title: Extending a class in another file
body: <p>I have some TypeScript code that is being generated by a tool. I'd like to extend this class in another file. As of 0.9.1.1, what's the best way to go about this? </p>
  
  <p>I thought maybe I could staple my additional functions onto the prototype, but this is giving various errors (which change depending what mood the compiler is in).</p>
  
  <p>For example:</p>
  
  <p>Foo.ts (generated by a tool)</p>
  
  <pre><code>module MyModule {
      export class Dog { }
  }
  </code></pre>
  
  <p>Bar.ts</p>
  
  <pre><code>module MyModule {
      function bark(): string {return 'woof';}
  
      Dog.prototype.bark = bark;
  }
  </code></pre>