title: How to skip useless nodes for parser rule
body: <p>I have a simple Antlr4 grammar:</p>
  
  <pre><code>grammar: test;
  expression: 
      IF LPAREN logical ',' otherrule',' otherrule RPAREN # myExpression
  
  logical:
          ......;
  otherrule:
          ......;
  IF: 'if'; 
  LPAREN : '(';
  RPAREN : ')';
  WS: (' ' | '\t' | '\r' | '\n')-&gt;channel(HIDDEN);
  </code></pre>
  
  <p>When I use this grammer to parse:</p>
  
  <pre><code> if(a&gt;b, 1, 2)
  </code></pre>
  
  <p>the instance MyExpressionContext will have 8 children:</p>
  
  <pre><code>1 if
  2 (
  3 a&gt;b
  4 ,
  5 1
  6 ,
  7 2
  8 )
  </code></pre>
  
  <p>But I don't need ( ) and , those kind of separators, how can I make the children only have these?</p>
  
  <pre><code>1 if
  2 a&gt;b
  3 1
  4 2
  </code></pre>