[clang] [libc++] Implement ranges::contains (PR #65148)

via cfe-commits cfe-commits at lists.llvm.org
Mon Sep 11 17:41:33 PDT 2023


https://github.com/ZijunZhaoCCK updated https://github.com/llvm/llvm-project/pull/65148:

>From 02e9afd761228f401df4d9f8dfaaca44ffae0c6e Mon Sep 17 00:00:00 2001
From: zijunzhao <zijunzhao at google.com>
Date: Thu, 31 Aug 2023 20:08:32 +0000
Subject: [PATCH 1/7] [libc++] Implement ranges::contains

Differential Revision: https://reviews.llvm.org/D159232
---
 libcxx/include/CMakeLists.txt                 |   1 +
 libcxx/include/__algorithm/ranges_contains.h  |  60 ++++++
 libcxx/include/algorithm                      |   9 +
 ...obust_against_copying_projections.pass.cpp |   4 +
 .../alg.contains/ranges.contains.pass.cpp     | 190 ++++++++++++++++++
 .../niebloid.compile.pass.cpp                 |   1 +
 6 files changed, 265 insertions(+)
 create mode 100644 libcxx/include/__algorithm/ranges_contains.h
 create mode 100644 libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 77a7269121ec142..024aa8959fb7200 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -104,6 +104,7 @@ set(files
   __algorithm/ranges_any_of.h
   __algorithm/ranges_binary_search.h
   __algorithm/ranges_clamp.h
+  __algorithm/ranges_contains.h
   __algorithm/ranges_copy.h
   __algorithm/ranges_copy_backward.h
   __algorithm/ranges_copy_if.h
diff --git a/libcxx/include/__algorithm/ranges_contains.h b/libcxx/include/__algorithm/ranges_contains.h
new file mode 100644
index 000000000000000..647b7ea34be3421
--- /dev/null
+++ b/libcxx/include/__algorithm/ranges_contains.h
@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___ALGORITHM_RANGES_CONTAINS_H
+#define _LIBCPP___ALGORITHM_RANGES_CONTAINS_H
+
+#include <__algorithm/in_in_result.h>
+#include <__algorithm/ranges_find.h>
+#include <__config>
+#include <__functional/identity.h>
+#include <__functional/ranges_operations.h>
+#include <__functional/reference_wrapper.h>
+#include <__iterator/concepts.h>
+#include <__iterator/indirectly_comparable.h>
+#include <__iterator/projected.h>
+#include <__ranges/access.h>
+#include <__ranges/concepts.h>
+#include <__utility/move.h>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 23
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace ranges {
+namespace __contains {
+struct __fn {
+  template <input_iterator _Iter, sentinel_for<_Iter> _Sent, class _Type, class _Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<_Iter, _Proj>, const _Type*>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool
+  operator()(_Iter __first, _Sent __last, const _Type& __value, _Proj __proj = {}) const {
+    return ranges::find(std::move(__first), std::move(__last), __value, std::ref(__proj)) != __last;
+  }
+
+  template <input_range _Range, class _Type, class _Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<_Range>, _Proj>, const _Type*>
+  _LIBCPP_NODISCARD_EXT _LIBCPP_HIDE_FROM_ABI constexpr bool
+  operator()(_Range&& __range, const _Type& __value, _Proj __proj = {}) const {
+    return ranges::find(ranges::begin(__range), ranges::end(__range), __value, std::ref(__proj)) != ranges::end(__range);
+  }
+};
+} // namespace __contains
+inline namespace __cpo {
+inline constexpr auto contains = __contains::__fn{};
+} // namespace __cpo
+} // namespace ranges
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER >= 23
+
+#endif // _LIBCPP___ALGORITHM_RANGES_CONTAINS_H
diff --git a/libcxx/include/algorithm b/libcxx/include/algorithm
index 76e0d22bf73ef85..003bf132b38b4d8 100644
--- a/libcxx/include/algorithm
+++ b/libcxx/include/algorithm
@@ -226,6 +226,14 @@ namespace ranges {
   template<class I1, class I2>
     using copy_backward_result = in_out_result<I1, I2>;                                     // since C++20
 
