Xcode 6.3 Crashes when navigating from storyboard to other Swift 1.2 file

Question

I installed Xcode 6.3 which includes support for Swift 1.2. It turned up a ton of error messages, which are mostly casting issues.

I navigated to the storyboard, an

Answer 1

It is not a bug anymore since Apple fixed it in Xcode 6.3.1.