title: error TS2304: Cannot find name 'Generator'
body: <p>I updated typescript
  $ tsc -v
  Version 3.6.2</p>
  
  <p>and tried the Generator example in the page below:
  <a href="https://devblogs.microsoft.com/typescript/announcing-typescript-3-6/" rel="nofollow noreferrer">https://devblogs.microsoft.com/typescript/announcing-typescript-3-6/</a></p>
  
  <pre class="lang-js prettyprint-override"><code>function* counter(): Generator&lt;number, string, boolean&gt; {
      let i = 0;
      while (true) {
          if (yield i++) {
              break;
          }
      }
      return "done!";
  }
  
  var iter = counter();
  var curr = iter.next()
  while (!curr.done) {
      console.log(curr.value);
      curr = iter.next(curr.value === 5)
  }
  console.log(curr.value.toUpperCase());
  </code></pre>
  
  <p>error TS2318: Cannot find global type 'IterableIterator'.</p>
  
  <p>gen2.ts:6:22 - error TS2304: Cannot find name 'Generator'.</p>
  
  <p>6 function* counter(): Generator {
                         ~~~~~~~~~</p>
  
  <p>Found 2 errors.</p>