Hi guys, is this some compiler bug? With the code ...

# announcements

[Timothy Wong]

Hi guys, is this some compiler bug?
With the code https://hasteb.in/tosejohu.kotlin,
the node.left and node.right are not automatically casted as thecorrect types, even though the if statement checks, and we can see from the docs that it technicaly should.

https://kotlinlang.org/docs/reference/typecasts.html

var local variables - if the variable is not modified between the check and the usage, is not captured in a lambda that modifies it, and is not a local delegated property;

[karelpeeters]

The segment from the doc you quote is about smartcasting the var itself, not its properties. Right below that it says:

var properties - never (because the variable can be modified at any time by other code).

[Shawn]

it’s a local var though, and smartcasting works at least at the top level (of those nodes)

[karelpeeters]

Yeah I agree that it's weird, but at least it matches the docs simple smile

[Shawn]

fun test() {
    var node = createBin()

    if (node is BinaryOp) {
        var left = node.left
        var right = node.right
        if (left is IntLit && right is IntLit) {
            right.token.value // unresolved reference: value
            val right = node.right as IntLit
            right.token.value // no problem
        }
    }
}

this works, and I feel like it shouldn’t if that were the case

[Timothy Wong]

i also saw that, but if that is talking about vars in local contexts too, it is contradictory

[streetsofboston]

Hmmm… this works:

if(node is BinaryOp) {
        val l = node.left
        val r = node.right
        if(l is IntLit && r is IntLit) {
            r.token.value 
            l.token.value 
        }        
    }

[karelpeeters]

@Shawn That just compiles for me fine, what is that comment about?

[Timothy Wong]

i think he left the comment in the snippet from my example

[karelpeeters]

@streetsofboston Of course if you explicitly create temporary vars you're in the local var case again which indeed works.

[Shawn]

@Timothy Wong yeah, my b

[Shawn]

My point is that if smartcasting works on that top node item, smartcasting should apply to its children members too

[streetsofboston]

Yep, exactly… whether you put node.left (and same for node.right) in a temporary variable l or not should not matter….