title: Override non-dynamic class delaration
body: <p>With new Xcode 8.3, I get the error:</p>
  <blockquote>
  <p>Cannot override a non-dynamic class declaration from an extension</p>
  </blockquote>
  <p>from the line of code:</p>
  <pre><code>override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -&gt; UITableViewCell
  </code></pre>
  <p>How I can avoid this warning?</p>