parent languages in that the parent&rsquo;s tokens do not support start and end
    rules. This mostly goes unnoticed, but code like</p>

    <pre><code>
    &lt;div id="&lt;?php echo $id; ?&gt;"&gt;
    </code></pre>

    <p>will not style correctly.</p>

    <p><a id="lexer.Troubleshooting"></a></p>

    <h4>Troubleshooting</h4>

    <p>Errors in lexers can be tricky to debug. Lexers print Lua errors to
    <code>io.stderr</code> and <code>_G.print()</code> statements to <code>io.stdout</code>. Running yo