Carthage: Can't use Swift 4 and Swift 3.2 projects in Xcode 9

[dannymout]

At WWDC, they've announced support for using both Swift 3 and 4 code in the same project. Currently, trying to use Xcode 9 and Swift 4 to write an app with Swift 3.2 frameworks will not work. I spoke to an Apple engineer who stated that this is a Carthage issue. Are there any workarounds?

• carthage version: 0.23
• xcodebuild -version: 9M136h

Carthage Output

*** Skipped installing (framework) binary due to the error:
    "Incompatible Swift version - framework was built with 3.1 and the local version is 4.0."

[mdiep]

* Skipped installing (framework) binary due to the error:

This is just a warning and doesn't mean anything except that we don't think we can use the prebuilt binary. Was your project otherwise able to build?

I'm planning to visit a lab later today to talk to the Xcode team about how Carthage can best support mixed Swift versions.

[marcin-zbijowski]

Workaround for now is to just switch to new Xcode and carthage picks that up and compiles dependencies with new xcodebuild

sudo xcode-select -s /Applications/Xcode-beta.app/Contents/Developer

After that, I was able to compile the app with new Xcode successfully.

[lvandal]

Doesn't work for me. I get these errors when setting Xcode 9 as the default:

Invalid architecture UUIDs: Could not parse UUIDs using dwarfdump from /Users/[some path]/Vendor/Carthage/Build/Mac/ObjectiveDropboxOfficial.framework/ObjectiveDropboxOfficial

Invalid architecture UUIDs: Could not parse UUIDs using dwarfdump from /Users/[some path]/Vendor/Carthage/Build/Mac/Reachability.framework/Reachability

[ikesyo]

I get these errors when setting Xcode 9 as the default:

Can't reproduce that locally using https://github.com/dropbox/dropbox-sdk-obj-c.

[dannymout]

Maybe there was something off on my computer. I tried using Xcode 9 for building, and everything seems to work well. I'm going to close this.

@lvandal: I doubt your issue is with Carthage, it might be the frameworks.