[libc++][iterator][ranges] P2997R1: Removing the common reference requirement from the indirectly invocable concepts

libcxx/docs/ReleaseNotes/19.rst

@@ -47,6 +47,7 @@ Implemented Papers
 - P3142R0 - Printing Blank Lines with ``println`` (as DR against C++23)
 - P2944R3 - Comparisons for ``reference_wrapper`` (comparison operators for ``reference_wrapper`` only)
 - P2968R2 - Make ``std::ignore`` a first-class object
+- P2997R1 - Removing the common reference requirement from the indirectly invocable concepts
 - P2302R4 - ``std::ranges::contains``
 - P1659R3 - ``std::ranges::starts_with`` and ``std::ranges::ends_with``
 - P3029R1 - Better ``mdspan``'s CTAD

libcxx/include/__iterator/concepts.h

@@ -177,46 +177,43 @@ concept __has_arrow = input_iterator<_Ip> && (is_pointer_v<_Ip> || requires(_Ip
 template <class _Fp, class _It>
 concept indirectly_unary_invocable =
     indirectly_readable<_It> && copy_constructible<_Fp> && invocable<_Fp&, iter_value_t<_It>&> &&
-    invocable<_Fp&, iter_reference_t<_It>> && invocable<_Fp&, iter_common_reference_t<_It>> &&
+    invocable<_Fp&, iter_reference_t<_It>> &&
     common_reference_with< invoke_result_t<_Fp&, iter_value_t<_It>&>, invoke_result_t<_Fp&, iter_reference_t<_It>>>;
 
 template <class _Fp, class _It>
 concept indirectly_regular_unary_invocable =
     indirectly_readable<_It> && copy_constructible<_Fp> && regular_invocable<_Fp&, iter_value_t<_It>&> &&
-    regular_invocable<_Fp&, iter_reference_t<_It>> && regular_invocable<_Fp&, iter_common_reference_t<_It>> &&
+    regular_invocable<_Fp&, iter_reference_t<_It>> &&
     common_reference_with< invoke_result_t<_Fp&, iter_value_t<_It>&>, invoke_result_t<_Fp&, iter_reference_t<_It>>>;
 
 template <class _Fp, class _It>
 concept indirect_unary_predicate =
     indirectly_readable<_It> && copy_constructible<_Fp> && predicate<_Fp&, iter_value_t<_It>&> &&
-    predicate<_Fp&, iter_reference_t<_It>> && predicate<_Fp&, iter_common_reference_t<_It>>;
+    predicate<_Fp&, iter_reference_t<_It>>;
 
 template <class _Fp, class _It1, class _It2>
 concept indirect_binary_predicate =
     indirectly_readable<_It1> && indirectly_readable<_It2> && copy_constructible<_Fp> &&
     predicate<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&> &&
     predicate<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>> &&
     predicate<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&> &&
-    predicate<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>> &&
-    predicate<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>;
+    predicate<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>>;
 
 template <class _Fp, class _It1, class _It2 = _It1>
 concept indirect_equivalence_relation =
     indirectly_readable<_It1> && indirectly_readable<_It2> && copy_constructible<_Fp> &&
     equivalence_relation<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&> &&
     equivalence_relation<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>> &&
     equivalence_relation<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&> &&
-    equivalence_relation<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>> &&
-    equivalence_relation<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>;
+    equivalence_relation<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>>;
 
 template <class _Fp, class _It1, class _It2 = _It1>
 concept indirect_strict_weak_order =
     indirectly_readable<_It1> && indirectly_readable<_It2> && copy_constructible<_Fp> &&
     strict_weak_order<_Fp&, iter_value_t<_It1>&, iter_value_t<_It2>&> &&
     strict_weak_order<_Fp&, iter_value_t<_It1>&, iter_reference_t<_It2>> &&
     strict_weak_order<_Fp&, iter_reference_t<_It1>, iter_value_t<_It2>&> &&
-    strict_weak_order<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>> &&
-    strict_weak_order<_Fp&, iter_common_reference_t<_It1>, iter_common_reference_t<_It2>>;
+    strict_weak_order<_Fp&, iter_reference_t<_It1>, iter_reference_t<_It2>>;
 
 template <class _Fp, class... _Its>
   requires(indirectly_readable<_Its> && ...) && invocable<_Fp, iter_reference_t<_Its>...>

libcxx/test/std/iterators/iterator.requirements/indirectcallable/indirectinvocable/indirect_binary_predicate.compile.pass.cpp

@@ -76,12 +76,12 @@ struct BadPredicate5 {
 };
 static_assert(!std::indirect_binary_predicate<BadPredicate5, It1, It2>);
 
-// Should fail when the predicate can't be called with (iter_common_reference_t, iter_common_reference_t)
+// This case was made valid by P2997R1.
 struct BadPredicate6 {
     template <class T, class U> bool operator()(T const&, U const&) const;
     bool operator()(std::iter_common_reference_t<It1>, std::iter_common_reference_t<It2>) const = delete;
 };
-static_assert(!std::indirect_binary_predicate<BadPredicate6, It1, It2>);
+static_assert(std::indirect_binary_predicate<BadPredicate6, It1, It2>);
 
