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WIP [libc++][string] P3044R2: sub-string_view from string
Implements [P3044R2](https://wg21.link/P3044R2) - cplusplus/draft#7975
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-125
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5 files changed

+208
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lines changed

‎libcxx/include/string

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@@ -280,6 +280,8 @@ public:
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basic_string substr(size_type pos = 0, size_type n = npos) const; // constexpr in C++20, removed in C++23
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basic_string substr(size_type pos = 0, size_type n = npos) const&; // since C++23
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constexpr basic_string substr(size_type pos = 0, size_type n = npos) &&; // since C++23
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constexpr basic_string_view<charT, traits> subview(size_type pos = 0,
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size_type n = npos) const; // since C++26
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void swap(basic_string& str)
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noexcept(allocator_traits<allocator_type>::propagate_on_container_swap::value ||
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allocator_traits<allocator_type>::is_always_equal::value); // C++17, constexpr since C++20
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}
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# endif
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# if _LIBCPP_STD_VER >= 26
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_LIBCPP_HIDE_FROM_ABI constexpr basic_string_view<_CharT, _Traits>
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subview(size_type __pos = 0, size_type __n = npos) const {
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return basic_string_view<_CharT, _Traits>(*this).subview(__pos, __n);
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}
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# endif
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_LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 void swap(basic_string& __str)
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# if _LIBCPP_STD_VER >= 14
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_NOEXCEPT;

‎libcxx/include/string_view

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@@ -130,6 +130,8 @@ namespace std {
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size_type copy(charT* s, size_type n, size_type pos = 0) const; // constexpr in C++20
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constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
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constexpr basic_string_view subview(size_type pos = 0,
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size_type n = npos) const; // freestanding-deleted, since C++26
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constexpr int compare(basic_string_view s) const noexcept;
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constexpr int compare(size_type pos1, size_type n1, basic_string_view s) const;
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constexpr int compare(size_type pos1, size_type n1,
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: basic_string_view(__assume_valid(), data() + __pos, std::min(__n, size() - __pos));
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}
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# if _LIBCPP_STD_VER >= 26
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_LIBCPP_HIDE_FROM_ABI constexpr basic_string_view subview(size_type __pos = 0, size_type __n = npos) const {
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return this->substr(__pos, __n);
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}
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# endif
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_LIBCPP_CONSTEXPR_SINCE_CXX14 int compare(basic_string_view __sv) const _NOEXCEPT {
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size_type __rlen = std::min(size(), __sv.size());
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int __retval = _Traits::compare(data(), __sv.data(), __rlen);

‎libcxx/test/std/strings/basic.string/string.ops/string_substr/subview.pass.cpp

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// REQUIRES: std-at-least-c++26
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// <string>
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// constexpr basic_string_view<_CharT, _Traits> subview(size_type __pos = 0, size_type __n = npos) const;
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#include <cassert>
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#include <string>
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constexpr bool test() {
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std::string s{"Hello cruel world!"};
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auto sub = s.subview(6);
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assert(sub == "cruel world!");
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auto subsub = sub.subview(0, 5);
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assert(subsub == "cruel");
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return true;
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}
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int main(int, char**) {
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test();
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static_assert(test());
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return 0;
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}

‎libcxx/test/std/strings/string.view/string.view.ops/substr.pass.cpp

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This file was deleted.

