title: Dhall Association List
body: <p>I have a Union type that I wish one field to be an association list.</p>
  
  <pre><code>let Blah = &lt; First : { name : Text, params: XXX } | Second : { name : Text } &gt;
  </code></pre>
  
  <p>Here, I wish <code>params</code> to be an association list so when I type check Record values it will pass, e.g.</p>
  
  <pre><code>Blah.First { name = "Alex", params: [{ mapKey = "a", mapValue = 1 }] }
  </code></pre>
  
  <p>So, what type should <code>XXX</code> be in <code>Blah</code>?</p>