Swift 5.8 compilation failure `/Package.swift:4:8: error: no such module 'CompilerPluginSupport'` -> ⚠️ SemVer break

[weissi]

As per Package.swift we support Swift 5.8 here. But an actual compilation fails with

error: Invalid manifest (compiled with: ["/usr/bin/swiftc", "-vfsoverlay", "/tmp/TemporaryDirectory.ImEdbq/vfs.yaml", "-L", "/usr/lib/swift/pm/ManifestAPI", "-lPackageDescription", "-Xlinker", "-rpath", "-Xlinker", "/usr/lib/swift/pm/ManifestAPI", "-swift-version", "5", "-I", "/usr/lib/swift/pm/ManifestAPI", "-package-description-version", "5.8.0", "/Package.swift", "-Xfrontend", "-disable-implicit-concurrency-module-import", "-Xfrontend", "-disable-implicit-string-processing-module-import", "-o", "/tmp/TemporaryDirectory.qU2Iyh/swift-async-algorithms-manifest"])
     /Package.swift:4:8: error: no such module 'CompilerPluginSupport'
     import CompilerPluginSupport
            ^ in https://github.com/apple/swift-async-algorithms.git

This is a SemVer break so needs urgent fixing.

[weissi]

CC @FranzBusch this also suggests the CI isn't setup correctly

[FranzBusch]

5.8 is out of the support policy already so this is expected https://forums.swift.org/t/dropping-support-for-swift-5-8-on-linux/78533

[weissi]

5.8 is out of the support policy already so this is expected https://forums.swift.org/t/dropping-support-for-swift-5-8-on-linux/78533

This cannot be expected. The Package.swift says swift-tools-version:5.8 so this will break people. We need to release a final version that is compatible with 5.8 and then we can change it to swift-tools-version:5.10 or whatever and move on. But what's not okay is to leave the last released version that claims 5.8 support not supporting 5.8