Is there any explanation?

# coroutines

[marcinmoskala]

Is there any explanation?

[elizarov]

var prime: Int is captured into the lambda to be executed later.

[elizarov]

I’ve hit the same ~1.5 years ago when prototyping channels for Kotlin.

[elizarov]

Filed this one back then: https://youtrack.jetbrains.com/issue/KT-15514

[elizarov]

(2 years ago, oh my!)

[marcinmoskala]

I guessed that it is because of problems with capturing by lambda. Should I add it as an error or someone else already done it? This is build-in Kotlin problem so I think that issue tracker is the place.

[marcinmoskala]

https://youtrack.jetbrains.com/issue/KT-27559

[ilya.gorbunov]

But is this related to suspending functions?
I mean the problem is that a mutable variable is captured in filter plain lambda.

[elizarov]

Yes. That is exactly the issue I’ve filed. In general, capturing mutable variable into a lambda that is executed “not in place” should be at least a warning. There are cases where it is Ok, though. It would be hard to distinguish them.

[marcinmoskala]

😱 I see it now. @antonkeks This is even better puzzler!

[ilya.gorbunov]

A simplified puzzler on this subject was already presented on the latest KotlinConf:
https://github.com/angryziber/kotlin-puzzlers/blob/master/src/functions/closeCapture/CloseCapture.kts

https://youtu.be/Xq9vBZs0j-8?t=1796▾