‎libcxx/test/std/strings/string.view/string.view.ops/substr_subview.pass.cpp

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// UNSUPPORTED: !stdlib=libc++ && (c++03 || c++11 || c++14)
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// <string_view>
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// constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
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// constexpr basic_string_view subview(size_type pos = 0,
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// size_type n = npos) const; // freestanding-deleted
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// subview is alternative name of substr
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// Throws: out_of_range if pos > size().
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// Effects: Determines the effective length rlen of the string to reference as the smaller of n and size() - pos.
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// Returns: basic_string_view(data()+pos, rlen).
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#include <algorithm>
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#include <cassert>
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#include <cstddef>
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#include <stdexcept>
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#include <string_view>
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#include "test_macros.h"
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template <typename CharT>
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struct Test {
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typedef std::basic_string_view<CharT> (std::basic_string_view<CharT>::*Sub)(
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typename std::basic_string_view<CharT>::size_type, typename std::basic_string_view<CharT>::size_type) const;
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};
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template <typename CharT>
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void testDetail(std::basic_string_view<CharT> sv, typename Test<CharT>::Sub testSub, std::size_t n, size_t pos) {
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(void)testSub; // Avoid unused parameter warning
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std::basic_string_view<CharT> sv1;
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#ifdef TEST_HAS_NO_EXCEPTIONS
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if (pos > sv.size())
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return; // would throw if exceptions were enabled
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sv1 = (sv.*testSub)(pos, n);
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#else
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try {
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sv1 = (sv.*testSub)(pos, n);
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assert(pos <= sv.size());
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} catch (const std::out_of_range&) {
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assert(pos > sv.size());
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return;
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}
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#endif
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const std::size_t rlen = std::min(n, sv.size() - pos);
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assert(sv1.size() == rlen);
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for (std::size_t i = 0; i < rlen; ++i)
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assert(sv[pos + i] == sv1[i]);
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}
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template <typename CharT>
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void testCases(std::basic_string_view<CharT> sv, typename Test<CharT>::Sub testSub) {
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testDetail(sv, testSub, 0, 0);
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testDetail(sv, testSub, 1, 0);
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testDetail(sv, testSub, 20, 0);
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testDetail(sv, testSub, sv.size(), 0);
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testDetail(sv, testSub, 100, 3);
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testDetail(sv, testSub, 0, std::basic_string_view<CharT>::npos);
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testDetail(sv, testSub, 2, std::basic_string_view<CharT>::npos);
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testDetail(sv, testSub, sv.size(), std::basic_string_view<CharT>::npos);
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testDetail(sv, testSub, sv.size() + 1, 0);
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testDetail(sv, testSub, sv.size() + 1, 1);
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testDetail(sv, testSub, sv.size() + 1, std::basic_string_view<CharT>::npos);
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}
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template <typename CharT>
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void testSubs(const CharT* s) {
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std::basic_string_view<CharT> sv(s);
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testCases(sv, &std::basic_string_view<CharT>::substr);
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#if TEST_STD_VER >= 26
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testCases(sv, &std::basic_string_view<CharT>::subview);
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#endif // TEST_STD_VER >= 26
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}
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void test() {
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testSubs("ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE");
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testSubs("ABCDE");
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testSubs("a");
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testSubs("");
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#ifndef TEST_HAS_NO_WIDE_CHARACTERS
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testSubs(
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L"ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE");
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testSubs(L"ABCDE");
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testSubs(L"a");
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testSubs(L"");
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#endif
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#if TEST_STD_VER >= 11
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testSubs(
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u"ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE");
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testSubs(u"ABCDE");
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testSubs(u"a");
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testSubs(u"");
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testSubs(
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U"ABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDEABCDE");
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testSubs(U"ABCDE");
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testSubs(U"a");
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testSubs(U"");
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#endif
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}
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#if TEST_STD_VER >= 14
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template <typename Test<char>::Sub TestSub>
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constexpr void testConstexprDetail() {
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constexpr std::string_view sv{"ABCDE", 5};
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{
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constexpr std::string_view sv2 = (sv.*TestSub)(0, 3);
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static_assert(sv2.size() == 3, "");
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static_assert(sv2[0] == 'A', "");
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static_assert(sv2[1] == 'B', "");
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static_assert(sv2[2] == 'C', "");
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}
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{
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constexpr std::string_view sv2 = (sv.*TestSub)(3, 0);
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static_assert(sv2.size() == 0, "");
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}
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{
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constexpr std::string_view sv2 = (sv.*TestSub)(3, 3);
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static_assert(sv2.size() == 2, "");
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static_assert(sv2[0] == 'D', "");
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static_assert(sv2[1] == 'E', "");
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}
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}
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void test_constexpr() {
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testConstexprDetail<&std::string_view::substr>();
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# if TEST_STD_VER >= 26
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testConstexprDetail<&std::string_view::subview>();
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# endif
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}
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#endif
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int main(int, char**) {
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test();
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#if TEST_STD_VER >= 14
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test_constexpr();
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#endif
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return 0;
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}

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