Why can't T be deduced from Template<T>::Type?

What is wrong in this code?

#include <map>

template<typename T>
struct TMap
{
    typedef std::map<T, T> Type;
};

template<typename T>
T test(typename TMap<T>::Type &tmap_) { return 0.0; }

int _tmain(int argc, _TCHAR* argv[])
{
    TMap<double>::Type tmap;
    tmap[1.1] = 5.2;
    double d = test(tmap); //Error: could not deduce template argument for T
    return 0;
}