Consider:

struct X { typedef int type; };
template<typename T> void f() { sizeof(T::type); }
template void f<X>();

Clang diagnoses this as:

<stdin>:2:43: error: unexpected type name 'type': expected expression
template<typename T> void f() { sizeof(T::type); }
                                          ^
<stdin>:3:15: note: in instantiation of function template specialization 'f<X>' requested here
template void f<X>();
              ^

... but this sort of thing apparently happens inside MS system headers. We should support this case of missing 'typename' more elegantly -- perhaps we can teach TreeTransform to cope with this during instantiation.