title: Using enum as interface key in typescript
body: <p>I was wonder if I can use enum as an object key in interfaces..
  I've built a little test for it:</p>
  
  <pre><code>export enum colorsEnum{
  red,blue,green
  }
  
  export interface colorsInterface{
  [colorsEnum.red]:boolean,
  [colorsEnum.blue]:boolean,
  [colorsEnum.green]:boolean
  }
  </code></pre>
  
  <p>When I run it I'm getting the following error:</p>
  
  <pre><code>A computed property name in an interface must directly refer to a built-in symbol.
  </code></pre>
  
  <p>I'm doing it wrong or it just not possible?</p>