title: Left-hand side of assignment expression cannot be a constant or a read-only property
body: <p>When I use this line on my Express server, it works well in TypeScript 1.x</p>
  
  <pre><code>mongoose.Promise = global.Promise;
  </code></pre>
  
  <p>( The usage of <code>mongoose.Promise = global.Promise;</code> is from <a href="http://mongoosejs.com/docs/promises.html">the mongoose document</a> )</p>
  
  <p>After updating to TypeScript 2.x, it shows this error in the terminal, and won't let me start the server.</p>
  
  <blockquote>
    <p>Left-hand side of assignment expression cannot be a constant or a
    read-only property.</p>
  </blockquote>
  
  <p>How can I solve this? Thanks</p>