title: Typescript map string literal types to uppercase
body: <pre class="lang-js prettyprint-override"><code>type a = 'one' | 'two'
  </code></pre>
  <p>I would like to have a <code>type b</code> like</p>
  <pre class="lang-js prettyprint-override"><code>type b = 'ONE' | 'TWO'
  </code></pre>
  <p>So I tried</p>
  <pre class="lang-js prettyprint-override"><code>type a = 'one' | 'two'
  type b = {[P in a]: P['toUpperCase']}
  </code></pre>
  <p>But that does not do what I want it to do.</p>
  <p>Thank you for reading :)</p>