title: Typescript Cannot find name 'IterableIterator'
body: <p>I have problem with my code in typescript
  After compile by tsc, I have errors like about cannot find some names.</p>
  
  <pre><code>app.ts(1,22): error TS2304: Cannot find name 'IterableIterator'.
  app.ts(8,20): error TS2304: Cannot find name 'IteratorResult'.
  app.ts(26,6): error TS2304: Cannot find name 'Symbol'.
  app.ts(26,26): error TS2304: Cannot find name 'IterableIterator'.
  </code></pre>
  
  <p>My code is:</p>
  
  <pre><code>class Fib implements IterableIterator&lt;number&gt; {
      protected fn1 = 0;
      protected fn2 = 1;
  
      constructor(protected maxValue?: number) {}
  
      public next(): IteratorResult&lt;number&gt; {
          var current = this.fn1;
          this.fn1 = this.fn2;
          this.fn2 = current + this.fn1;
  
          if (this.maxValue &amp;&amp; current &lt;= this.maxValue) {
              return {
                  done: false,
                  value: current
              }
          }
  
          return {
              done: true
          }
      }
  
      [Symbol.iterator](): IterableIterator&lt;number&gt; {
          eturn this;
      }
  }
  
  fib = new Fib();
  console.log(fib.next());
  </code></pre>
  
  <p>version tsc is Version 2.1.0-dev.20160716</p>