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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?

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?

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

```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 -&gt; when (x) {
            is Y -&gt; 1
            is Z -&gt; 2
        }
        is C -&gt; when (x) {
            is Y -&gt; 3
            is Z -&gt; 4
        }
    }
}```

Can't push it into a single `when` statement?

Should the exhaustiveness check also work with
```sealed class DesiredState: Parcelable {
    @Parcelize
    object MainPage: DesiredState()
    @Parcelize
    object AcceptCall: DesiredState()
}```
?

Currently tells me I also need an `else` branch

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

fun test(state: DesiredState) = when (state) {
    is DesiredState.MainPage -&gt; "OK"
    is DesiredState.AcceptCall -&gt; "Error"
}```
Works fine

Looks like intellij got stuck somewhere, works fine.

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

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