public Node Expr()
        {
            var node = ExprAnd();

            while (CurrentToken == TokenCategory.OR)
            {
                var node1 = new ExprOrNode()
                {
                    AnchorToken = Expect(TokenCategory.OR)
                };
                node1.Add(node);
                node1.Add(ExprAnd());
                node = node1;
            }
            return(node);
        }