is the following possible w.r.t. the return statem...

# kotlin-native

[Kris Wong]

is the following possible w.r.t. the return statement within the let block?

NSURLSession.sharedSession.dataTaskWithRequest(
            NSURLRequest(NSURL(string = "<http://lsudflasfnlnf>")),
            requestBlock@ { data: NSData?, urlResponse: NSURLResponse?, error: NSError? ->
                error?.let {
                    return@requestBlock
                }
            }.freeze()
        ).resume()

[Kris Wong]

interestingly, this causes an ICE as written: e: Compilation failed: No DECLARATION_TO_DESCRIPTOR for DOT_QUALIFIED_EXPRESSION: KtReturnExpression:
return@requestBlock: KtLambdaExpression: ...

[Kristoffer Andersen]

Can you provide a self-contained example? Perhaps the right imports are enough.

[Kris Wong]

sure. just a little tweaking and the above can be self contained.

[Kris Wong]

edited. that should do it.

[Kristoffer Andersen]

Hmm, didn't see we were in /Native, sorry. But it does appear to be a native back-end bug, you should definitely put it on YouTrack if it isn't there already.

[Kris Wong]

got it. so the code is correct as written?

[Kristoffer Andersen]

I guess so. I can reproduce something of similar shape that the front-end + JVM/JVMIR be is happy with:

object Test {
    fun foo(a: Int, action: (Int?) -> Unit) {
        action(2)
    }
}


fun main() {
    Test.foo(2, test@
        { a: Int? ->
            a?.let {
                println(it)
                return@test
            }
            println(4)
        })
}

[Kristoffer Andersen]

Wait, looking closer at it -- what is .freeze() invoked on?

[Kris Wong]

the lambda

[Kristoffer Andersen]

Perfect, just double checking. It's an extention?

[Kris Wong]

yes

[Kris Wong]

it's part of K/N apis

[Kristoffer Andersen]

Hah! Awesome 😄

[Kristoffer Andersen]

I can reproduce the crash now!

[Kristoffer Andersen]

It's an exception in Psi2IR, the link between front and back-ends.

[Kristoffer Andersen]

So, scratch my previous comment that it should work. Possibly it should not, but the front-end doesn't correctly identify this,

[Kristoffer Andersen]

My conclusion is a front-end bug:

fun (() -> Nothing?).ext(): String = "OK"

fun box() =
    foo@{
        return@foo
    }.ext()

[Kristoffer Andersen]

This throws the same error.

[Kristoffer Andersen]

But should probably be rejected by the front-end. The IDE "infos" that the label is nonsensical.

[Kris Wong]

hmm

[Kris Wong]

so you believe it shouldn't work for K/N?

[Kristoffer Andersen]

I am not sure of the specs for labels and lambdas; this works:

fun (() -> Unit).ext(): String = "OK"


fun box() =
    foo@{
        return@foo
    }

fun main() {
    println(box().ext())
}

So it should probably work.

[Kristoffer Andersen]

I'll file it on YouTrack 🙂

[Kris Wong]

awesome, thanks!

[Kristoffer Andersen]

Sure thing! You can follow at https://youtrack.jetbrains.com/issue/KT-36217 🙂

[Kristoffer Andersen]

Good news! My colleague worked out that label annotations bind very weakly in the parser, weaker than calls.

[Kristoffer Andersen]

So, put parentheses around the labelled lambda, and it should work. Something like:

[Kristoffer Andersen]

NSURLSession.sharedSession.dataTaskWithRequest(
            NSURLRequest(NSURL(string = "<http://lsudflasfnlnf>")),
            (requestBlock@ { data: NSData?, urlResponse: NSURLResponse?, error: NSError? ->
                error?.let {
                    return@requestBlock
                }
            }).freeze()
        ).resume()

[Kristoffer Andersen]

Try that for me, @Kris Wong?

[Kris Wong]

👍

[Kristoffer Andersen]

Cool 🙂

[Kris Wong]

this works

[Kristoffer Andersen]

Awesome! 🙂

[Kristoffer Andersen]

The CLI kotlinc rejects the old code in the front-end. Hence the ICE you saw in the IDE must be because the IDE uses only parts of the frontend.