Re: [swift-dev] Property modification not taking effect

[Pushkar N Kulkarni via swift-dev]

The issue is seen with the 05-09 dev snapshot. However after updating the repos today, I no longer see it! 

Looks like one of yesterday's commits (which did not go into 05-09)  fixed it. I am closing the JIRA report. Thanks!

Pushkar N Kulkarni,

IBM Runtimes

Simplicity is prerequisite for reliability - Edsger W. Dijkstra

-----swift-dev-boun...@swift.org wrote: -----

To: John McCall <rjmcc...@apple.com>
From: Pushkar N Kulkarni via swift-dev
Sent by: swift-dev-boun...@swift.org
Date: 05/10/2017 06:00PM
Cc: swift-dev <swift-dev@swift.org>
Subject: Re: [swift-dev] Property modification not taking effect

Thanks John. This is the JIRA bug report: https://bugs.swift.org/browse/SR-4852

I was able to write a small test case that shows the regression:

enum State {

    case ready(TState)

    case inProgress(TState)

    var isPaused: Bool {

        switch self {

        case .ready: return false

        case .inProgress: return false

        }

    }

}

enum Drain {

    case foo(String)

    case bar(Int, String)

}

struct TState {

    let drain: Drain

}

class Task {

    var state = State.ready(TState(drain: .foo("wow"))) { 

        willSet {

            if newValue.isPaused { }

        }

    }

    func resume() {

        if case .ready(let tState) = state {

            print("before => \(state)")

            state = .inProgress(tState) //doesn't take effect

            print("after => \(state)")

        }

    }

}    

//main

Task().resume()

Output with the latest master:

before => ready(Test.TState(drain: Test.Drain.foo("wow")))

after => ready(Test.TState(drain: Test.Drain.foo("wow")))

Expected output (and with the 04-24 snapshot as well):

before => ready(Test.TState(drain: Test.Drain.foo("wow")))

after => inProgress(Test.TState(drain: Test.Drain.foo("wow")))

Pushkar N Kulkarni,

IBM Runtimes

Simplicity is prerequisite for reliability - Edsger W. Dijkstra

-----rjmcc...@apple.com wrote: -----

To: Pushkar N Kulkarni <pushkar...@in.ibm.com>
From: John McCall
Sent by: rjmcc...@apple.com
Date: 05/10/2017 04:19AM
Cc: swift-dev <swift-dev@swift.org>
Subject: Re: [swift-dev] Property modification not taking effect

On May 9, 2017, at 3:07 PM, Pushkar N Kulkarni via swift-dev <swift-dev@swift.org> wrote:

In the process of debugging a bunch of consistent failures in TestFoundation/TestNSURLSession, I came across a weird problem symptom in this line of code.

internalState = .transferInProgress(transferState)

I had a suspicion that the above modification is not taking effect, since, only based on this change the didSet observer for the `internalState` property triggers data transfers using libcurl. So, I simply printed the property before and after the assignment. 

print("before => \(internalState)")

internalState = .transferInProgress(transferState)

print("after => \(internalState)")

Surprisingly, I don't see any change in the property value:

before => transferReady(Foundation.URLSessionTask._TransferState(... <redacted> ...))

after  => transferReady(Foundation.URLSessionTask._TransferState(... <redacted> ...))

When I switched back to the "swift-DEVELOPMENT-SNAPSHOT-2017-04-24-a" tag on all the repos (except swift-corelibs-foundation), I do not see this problem. I see:

before => transferReady(Foundation.URLSessionTask._TransferState(... <redacted> ...))

after  => transferInProgress(Foundation.URLSessionTask._TransferState(... <redacted> ...))

To put it in simple terms, the modification doesn't seem to be taking effect with the current HEAD. 

I haven't been able to isolate this problem in an independent test case. However, anybody who wants to reproduce it can simply run TestFoundation after enabling the URLSession tests (which have been disabled for now) in TestFoundation/main.swift. 

I did compare the `-emit-ir` outputs from the passing and failing levels. There seems to be a clear difference in the way we store the new value of this property. But given my limited exposure to debugging Swift compiler issues, I wasn't able to progress further.  

 

Can someone help us here please? Thanks. 

That sounds like a serious bug; please file it in JIRA.

John.

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