Fabric/Crashlytics incompatible swift versions
I received this official response from Fabric support:
Thank you for reaching out to us and sorry that you are running into this issue, We are aware of this and are actively working on a fix! The following work around should unblock you till then:
There seems to be an issue impacting manual downloads (Latest SDKs) and Xcode 10.2. This is a bug with Xcode checking binaries for Swift versions, even when the binaries aren't actually bundled with the app.
In the meantime, to unblock these customers, have them:
1) Go into "Build Phases"
2) Remove Fabric.framework and Crashlytics.framework
For both Crashlytics and Fabric:
3) Click the + and then "Add Other..." in the lower left corner
4) Navigate to the .framework folder, and instead of selecting the .framework, select the "Crashlytics" and "Fabric" binaries themselves (they're at the top level of the framework)
Make you you do not still have Fabric.framework or Crashlytics.framework in your project.