Hi, not sure if I am right herem but as it has something to do with compiling I was thinking maybe h...

# compiler

[huehnerlady]

Hi, not sure if I am right herem but as it has something to do with compiling I was thinking maybe here?

It is about the smartCast. I appreciate that not all possibilities are covered, but I thought this scenario would work. I seem to be wrong? Or I did not add something which enables smartcast?

I have the following sample function:

fun test(){
  val testString: String?  = null
  testString ?: throw IllegalArgumentException("null")
  print(testString.length)
}

I now want to extract the exception throwing to make clear why I do this:

fun test2(){
  val testString: String?  = null
  testString ?: handleUnexpectedNull()
  print(testString.length)
}

private fun handleUnexpectedNull() {
  throw IllegalArgumentException("null")
}

But here I get a compile error (see screenshot).
Why is this happening and can I extract the exception in a way that still supports smartcast?

I am using the jvm compiling and kotlin 1.3.72

[gildor]

because Kotlin doesn’t know how handleUnexpectedNull work

[gildor]

so it cannot assume that it will always throw exception

[gildor]

But you can make compiler know about it, change return type of handleUnexpectedNull from Unit to Nothing

[huehnerlady]

@gildor aah super cool, did not know anything about nothing yet, thanks 🙂

[gildor]

see stdlib functions such as error() it’s the same case