How to replace ref-qualifiers of member functions with concept?

Question

Is it possible to replace following ref-qualifiers with concepts?

That is, instead of

struct S 
{
   void func() && {}
   void func() & {}
};

have something like this

struct S 
{
   void func() requires rvalue_concept< decltype(*this) > {}
   void func() requires lvalue_concept< decltype(*this) > {}
};

---

Note: This is not a duplicate of How can I make a forwarding-reference parameter bind only to rvalue references? because my question is about checking whether the struct S is used as an r-value-reference, but the other question is about a function which shall only accept r-value-references.

Answer 1

Is it possible to replace ref-qualifiers with concepts?

You can use the explicit object parameter syntax introduced in c++23, which allows us to deduce the type of this. With that, you could write:

template<typename T>
concept rvalue_concept = std::is_rvalue_reference_v<T&&>;

template<typename T>
concept lvalue_concept = !rvalue_concept<T>;

struct S 
{
    template<typename Self>
    void func(this Self&& self) requires rvalue_concept<Self> 
    {
        std::cout << "rvalue version called\n";
    }

    template<typename Self>
    void func(this Self&& self) requires lvalue_concept<Self> 
    {
        std::cout << "lvalue version called\n";
    }
};

See live demo