[PATCH 2/2] libstdc++: Implement range_adaptor_closure from P2387R3 [PR108827]

[Patrick Palka <ppalka@redhat.com>]

Tested on x86_64-pc-linux-gnu, does this look OK for trunk?

	PR libstdc++/108827

libstdc++-v3/ChangeLog:

	* include/bits/ranges_cmp.h (__cpp_lib_ranges): Bump value
	for C++23.
	* include/std/ranges (range_adaptor_closure): Define for C++23.
	* include/std/version (__cpp_lib_ranges): Bump value for
	C++23.
	* testsuite/std/ranges/version_c++23.cc: Bump expected value
	of __cpp_lib_ranges.
	* testsuite/std/ranges/range_adaptor_closure.cc: New test.
---
 libstdc++-v3/include/bits/ranges_cmp.h        |  4 ++
 libstdc++-v3/include/std/ranges               |  8 ++++
 libstdc++-v3/include/std/version              |  3 ++
 .../std/ranges/range_adaptor_closure.cc       | 42 +++++++++++++++++++
 .../testsuite/std/ranges/version_c++23.cc     |  2 +-
 5 files changed, 58 insertions(+), 1 deletion(-)
 create mode 100644 libstdc++-v3/testsuite/std/ranges/range_adaptor_closure.cc

diff --git a/libstdc++-v3/include/bits/ranges_cmp.h b/libstdc++-v3/include/bits/ranges_cmp.h
index 85c1a77ccf7..6710d829a37 100644
--- a/libstdc++-v3/include/bits/ranges_cmp.h
+++ b/libstdc++-v3/include/bits/ranges_cmp.h
@@ -57,7 +57,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 #ifdef __cpp_lib_concepts
 // Define this here, included by all the headers that need to define it.
+#if __cplusplus > 202002L
+#define __cpp_lib_ranges 202202L
+#else
 #define __cpp_lib_ranges 202110L
+#endif
 
 namespace ranges
 {
diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges
index 531ec6f68b3..bf3c246f95d 100644
--- a/libstdc++-v3/include/std/ranges
+++ b/libstdc++-v3/include/std/ranges
@@ -1137,6 +1137,14 @@ namespace views::__adaptor
     };
 } // namespace views::__adaptor
 
+#if __cplusplus > 20202L
+  template<typename _Derived>
+    requires is_class_v<_Derived> && same_as<_Derived, remove_cv_t<_Derived>>
+    class range_adaptor_closure
+    : public views::__adaptor::_RangeAdaptorClosure<_Derived>
+    { };
+#endif
+
   template<range _Range> requires is_object_v<_Range>
     class ref_view : public view_interface<ref_view<_Range>>
     {
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index 9f31f25f1e9..ad928a225ef 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -265,8 +265,10 @@
 #define __cpp_lib_interpolate 201902L
 #if __cpp_lib_concepts
 # define __cpp_lib_move_iterator_concept 202207L
+#if __cplusplus <= 202002L // N.B. updated value in C++23
 # define __cpp_lib_ranges 202110L
 #endif
+#endif
 #define __cpp_lib_shift 201806L
 
 #if _GLIBCXX_HOSTED
@@ -330,6 +332,7 @@
 #define __cpp_lib_reference_from_temporary 202202L
 #define __cpp_lib_to_underlying 202102L
 #define __cpp_lib_unreachable 202202L
+#define __cpp_lib_ranges 202202L
 #define __cpp_lib_ranges_zip 202110L
 #define __cpp_lib_ranges_chunk 202202L
 #define __cpp_lib_ranges_slide 202202L
diff --git a/libstdc++-v3/testsuite/std/ranges/range_adaptor_closure.cc b/libstdc++-v3/testsuite/std/ranges/range_adaptor_closure.cc
new file mode 100644
index 00000000000..c642712ed9e
--- /dev/null
+++ b/libstdc++-v3/testsuite/std/ranges/range_adaptor_closure.cc
@@ -0,0 +1,42 @@
+// { dg-options "-std=gnu++23" }
+// { dg-do run { target c++23 } }
+
+#include <ranges>
+#include <algorithm>
+#include <testsuite_hooks.h>
+
+namespace ranges = std::ranges;
+namespace views = std::views;
+
+struct _Negate : ranges::range_adaptor_closure<_Negate>
+{
+  template<ranges::viewable_range _Range>
+  constexpr auto
+  operator()(_Range&& __r) const
+  requires requires { views::transform(std::declval<_Range>(), std::negate{}); }
+  { return views::transform(std::forward<_Range>(__r), std::negate{}); }
+};
+
+constexpr _Negate negate;
+
+constexpr bool
+test01()
+{
+  int x[] = {1, 2, 3};
+  VERIFY( ranges::equal(x | negate, (int[]){-1, -2, -3}) );
+  VERIFY( ranges::equal(x | negate | negate, x) );
+  VERIFY( ranges::equal(x | (negate | negate), x) );
+  VERIFY( ranges::equal(x | views::reverse | negate, x | negate | views::reverse) );
+  VERIFY( ranges::equal(x | (views::reverse | negate), x | (negate | views::reverse)) );
+  static_assert( sizeof(negate | views::reverse | views::join) == 1 );
+  static_assert( sizeof(views::reverse | negate | views::join) == 1 );
+  static_assert( sizeof(views::reverse | views::join | negate) == 1 );
+
+  return true;
+}
+
+int
+main()
+{
+  static_assert(test01());
+}
diff --git a/libstdc++-v3/testsuite/std/ranges/version_c++23.cc b/libstdc++-v3/testsuite/std/ranges/version_c++23.cc
index e2c14edc8ef..90cfceb626c 100644
--- a/libstdc++-v3/testsuite/std/ranges/version_c++23.cc
+++ b/libstdc++-v3/testsuite/std/ranges/version_c++23.cc
@@ -4,7 +4,7 @@
 #include <version>
 
 #if __STDC_HOSTED__
-# if __cpp_lib_ranges != 202110L
+# if __cpp_lib_ranges != 202202L
 #  error "Feature-test macro __cpp_lib_ranges has wrong value in <version>"
 # endif
 #endif
-- 
2.40.0.335.g9857273be0