Question

I have the following test code

#include <iostream>
template <typename T>

struct PS
{
   template <typename U>
   static void foo()
   {
       std::cout<<"Some test code";
   }
};

template <typename T>
void bar()
{
   PS<T>::template foo<T>(); //won't compile without `::template`
}

int main()
{
   bar<int>();
}

ISO C++03 14.2/4: says

When the name of a member template specialization appears after . or -> in a postfix-expression, or after nested-name-specifier in a qualified-id, and the postfix-expression or qualified-id explicitly depends on a template-parameter (14.6.2), the member template name must be prefixed by the keyword template. Otherwise the name is assumed to name a non-template.

The Standard talks about -> and . but not about ::. Is it a defect in the C++03 Standard or am I missing something? Someone please enlighten me.

However the wording has been changed in N3126

When the name of a member template specialization appears after . or -> in a postfix-expression or after a nested-name-specifier in a qualified-id, and the object or pointer expression of the postfix-expression or the nested-name-specifier in the qualified-id depends on a template parameter (14.6.2) but does not refer to a member of the current instantiation (14.6.2.1), the member template name must be
prefixed by the keyword template. Otherwise the name is assumed to name a non-template.

Can someone give an example to illustrate what but does not refer to a member of the current instantiation means in context of C++0x?

-PS

Answer 1

The Standard talks about -> and . but not about ::.

The scope resolution operator (::) is part of the qualified-id referred to by “or after nested-name-specifier in a qualified-id.”

The additional verbiage in C++0x is part of the resolution to CWG defect 224. Effectively, the definition of dependent names has been changed:

The decision on whether a name is dependent or non-dependent should be based on lookup, not on the form of the name: if the name can be looked up in the definition context and cannot be anything else as the result of specialization, the name should be non-dependent.