I've got two sealed classes `CurrentState` and `DesiredState`. When doing `val x = when (CurrentStat...

# compiler

[reactormonk]

I've got two sealed classes CurrentState and DesiredState. When doing val x = when (CurrentState to DesiredState) { ... }, the exhaustiveness checker doesn't seem to like the non-existence of an else, even if I covered all branches. Any way to help it out a bit?

[dmitriy.novozhilov]

Exhautive checker does not work this way, because Pair of to sealed classes is not exhaustive class
BTW how do you check for pair components are is instance of some inheritor?

[reactormonk]

Is there a way to make an exhaustive check for a product of sealed classes?

[dmitriy.novozhilov]

sealed class A
class B : A()
class C : A()

sealed class X
class Y : X()
class Z : X()

fun test(a: A, x: X) {
    val result = when (a) {
        is B -> when (x) {
            is Y -> 1
            is Z -> 2
        }
        is C -> when (x) {
            is Y -> 3
            is Z -> 4
        }
    }
}

[reactormonk]

Can't push it into a single when statement?

[dmitriy.novozhilov]

No

[reactormonk]

Should the exhaustiveness check also work with

sealed class DesiredState: Parcelable {
    @Parcelize
    object MainPage: DesiredState()
    @Parcelize
    object AcceptCall: DesiredState()
}

?

[reactormonk]

Currently tells me I also need an else branch

[dmitriy.novozhilov]

sealed class DesiredState: Parcelable {
    @Parcelize
    object MainPage: DesiredState()
    @Parcelize
    object AcceptCall: DesiredState()
}

fun test(state: DesiredState) = when (state) {
    is DesiredState.MainPage -> "OK"
    is DesiredState.AcceptCall -> "Error"
}

Works fine

[reactormonk]

Looks like intellij got stuck somewhere, works fine.

[reactormonk]

I've got a weird case here where Intellij tells me I need an else branch, but the compiler is fine with it 🤔

[dmitriy.novozhilov]

Please report issue about it to YT

[reactormonk]

Probably https://youtrack.jetbrains.com/issue/KTIJ-19528/IDE-Scripts-false-positive-NOELSEINWHEN-for-sealed-hierarchy

[dmitriy.novozhilov]

Looks similar