title: CoffeeScript, implementing 'implements'
body: <p>CoffeeScript is fantastic, the class system is really all javascript ever needed, a few keywords and a lot less proto* and braces everywhere.  I've seen people implement mixins in classes, but I'm wondering if there is a path to implementing an analogy to Java interfaces?</p>
  
  <p>If not it might be a good addition..  After all, it would be good to know if my code can successfully walk/quack like a duck at compile time.  The following instructions might better help what would be ideal...  Right now you can work around it by creating unit tests (which you should do anyway) so its not that big a deal, but still would be nice.</p>
  
  <pre><code>class definitiona
  class definitionb
  
  class featurex
  class featurey
  
  class childa extends definitiona implements featurex
  class childb extends definitionb implements featurex, featurey
  </code></pre>