title: Why am I getting a 'value unused' warning, in a match statement, in F#
body: <p>I have the following code:</p>
  
  <pre><code>   try
          let s = orderId.Split('|')
          match (s.[0], s.[1]) with
          | "G", coreGuid -&gt;  OrderClass.Grid
          | "C", coreGuid -&gt;  OrderClass.Close
          | _, _          -&gt;  OrderClass.External
      with _ -&gt;
          OrderClass.External
  </code></pre>
  
  <p>It takes a string in the form of "letter|guid", and then tries to match it.
  The logic I want to achieve is:</p>
  
  <pre><code>if s.[0] = "G" &amp;&amp; s.[1] = coreGuid   for the first line, and
  if s.[0] = "C" &amp;&amp; s.[1] = coreGuid   for the second line
  </code></pre>
  
  <p>but my IDE (Rider 2020.1 MacOs) is giving me this warning:</p>
  
  <p><a href="https://i.stack.imgur.com/s1NT7.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/s1NT7.png" alt="enter image description here"></a></p>
  
  <p>I don't understand why?</p>