[libcxx-commits] [libcxx] [libc++][sstream] P2495R3: Interfacing `stringstream`s with `string_view` (PR #80552)

[Mark de Wever via libcxx-commits]

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@@ -0,0 +1,145 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+
+// <sstream>
+
+// template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT>>
+// class basic_stringstream
+
+// template<class T>
+//   basic_istringstream(const T& t, ios_base::openmode which, const Allocator& a);
+
+#include <cassert>
+#include <concepts>
+#include <sstream>
+#include <string>
+#include <string_view>
+
+#include "make_string.h"
+#include "test_allocator.h"
+#include "test_convertible.h"
+#include "test_macros.h"
+
+template <typename CharT>
+void test_sfinae() {
+  struct SomeObject {};
+  struct NonAllocator {};
+
+  // `const CharT*`
+  static_assert(std::constructible_from<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                        const CharT*,
+                                        test_allocator<CharT>>);
+  static_assert(test_convertible<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                 const CharT*,
+                                 std::ios_base::openmode,
+                                 const test_allocator<CharT>>());
+  // `std::basic_string_view<CharT>`
+  static_assert(std::constructible_from<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                        std::basic_string_view<CharT>,
+                                        std::ios_base::openmode,
+                                        test_allocator<CharT>>);
+  static_assert(test_convertible<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                 const std::basic_string_view<CharT>,
+                                 std::ios_base::openmode,
+                                 const test_allocator<CharT>>());
+  // `std::basic_string<CharT>`
+  static_assert(std::constructible_from<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                        const std::basic_string<CharT>,
+                                        std::ios_base::openmode,
+                                        const test_allocator<CharT>>);
+  static_assert(test_convertible<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                 const std::basic_string<CharT>,
+                                 std::ios_base::openmode,
+                                 const test_allocator<CharT>>());
+
+  // String-view-like
+  static_assert(
+      !std::constructible_from<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                               const int,
+                               std::ios_base::openmode,
+                               const test_allocator<CharT>>);
+  static_assert(!test_convertible<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                  const int,
+                                  std::ios_base::openmode,
+                                  const test_allocator<CharT>>());
+
+  static_assert(
+      !std::constructible_from<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                               const SomeObject,
+                               std::ios_base::openmode,
+                               const test_allocator<CharT>>);
+  static_assert(!test_convertible<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                  const SomeObject,
+                                  std::ios_base::openmode,
+                                  const test_allocator<CharT>>());
+
+  // Mode
+  static_assert(
+      !std::constructible_from<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                               const std::basic_string_view<CharT>,
+                               SomeObject,
+                               const NonAllocator>);
+  static_assert(!test_convertible<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                  const std::basic_string_view<CharT>,
+                                  SomeObject,
+                                  const NonAllocator>());
+
+  // Allocator
+  static_assert(
+      !std::constructible_from<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                               const std::basic_string_view<CharT>,
+                               std::ios_base::openmode,
+                               const NonAllocator>);
+  static_assert(!test_convertible<std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>>,
+                                  const std::basic_string_view<CharT>,
+                                  std::ios_base::openmode,
+                                  const NonAllocator>());
+}
+
+#define CS(S) MAKE_CSTRING(CharT, S)
+#define ST(S) MAKE_STRING(CharT, S)
+#define SV(S) MAKE_STRING_VIEW(CharT, S)
+
+template <class CharT>
+static void test() {
+  const test_allocator<CharT> ca;
+
+  // const CharT*
+  {
+    std::basic_istringstream<CharT, std::char_traits<CharT>, test_allocator<CharT>> ss(
+        CS("zmt"), std::ios_base::binary, ca);
+    assert(ss.str() == CS("zmt"));
+    assert(ss.rdbuf()->get_allocator() == ca);
+  }
+  // std::basic_string_view<CharT>
+  {
+    const auto csv = SV("zmt");
----------------
mordante wrote:

please don't use `auto` here, it does not really help to make the code more readable.

https://github.com/llvm/llvm-project/pull/80552