title: Firebase 4.0 DatabaseReference Error
body: <p>After migrating to Firebase 4.0 , I have this REALLY annoying issue with the Reference to the DB.*</p>
  
  <blockquote>
    <p>"Cannot convert return expression of type 'DatabaseReference' to
    return type 'DatabaseReference'</p>
  </blockquote>
  
  <p>Very frustating , I try to make a switch on a <em>enum</em>, to set multiple <em>ref</em>.</p>
  
  <p>Even when I try to follow the new Docs. </p>
  
  <p><a href="https://i.stack.imgur.com/KtTQ2.png" rel="nofollow noreferrer">enter image description here</a></p>