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

Launching Xcode while holding shift fixed it for me.

(This suppresses Xcode's state restoration.)

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Update: Xcode 6.3.1, released today, resolves this issue.