From 6812458f64d58db38a7f0c87840055727b377276 Mon Sep 17 00:00:00 2001
From: "A. Jiang" <de34@live.cn>
Date: Sat, 3 Dec 2022 01:59:50 +0800
Subject: [PATCH 1/3] Test coverage for CPO changes in P2162R3

---
 .../std/tests/P0768R1_spaceship_cpos/test.cpp | 59 +++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/tests/std/tests/P0768R1_spaceship_cpos/test.cpp b/tests/std/tests/P0768R1_spaceship_cpos/test.cpp
index b681f65a26..b6ded80f94 100644
--- a/tests/std/tests/P0768R1_spaceship_cpos/test.cpp
+++ b/tests/std/tests/P0768R1_spaceship_cpos/test.cpp
@@ -326,6 +326,65 @@ namespace {
     static_assert(is_same_v<CpoResult<compare_partial_order_fallback, F<13>, const F<13>>, Partial>); // [cmp.alg]/6.3
 } // namespace
 
+// Test strengthened requirements in P2162R3: compare_*_order_fallback CPOs require return types to be boolean-testable.
+enum class ResultKind : bool {
+    Bad,
+    Good,
+};
+
+template <ResultKind K>
+struct ComparisonResult {
+    bool value;
+
+    constexpr operator bool() const noexcept {
+        return value;
+    }
+
+    constexpr auto operator!() const noexcept {
+        if constexpr (K == ResultKind::Good) {
+            return ComparisonResult{!value};
+        }
+    }
+};
+
+template <ResultKind EqKind, ResultKind LeKind>
+struct BoolTestType {
+    friend constexpr ComparisonResult<EqKind> operator==(BoolTestType, BoolTestType) noexcept {
+        return ComparisonResult<EqKind>{true};
+    }
+
+    friend constexpr ComparisonResult<LeKind> operator<(BoolTestType, BoolTestType) noexcept {
+        return ComparisonResult<LeKind>{false};
+    }
+};
+
+static_assert(is_same_v<CpoResult<compare_strong_order_fallback, BoolTestType<ResultKind::Bad, ResultKind::Bad>>,
+    IllFormed>); // [cmp.alg]/4.3
+static_assert(is_same_v<CpoResult<compare_strong_order_fallback, BoolTestType<ResultKind::Bad, ResultKind::Good>>,
+    IllFormed>); // [cmp.alg]/4.3
+static_assert(is_same_v<CpoResult<compare_strong_order_fallback, BoolTestType<ResultKind::Good, ResultKind::Bad>>,
+    IllFormed>); // [cmp.alg]/4.3
+static_assert(is_same_v<CpoResult<compare_strong_order_fallback, BoolTestType<ResultKind::Good, ResultKind::Good>>,
+    strong_ordering>); // [cmp.alg]/4.3
+
+static_assert(is_same_v<CpoResult<compare_weak_order_fallback, BoolTestType<ResultKind::Bad, ResultKind::Bad>>,
+    IllFormed>); // [cmp.alg]/5.3
+static_assert(is_same_v<CpoResult<compare_weak_order_fallback, BoolTestType<ResultKind::Bad, ResultKind::Good>>,
+    IllFormed>); // [cmp.alg]/5.3
+static_assert(is_same_v<CpoResult<compare_weak_order_fallback, BoolTestType<ResultKind::Good, ResultKind::Bad>>,
+    IllFormed>); // [cmp.alg]/5.3
+static_assert(is_same_v<CpoResult<compare_weak_order_fallback, BoolTestType<ResultKind::Good, ResultKind::Good>>,
+    weak_ordering>); // [cmp.alg]/5.3
+
+static_assert(is_same_v<CpoResult<compare_partial_order_fallback, BoolTestType<ResultKind::Bad, ResultKind::Bad>>,
+    IllFormed>); // [cmp.alg]/6.3
+static_assert(is_same_v<CpoResult<compare_partial_order_fallback, BoolTestType<ResultKind::Bad, ResultKind::Good>>,
+    IllFormed>); // [cmp.alg]/6.3
+static_assert(is_same_v<CpoResult<compare_partial_order_fallback, BoolTestType<ResultKind::Good, ResultKind::Bad>>,
+    IllFormed>); // [cmp.alg]/6.3
+static_assert(is_same_v<CpoResult<compare_partial_order_fallback, BoolTestType<ResultKind::Good, ResultKind::Good>>,
+    partial_ordering>); // [cmp.alg]/6.3
+
 // Test when the type is comparable through ADL. Part B, exception specifications.
 static_assert(!NoexceptCpo<std::strong_order, TestAdl::StrongType<Throwing>>); // [cmp.alg]/1.2
 static_assert(!NoexceptCpo<std::weak_order, TestAdl::WeakType<Throwing>>); // [cmp.alg]/2.2

