Swift 6.2 / Xcode 26 compatibility: swift-syntax upper bound excludes 620.x

[mjcaboose001]

Description

The current Package.swift constrains swift-syntax to "600.0.0"..<"603.0.0", which excludes Swift 6.2 (620.x) shipped with Xcode 26. This causes Swift macro compilation to fail with "malformed response" errors on Xcode 26.2 and 26.3.
The fix is a one-line change to expand the upper bound:

swift

// current
.package(url: "https://github.com/swiftlang/swift-syntax", "600.0.0"..<"603.0.0")

// suggested
.package(url: "https://github.com/swiftlang/swift-syntax", "600.0.0"..<"621.0.0")

This affects downstream consumers including sqlite-data and immich-app/immich whose iOS app uses sqlite-data. The same fix is needed in sqlite-data's Package.swift once swift-structured-queries ships a new release.

Environment:

Xcode 26.2 and 26.3
Swift 6.2 (620.x)
swift-structured-queries 0.31.0
sqlite-data 1.6.0

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

Adding swift-structured-queries as a dependency and building a project with Swift macros should succeed on Xcode 26 / Swift 6.2.

Actual behavior

Building fails with Swift compiler errors:
Swift Compiler Error: External macro implementation type 'StructuredQueriesMacros.TableMacro' could not be found; '...StructuredQueriesMacros' produced malformed response
This affects all macro types including TableMacro, ColumnMacro, SelectionMacro, etc. The root cause is that Package.swift constrains swift-syntax to "600.0.0"..<"603.0.0", which excludes Swift 6.2 (620.x). Swift macro plugins must be built with a swift-syntax version matching the host compiler, so the macro binary produces a malformed response when run under Swift 6.2.

Reproducing project

No standalone project needed. The issue is directly visible in Package.swift:
swift.package(url: "https://github.com/swiftlang/swift-syntax", "600.0.0"..<"603.0.0")

The upper bound needs to be extended to include 620.x. Suggested fix:
swift.package(url: "https://github.com/swiftlang/swift-syntax", "600.0.0"..<"621.0.0")

Structured Queries version information

0.31.0

Destination operating system

iOS

Xcode version information

26.2 (17C52) and 26.3 (17C529)

Swift Compiler version information

Swift 6.2 (swiftlang-6.2.0 / Xcode 26)

[mbrandonw]

Hi @mjcaboose001,

The current Package.swift constrains swift-syntax to "600.0.0"..<"603.0.0", which excludes Swift 6.2 (620.x) shipped with Xcode 26. This causes Swift macro compilation to fail with "malformed response" errors on Xcode 26.2 and 26.3.

This is not how versioning works for Swift Syntax. The release "602.0.0" corresponds to Swift 6.2. You can see this by looking at the release page for Swift Syntax: https://github.com/swiftlang/swift-syntax/releases

Swift Compiler Error: External macro implementation type 'StructuredQueriesMacros.TableMacro' could not be found; '...StructuredQueriesMacros' produced malformed response

This sounds more like a misconfigured project than something wrong with this library.

You will need to provide a reproducing project for us to understand what issue you are running into. But I'm pretty sure this isn't an issue with the library, so I am going to convert it to a discussion. Please feel free to continue the conversation over there!

[mjcaboose001]

@mbrandonw actually one other thing - After testing with Xcode 26.4 beta (Build 17E5179g / Swift 6.3), the previous build system issues are resolved. The build now fails with just two errors:
Swift Compiler Error: Ambiguous use of '_group(by:)'
Sources/StructuredQueriesCore/Statements/Select.swift:1397:4
Sources/StructuredQueriesCore/Statements/Select.swift:1412:4
I can see that main already has @_disfavoredOverload on _group(by:) which should fix this. Would it be possible to tag a new release with that fix? That would fully unblock building with Xcode 26.4 / Swift 6.3.
Environment:

Xcode 26.4 beta (17E5179g)
Swift 6.3 (swiftlang-6.3.0.123.5)
swift-structured-queries 0.30.0

Thanks

[mjcaboose001]

@mbrandonw one more update: A "malformed response" error persists on Xcode 26.4 beta (Swift 6.3) with both 0.30.0 and 0.31.0. Given your blog post references Xcode 26.4 beta, you may already be aware of this. Both Plugin.swift files I'm using use standard @main + CompilerPlugin declarations with no custom configuration. The "malformed response" appears to be a binary compatibility issue between the compiled macro plugin and Swift 6.3's plugin execution environment, not a source code issue. Reproduced on Xcode 26.4 beta (17E5179g) / Swift 6.3 (swiftlang-6.3.0.123.5) with both swift-structured-queries 0.30.0 and 0.31.0.

[mbrandonw]

We really need to see a project that reproduces the problem. There isn't much I can do from your description alone.

[mjcaboose001]

@mbrandonw right now just trying to load an established iOS app from source as a starting point for a fork. The failures are happening on a clean build.

Repo: https://github.com/immich-app/immich

The mobile app is in the /mobile subdirectory, and the iOS workspace is at mobile/ios/Runner.xcworkspace.​​​​​​​​​​​​​​​​

[mbrandonw]

Sorry I need a smaller reproducing project than that. Any problems you are seeing could be due to something else in the project that has nothing to do with our library.

[mjcaboose001]

Gotcha - was also able to reproduce cleanly on a blank Flutter with just sqlite-data added. It's failing on two macro packages:

• swift-structured-queries (via sqlite-data)
• swift-perception

Reproduction:

bash
flutter create macro_repro
cd macro_repro

Then add sqlite-data 1.5.1 from https://github.com/pointfreeco/sqlite-data as a Swift Package dependency to the Runner target in Xcode.

bash
flutter run -d

Environment:

Flutter 3.41.4
Xcode 26.3 (also tested 26.2 and 26.4 beta)
macOS 26.3.1

Result: Build fails with "Unable to find module dependency" for SwiftSyntax, SwiftBasicFormat, SwiftParser etc. in both swift-structured-queries and swift-perception macro targets. No custom code, just a blank Flutter app.

[mbrandonw]

Please just provide an actual project that is as minimal as possible. It should not be using Flutter. Just a plain Xcode project or SPM package.