Build failed for Swift 5.3 using Xcode 12.4, have no idea why

[Janneman84]

My package fails to build on the Swift 5.3 test and I'm looking for help. The report is here:
https://swiftpackageindex.com/builds/781136EE-2076-4691-BCFD-119C733E2F6F

I even downloaded Xcode 12.4 to see for myself but when I try it seems to build fine.

I get this generic error:
error: failed to produce diagnostic for expression; please file a bug report

About this line of code:

DispatchQueue.main.asyncAfter(deadline: .now() + delay) { [weak viewController, weak subview] in

Any Swift experts that can tell me why this would fail on Swift 5.3? Thanks!

[finestructure]

Sorry to hear you're having trouble with the build system!

I'm a bit confused - you say it seems to build fine but you're getting a generic error?

Does the actual build command:

env DEVELOPER_DIR="/Applications/Xcode-12.4.0.app" xcrun xcodebuild -IDEClonedSourcePackagesDirPathOverride="$PWD/.dependencies" -derivedDataPath "$PWD/.derivedData" build -scheme "LeakedViewControllerDetector" -destination "generic/platform=ios"

work for you?

Unfortunately, I can't easily test builds with 12.4 on my machine but we'll try and reproduce it ourselves as well.

[Janneman84]

I'm trying but whatever I try it just says
xcrun: error: missing DEVELOPER_DIR path: /Downloads/Xcode.app

I've tried with ~ and other things but no luck.

[finestructure]

You need to substitute in the path where you installed Xcode 12.4. That's probably /Application/Xcode-12.4. You can run

ls /Application/Xcode*

to verify what it's called exactly. It should list all the Xcodes in your Application folder.

[finestructure]

Note that if the path has a space in it, it's important you keep the quotes in the command, like so:

env DEVELOPER_DIR="/Applications/Xcode 12.4.app" ...

[Janneman84]

Yes I finally got it working after apparently some silly mistake.

It does trigger the error here too. After some experimenting it seems to have an issue with adding a weak declaration of a callback var:

view.iterateTopSubViews(viewController: viewController) { subview in
    DispatchQueue.main.asyncAfter(deadline: .now() + delay) { [weak viewController, weak subview] in

As you can see subview is a callback var that is passed on as weak in the other callback of the next line, which triggers the error. To fix I simply added this between the two lines:

let subview = subview

Everything seems to function fine with this somehow.

I also had to explicitly type UIColor.systemPink instead of the shorter .systemPink.

Thanks for sticking around to help me!

[finestructure]

No worries, glad you got it working!

[Janneman84]

After updating to Sonoma I am unable to run Xcode 12.4's CLI anymore, is this a known problem?

It's unable to find CoreChart or something.

Library not loaded: /System/Library/PrivateFrameworks/CoreChart.framework/Versions/A/CoreChart

Is it Sonoma or me?

[finestructure]

Sonoma doesn't support Xcode versions earlier than 15. You can get Xcode 14 to work with a little trick but it's not officially supported, not sure about versions even earlier than that. The only reliable way I know to run Xcode < 15 on Sonoma is to virtualise an older macOS version.

[Janneman84]

I realized SPI upped the lowest tested Swift version to 5.6. So I tried Xcode 13.3 instead, which works fine thanks!