title: Typescript: Check that type is not any
body: <p>Let's say i have a type <code>AnyWidget</code> that is the union of a lot of different types.
  <code>type AnyWidget = Button | Label | HeaderComponent | ...</code>
  Since this type will be extended by whoever adds a widget i want to prevent it from accidentally becoming <code>any</code> just because someone forgot to properly type a widget.</p>
  <p>So I would like to add a check that this type is not <code>any</code>. Any ideas how I would be able to do that?</p>
  <p>Some more context:</p>
  <ul>
  <li><code>no-implicit-any</code> is unfortunately set to false in this project</li>
  <li>As Fabian Lauer already pointed out a unit test is not possible in this case. So I am looking for other ideas. Such as custom lint rules or a different type definition to achieve this goal.</li>
  <li>A superclass is not useful in this case since the type is being used to generate a json schema out of it.</li>
  </ul>