E2295 Too many candidate template specializations from 'specifier' (C++)
When reference a class template specialization, it is possible that more than one possible candidate might result from a single reference. This can only really happen among class partial specializations, when more than one partial specialization is contending for a possible match:
template<class T, class U> class foo; template<class T> class foo<T, T *>; template<class T> class foo<T *, T>; foo<int *, int *> x; // error: which partial specialization to use?
In this example, both partial specializations are equally valid, and neither is more specialized than the other, so an error would result.