title: Typescript extending class in another file
body: <p>I am trying to extend a typescript class in another file like so:</p>
  
  <p>a.ts:</p>
  
  <pre><code>module MyModule {
      public Name: string;
      export class MyClassA
      {
      }
  }
  </code></pre>
  
  <p>b.ts:</p>
  
  <pre><code>module MyModule {
      export class MyClassB extends MyClassA
      {
      }
  }
  </code></pre>
  
  <p>But I get the error that MyClassA cannot be found.</p>
  
  <p>Both files are inside my tsconfig.json files array. 
  What am I doing wrong?</p>