Swift 6 concurrency error on _StorageClass.defaultInstance

[rebello95]

When building with Xcode 16.0 and the Swift 6 toolchain, the following error occurs with a generated _StorageClass type:

Static property 'defaultInstance' is not concurrency-safe because non-'Sendable' type

I read through #1560 which discussed this a bit, but based on this comment I opted to open a new issue.

This can reproduced on this Connect-Swift branch, but I think this is an issue with any generated _StorageClass when building with Swift 6.

[thomasvl]

@FranzBusch @gjcairo fyi - since I think you all mentioned working on full Swift 6 language mode. I guess starting with generated code would unblock folks first.

While #1561 might be sorta large to pull off in a non breaking way, I do wonder if that resolves a lot of this since I think the name map could get a lot simpler (no need for interning, etc.)

[thomasvl]

@tbkka fyi also

[FranzBusch]

since I think you all mentioned working on full Swift 6 language mode. I guess starting with generated code would unblock folks first.

I agree tackling the generated code is the most important thing. I do think we need to do all of this in a non-breaking way for now. Right now we are working through our other repos to make sure they compile without errors in Swift 6.

[jhump]

Do you have any idea of how soon this repo can be made compatible with Swift 6? We have a library that depends on this repo, and we're nearing a v1.0 release for it. We were hoping the v1.0 release could use Swift 6, but this issue is a blocker for that.

[Lukasa]

I think it'd be very helpful to get a complete list of Swift 6 issues you see. The specific concurrency issue here should be solveable using nonisolated(unsafe) on this static let, but I'd love to know if there were more.

[thomasvl]

Can someone that is seeing this issue see if they can recreated it by modifying #1737? I made attempt at ensuring the generate file had the Storage and also enabling v6 language mode on the packages, but I can't seem to get the warnings/errors in the new CI step.

[rebello95]

I think it'd be very helpful to get a complete list of Swift 6 issues you see. The specific concurrency issue here should be solveable using nonisolated(unsafe) on this static let, but I'd love to know if there were more.

@Lukasa Manually changing that line to nonisolated(unsafe) static let defaultInstance = _StorageClass() allowed me to build without further errors/warnings in my case.

Can someone that is seeing this issue see if they can recreated it by modifying #1737? I made attempt at ensuring the generate file had the Storage and also enabling v6 language mode on the packages, but I can't seem to get the warnings/errors in the new CI step.

@thomasvl I wonder if this could be related to the fact that CI is running on ubuntu-latest 🤔 are you able to repro the issue locally?

[thomasvl]

@thomasvl I wonder if this could be related to the fact that CI is running on ubuntu-latest 🤔 are you able to repro the issue locally?

On my Mac with Xcode 16.2 installed, using the github main branch, make test-spm-plugin SWIFT_BUILD_TEST_HOOK="-Xswiftc -warnings-as-errors" passes. So, no; I can't seem to repo it, so I'm hoping other folks that see the failure(s) can provide some insights so we can get something to repo it to track it going forward.

[thomasvl]

@rebello95 skimming back through, I don't think it was said, what version of SwiftProtobuf are you pulling in? Are you maybe on an older release?

[rebello95]

@rebello95 skimming back through, I don't think it was said, what version of SwiftProtobuf are you pulling in? Are you maybe on an older release?

I'm seeing this on 1.28.2. It's reproducible on this commit when trying to build the Connect-Swift project in Xcode 16.2.

[thomasvl]

@rebello95 skimming back through, I don't think it was said, what version of SwiftProtobuf are you pulling in? Are you maybe on an older release?

I'm seeing this on 1.28.2. It's reproducible on this commit when trying to build the Connect-Swift project in Xcode 16.2.

That commit is changing the main Package.swift, so it is changing how the SwiftProtobuf runtime is compiled, it isn't just about the generated code, and I thought your original comment in opening this issue was just about the generated code. How are you getting the original error from generated code without changing out the SwiftProtobuf code itself is compiled? SwiftPM should be fine with this library compiled in Swift 5 Language Mode and your code (and the generated code for Protos) being compiled in the 6 mode. If you have a problem in that setup, we'd like to recreate that to ensure we keep that building at all times.

[rebello95]

Ah, I dug through all the config files in the connect-swift project after reading your comment and noticed that one of them was still running on 1.25.2 instead of 1.28.2 🤦🏽 so importantly it was missing the changes from 3bc7630. I was able to get it working by updating that in connectrpc/connect-swift#331.

I apologize for the unnecessary concern. Thank you for your help with this @thomasvl 🙏🏽