[bodyfour]

I think concentrating on the move part is the wrong way to look at rvalue-ref methods. The advantage is that if the compiler knows an object is a temporary it you can safely let the caller safely "steal" a member object.

  #include <string>
  #include <stdio.h>

  struct A {
    const std::string& str() const & { return m_str; }
    std::string&& str() && { return std::move(m_str); }

    std::string m_str;
  };

  void func(const std::string& s) { puts("Got const value"); }
  void func(std::string&& s) { puts("Got rvalue"); }

  A returns_a() { A a; return a; }

  int main()
  {
    func(returns_a().str());
    A b;
    func(b.str());
    return 0;
  }