System.Linq.Expressions.Expression.Decrement C# (CSharp) Method

        public static UnaryExpression Decrement(Expression expression, MethodInfo method)
        {
            RequiresCanRead(expression, nameof(expression));
            if (method == null)
            {
                if (expression.Type.IsArithmetic())
                {
                    return new UnaryExpression(ExpressionType.Decrement, expression, expression.Type, null);
                }
                return GetUserDefinedUnaryOperatorOrThrow(ExpressionType.Decrement, "op_Decrement", expression);
            }
            return GetMethodBasedUnaryOperator(ExpressionType.Decrement, expression, method);
        }

        protected override Expression1 VisitBinary(BinaryExpression node)
        {
            if (node.NodeType != ExpressionType.Add && node.NodeType != ExpressionType.Subtract)
            {
                return(base.VisitBinary(node));
            }
            if (node.Left.NodeType != ExpressionType.Parameter && node.Left.NodeType != ExpressionType.Constant)
            {
                return(base.VisitBinary(node));
            }

            ParameterExpression param    = (ParameterExpression)node.Left;
            ConstantExpression  constant = (ConstantExpression)node.Right;

            if (constant.Type != typeof(int) || (int)constant.Value != 1)
            {
                return(base.VisitBinary(node));
            }

            if (node.NodeType == ExpressionType.Add)
            {
                return(Expression1.Increment(param));
            }

            return(Expression1.Decrement(param));
        }