pe <code>T</code>.</p>

<p><strong>Warning:</strong> This function trades safety for performance. Use
  <code>unsafeDowncast(_:to:)</code> only when you are confident that <code>x is T</code> always
  evaluates to <code>true</code>, and only after <code>x as! T</code> has proven to be a
  performance problem.</p>

<p><strong>Parameters:</strong>
  <strong>x:</strong> An instance to cast to type <code>T</code>.
  <strong>type:</strong> The type <code>T</code> to which <code>x</code> is cast.
<strong>Returns: