#include <optional>

struct derived_optional : std::optional<int> {
    friend bool operator==(const derived_optional&, const derived_optional&) = default;
    friend auto operator<=>(const derived_optional&, const derived_optional&) = default;
};

int main()
{
    derived_optional a;
    std::optional<derived_optional> b;
#ifdef LESS // If b < a is not skipped, then MSVC accepts b <=> a.
    (void) (b < a);
#endif
    (void) (b <=> a);
}