[Adopted as a DR at the February/March, 2017 meeting.]
13.9.4 [temp.expl.spec] paragraph 2 requires that explicit specializations of member templates be declared in namespace scope, not in the class definition. This restriction does not apply to partial specializations of member templates; that is,
struct A { template<class T> struct B; template <class T> struct B<T*> { }; // well-formed template <> struct B<int*> { }; // ill-formed };
There does not seem to be a good reason for this inconsistency.