clang bug? namespaced template class' friend

Question

The following code which doesn\'t compile under clang but does under gcc and VS:

template class bar;

namespace NS
{
    template

        

Answer 1

Changing the code to

template class bar;

namespace NS
{
    template
    class foo
    {
        foo() {}

        template friend class ::bar;
    };
}

template
class bar
{
public:
    bar()
    {
        NS::foo f;
    }
};


int main(int, char **)
{
    bar b;

    return 0;
}

compiles with clang. The problem seems to be the namespace lookup. The code

template friend class bar;

actually declared the class NS::bar a friend of NS::foo, so foo should not have been affected. My guess would be that clang is standard conformant and the code should not compile.