error C2563: mismatch in formal parameter list by Jinhao.CPP

void foo(int){}
void foo(){}

template<typename Ft>
struct T
{
    T(){}
    T(Ft){}
};

int main()
{
    T<void()> t;
    t = foo; //Error, the foo() should be matched by overload resolution.
}

generates this error:
error C2563: mismatch in formal parameter list
error C2568: '=' : unable to resolve function overload
could be 'void foo(void)'
or     'void foo(int)'