Xcode 16 reports incorrect syntax errors on Todos sample project

[sleepygarden]

Description

I'm trying to teach myself TCA, and referring the the Todos sample project as a point of reference. The unit tests inside the project compile and run fine, but syntax highlighting shows that most of the file is invalid code. Is this to be expected with Xcode 16.0? The issue persists after building, after cleaning the project, after rebooting, and after deleting derived data.

I think the issue stems from the fact that Xcode doesn't see Todos as a Reducer, and thus can't infer the base type on all of the keypaths and Action cases

Checklist

• I have determined whether this bug is also reproducible in a vanilla SwiftUI project.
• If possible, I've reproduced the issue using the main branch of this package.
• This issue hasn't been addressed in an existing GitHub issue or discussion.

Expected behavior

Unit test targets are able to correctly identify types annotated with macros for the purposes of syntax highlighting

Actual behavior

Unit test target is not able to determine that a type which has Reducer applied via macro is a Reducer for the purposes of syntax highlighting

Reproducing project

The reproducing project is just the Todos app on main as of 2/10/25

The Composable Architecture version information

1.17.1

Destination operating system

iOS 18

Xcode version information

Version 16.0 (16A242d)

Swift Compiler version information

swift-driver version: 1.115 Apple Swift version 6.0 (swiftlang-6.0.0.9.10 clang-1600.0.26.2)
Target: arm64-apple-macosx14.0

[mbrandonw]

Hi @sleepygarden, this is not to be expected, but unfortunately it is just an Xcode bug. I am not seeing this in 16.2, so perhaps if you update your Xcode it will work better.

Since this isn't an issue with the library I am going to convert it to a discussion. Please feel free to continue the conversation over there!

[sleepygarden]

Confirmed @mbrandonw, this appears to be a uniquely Xcode 16.0 bug. 16.2 Works perfectly

[OddMagnet]

I'm using Xcode 16.2, but the problem still exists for me :(
TCA version is 1.18.0

[mbrandonw]

Hi @OddMagnet, make sure that you have enabled macros and that you have built the full project. This sometimes happens when Xcode cannot build the macros because they have not been enabled yet, and then due to an unfortunate Xcode bug, ghost errors stick around for far too long. But I find that eventually they do go away.

Though if they do not go away you may want to close the project, delete derived data, re-open the project, and then immediate enable macros.

[OddMagnet]

Hey @mbrandonw, thanks for the quick reply! :)

The weird thing is, I had enabled macros, fully build and run the project and only after that I started adding tests, so I would've expected to not run into this issue in the first place.

When I close, delete DerivedData and reopen it seems to work correctly again. Though there is no prompt for enabling macros again. Even after quite some timing developing for iOS it boggles my mind how often deleting DerivedData is the solution, lol

[OddMagnet]

Hey @mbrandonw, sorry to bother you, but I'm still a bit confused on this problem.

So I added another feature in the same app, build and ran the app, everything good so far. Then I added tests for that feature and the same problem appeared again.

Obviously closing Xcode and clearing DerivedData solved the problem, but I'd prefer to not have to do that over and over.

Is there anything I need to keep in mind when adding a new feature and following that new tests?