+  template<input_iterator I, sentinel_for<I> S, class T, class Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*>
+    constexpr bool ranges::contains(I first, S last, const T& value, Proj proj = {});       // since C++23
+
+  template<input_range R, class T, class Proj = identity>
+    requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
+    constexpr bool ranges::contains(R&& r, const T& value, Proj proj = {});                 // since C++23
+
   template<input_iterator I, sentinel_for<I> S, weakly_incrementable O>
     requires indirectly_copyable<I, O>
     constexpr ranges::copy_result<I, O> ranges::copy(I first, S last, O result);            // since C++20
@@ -1827,6 +1835,7 @@ template <class BidirectionalIterator, class Compare>
 #include <__algorithm/ranges_any_of.h>
 #include <__algorithm/ranges_binary_search.h>
 #include <__algorithm/ranges_clamp.h>
+#include <__algorithm/ranges_contains.h>
 #include <__algorithm/ranges_copy.h>
 #include <__algorithm/ranges_copy_backward.h>
 #include <__algorithm/ranges_copy_if.h>
diff --git a/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp b/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp
index 111b0ff655f5342..e50f4ef2ed719c7 100644
--- a/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp
+++ b/libcxx/test/libcxx/algorithms/ranges_robust_against_copying_projections.pass.cpp
@@ -80,6 +80,10 @@ constexpr bool all_the_algorithms()
     (void)std::ranges::binary_search(first, last, value, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::binary_search(a, value, Less(), Proj(&copies)); assert(copies == 0);
     (void)std::ranges::clamp(T(), T(), T(), Less(), Proj(&copies)); assert(copies == 0);
+#if TEST_STD_VER >= 23
+    (void)std::ranges::contains(first, last, value, Proj(&copies)); assert(copies == 0);
+    (void)std::ranges::contains(a, value, Proj(&copies)); assert(copies == 0);
+#endif
     (void)std::ranges::count(first, last, value, Proj(&copies)); assert(copies == 0);
     (void)std::ranges::count(a, value, Proj(&copies)); assert(copies == 0);
     (void)std::ranges::count_if(first, last, UnaryTrue(), Proj(&copies)); assert(copies == 0);
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
new file mode 100644
index 000000000000000..8e67e971c2f040b
--- /dev/null
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -0,0 +1,190 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+// template<input_iterator I, sentinel_for<I> S, class T, class Proj = identity>
+//     requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*>
+//     constexpr bool ranges::contains(I first, S last, const T& value, Proj proj = {});       // since C++23
+
+// template<input_range R, class T, class Proj = identity>
+//     requires indirect_binary_predicate<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
+//     constexpr bool ranges::contains(R&& r, const T& value, Proj proj = {});                 // since C++23
+
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <ranges>
+#include <vector>
+
+#include "almost_satisfies_types.h"
+#include "boolean_testable.h"
+#include "test_iterators.h"
+
+struct NotEqualityComparable {};
+
+template <class Iter, class Sent = Iter>
+concept HasContainsIt = requires(Iter iter, Sent sent) { std::ranges::contains(iter, sent, *iter); };
+
+static_assert(HasContainsIt<int*>);
+static_assert(!HasContainsIt<NotEqualityComparable*>);
+static_assert(!HasContainsIt<InputIteratorNotDerivedFrom>);
+static_assert(!HasContainsIt<InputIteratorNotIndirectlyReadable>);
+static_assert(!HasContainsIt<InputIteratorNotInputOrOutputIterator>);
+static_assert(!HasContainsIt<cpp20_input_iterator<int*>, SentinelForNotSemiregular>);
+static_assert(!HasContainsIt<cpp20_input_iterator<int*>, InputRangeNotSentinelEqualityComparableWith>);
+
+static_assert(!HasContainsIt<int*, int>);
+static_assert(!HasContainsIt<int, int*>);
+
+template <class Range, class ValT>
+concept HasContainsR = requires(Range range) { std::ranges::contains(range, ValT{}); };
+
+static_assert(HasContainsR<std::array<int, 1>, int>);
+static_assert(!HasContainsR<int, int>);
+static_assert(!HasContainsR<std::array<NotEqualityComparable, 1>, NotEqualityComparable>);
+static_assert(!HasContainsR<InputRangeNotDerivedFrom, int>);
+static_assert(!HasContainsR<InputRangeNotIndirectlyReadable, int>);
+static_assert(!HasContainsR<InputRangeNotInputOrOutputIterator, int>);
+static_assert(!HasContainsR<InputRangeNotSentinelSemiregular, int>);
+static_assert(!HasContainsR<InputRangeNotSentinelEqualityComparableWith, int>);
+
+static std::vector<int> comparable_data;
+
+// clang-format off
+template <class Iter, class Sent = Iter>
