the right way to use 'auto' keyword

[AlexStocks]

Describe the bug
A clear and concise description of what the bug is.

#include <string>
#include <iostream>
#include <vector>

using namespace std;

template <class T>
constexpr
std::string_view
type_name()
{
    using namespace std;
#ifdef __clang__
    string_view p = __PRETTY_FUNCTION__;
    return string_view(p.data() + 34, p.size() - 34 - 1);
#elif defined(__GNUC__)
    string_view p = __PRETTY_FUNCTION__;
#  if __cplusplus < 201402
    return string_view(p.data() + 36, p.size() - 36 - 1);
#  else
    return string_view(p.data() + 49, p.find(';', 49) - 49);
#  endif
#elif defined(_MSC_VER)
    string_view p = __FUNCSIG__;
    return string_view(p.data() + 84, p.size() - 84 - 7);
#endif
}

/**
 * description   : to .<br/><br/>
 *
 * @val          : value
 **/
class A
{
    public:
        A() {}
        ~A() {}

        vector<int>& vref() {
            return v_;
        }

        vector<int>* vpoint() {
            return &v_;
        }

        void output() {
            for (auto i : v_) {
                cout << i << endl;
            }
        }

    private:
        vector<int> v_;
};

int main(int argc, char** argv)
{
    A ca;

    cout << "ref:" << endl;
    auto &v = ca.vref();
    v.push_back(1);
    v.push_back(2);
    v.push_back(3);
    ca.output();
    std::cout << type_name<decltype(v)>() << endl;

    cout << "value:" << endl;
    auto vv = ca.vref();
    vv.push_back(4);
    ca.output();
    std::cout << type_name<decltype(vv)>() << endl;

    cout << "point ref:" << endl;
    auto *vpr = ca.vpoint();
    vpr->push_back(5);
    ca.output();
    std::cout << type_name<decltype(vpr)>() << endl;

    cout << "point value:" << endl;
    auto vpv = ca.vpoint();
    vpv->push_back(6);
    ca.output();
    std::cout << type_name<decltype(vpv)>() << endl;

    // cout << "point value ref:" << endl;
    // [a.cc](http://a.cc/):90:11: error: non-const lvalue reference to type 'std::vector<int> *' cannot bind to a temporary of type 'vector<int> *'
    // auto &vpvr = ca.vpoint();
    // vpvr->push_back(7);
    // ca.output();
    // std::cout << type_name<decltype(vpvr)>() << endl;

    return 0;
}

output