[libc++][P1679] add string contains

C++23 string contains implementation and tests

Paper: https://wg21.link/P1679R3
Standard (string): https://eel.is/c++draft/string.contains
Standard (string_view): https://eel.is/c++draft/string.view.ops#lib:contains,basic_string_view

Differential Revision: https://reviews.llvm.org/D93912

1 files changed, 44 insertions, 0 deletions

diff --git a/libcxx/test/std/strings/string.view/string.view.template/contains.char.pass.cpp b/libcxx/test/std/strings/string.view/string.view.template/contains.char.pass.cpp
new file mode 100644
index 000000000000..658e10d21182
--- /dev/null
+++ b/libcxx/test/std/strings/string.view/string.view.template/contains.char.pass.cpp
@@ -0,0 +1,44 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++2a
+
+// <string_view>
+
+//   constexpr bool contains(charT x) const noexcept;
+
+#include <string_view>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool test()
+{
+    using SV = std::string_view;
+
+    SV sv1 {};
+    SV sv2 {"abcde", 5};
+
+    ASSERT_NOEXCEPT(sv1.contains('e'));
+
+    assert(!sv1.contains('c'));
+    assert(!sv1.contains('e'));
+    assert(!sv1.contains('x'));
+    assert( sv2.contains('c'));
+    assert( sv2.contains('e'));
+    assert(!sv2.contains('x'));
+
+    return true;
+}
+
+int main(int, char**)
+{
+    test();
+    static_assert(test());
+
+    return 0;
+}