title: Why is a custom SyntaxNode subclass not working with parentheses?
body: <p>I have a treetop grammar like below:</p>
  
  <pre><code>grammar Addme
  
    rule AddExpr
      Num '+' Num
    end
  
    rule Num
      [0-9]+ &lt;ExprNumber&gt;
    end
  
  end
  </code></pre>
  
  <p>This is working when I parse the expression:</p>
  
  <pre><code>g = AddmeParser.new
  t = g.parse("1234+56789")
  </code></pre>
  
  <p>. . . there is a syntax node that matches <code>"1234"</code> with type <code>ExprNumber</code>.
  But, if I add parentheses to the rule like this:</p>
  
  <pre><code>rule Num
      ([0-9]+) &lt;ExprNumber&gt;
  end
  </code></pre>
  
  <p>It will not match the class <code>ExprNumber</code>. Why would this happen?</p>