Xcode 9 stuck on Swift 4 migration

Question

I'm trying to migrate my Swift 3 project to Swift 4 in Xcode 9. After selecting target and choosing either of @obcj inference options, Xcode stuck on Generating preview spinning wheel forever. How can I migrate my project?

Answer 1

On the same conversion dialog uncheck Remind me checkbox and click Convert Later . Now go to Build Settings and change Swift Language Version to Swift 4.0 . Most likely this will produce a lot of warnings or errors. Unfortunately you have to fix them manually.