Explicit Specialization Cannot Be Friend Declaration

Question

The code

template <typename T>
void foo(const T& t)
{}

template <typename T>
class A
{
    template <>
    friend void foo<T>(const T& t)
    {}
};

gives a compilation error

"defining explicit specialization ‘foo<T>’ in friend declaration friend void foo<T>(const T& t)"

when compiling with gcc and

"error C3637: 'A<int>::foo' : a friend function definition cannot be a specialization of a unction template"

when compiling in VS2013

I understand that the standard says so, but why? I want to understand the reason (under the hood) There are many articles that say: “Explicit specialization cannot be a friend’s declaration”, but I can’t understand why. Any ideas?

Answer 1

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friend void foo<T>(const T&);

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