Is this a bug that `Collections.singletonList()` i...

# announcements

[dead.fish]

Is this a bug that Collections.singletonList() is seen as a MutableList in Kotlin?

[Joost Klitsie]

I think the translation between Java and Kotlin might be the problem here

[Joost Klitsie]

How would Kotlin understand a Java Collection is immutable?

[Joost Klitsie]

In the end a Collections.singletonList returns a Java List<>, which has mutable properties

[Joost Klitsie]

and then I guess it doesn't matter to the compiler that under the hood it will just crash if you try to edit the list

[dead.fish]

Yep, thought as much - the thing is in certain circumstances you get something that Kotlin just tells you is a List and you don’t exactly know where this comes from.

[dead.fish]

And to make matters more pressing, the original list I got was from Kotlin itself, because I have no Java code I interop with in this particular place.

[dead.fish]

i.e. listOf is defined as public fun <T> listOf(element: T): List<T> = java.util.Collections.singletonList(element)

[dead.fish]

All old news, I guess: https://youtrack.jetbrains.com/issue/KT-15126

[E.Kisaragi]

you may define your original one which has @UnmodifiableView and import it?