title: immutables typescript type definitions: why is concat operating on any?
body: <p>I don't understand why <a href="https://github.com/facebook/immutable-js/blob/b7238a7f2ec421fbf103d4d1e6138b9d3d4e8b3e/type-definitions/Immutable.d.ts#L3529" rel="nofollow noreferrer">the definition of <code>concat</code></a> in <code>Collection&lt;K, V&gt;</code> for instance uses <code>any</code>:</p>
  
  <pre><code>concat(...valuesOrCollections: Array&lt;any&gt;): Collection&lt;any, any&gt;;
  </code></pre>
  
  <p>why couldn't it be:</p>
  
  <pre><code>concat(...valuesOrCollections: Array&lt;V&gt;): Collection&lt;K, V&gt;;
  </code></pre>
  
  <p>?</p>