Hello, I feel I should know this, but why do I need the `else` in this `when`? and please, elaborat...

# getting-started

[thanksforallthefish]

Hello,

I feel I should know this, but why do I need the else in this when? and please, elaborate on the "type erasure" answer 😄

sealed interface Test

class Test1: Test
class Test2: Test

fun <T: Test> T.call() = when (this) {
  is Test1 -> Unit
  is Test2 -> Unit
  else -> throw IllegalArgumentException("why?")
}

Thanks 🙂

[Joffrey]

You theoretically don't need it, but the Kotlin compiler doesn't go that far (yet). There is an issue about this:
https://youtrack.jetbrains.com/issue/KT-21908/Support-when-exhaustiveness-checking-for-generic-type-parameter-with-sealed-class-upper-bound

And this is going to be fixed in Kotlin 2.1 (if I understand correctly)

[thanksforallthefish]

thanks, I thought there was going to be a yourtrack already, just did not find myself

[Youssef Shoaib [MOD]]

If you do when (this as Test) It will work then I believe!

[thanksforallthefish]

uh, trickster 😄 (it does work as expected then)