title: 'Pick' only refers to a type, but is being used as a value here when trying to extend Pick<
body: <p>I'm trying to have only some properties of <em>ancestor</em> exposed on my <em>descendant</em>. I try to achieve it through <code>Pick</code></p>
  
  <pre><code>export class Base {
      public a;
      public b;
      public c;
  }
  
  export class PartialDescendant extends Pick&lt;Base, 'a' |'b'&gt; {
     public y;
  }
  </code></pre>
  
  <p>but I receive two errors - </p>
  
  <blockquote>
    <p>Error: TS2693: 'Pick' only refers to a type, but is being used as a value here.</p>
  </blockquote>
  
  <p>and </p>
  
  <blockquote>
    <p>Error:TS4020: 'extends' clause of exported class 'PartialDescendant' has or is using private name 'Pick'.</p>
  </blockquote>
  
  <p>Am I doing something wrong, and is there another way to expose only chosen properties of the base class?</p>