public override void CheckLL1(ParseNode_Root parser)
 {
     if (!contextualKeyword)
     {
         base.CheckLL1(parser);
         rhs.CheckLL1(parser);
     }
 }
 // subtree is checked.
 public override void CheckLL1(ParseNode_Root parser)
 {
     // trust the predicate!
     //base.CheckLL1(parser);
     if (FollowSet == null)
     {
         throw new Exception(this + ": follow not set");
     }
     node.CheckLL1(parser);
 }