Why shouldn't I extend an instance initialized by Struct.new? : <p>We have a legacy codebase where rubocop reports some of these errors which I never could wrap my head around:</p>

<blockquote>
  <p>Don't extend an instance initialized by <code>Struct.new</code>.
  Extending it introduces a superfluous class level and may also introduce
  weird errors if the file is required multiple times.</p>
</blockquote>

<p>What exactly is meant by "a superfluous class level" and what kind of "weird errors" may be introduced?</p>

<p>(Asking because obviously we didn't have any such problems over the last years.)</p>
