title: undefined outcome with spread operator
body: <p>What am I doing wrong in my little code snippet that I get <code>undefined</code> instead of <code>number</code> outcome?</p>
  <pre><code>function multiply(multiplier: number, ...args: [number, number, number]) {
      return args.map(
          element =&gt; { multiplier * element; }
      );
  }
  
  console.log(multiply(2, 5,6,7));
  </code></pre>
  <p>output: <code>[ undefined, undefined, undefined ]</code></p>