Resource subclass compatibility issue with Xcode 8.3

[kgenoe]

After updating the the Xcode 8.3 beta, I started getting an error on my Resource subclass. I created a new project with a fresh Spine installation from cocoapods to make sure it was coming from Spine. The error was not caused by importing Spine or even declaring an instance of spine (let spine = Spine(...)). Only creating a Resource subclass caused the error.

The error:

The only changes made to the template project to cause the error:

Any idea what the problem might be?