The specialization of InterlockedImpl in the class is illegal in atomic_intrisics_win32.h:

An explicit specialization shall be declared in the namespace of which the template is a member, or, for member templates, in the namespace of which the enclosing class or enclosing class template is a member.

An explicit specialization of a member function, member class or static data member of a class template shall be declared in the namespace of which the class template is a member.

The definition should be moved up to namespace scope, which probably implies some code motion.