 // Test ADL-proofing (P2538R1)
 #if TEST_STD_VER >= 26 || defined(_LIBCPP_VERSION)

libcxx/test/std/iterators/iterator.requirements/indirectcallable/indirectinvocable/indirect_equivalence_relation.compile.pass.cpp

@@ -91,12 +91,12 @@ struct BadRelation5 {
 };
 static_assert(!std::indirect_equivalence_relation<BadRelation5, It1, It2>);
 
-// Should fail when the function can't be called with (iter_common_reference_t, iter_common_reference_t)
+// This case was made valid by P2997R1.
 struct BadRelation6 {
     template <class T, class U> bool operator()(T const&, U const&) const;
     bool operator()(std::iter_common_reference_t<It1>, std::iter_common_reference_t<It2>) const = delete;
 };
-static_assert(!std::indirect_equivalence_relation<BadRelation6, It1, It2>);
+static_assert(std::indirect_equivalence_relation<BadRelation6, It1, It2>);
 
 // Test ADL-proofing (P2538R1)
 #if TEST_STD_VER >= 26 || defined(_LIBCPP_VERSION)

libcxx/test/std/iterators/iterator.requirements/indirectcallable/indirectinvocable/indirect_strict_weak_order.compile.pass.cpp

@@ -91,12 +91,12 @@ struct BadOrder5 {
 };
 static_assert(!std::indirect_strict_weak_order<BadOrder5, It1, It2>);
 
-// Should fail when the function can't be called with (iter_common_reference_t, iter_common_reference_t)
+// This case was made valid by P2997R1.
 struct BadOrder6 {
     template <class T, class U> bool operator()(T const&, U const&) const;
     bool operator()(std::iter_common_reference_t<It1>, std::iter_common_reference_t<It2>) const = delete;
 };
-static_assert(!std::indirect_strict_weak_order<BadOrder6, It1, It2>);
+static_assert(std::indirect_strict_weak_order<BadOrder6, It1, It2>);
 
 // Test ADL-proofing (P2538R1)
 #if TEST_STD_VER >= 26 || defined(_LIBCPP_VERSION)

libcxx/test/std/iterators/iterator.requirements/indirectcallable/indirectinvocable/indirect_unary_predicate.compile.pass.cpp

@@ -57,12 +57,12 @@ struct BadPredicate3 {
 };
 static_assert(!std::indirect_unary_predicate<BadPredicate3, It>);
 
-// Should fail when the predicate can't be called with std::iter_common_reference_t<It>
+// This case was made valid by P2997R1.
 struct BadPredicate4 {
     template <class T> bool operator()(T const&) const;
     bool operator()(std::iter_common_reference_t<It>) const = delete;
 };
-static_assert(!std::indirect_unary_predicate<BadPredicate4, It>);
+static_assert(std::indirect_unary_predicate<BadPredicate4, It>);
 
 // Test ADL-proofing (P2538R1)
 #if TEST_STD_VER >= 26 || defined(_LIBCPP_VERSION)

libcxx/test/std/iterators/iterator.requirements/indirectcallable/indirectinvocable/indirectly_regular_unary_invocable.compile.pass.cpp

@@ -56,12 +56,12 @@ struct BadInvocable3 {
 };
 static_assert(!std::indirectly_regular_unary_invocable<BadInvocable3, It>);
 
-// Should fail when the invocable can't be called with (iter_common_reference_t)
+// This case was made valid by P2997R1.
 struct BadInvocable4 {
     template <class T> R1 operator()(T const&) const;
     R1 operator()(std::iter_common_reference_t<It>) const = delete;
 };
-static_assert(!std::indirectly_regular_unary_invocable<BadInvocable4, It>);
+static_assert(std::indirectly_regular_unary_invocable<BadInvocable4, It>);
 
 // Should fail when the invocable doesn't have a common reference between its return types
 struct BadInvocable5 {

libcxx/test/std/iterators/iterator.requirements/indirectcallable/indirectinvocable/indirectly_unary_invocable.compile.pass.cpp

@@ -56,12 +56,12 @@ struct BadInvocable3 {
 };
 static_assert(!std::indirectly_unary_invocable<BadInvocable3, It>);
 
-// Should fail when the invocable can't be called with (iter_common_reference_t)
+// This case was made valid by P2997R1.
 struct BadInvocable4 {
     template <class T> R1 operator()(T const&) const;
     R1 operator()(std::iter_common_reference_t<It>) const = delete;
 };
-static_assert(!std::indirectly_unary_invocable<BadInvocable4, It>);
+static_assert(std::indirectly_unary_invocable<BadInvocable4, It>);
 
 // Should fail when the invocable doesn't have a common reference between its return types
 struct BadInvocable5 {

libcxx/utils/generate_feature_test_macro_components.py

@@ -993,7 +993,8 @@ def add_version_header(tc):
             "name": "__cpp_lib_ranges",
             "values": {
                 "c++20": 202207,
-                # "c++26": 202406, # P2997R1 Removing the common reference requirement from the indirectly invocable concepts
+                # "c++23": 202302,  # Relaxing Ranges Just A Smidge
+                # "c++26": 202406,  # P2997R1 Removing the common reference requirement from the indirectly invocable concepts
             },
             "headers": ["algorithm", "functional", "iterator", "memory", "ranges"],
         },