Should smart casting work normally when using nested `sealed` classes? I see a lot of issues like t...

# announcements

[Jeisson Sáchica]

Should smart casting work normally when using nested sealed classes? I see a lot of issues like this https://youtrack.jetbrains.com/issue/KT-13495 marked as fixed a long time ago yet I experience this problem in 1.4.21

[Jeisson Sáchica]

sealed class User {
    object Unauthenticated: User()
    sealed class Authenticated: User() {
        object Client: Authenticated()
        object Owner: Authenticated()
    }
}

fun getUser(): User {
    return User.Authenticated.Client
}

fun main() {
    when (val user: User = getUser()) {
        is User.Unauthenticated -> { println("Not Authenticated!") }
        is User.Authenticated -> {
            when (user) {
                is User.Authenticated.Client -> { println("Hello Client!") }
                is User.Authenticated.Owner -> { println("Hello Owner!") }
            }
        }
    }
}

The second when expression shows the warning:

[Jeisson Sáchica]

I can add to the when expression user as Authenticated but then it is marked as "unnecessary":

[Rafs]

The cast happens during the is evaluation that is why your as cast has been marked as useless

[Jeisson Sáchica]

Yes, except that if the explicit casting is removed the compiler gives a warning asking for exhaustive checking on the when expression, the warning is in the first screenshot

[Jeisson Sáchica]

I found two issues related to this problem, one is from 2 years ago https://youtrack.jetbrains.com/issue/KT-29087, and the other is from 4 months ago https://youtrack.jetbrains.com/issue/KT-41305. Both are unassigned so I guess all we can do is wait and ignore the warning

[Javier]

https://github.com/cashapp/exhaustive