title: Cannot use new with expression typescript
body: <pre><code>interface Window {
      AudioContext: AudioContext;
      webkitAudioContext: Function
  }
  
  let contextClass = window.AudioContext || window.webkitAudioContext;
  let context: AudioContext = new contextClass();
  </code></pre>
  
  <p>The last line is giving me this error,</p>
  
  <blockquote>
    <p>Cannot use 'new' with an expression whose type lacks a call or
    construct signature</p>
  </blockquote>
  
  <p>How can I resolve this?</p>