utility.h 编译报错

[metahys]

g++ 4.2.1

../Utility.h:31:19: error: declaration of 'T1' shadows template parameter
template <class T1, class T2>

template<class T1, class T2>
    struct pair{
    public:
        typedef T1 first_type;
        typedef T2 second_type;
    public:
        T1 first;
        T2 second;
    public:
        pair(){}
        template<class U, class V> 
        pair(const pair<U, V>& pr);
        pair(const first_type& a, const second_type& b);
        pair& operator= (const pair& pr);
        void swap(pair& pr);
    public:
        template <class T1, class T2>
        friend bool operator== (const pair<T1, T2>& lhs, const pair<T1, T2>& rhs);
        template <class T1, class T2>
        friend bool operator!= (const pair<T1, T2>& lhs, const pair<T1, T2>& rhs);
        template <class T1, class T2>
        friend bool operator<  (const pair<T1, T2>& lhs, const pair<T1, T2>& rhs);
        template <class T1, class T2>
        friend bool operator<= (const pair<T1, T2>& lhs, const pair<T1, T2>& rhs);
        template <class T1, class T2>
        friend bool operator>  (const pair<T1, T2>& lhs, const pair<T1, T2>& rhs);
        template <class T1, class T2>
        friend bool operator>= (const pair<T1, T2>& lhs, const pair<T1, T2>& rhs);
        template <class T1, class T2>
        friend void swap(pair<T1, T2>& x, pair<T1, T2>& y);

    };

应该是友元函数的模版形参使用T1、T2会屏蔽外层的T1、T2？
Accessing template parameters of the member templates

[fateorder]

恩，改完就能通过了

    public:
        template <class U, class V>
        friend bool operator== (const pair<U, V>& lhs, const pair<U, V>& rhs);
        template <class U, class V>
        friend bool operator!= (const pair<U, V>& lhs, const pair<U, V>& rhs);
        template <class U, class V>
        friend bool operator<  (const pair<U, V>& lhs, const pair<U, V>& rhs);
        template <class U, class V>
        friend bool operator<= (const pair<U, V>& lhs, const pair<U, V>& rhs);
        template <class U, class V>
        friend bool operator>  (const pair<U, V>& lhs, const pair<U, V>& rhs);
        template <class U, class V>
        friend bool operator>= (const pair<U, V>& lhs, const pair<U, V>& rhs);
        template <class U, class V>
        friend void swap(pair<U, V>& x, pair<U, V>& y);

    };