I have a piece of code that looks like this:

fun pairTest(foo: Boolean, bar: Boolean) =
        when (foo to bar) {
            (true to true) -> 1
            (true to false) -> 2
            (false to true) -> 3
            (false to false) -> 4
        }

IntelliJ is saying that I need an else branch here. How come? And is there a better way to do this?

The compiler is just not that smart….. An exhaustive when class only works with enums and sealed classes. And even then, you can not get complex in your

when

conditions.

Boolean is not implemented in Kotlin as a sealed union and the compiler doesn't know that your match covers all cases in the Pair.

Might look better with an enum class (Boolean, Boolean) anyway?

makes sense. Thanks