Swift package build fails when swift syntax prebuilt is enabled

[soumyamahunt]

Is it reproducible with SwiftPM command-line tools: swift build, swift test, swift package etc?

• Confirmed reproduction steps with SwiftPM CLI. The description text must include reproduction steps with either of command-line SwiftPM commands, swift build, swift test, swift package etc.

Description

When building package: https://github.com/SwiftyLab/MetaCodable with swift build in official docker image 6.2-noble. Following build errors are received: buildlogs.txt

On building with swift build --disable-experimental-prebuilts build passes successfully.

Expected behavior

The default build command should not introduce a breaking change in minor version release. The prebuilt option needs to be disabled by default or fixed to support the build.

Actual behavior

The package that built successfully in Swift 6.1 fails to build in Swift 6.2.

Steps to reproduce

1. Use official 6.2-noble docker image.
2. Clone repo https://github.com/SwiftyLab/MetaCodable
3. Build the package with command swift build.

Swift Package Manager version/commit hash

6.2

Swift & OS version (output of swift --version ; uname -a)

Swift version 6.2 (swift-6.2-RELEASE)
Target: x86_64-unknown-linux-gnu
Linux codespaces-024db1 6.8.0-1030-azure #35~22.04.1-Ubuntu SMP Mon May 26 18:08:30 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

[dschaefer2]

This may be the same issue as #9196