title: What is the TS type of a class extending another class?
body: <pre><code>const Err: ErrorConstructor = class Err extends Error {};
  </code></pre>
  <p><code>ErrorConstructor</code> isn't correct here, but I'm not sure how to correctly define it.  Typescript isn't being helpful here and if I don't define the type it just says it's &quot;typeof Err&quot;</p>
  <p>Note that this is a very condensed version of what I'm running into, I know I don't have to define it in this exact example but this is a minimal repro.</p>