title: Xcode not displaying compile errors
body: <p>I'm working in a specific Xcode project  and deliberatly making errors in my code (like using <em>undeclared</em> variables), but Xcode doesnt seem to show any compile errors in my code.</p>
  
  <ul>
  <li><p>It shows errors only when its build or clean.</p></li>
  <li><p>Tried clean and build, cleaning derived data and restarted both Xcode and system, none of it works.</p></li>
  <li><p>Using Xcode 8.2.1 (8C1002) and Swift 3</p></li>
  </ul>