+constexpr void test_iterators() {
+  using ValueT = std::iter_value_t<Iter>;
+  {  // simple tests
+    {
+      ValueT a[] = {1, 2, 3, 4, 5, 6};
+      std::same_as<bool> auto ret =
+        std::ranges::contains(Iter(a), Sent(Iter(a + 6)), 3);
+      assert(ret);
+    }
+    {
+      ValueT a[] = {1, 2, 3, 4, 5, 6};
+      auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 6)));
+      std::same_as<bool> decltype(auto) ret =
+        std::ranges::contains(range, 3);
+      assert(ret);
+    }
+  }
+
+  { // check that an empty range works
+    {
+      ValueT a[] = {};
+      auto ret = std::ranges::contains(Iter(a), Sent(Iter(a)), 1);
+      assert(!ret);
+    }
+    {
+      ValueT a[] = {};
+      auto range = std::ranges::subrange(Iter(a), Sent(Iter(a)));
+      auto ret = std::ranges::contains(range, 1);
+      assert(!ret);
+    }
+  }
+
+  { // check that no match
+    {
+      ValueT a[] = {13, 1, 21, 4, 5};
+      auto ret = std::ranges::contains(Iter(a), Sent(Iter(a + 5)), 10);
+      assert(!ret);
+    }
+    {
+      ValueT a[] = {13, 1, 21, 4, 5};
+      auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 5)));
+      auto ret = std::ranges::contains(range, 10);
+      assert(!ret);
+    }
+  }
+
+  if (!std::is_constant_evaluated())
+    comparable_data.clear();
+}
+template <class ElementT>
+class TriviallyComparable {
+  ElementT el_;
+
+public:
+  TEST_CONSTEXPR TriviallyComparable(ElementT el) : el_(el) {}
+  bool operator==(const TriviallyComparable&) const = default;
+};
+
+template <class IndexT>
+class Comparable {
+  IndexT index_;
+
+public:
+  Comparable(IndexT i)
+      : index_([&]() {
+          IndexT size = static_cast<IndexT>(comparable_data.size());
+          comparable_data.push_back(i);
+          return size;
+        }()) {}
+
+  bool operator==(const Comparable& other) const {
+    return comparable_data[other.index_] == comparable_data[index_];
+  }
+
+  friend bool operator==(const Comparable& lhs, long long rhs) { return comparable_data[lhs.index_] == rhs; }
+};
+
+constexpr bool test() {
+  types::for_each(types::type_list<char, wchar_t, int, long, 
+                  TriviallyComparable<char>, TriviallyComparable<wchar_t>>{},
+                  []<class T> {
+                    types::for_each(types::cpp20_input_iterator_list<T*>{}, 
+                      []<class Iter> {
+                      if constexpr (std::forward_iterator<Iter>)
+                        test_iterators<Iter>();
+                      test_iterators<Iter, sentinel_wrapper<Iter>>();
+                      test_iterators<Iter, sized_sentinel<Iter>>();
+                    });
+                  });
+
+  {
+    // count invocations of the projection
+    {
+      int a[] = {1, 9, 0, 13, 25};
+      int projection_count = 0;
+      auto ret = std::ranges::contains(a, a + 5, 0,
+                                [&](int i) { ++projection_count; return i; });
+      assert(ret);
+      assert(projection_count == 3);
+    }
+    {
+      int a[] ={1, 9, 0, 13, 25};
+      int projection_count = 0;
+      auto range = std::ranges::subrange(a, a + 5);
+      auto ret = std::ranges::contains(range, 0, [&](int i) { ++projection_count; return i; });
+      assert(ret);
+      assert(projection_count == 3);
+    }
+  }
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  types::for_each(types::type_list<Comparable<char>, Comparable<wchar_t>>{},
+                []<class T> {
+                  types::for_each(types::cpp20_input_iterator_list<T*>{}, 
+                    []<class Iter> {
+                    if constexpr (std::forward_iterator<Iter>)
+                      test_iterators<Iter>();
+                    test_iterators<Iter, sentinel_wrapper<Iter>>();
+                    test_iterators<Iter, sized_sentinel<Iter>>();
+                  });
+                });
+
+  return 0;
+}
diff --git a/libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp b/libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp
index 9e00a57ba80c631..8884941fee32345 100644
--- a/libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp
+++ b/libcxx/test/std/library/description/conventions/customization.point.object/niebloid.compile.pass.cpp
@@ -65,6 +65,7 @@ static_assert(test(std::ranges::all_of, a, odd));
 static_assert(test(std::ranges::any_of, a, odd));
 static_assert(test(std::ranges::binary_search, a, 42));
 static_assert(test(std::ranges::clamp, 42, 42, 42));
+static_assert(test(std::ranges::contains, a, 42));
 static_assert(test(std::ranges::copy, a, a));
 static_assert(test(std::ranges::copy_backward, a, a));
 static_assert(test(std::ranges::copy_if, a, a, odd));

