title: How to avoid "‘main’ is not defined in module ‘Main’" when using syntastic
body: <p>I'm trying to write a module in Haskell. It does not have a <code>main</code> because it's not meant to be a stand-alone program.</p>
  
  <p>I just started using syntastic, and it is constantly reporting:</p>
  
  <pre><code>The IO action ‘main’ is not defined in module ‘Main’
  </code></pre>
  
  <p>This is preventing it from reporting other real errors in my module. If I try to work around this by adding a dummy main, it starts complaining that everything else is "Defined but not used".</p>
  
  <p>How can I tell syntastic (and whatever checker it's using under the covers) that there isn't supposed to be a <code>main</code>?</p>