title: Calling "super" keyword with modules and inheritance
body: <p>I thought that including a module as a mixin in a class "added the functions" to the class.</p>
  
  <p>I do not understand why this does not work as expected:</p>
  
  <pre><code>module A
      def blah
          super if defined?(super)
          puts "hello, world!"
      end
  end
  
  class X
      include A
  end
  
  class Y &lt; X
      include A
  end
  
  y = Y.new
  y.blah
  </code></pre>
  
  <p>I was expecting "y" to call its super blah() (since its included in class X?) but instead i got:</p>
  
  <blockquote>
    <p>test.rb:3:in blah: super: no superclass method `blah'</p>
  </blockquote>