Get value reference declaration

template<typename T>
struct value_category {
    // Or can be an integral or enum value
    static constexpr auto value = "prvalue";
};

template<typename T>
struct value_category<T&> {
    static constexpr auto value = "lvalue";
};

template<typename T>
struct value_category<T&&> {
    static constexpr auto value = "xvalue";
};

// Double parens for ensuring we inspect an expression,
// not an entity
#define VALUE_CATEGORY(expr) value_category<decltype((expr))>::value


int main() {
    int x;

    cout << VALUE_CATEGORY(x)       << endl; // prints lvalue
    cout << VALUE_CATEGORY(move(x)) << endl; // prints xvalue
    cout << VALUE_CATEGORY(42)      << endl; // prints prvalue
}