// PassStatement
 public bool Walk(PassStatement node)
 {
     return Process(node);
 }
 public void PostWalk(PassStatement node)
 {
     PostProcess(node);
 }
 public virtual void PostWalk(PassStatement node)
 {
 }
 public override bool Walk(PassStatement node)
 {
     Emit(node); return false;
 }
 // PassStatement
 public virtual bool Walk(PassStatement node)
 {
     return true;
 }