From d79975e8c06d6cff99e436a8f25788a7d5b4d208 Mon Sep 17 00:00:00 2001
From: "A. Jiang" <de34@live.cn>
Date: Sat, 3 Dec 2022 02:06:47 +0800
Subject: [PATCH 2/3] Implement changes for CPOs in P2167R3

---
 stl/inc/compare      | 10 +++++-----
 stl/inc/yvals_core.h |  1 +
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/stl/inc/compare b/stl/inc/compare
index 9d605211d8..745a89a732 100644
--- a/stl/inc/compare
+++ b/stl/inc/compare
@@ -641,8 +641,8 @@ inline namespace _Cpos {
 
 template <class _Ty1, class _Ty2>
 concept _Can_fallback_eq_lt = requires(_Ty1& _Left, _Ty2& _Right) {
-                                  { _Left == _Right } -> _Implicitly_convertible_to<bool>;
-                                  { _Left < _Right } -> _Implicitly_convertible_to<bool>;
+                                  { _Left == _Right } -> _Boolean_testable;
+                                  { _Left < _Right } -> _Boolean_testable;
                               };
 
 template <class _Ty1, class _Ty2>
@@ -751,9 +751,9 @@ concept _Can_partial_order = requires(_Ty1& _Left, _Ty2& _Right) { _STD partial_
 namespace _Compare_partial_order_fallback {
     template <class _Ty1, class _Ty2>
     concept _Can_fallback_eq_lt_twice = requires(_Ty1& _Left, _Ty2& _Right) {
-                                            { _Left == _Right } -> _Implicitly_convertible_to<bool>;
-                                            { _Left < _Right } -> _Implicitly_convertible_to<bool>;
-                                            { _Right < _Left } -> _Implicitly_convertible_to<bool>;
+                                            { _Left == _Right } -> _Boolean_testable;
+                                            { _Left < _Right } -> _Boolean_testable;
+                                            { _Right < _Left } -> _Boolean_testable;
                                         };
 
     class _Cpo {
diff --git a/stl/inc/yvals_core.h b/stl/inc/yvals_core.h
index ad10a9d0e8..cf75ae7f19 100644
--- a/stl/inc/yvals_core.h
+++ b/stl/inc/yvals_core.h
@@ -265,6 +265,7 @@
 // P2102R0 Making "Implicit Expression Variations" More Explicit
 // P2106R0 Range Algorithm Result Types
 // P2116R0 Removing tuple-Like Protocol Support From Fixed-Extent span
+// P2167R3 Improving boolean-testable Usage
 // P2210R2 Superior String Splitting
 // P2216R3 std::format Improvements
 // P2231R1 Completing constexpr In optional And variant

From 123e763c3556c75f96207288e4b808ca326aebaf Mon Sep 17 00:00:00 2001
From: "A. Jiang" <de34@live.cn>
Date: Sat, 3 Dec 2022 13:48:15 +0800
Subject: [PATCH 3/3] Fix typo: s/P2162R3/P2167R3

---
 tests/std/tests/P0768R1_spaceship_cpos/test.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/std/tests/P0768R1_spaceship_cpos/test.cpp b/tests/std/tests/P0768R1_spaceship_cpos/test.cpp
index b6ded80f94..e6e6d5ec77 100644
--- a/tests/std/tests/P0768R1_spaceship_cpos/test.cpp
+++ b/tests/std/tests/P0768R1_spaceship_cpos/test.cpp
@@ -326,7 +326,7 @@ namespace {
     static_assert(is_same_v<CpoResult<compare_partial_order_fallback, F<13>, const F<13>>, Partial>); // [cmp.alg]/6.3
 } // namespace
 
-// Test strengthened requirements in P2162R3: compare_*_order_fallback CPOs require return types to be boolean-testable.
+// Test strengthened requirements in P2167R3: compare_*_order_fallback CPOs require return types to be boolean-testable.
 enum class ResultKind : bool {
     Bad,
     Good,