>From 80c08f6f2f86ae650ef0cbbc5d4a5f5ce39e0916 Mon Sep 17 00:00:00 2001
From: zijunzhao <zijunzhao at google.com>
Date: Thu, 31 Aug 2023 20:08:32 +0000
Subject: [PATCH 2/7] [libc++] Implement ranges::contains

Differential Revision: https://reviews.llvm.org/D159232
---
 libcxx/include/__algorithm/ranges_contains.h                  | 1 +
 .../alg.nonmodifying/alg.contains/ranges.contains.pass.cpp    | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/libcxx/include/__algorithm/ranges_contains.h b/libcxx/include/__algorithm/ranges_contains.h
index 647b7ea34be3421..018d362900e3949 100644
--- a/libcxx/include/__algorithm/ranges_contains.h
+++ b/libcxx/include/__algorithm/ranges_contains.h
@@ -48,6 +48,7 @@ struct __fn {
   }
 };
 } // namespace __contains
+
 inline namespace __cpo {
 inline constexpr auto contains = __contains::__fn{};
 } // namespace __cpo
diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
index 8e67e971c2f040b..a0c4acb08f5c92a 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -9,6 +9,7 @@
 // <algorithm>
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
+
 // template<input_iterator I, sentinel_for<I> S, class T, class Proj = identity>
 //     requires indirect_binary_predicate<ranges::equal_to, projected<I, Proj>, const T*>
 //     constexpr bool ranges::contains(I first, S last, const T& value, Proj proj = {});       // since C++23
@@ -108,6 +109,7 @@ constexpr void test_iterators() {
   if (!std::is_constant_evaluated())
     comparable_data.clear();
 }
+
 template <class ElementT>
 class TriviallyComparable {
   ElementT el_;
@@ -160,7 +162,7 @@ constexpr bool test() {
       assert(projection_count == 3);
     }
     {
-      int a[] ={1, 9, 0, 13, 25};
+      int a[] = {1, 9, 0, 13, 25};
       int projection_count = 0;
       auto range = std::ranges::subrange(a, a + 5);
       auto ret = std::ranges::contains(range, 0, [&](int i) { ++projection_count; return i; });

