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// { dg-options "-std=gnu++20" }
// { dg-do compile { target c++20 } }
#include <compare>
using std::strong_ordering;
using std::partial_ordering;
namespace adl
{
struct S { };
void strong_ordering(const S&, const S&);
bool operator==(const S&, S&) { return true; }
bool operator<(const S&, S&) { return true; }
}
template<typename T, typename U>
concept has_strong_order_fallback = requires (T& t, U& u) {
std::compare_strong_order_fallback(t, u);
};
template<typename T, typename U>
concept has_weak_order_fallback = requires (T& t, U& u) {
std::compare_weak_order_fallback(t, u);
};
template<typename T, typename U>
concept has_partial_order_fallback = requires (T& t, U& u) {
std::compare_partial_order_fallback(t, u);
};
using adl::S;
static_assert( has_strong_order_fallback<S, S> );
static_assert( has_strong_order_fallback<const S, S> );
static_assert( ! has_strong_order_fallback<const S, const S> );
static_assert( has_weak_order_fallback<S, S> );
static_assert( has_weak_order_fallback<const S, S> );
static_assert( ! has_weak_order_fallback<const S, const S> );
static_assert( has_partial_order_fallback<S, S> );
static_assert( ! has_partial_order_fallback<const S, S> ); // LWG 3465
static_assert( ! has_partial_order_fallback<const S, const S> );
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