libcxx/test/std/strings/basic.string/string.cons/string_view_deduction.pass.cpp

   1 //===----------------------------------------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 // <string>
  10 // UNSUPPORTED: c++03, c++11, c++14
  11
  12 // template<class charT,
  13 //          class traits,
  14 //          class Allocator = allocator<charT>
  15 //          >
  16 // basic_string(basic_string_view<charT, traits>, const Allocator& = Allocator())
  17 //   -> basic_string<charT, traits, Allocator>;
  18 //
  19 //  The deduction guide shall not participate in overload resolution if Allocator
  20 //  is a type that does not qualify as an allocator.
  21
  22 #include <string>
  23 #include <string_view>
  24 #include <iterator>
  25 #include <memory>
  26 #include <type_traits>
  27 #include <cassert>
  28 #include <cstddef>
  29
  30 #include "test_macros.h"
  31 #include "test_allocator.h"
  32 #include "min_allocator.h"
  33
  34 template <class StringView, class Allocator, class = void>
  35 struct CanDeduce : std::false_type {};
  36
  37 template <class StringView, class Allocator>
  38 struct CanDeduce<StringView,
  39                  Allocator,
  40                  decltype((void)std::basic_string{std::declval<StringView>(), std::declval<Allocator>()})>
  41     : std::true_type {};
  42
  43 struct NotAnAllocator {};
  44 static_assert(CanDeduce<std::string_view, std::allocator<char>>::value);
  45 static_assert(!CanDeduce<std::string_view, NotAnAllocator>::value);
  46
  47 TEST_CONSTEXPR_CXX20 bool test() {
  48   {
  49     std::string_view sv = "12345678901234";
  50     std::basic_string s1(sv);
  51     using S = decltype(s1); // what type did we get?
  52     static_assert(std::is_same_v<S::value_type, char>, "");
  53     static_assert(std::is_same_v<S::traits_type, std::char_traits<char>>, "");
  54     static_assert(std::is_same_v<S::allocator_type, std::allocator<char>>, "");
  55     assert(s1.size() == sv.size());
  56     assert(s1.compare(0, s1.size(), sv.data(), s1.size()) == 0);
  57   }
  58
  59   {
  60     std::string_view sv = "12345678901234";
  61     std::basic_string s1{sv, std::allocator<char>{}};
  62     using S = decltype(s1); // what type did we get?
  63     static_assert(std::is_same_v<S::value_type, char>, "");
  64     static_assert(std::is_same_v<S::traits_type, std::char_traits<char>>, "");
  65     static_assert(std::is_same_v<S::allocator_type, std::allocator<char>>, "");
  66     assert(s1.size() == sv.size());
  67     assert(s1.compare(0, s1.size(), sv.data(), s1.size()) == 0);
  68   }
  69 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
  70   {
  71     std::wstring_view sv = L"12345678901234";
  72     std::basic_string s1{sv, test_allocator<wchar_t>{}};
  73     using S = decltype(s1); // what type did we get?
  74     static_assert(std::is_same_v<S::value_type, wchar_t>, "");
  75     static_assert(std::is_same_v<S::traits_type, std::char_traits<wchar_t>>, "");
  76     static_assert(std::is_same_v<S::allocator_type, test_allocator<wchar_t>>, "");
  77     assert(s1.size() == sv.size());
  78     assert(s1.compare(0, s1.size(), sv.data(), s1.size()) == 0);
  79   }
  80 #endif
  81 #ifndef TEST_HAS_NO_CHAR8_T
  82   {
  83     std::u8string_view sv = u8"12345678901234";
  84     std::basic_string s1{sv, min_allocator<char8_t>{}};
  85     using S = decltype(s1); // what type did we get?
  86     static_assert(std::is_same_v<S::value_type, char8_t>, "");
  87     static_assert(std::is_same_v<S::traits_type, std::char_traits<char8_t>>, "");
  88     static_assert(std::is_same_v<S::allocator_type, min_allocator<char8_t>>, "");
  89     assert(s1.size() == sv.size());
  90     assert(s1.compare(0, s1.size(), sv.data(), s1.size()) == 0);
  91   }
  92 #endif
  93   {
  94     std::u16string_view sv = u"12345678901234";
  95     std::basic_string s1{sv, min_allocator<char16_t>{}};
  96     using S = decltype(s1); // what type did we get?
  97     static_assert(std::is_same_v<S::value_type, char16_t>, "");
  98     static_assert(std::is_same_v<S::traits_type, std::char_traits<char16_t>>, "");
  99     static_assert(std::is_same_v<S::allocator_type, min_allocator<char16_t>>, "");
 100     assert(s1.size() == sv.size());
 101     assert(s1.compare(0, s1.size(), sv.data(), s1.size()) == 0);
 102   }
 103   {
 104     std::u32string_view sv = U"12345678901234";
 105     std::basic_string s1{sv, explicit_allocator<char32_t>{}};
 106     using S = decltype(s1); // what type did we get?
 107     static_assert(std::is_same_v<S::value_type, char32_t>, "");
 108     static_assert(std::is_same_v<S::traits_type, std::char_traits<char32_t>>, "");
 109     static_assert(std::is_same_v<S::allocator_type, explicit_allocator<char32_t>>, "");
 110     assert(s1.size() == sv.size());
 111     assert(s1.compare(0, s1.size(), sv.data(), s1.size()) == 0);
 112   }
 113
 114   return true;
 115 }
 116
 117 int main(int, char**) {
 118   test();
 119 #if TEST_STD_VER > 17
 120   static_assert(test());
 121 #endif
 122
 123   return 0;
 124 }