struct with template member function cannot be used as template param unless using template deduction

Question

Below code block won't compile when invoking template member function (on template parameter) without taking advantage template argument deduction. Can someone point out what I'm missing here, TIA.

struct Foo
{
    template<typename T>
    void set(const T& thing) { }
};

template<typename T>
class Bar 
{
public:
    Bar() {
        // struct Foo declared 
        f.set(5);       // compiles
        f.set<int>(5);  // compiles

        // struct Foo via template parameter type T
        t.set(5);       // compiles
        t.set<int>(5);  // doesn't compile
    }

    Foo f;
    T t;
};

int
main(int argc, char* argv[])
{
    Bar<Foo> b;
}

Code also available at http://coliru.stacked-crooked.com/a/50294c63b3acdef9