                 printSTDERR("parsing \(file.lastPathComponent) (\(index + 1)/\(swiftFiles.count))")
                 var self_arguments = ["--single-file", file]
                 self_arguments.extend(swiftcArguments)
-                println(run_self(self_arguments))
-                if index < swiftFiles.count-1 {
+                let selfOutput = run_self(self_arguments)
+                println(selfOutput)
+                if selfOutput != nil && index < swiftFiles.count-1 {
                     println(",")
                 }
             }

    let output = NSString(data: file.readDataToEndOfFile(), encoding: NSUTF8StringEncoding)
    file.closeFile()

    return output!
}

/**

:param: processArguments arguments to pass to new sourcekitten process
:returns: sourcekitten STDOUT output
*/
func run_self(processArguments: [String]) -> String? {
    let task = NSTask()
    task.launchPath = NSBundle.mainBundle().executablePath!
    task.arguments = processArguments
