title: Superclass mismatch for class
body: <p>When I wrote the following code, it runs normally:</p>
  
  <pre><code>class Application
    def initialize(name)
      @name = name
    end
  end
  
  class Email2 &lt; Application
  end
  </code></pre>
  
  <p>But when I changed <code>Email2</code> to <code>Email</code> like this:</p>
  
  <pre><code>class Application
    def initialize(name)
      @name = name
    end
  end
  
  class Email &lt; Application
  end
  </code></pre>
  
  <p>I got the error message: <code>superclass mismatch for class Email</code>. Please help me.</p>