title: Haskell's `otherwise` is a synonym for `_`?
body: <p>I ran across a piece of code recently that used Haskell's <code>otherwise</code> to pattern match on a list. This struck me as odd, since:</p>
  
  <pre><code>ghci&gt; :t otherwise
  otherwise :: Bool
  </code></pre>
  
  <p>So, I tried the following:</p>
  
  <pre><code>ghci&gt; case [] of otherwise -&gt; "!?"
  "!?"
  </code></pre>
  
  <p>I also tried it with various other patterns of different types and with <code>-XNoImplicitPrelude</code> turned on (to remove <code>otherwise</code> from scope), and it still works. Is this supposed to happen? Where is this documented?</p>