[libcxx-commits] [libcxx] [libc++][strings] P2591R5: Concatenation of strings and string views (PR #88389)

[Mark de Wever via libcxx-commits]

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@@ -0,0 +1,155 @@
+//===----------------------------------------------------------------------===//
+//
+// 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++20, c++23
+
+// <string>
+
+// [string.op.plus]
+//
+// template<class charT, class traits, class Allocator>
+//   constexpr basic_string<charT, traits, Allocator>
+//     operator+(const basic_string<charT, traits, Allocator>& lhs,
+//               type_identity_t<basic_string_view<charT, traits>> rhs);                           // Since C++26
+// template<class charT, class traits, class Allocator>
+//   constexpr basic_string<charT, traits, Allocator>
+//     operator+(basic_string<charT, traits, Allocator>&& lhs,
+//               type_identity_t<basic_string_view<charT, traits>> rhs);                           // Since C++26
+// template<class charT, class traits, class Allocator>
+//   constexpr basic_string<charT, traits, Allocator>
+//     operator+(type_identity_t<basic_string_view<charT, traits>> lhs,
+//               const basic_string<charT, traits, Allocator>& rhs);                               // Since C++26
+// template<class charT, class traits, class Allocator>
+//   constexpr basic_string<charT, traits, Allocator>
+//     operator+(type_identity_t<basic_string_view<charT, traits>> lhs,
+//               basic_string<charT, traits, Allocator>&& rhs);                                    // Since C++26
+
+#include <cassert>
+#include <concepts>
+#include <string>
+#include <utility>
+
+#include "asan_testing.h"
+#include "constexpr_char_traits.h"
+#include "make_string.h"
+#include "min_allocator.h"
+#include "test_macros.h"
+
+#define CS(S) MAKE_CSTRING(CharT, S)
+#define ST(S, a) std::basic_string<CharT, TraitsT, AllocT>(MAKE_CSTRING(CharT, S), MKSTR_LEN(CharT, S), a)
+#define SV(S) std::basic_string_view<CharT, TraitsT>(MAKE_CSTRING(CharT, S), MKSTR_LEN(CharT, S))
+
+template <typename CharT, typename TraitsT, typename AllocT>
+constexpr void test(const CharT* x, const CharT* y, const CharT* expected) {
+  AllocT allocator;
+
+  // string& + string_view
+  {
+    std::basic_string<CharT, TraitsT, AllocT> st{x, allocator};
+    std::basic_string_view<CharT, TraitsT> sv{y};
+
+    std::same_as<std::basic_string<CharT, TraitsT, AllocT>> decltype(auto) result = st + sv;
+    assert(result == expected);
+    assert(result.get_allocator() == allocator);
+    LIBCPP_ASSERT(is_string_asan_correct(st + sv));
+  }
+  // const string& + string_view
+  {
+    const std::basic_string<CharT, TraitsT, AllocT> st{x, allocator};
+    std::basic_string_view<CharT, TraitsT> sv{y};
+
+    std::same_as<std::basic_string<CharT, TraitsT, AllocT>> decltype(auto) result = st + sv;
+    assert(result == expected);
+    assert(result.get_allocator() == allocator);
+    LIBCPP_ASSERT(is_string_asan_correct(st + sv));
+  }
+  // string&& + string_view
+  {
+    std::basic_string<CharT, TraitsT, AllocT> st{x, allocator};
+    std::basic_string_view<CharT, TraitsT> sv{y};
+
+    std::same_as<std::basic_string<CharT, TraitsT, AllocT>> decltype(auto) result = std::move(st) + sv;
+    assert(result == expected);
+    assert(result.get_allocator() == allocator);
+    LIBCPP_ASSERT(is_string_asan_correct(st + sv));
+  }
+  // string_view + string&
+  {
+    std::basic_string_view<CharT, TraitsT> sv{x};
+    std::basic_string<CharT, TraitsT, AllocT> st{y, allocator};
+
+    std::same_as<std::basic_string<CharT, TraitsT, AllocT>> decltype(auto) result = sv + st;
+    assert(result == expected);
+    assert(result.get_allocator() == allocator);
+    LIBCPP_ASSERT(is_string_asan_correct(sv + st));
+  }
+  // string_view + const string&
+  {
+    std::basic_string_view<CharT, TraitsT> sv{x};
+    const std::basic_string<CharT, TraitsT, AllocT> st{y, allocator};
+
+    std::same_as<std::basic_string<CharT, TraitsT, AllocT>> decltype(auto) result = sv + st;
+    assert(result == expected);
+    assert(result.get_allocator() == allocator);
+    LIBCPP_ASSERT(is_string_asan_correct(sv + st));
+  }
+  // string_view + string&&
+  {
+    std::basic_string_view<CharT, TraitsT> sv{x};
+    std::basic_string<CharT, TraitsT, AllocT> st{y, allocator};
+
+    std::same_as<std::basic_string<CharT, TraitsT, AllocT>> decltype(auto) result = sv + std::move(st);
+    assert(result == expected);
+    assert(result.get_allocator() == allocator);
+    LIBCPP_ASSERT(is_string_asan_correct(sv + st));
+  }
+}
+
+template <typename CharT, typename TraitsT = std::char_traits<CharT>, typename AllocT = std::allocator<CharT>>
+constexpr void test() {
+  // Concatinate with an empty `string`/`string_view`
+  test<CharT, TraitsT, AllocT>(CS(""), CS(""), CS(""));
+  test<CharT, TraitsT, AllocT>(CS(""), CS("short"), CS("short"));
+  test<CharT, TraitsT, AllocT>(CS(""), CS("not so short"), CS("not so short"));
+  test<CharT, TraitsT, AllocT>(CS(""), CS("this is a much longer string"), CS("this is a much longer string"));
+
+  test<CharT, TraitsT, AllocT>(CS(""), CS(""), CS(""));
+  test<CharT, TraitsT, AllocT>(CS("short"), CS(""), CS("short"));
+  test<CharT, TraitsT, AllocT>(CS("not so short"), CS(""), CS("not so short"));
+  test<CharT, TraitsT, AllocT>(CS("this is a much longer string"), CS(""), CS("this is a much longer string"));
+
+  // Non empty
+  test<CharT, TraitsT, AllocT>(CS("B"), CS("D"), CS("BD"));
+  test<CharT, TraitsT, AllocT>(CS("zmt94"), CS("+hkt82"), CS("zmt94+hkt82"));
+  test<CharT, TraitsT, AllocT>(CS("not so short"), CS("+is not bad"), CS("not so short+is not bad"));
+  test<CharT, TraitsT, AllocT>(
+      CS("this is a much longer string"),
+      CS("+which is so much better"),
+      CS("this is a much longer string+which is so much better"));
+}
+
+constexpr bool test() {
+  test<char, std::char_traits<char>>();
+  test<char, std::char_traits<char>, min_allocator<char>>();
+  test<char, std::char_traits<char>, safe_allocator<char>>();
+
+#ifndef TEST_HAS_NO_WIDE_CHARACTERS
+  test<wchar_t, std::char_traits<wchar_t>>();
+  test<wchar_t, std::char_traits<wchar_t>, min_allocator<wchar_t>>();
+  test<wchar_t, std::char_traits<wchar_t>, safe_allocator<wchar_t>>();
+#endif
----------------
mordante wrote:

Can you test with the following additional types `char8_t`, `char16_t`, and `char32_t`?
Maybe it would be good to have another layer of indirection with a templated function for  `class CharT` 

https://github.com/llvm/llvm-project/pull/88389