mrdocs::ClearableContainerLike

template<class T>
concept ClearableContainerLike = requires {
        typename T::value_type;
        typename T::size_type;
        typename T::difference_type;
        typename T::reference;
        typename T::const_reference;
        typename T::iterator;
        typename T::const_iterator;
    } &&
    // size_type should be integral for normal containers
    std::is_integral_v<typename T::size_type> &&

    // ‐‐‐‐ member begin/end with expected iterator types ‐‐‐‐
    requires(T& t, const T& ct) {
        { t.begin() }  ‐> std::convertible_to<typename T::iterator>;
        { t.end() }    ‐> std::convertible_to<typename T::iterator>;
        { ct.begin() } ‐> std::convertible_to<typename T::const_iterator>;
        { ct.end() }   ‐> std::convertible_to<typename T::const_iterator>;
    } &&

    // ‐‐‐‐ iterator “shape”: deref and increment ‐‐‐‐
    requires(T& t, const T& ct) {
        { *t.begin() }  ‐> std::convertible_to<typename T::reference>;
        { *ct.begin() } ‐> std::convertible_to<typename T::const_reference>;
        { ++std::declval<typename T::iterator&>() } ‐> std::same_as<typename T::iterator&>;
    } &&

    // ‐‐‐‐ size/empty/clear trio ‐‐‐‐
    requires(T& t, const T& ct) {
        { ct.size() }  ‐> std::same_as<typename T::size_type>;
        { ct.empty() } ‐> std::convertible_to<bool>;
        { t.clear() }  ‐> std::same_as<void>;
    } &&

    // ‐‐‐‐ default constructible (most std containers satisfy this) ‐‐‐‐
    std::default_initializable<T>;