Can a parameter of a template template parameter cause shadowing?

Question

Is this legal C++?

template <typename T, template <typename T> class>
struct S { };

Clang (3.7.1) rejects it, complaining the second T shadows the first T . GCC seems not to care about it and I think that's reasonable. I think it is only the number of parameters that matters in a template template parameter.

• http://goo.gl/51bHVG (gcc.godbolt.org)

Answer 1

No. [temp.local]/6 :

A template-parameter shall not be redeclared within its scope (including nested scopes).

Answer 2

While the right answer exists, it toke some time for myself to understand, and I just wanted to add an example:

template <class Key, class T>
class MyData {
public:
    // ...

    template <class Key, class T>
    inline static MyData<Key, T> *get(MyMap<Key, T> *ptr)
    {
        return NULL: // Logic here...
    }

    // ...
}

As " Template-parameters shall not be re-declared within its scope (including nested scopes) ", above get(..) method should be changed and use other names, like:

template <class KeyType, class Type>
inline static MyData<KeyType, Type> *get(MyMap<KeyType, Type> *ptr)
{
    return NULL: // Logic here...
}