Hello, why is there no autocast in this case? Seem...

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[gcx11]

Hello, why is there no autocast in this case? Seems like a bug to me

open class Animal

class Dog: Animal() {
    fun bark() = println("Huf huf!")
}
class Cat: Animal()

fun main() {
    val numbers = arrayOf(1, 2, 3)
    foo(numbers, Cat())
}

fun foo(numbers: Array<Int>, animal: Animal) {
    if (numbers.isEmpty()) {
        return
    } else if (animal !is Dog) {
        return
    }

    println(animal) // no autocast here
}

[alex]

What cast do you expect?

[gcx11]

Cast to a Dog

[gcx11]

Nope, if it's not, it won't get past second condition

[gcx11]

@Andrew S

[Andrew S]

Are you saying that the editor informs you there is no cast necessary, but actually it is necessary?

[alex]

you have incorrect branching, remove else if and use if instead

[alex]

else if might never happen, so compiler can't guarantee than animal is always a Dog

[alex]

imagine that first "if" has print("Empty") instead of return

[gcx11]

Yeah, but that's different case

[alex]

Well, yeah, but it's too much for current smartcasting algorithm

[alex]

The situation you're describing is not a bug, it's just not implemented (and probably won't be in the nearest future, I think)

[Alowaniak]

You could argue that it's a bug in IntelliJ if IntelliJ shows that "No cast needed" though

[Andrew S]

Actually, there is no cast needed. I ran your code fine, without a cast, and it worked as expected. The autocomplete for bark() did not work, however:

fun foo(numbers: Array<Int>, animal: Animal) {

        if (numbers.isEmpty()) {
            return
        } else if (animal !is Dog) {
            return
        }

        println(animal) 
        val dog = animal
        println(dog)
        dog.bark()

    }

[Andrew S]

Output from this:

val numbers = arrayOf(1, 2, 3)
foo(numbers, Dog())

Is this:

AppKt$main$Dog@3f99bd52
AppKt$main$Dog@3f99bd52
Huf huf!

So the smart casting seems to work fine!