Outstanding program. Watching it will teach you a lot about flying. You'll become a more informed traveler and understand just how safe modern aviation is.

SourceKit issues fall into two categories. The source causes the compiler itself to crash (due to one of those compiler defects mentioned elsewhere in the thread), or some issue with the build configuration.

The latter category is especially nasty, and SourceKit won't inform you of this, except perhaps to crash. Oh, and that dumb bar in Xcode.

You can compile all the Swift source in your target successfully but have SourceKit choke on your build configuration. Accidentally introduce a duplicate set of headers in HEADER_SEARCH_PATHS? Degraded performance, and at worse, the compiler crashes everytime you edit text and SourceKit invokes the compiler. In cases like this the SOURCEKIT_LOGGING environment variable is your friend. Have fun combing through those logs to tease out what build option you set is causing your issue.

I spent the better part of two days sifting through SourceKit logs to figure out why a project's autocomplete wouldn't work. Yet, I wouldn't want to go back to writing Objective-C primarily. Because Swift as a language rocks.