How to implement template specialization methods in *.cpp files?

Question

1) Implement methods from a templated class in a CPP source file:

//foo.hpp

template<typename T>
class foo
{
public:
    void bar(const T &t);
};

//foo.cpp

template <class T>
void foo<T>::bar(const T &t)
{
    std::cout << "General." << std::endl;
}

template class foo<int>;

//main

foo<int> foo;

foo.bar(42);

2) Implement templated methods from a class in a CPP source file:

//foo.hpp

class foo
{
public:
    template<typename T>
    void bar(const T &t);
};

//foo.cpp

template <class T>
void foo::bar(const T &t)
{
    std::cout << "General." << std::endl;
}

template void foo::bar<int>(const int &t);

//main

foo toto;

toto.bar<int>(42);

3) Implement specialized templated method... ?

//foo.hpp

class foo
{
public:
    template<typename T>
    void bar(const T &t);
    template<>
    void bar<float>(const float &t);
};

//foo.cpp

template <class T>
void foo::bar(const T &t)
{
    std::cout << "General." << std::endl;
}


template <>
void foo::bar<float>(const float &t)
{
    std::cout << "Float specialization." << std::endl;
}

template void foo::bar<int>(const int &t);
template void foo::bar<float>(const float &t); //Seems to be not correct!

//main

foo toto;

toto.bar<float>(42);

//Compilation error:

error LNK2019: unresolved external link "public: void __thiscall foo::bar<float>(float const &)" (??$bar@M@foo@@QAEXABM@Z) referenced in _main function

I can't reach the solution to this problem.

Thanks very much in advance for your help.