Hi. With the following sealed class hierarchy, th...

# language-proposals

[natpryce]

Hi. With the following sealed class hierarchy, the function foo doesn’t compile in any version of Kotlin (I’ve tried up to 1.1-M4). The compiler complains that the when expression is not exhaustive, although it actually is.

sealed class Base {
	sealed class Mid : Base() {
        class A: Mid()
        class B: Mid()
    }
    class C: Base()
}


fun foo(b: Base): String = 
   when (b) {
       is Base.Mid.A -> "A"
       is Base.Mid.B -> "B"
       is Base.C -> "C"
    }

I think that the exhaustiveness check for sealed classes should take into account whether intermediate subclasses are also sealed.