title: Regexp type for closure compiler
body: <p>I'm currently adding type annotation to a personnal javascript module, but I'm currently stuck when trying to type function taking a regexp as a parameter, but none of the follwing tries is working :</p>
  
  <pre><code>/** @type {function(RegExp)} */
  /** @type {function(regex)} */
  </code></pre>
  
  <p>I'm only getting :</p>
  
  <pre><code>WARNING - Bad type annotation. Unknown type regexp
  </code></pre>
  
  <p>What type should I use in the declaration? thanks.</p>