Xcode 8 beta 4: Build fails with "The following binaries use incompatible versions of Swift:" error

Question

With new Xcode 8 beta 4 we started experiencing the following error during CopySwiftLibs build phase:

Effective srcDirs: {(      <DVTFilePath:0x7f865961e970:'/Volumes/Data/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/iphonesimulator'>,      <DVTFilePath:0x7f8657d02b20:'/Volumes/Data/Xcode-beta.app/Contents/Developer/Toolchains/Swift_2.3.xctoolchain/usr/lib/swift/iphonesimulator'>  )} 

error: The following binaries use incompatible versions of Swift:

/Users/user/Projects/git/iphone-swift-1/DerivedData/myApp/Build/Products/Debug-iphonesimulator/myApp.app/myApp

/Users/user/Projects/git/iphone-swift-1/myApp/myAppApi.framework/myAppApi

myAppApi is a subproject in the workspace that contains some shared code (it uses Alamofire).

One thing to note: originally we converted project from Swift 2.2 to Swift 2.3, and then manually upgraded to 3.0.

Does anyone have any idea what might be causing this error?

Thanks!

Answer 1

I had the same problem, but managed to fix it by:

1. Clean the project.
2. Close project and quit Xcode.
3. Clean derived data.
4. Open the project again and it's there, all nice and working.

I did this on Xcode 8 using Swift 3.