title: Ruby: Error: Cannot locate this method: String.
body: <p>Any idea why certain documentation does not work when using <code>show-doc</code> in <code>pry</code>? E.g. see <code>show-doc</code> with <code>String</code> and <code>Array</code> compared to <code>Set</code> here:</p>
  
  <pre><code>show-doc Set
  
  From: /Users/snowcrash/.rvm/rubies/ruby-2.0.0-p195/lib/ruby/2.0.0/set.rb @ line 3:
  Class name: Set
  Number of lines: 57
  
  --
  set.rb - defines the Set class
  ++
  Copyright (c) 2002-2008 Akinori MUSHA &lt;knu@iDaemons.org&gt;
  
  Documentation by Akinori MUSHA and Gavin Sinclair.
  
  All rights reserved.  You can redistribute and/or modify it under the same
  terms as Ruby.
  
    $Id: set.rb 37839 2012-11-24 18:51:45Z knu $
  
  == Overview
  
  This library provides the Set class, which deals with a collection
  
  show-doc String
  Error: Cannot locate this method: String.
  [7] pry(main)&gt; show-doc Array
  Error: Cannot locate this method: Array.
  </code></pre>