title: Swift - release build crashes unless I turn off optimization
body: <p>This is on XCode 6.2.</p>
  
  <p>If I run the app in release mode it will crash, but with optimizations off it does not crash. The code looks straightforward. I have programmed ObjC for over a decade, so not new to programming, etc.</p>
  
  <p>I note that in 32 bit it runs fine in release mode (Fastest -O), but on 64 bit real iOS hardware it crashes. </p>
  
  <p>Is this a compiler bug ? Or is it possible to have poor swift that crashes only for some compiler settings (which can happen in C!).</p>
  
  <p>I include code, but I'm not sure that it will help.</p>
  
  <pre><code>class func attemptLogin(completionHandler: (result: JSON?, error: NSError?) -&gt; ()) {
      // It appears that these variables are not working in the completion block in 64 with optimization on.
      let email = User.email
      let password = User.password
  
      // setup login.
      let parameters: [String : AnyObject] = [
          "action": "login",
          "login": [
              "email": email,
              "password": password,
              "type": User.type
          ]
      ]
  
      // Fire off REST POST Async
      request(.POST, baseUrl, parameters: parameters, encoding: .JSON)
          .responseSwiftyJSON { (request, response, jsonDict, error) in
  
                  // in release mode on 64 bit, things are seriously bad here. 
              println("jsonDict login attempt: ")
              print(jsonDict)
  
              if let token = jsonDict["login"]["token"].string {
                  println("token found is: " + token)
                  User.token = token;
                  User.email = email;
                  User.password = password;
                  completionHandler(result: jsonDict, error: nil)
              } else {
                  println("No Token")
                  User.token = "";
                  User.email = "";
                  User.password = "";
  
                  let errorNS = NSError(domain: "stethIoUser", code: 404, userInfo: nil)
  
                  completionHandler(result: jsonDict, error: errorNS)
              }
          }
  }
  </code></pre>