title: Crash using NSPredicate in swift after Xcode Beta 6
body: <p>My code worked good in Xcode beta 5 but after downloaded the beta 6, it crash.</p>
  
  <p>This is the code I have : </p>
  
  <pre><code>extension String {
  
      /**
      * http://stackoverflow.com/questions/3139619/check-that-an-email-address-is-valid-on-ios
      */
      func isValidEmail() -&gt; Bool {
          let emailRegex = ".+@([A-Za-z0-9-]+\\.)+[A-Za-z]{2}[A-Za-z]*";
          let emailTest = NSPredicate(format: "SELF MATCHES %@",emailRegex);
          return emailTest.evaluateWithObject(self);
      }
  }
  </code></pre>
  
  <p>When executing, it crash at the NSPredicate line :</p>
  
  <pre><code>let emailTest = NSPredicate(format: "SELF MATCHES %@",emailRegex);
  </code></pre>
  
  <p>Someone know something about this problem ?</p>