>From 34d8e29a0c9c6bd11d8d0ba1433015d8d22f0c4a Mon Sep 17 00:00:00 2001
From: zijunzhao <zijunzhao at google.com>
Date: Thu, 31 Aug 2023 20:08:32 +0000
Subject: [PATCH 3/7] [libc++] Implement ranges::contains

Differential Revision: https://reviews.llvm.org/D159232
---
 .../alg.contains/ranges.contains.pass.cpp     | 92 +++++++++++++------
 1 file changed, 65 insertions(+), 27 deletions(-)

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
index a0c4acb08f5c92a..b4c879bbc8ee26c 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -40,15 +40,17 @@ static_assert(!HasContainsIt<InputIteratorNotIndirectlyReadable>);
 static_assert(!HasContainsIt<InputIteratorNotInputOrOutputIterator>);
 static_assert(!HasContainsIt<cpp20_input_iterator<int*>, SentinelForNotSemiregular>);
 static_assert(!HasContainsIt<cpp20_input_iterator<int*>, InputRangeNotSentinelEqualityComparableWith>);
+static_assert(!HasContainsIt<cpp20_input_iterator<int*>, sentinel_wrapper<cpp20_input_iterator<int*>>>);
 
 static_assert(!HasContainsIt<int*, int>);
 static_assert(!HasContainsIt<int, int*>);
+static_assert(HasContainsIt<int*, int*>);
 
 template <class Range, class ValT>
-concept HasContainsR = requires(Range range) { std::ranges::contains(range, ValT{}); };
+concept HasContainsR = requires(Range&& range) { std::ranges::contains(std::forward<Range>(range), ValT{}); };
 
-static_assert(HasContainsR<std::array<int, 1>, int>);
 static_assert(!HasContainsR<int, int>);
+static_assert(HasContainsR<std::array<int, 1>, int>);
 static_assert(!HasContainsR<std::array<NotEqualityComparable, 1>, NotEqualityComparable>);
 static_assert(!HasContainsR<InputRangeNotDerivedFrom, int>);
 static_assert(!HasContainsR<InputRangeNotIndirectlyReadable, int>);
@@ -63,45 +65,81 @@ template <class Iter, class Sent = Iter>
 constexpr void test_iterators() {
   using ValueT = std::iter_value_t<Iter>;
   {  // simple tests
+    ValueT a[] = {1, 2, 3, 4, 5, 6};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 6)));
     {
-      ValueT a[] = {1, 2, 3, 4, 5, 6};
-      std::same_as<bool> auto ret =
-        std::ranges::contains(Iter(a), Sent(Iter(a + 6)), 3);
+      [[maybe_unused]] std::same_as<bool> decltype(auto) ret =
+        std::ranges::contains(whole.begin(), whole.end(), 3);
       assert(ret);
     }
     {
-      ValueT a[] = {1, 2, 3, 4, 5, 6};
-      auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 6)));
-      std::same_as<bool> decltype(auto) ret =
-        std::ranges::contains(range, 3);
+      [[maybe_unused]] std::same_as<bool> decltype(auto) ret =
+        std::ranges::contains(whole, 3);
+      assert(ret);
+    }
+  }
+
+  { // check that a range with a single element works
+    ValueT a[] = {32};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 1)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 32);
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 32);
       assert(ret);
     }
   }
 
