title: Type of keys of a generic type with a given type
body: <p>That's sound weird, so an exemple will defined the problem better:</p>
  <p>Having a <code>Model</code>, I wan't the keys <code>K</code> where <code>Model[K]</code> is a given type <code>GivenType</code> (non generic).</p>
  <p>So I guess a good start would be <code>&lt;Model, K extends keyof Model&gt;</code>, but this doesn't enforce <code>Model[K]</code> to be of type <code>GivenType</code>.</p>