title: Can ghc treat certain specified warnings as errors and others as warnings?
body: <p>Can ghc somehow be convinced to treat certain types of warnings as errors and others as warnings, while still reporting them?</p>
  
  <p>I hoped, this would be possible with something like this:</p>
  
  <pre><code>ghc -Werror -fwarn-missing-methods -Wwarn -fwarn-missing-signatures
  </code></pre>
  
  <p>, but I had no luck with that. (I think gcc doesn't support this either.)</p>