Why does the compiler try to instantiate a template that I don't actually instantiate anywhere?

Updated below.
The following is the entire code I have in my main.cpp:

template<class T>
struct other_traits;

template<class T>
struct some_traits{
    typedef decltype(&T::operator()) Fty;
    typedef typename other_traits<Fty>::type type;
};

int main(){
}

But I get the following errors with Visual Studio 2010 while g++ compiles just fine:

src\main.cpp(9): error C2146: syntax error : missing ';' before identifier 'type'
--src\main.cpp(10) : see reference to class template instantiation 'some_traits<T>' being compiled
src\main.cpp(9): error C2868: 'some_traits<T>::type' : illegal syntax for using-declaration; expected qualified-name

(I like that last one, total wtf.)

Can I take that as a bug in VC10 or is there any good reason for the early instantiation? Or is it a bug with decltype that makes the compiler think that Fty is not a dependent name?

Update: I tried to cheat the compiler in thinking that Fty is a dependent name using a base class to inherit from:

template<class T>
struct other_traits;

template<class R, class C>
struct other_traits<R (C::*)()>{
    typedef R type;
};

template<class Fty>
struct base_traits{
    typedef typename other_traits<Fty>::type type;
};

template<class T>
struct some_traits
    : public base_traits<decltype(&T::operator())>
{};

But the compiler still tries to instantiate / compile everything on the spot, spewing these errors:

src\main.cpp(13): error C2039: 'type' : is not a member of 'other_traits<T>'
          with
          [
              T=
          ]
          src\main.cpp(19) : see reference to class template instantiati