title: Xcode 7 does not show function callers for swift 2
body: <p>Looks like index is kinda broken. How to fix this?<br>
  <strong>P.S.</strong> Function, of course, is getting called multiple times.  </p>
  
  <p><strong>UPD:</strong>
  Works in Xcode 7.3</p>
  
  <p><a href="https://i.stack.imgur.com/vCzja.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/vCzja.png" alt="enter image description here"></a></p>