title: Using spread syntax and new Set() with typescript
body: <p>I am using following code to get unique numbers:</p>
  
  <pre><code>let uniques = [ ...new Set([1, 2, 3, 1, 1]) ]; // [1, 2, 3]
  </code></pre>
  
  <p>However, typescript report following error: <em>Type 'Set' is not an array type.</em>
  I am not typescript ninja, could someone tell me what is wrong here?</p>