title: the syntax requires an imported helper named __spreadArrays
body: <p>When I'm trying to use spreading in typescript like:</p>
  
  <pre><code>.reduce((unique, x) =&gt; {
      unique.some(element =&gt; element.machineName === x.machineName) ? unique : [...unique, x];
  }
  </code></pre>
  
  <p>I get warning with red marking from <code>Visual Studio Code</code>:</p>
  
  <pre><code>the syntax requires an imported helper named __spreadArrays
  
  typescript version: "2.3.4"
  target: "es5"
  </code></pre>
  
  <p>I think in later versions this issue is fixed, but right now I can't migrate. How can I fix it?</p>
  
  <p><em>Note:</em> Project gets compiled fine and works. But red underlying in <code>VS Code</code> in annoying.</p>