   { // check that an empty range works
+    ValueT a[] = {};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a)));
     {
-      ValueT a[] = {};
-      auto ret = std::ranges::contains(Iter(a), Sent(Iter(a)), 1);
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 1);
       assert(!ret);
     }
     {
-      ValueT a[] = {};
-      auto range = std::ranges::subrange(Iter(a), Sent(Iter(a)));
-      auto ret = std::ranges::contains(range, 1);
+      bool ret = std::ranges::contains(whole, 1);
       assert(!ret);
     }
   }
 
-  { // check that no match
+  { // check that the first element matches
+    ValueT a[] = {32, 3, 2, 1, 0, 23, 21, 9, 40, 100};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 10)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 32);
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 32);
+      assert(ret);
+    }
+  }
+
+  { // check that the last element matches
+    ValueT a[] = {3, 22, 1, 43, 99, 0, 56, 100, 32};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 9)));
+    {
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 32);
+      assert(ret);
+    }
+    {
+      bool ret = std::ranges::contains(whole, 32);
+      assert(ret);
+    }
+  }
+
+  { // no match
+    ValueT a[] = {13, 1, 21, 4, 5};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 5)));
     {
-      ValueT a[] = {13, 1, 21, 4, 5};
-      auto ret = std::ranges::contains(Iter(a), Sent(Iter(a + 5)), 10);
+      bool ret = std::ranges::contains(whole.begin(), whole.end(), 10);
       assert(!ret);
     }
     {
-      ValueT a[] = {13, 1, 21, 4, 5};
-      auto range = std::ranges::subrange(Iter(a), Sent(Iter(a + 5)));
-      auto ret = std::ranges::contains(range, 10);
+      bool ret = std::ranges::contains(whole, 10);
       assert(!ret);
     }
   }
@@ -115,7 +153,7 @@ class TriviallyComparable {
   ElementT el_;
 
 public:
-  TEST_CONSTEXPR TriviallyComparable(ElementT el) : el_(el) {}
+  constexpr TriviallyComparable(ElementT el) : el_(el) {}
   bool operator==(const TriviallyComparable&) const = default;
 };
 
@@ -152,20 +190,20 @@ constexpr bool test() {
                   });
 
   {
+    int a[] = {1, 9, 0, 13, 25};
+    int projection_count = 0;
     // count invocations of the projection
     {
-      int a[] = {1, 9, 0, 13, 25};
-      int projection_count = 0;
-      auto ret = std::ranges::contains(a, a + 5, 0,
+      projection_count = 0;
+      bool ret = std::ranges::contains(a, a + 5, 0,
                                 [&](int i) { ++projection_count; return i; });
       assert(ret);
       assert(projection_count == 3);
     }
     {
-      int a[] = {1, 9, 0, 13, 25};
-      int projection_count = 0;
+      projection_count = 0;
       auto range = std::ranges::subrange(a, a + 5);
-      auto ret = std::ranges::contains(range, 0, [&](int i) { ++projection_count; return i; });
+      bool ret = std::ranges::contains(range, 0, [&](int i) { ++projection_count; return i; });
       assert(ret);
       assert(projection_count == 3);
     }

>From 9db49ddab25affcd7c05d0c825ec2788dd53e5b5 Mon Sep 17 00:00:00 2001
From: zijunzhao <zijunzhao at google.com>
Date: Thu, 31 Aug 2023 20:08:32 +0000
Subject: [PATCH 4/7] [libc++] Implement ranges::contains

Differential Revision: https://reviews.llvm.org/D159232
---
 .../alg.nonmodifying/alg.contains/ranges.contains.pass.cpp       | 1 -
 1 file changed, 1 deletion(-)

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
index b4c879bbc8ee26c..29a686a1ae8eede 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -194,7 +194,6 @@ constexpr bool test() {
     int projection_count = 0;
     // count invocations of the projection
     {
-      projection_count = 0;
       bool ret = std::ranges::contains(a, a + 5, 0,
                                 [&](int i) { ++projection_count; return i; });
       assert(ret);

