title: Get union type from indexed object values
body: <p>Say I have an indexed type:</p>
  
  <pre><code>type X = {
   a: 'A',
   b: 'B'
  }
  </code></pre>
  
  <p>is it possible to get (derived) from it:</p>
  
  <pre><code>type V = 'A' | 'B'
  </code></pre>
  
  <p>not using explicit method like:</p>
  
  <pre><code>type V = X['a'] | X['b']
  </code></pre>
  
  <p>What I want is something like <code>keyof</code> (for getting keys union type), but for values.</p>