Open Radar

 
Add a file to a Swift project with these contents:

class Foo : Sequence {
    class FooGenerator : Generator {
        typealias Element = Int
        var current = 0

        func next() -> Element? {
            if current < 10 {
                return current
            } else {
                return nil
            }
        }
    }

    typealias Generator = FooGenerator

    func generate() -> FooGenerator {
        return FooGenerator()
    }
}

This pops up an error saying "SourceKitService Terminated" (and Xcode loses syntax highlighting, indentation, etc.), and trying to build the project results in a segfault:

1.	While type-checking 'Foo' at /Users/john/Documents/swift/SwiftSegfault2/Boom.swift:9:1
<unknown>:0: error: unable to execute command: Segmentation fault: 11
<unknown>:0: error: swift frontend command failed due to signal (use -v to see invocation)
Command /Applications/Xcode6-Beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift failed with exit code 254