>From 54bccdd7677000ae6d90bc0fc9790d9c2c69602b Mon Sep 17 00:00:00 2001
From: zijunzhao <zijunzhao at google.com>
Date: Thu, 31 Aug 2023 20:08:32 +0000
Subject: [PATCH 5/7] [libc++] Implement ranges::contains

Differential Revision: https://reviews.llvm.org/D159232
---
 .../alg.contains/ranges.contains.pass.cpp     | 23 +++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
index 29a686a1ae8eede..eb6567c786342a7 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -144,6 +144,29 @@ constexpr void test_iterators() {
     }
   }
 
+  { // check that the projections are used
+    int a[] = {1, 9, 0, 13, 25};
+    {
+      bool ret = std::ranges::contains(a, a + 5, -13, [&](int i) { return i * -1; });
+      assert(ret);
+    }
+    {
+      auto range = std::ranges::subrange(a, a + 5);
+      bool ret = std::ranges::contains(range, -13, [&](int i) { return i * -1; });
+      assert(ret);
+    }
+  }
+
+  { // check the nodiscard extension
+    // use #pragma around to suppress error: ignoring return value of function
+    // declared with 'nodiscard' attribute [-Werror,-Wunused-result]
+    #pragma clang diagnostic push
+    #pragma clang diagnostic ignored "-Wunused-result"
+    int a[] = {1, 9, 0, 13, 25};
+    std::ranges::contains(a, a + 5, -13, [&](int i) { return i * -1; });
+    #pragma clang diagnostic pop
+  }
+
   if (!std::is_constant_evaluated())
     comparable_data.clear();
 }

>From 826bd982d734c23fbe95d79cb446b5bb50341f34 Mon Sep 17 00:00:00 2001
From: zijunzhao <zijunzhao at google.com>
Date: Thu, 31 Aug 2023 20:08:32 +0000
Subject: [PATCH 6/7] [libc++] Implement ranges::contains

Differential Revision: https://reviews.llvm.org/D159232
---
 .../alg.nonmodifying/alg.contains/ranges.contains.pass.cpp   | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
index eb6567c786342a7..9e079b7dc427239 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -162,8 +162,9 @@ constexpr void test_iterators() {
     // declared with 'nodiscard' attribute [-Werror,-Wunused-result]
     #pragma clang diagnostic push
     #pragma clang diagnostic ignored "-Wunused-result"
-    int a[] = {1, 9, 0, 13, 25};
-    std::ranges::contains(a, a + 5, -13, [&](int i) { return i * -1; });
+    ValueT a[] = {1, 9, 0, 13, 25};
+    auto whole = std::ranges::subrange(Iter(a), Sent(Iter(a + 5)));
+    std::ranges::contains(whole.begin(), whole.end(), 12);
     #pragma clang diagnostic pop
   }
 

>From 32cf818aa8a74e7d2c8e30892e463a09a5dca4d6 Mon Sep 17 00:00:00 2001
From: zijunzhao <zijunzhao at google.com>
Date: Thu, 31 Aug 2023 20:08:32 +0000
Subject: [PATCH 7/7] [libc++] Implement ranges::contains

Differential Revision: https://reviews.llvm.org/D159232
---
 .../alg.nonmodifying/alg.contains/ranges.contains.pass.cpp       | 1 -
 1 file changed, 1 deletion(-)

diff --git a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
index 9e079b7dc427239..f91641b4a6de498 100644
--- a/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
+++ b/libcxx/test/std/algorithms/alg.nonmodifying/alg.contains/ranges.contains.pass.cpp
@@ -60,7 +60,6 @@ static_assert(!HasContainsR<InputRangeNotSentinelEqualityComparableWith, int>);
 
 static std::vector<int> comparable_data;
 
-// clang-format off
 template <class Iter, class Sent = Iter>
 constexpr void test_iterators() {
   using ValueT = std::iter_value_t<Iter>;



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