehow intentional? Is there a workaround?

[ephemient]

with <*> you are bypassing generic types - it is a raw type, not an "any type that works"

[ephemient]

JVM doesn't actually support intersection types, so both javac and kotlinc fake it by using the first type

[ephemient]

in other words, the interface looks like

interface Baz {
    val box: Foo // or whichever one is mentioned first
}

when you remove the type machinery (that magically inserts as T when you have an actual T)

[ephemient]

you can see this in the Java bytecode

[Sam]

Is this https://youtrack.jetbrains.com/issue/KT-7389? If so, it's fixed in Kotlin 2.0

[Saharath Kleips]

Super interesting, makes sense!

[Saharath Kleips]

That issue looks correct, maybe I can drag my feet until 2.0 release then 😆