libcxx/test/std/strings/basic.string/string.cons/iter_alloc_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 InputIterator,
  13 //      class Allocator = allocator<typename iterator_traits<InputIterator>::value_type>>
  14 //  basic_string(InputIterator, InputIterator, Allocator = Allocator())
  15 //    -> basic_string<typename iterator_traits<InputIterator>::value_type,
  16 //                 char_traits<typename iterator_traits<InputIterator>::value_type>,
  17 //                 Allocator>; // constexpr since C++20
  18 //
  19 //  The deduction guide shall not participate in overload resolution if InputIterator
  20 //  is a type that does not qualify as an input iterator, or if Allocator is a type
  21 //  that does not qualify as an allocator.
  22
  23 #include <cassert>
  24 #include <cstddef>
  25 #include <iterator>
  26 #include <string>
  27 #include <type_traits>
  28
  29 #include "test_macros.h"
  30 #include "test_allocator.h"
  31 #include "min_allocator.h"
  32
  33 class NotAnIterator {};
  34 using NotAnInputIterator = std::back_insert_iterator<std::basic_string<char16_t>>;
  35
  36 template <typename T>
  37 struct NotAnAllocator {
  38   typedef T value_type;
  39 };
  40
  41 template <class Iter, class Alloc, class = void>
  42 struct CanDeduce : std::false_type {};
  43
  44 template <class Iter, class Alloc>
  45 struct CanDeduce<Iter,
  46                  Alloc,
  47                  decltype((void)std::basic_string{std::declval<Iter>(), std::declval<Iter>(), std::declval<Alloc>()})>
  48     : std::true_type {};
  49
  50 static_assert(CanDeduce<char*, std::allocator<char>>::value);
  51 static_assert(!CanDeduce<NotAnIterator, std::allocator<char>>::value);
  52 static_assert(!CanDeduce<NotAnInputIterator, std::allocator<char16_t>>::value);
  53 static_assert(!CanDeduce<char*, NotAnAllocator<char>>::value);
  54 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
  55 static_assert(CanDeduce<wchar_t*, std::allocator<wchar_t>>::value);
  56 static_assert(!CanDeduce<wchar_t const*, NotAnAllocator<wchar_t>>::value);
  57 #endif
  58
  59 TEST_CONSTEXPR_CXX20 bool test() {
  60   {
  61     const char* s = "12345678901234";
  62     std::basic_string s1(s, s + 10); // Can't use {} here
  63     using S = decltype(s1);          // what type did we get?
  64     static_assert(std::is_same_v<S::value_type, char>, "");
  65     static_assert(std::is_same_v<S::traits_type, std::char_traits<char>>, "");
  66     static_assert(std::is_same_v<S::allocator_type, std::allocator<char>>, "");
  67     assert(s1.size() == 10);
  68     assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
  69   }
  70   {
  71     const char* s = "12345678901234";
  72     std::basic_string s1{s, s + 10, std::allocator<char>{}};
  73     using S = decltype(s1); // what type did we get?
  74     static_assert(std::is_same_v<S::value_type, char>, "");
  75     static_assert(std::is_same_v<S::traits_type, std::char_traits<char>>, "");
  76     static_assert(std::is_same_v<S::allocator_type, std::allocator<char>>, "");
  77     assert(s1.size() == 10);
  78     assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
  79   }
  80 #ifndef TEST_HAS_NO_WIDE_CHARACTERS
  81   {
  82     const wchar_t* s = L"12345678901234";
  83     std::basic_string s1{s, s + 10, test_allocator<wchar_t>{}};
  84     using S = decltype(s1); // what type did we get?
  85     static_assert(std::is_same_v<S::value_type, wchar_t>, "");
  86     static_assert(std::is_same_v<S::traits_type, std::char_traits<wchar_t>>, "");
  87     static_assert(std::is_same_v<S::allocator_type, test_allocator<wchar_t>>, "");
  88     assert(s1.size() == 10);
  89     assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
  90   }
  91 #endif
  92   {
  93     const char16_t* s = u"12345678901234";
  94     std::basic_string s1{s, s + 10, min_allocator<char16_t>{}};
  95     using S = decltype(s1); // what type did we get?
  96     static_assert(std::is_same_v<S::value_type, char16_t>, "");
  97     static_assert(std::is_same_v<S::traits_type, std::char_traits<char16_t>>, "");
  98     static_assert(std::is_same_v<S::allocator_type, min_allocator<char16_t>>, "");
  99     assert(s1.size() == 10);
 100     assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
 101   }
 102   {
 103     const char32_t* s = U"12345678901234";
 104     std::basic_string s1{s, s + 10, explicit_allocator<char32_t>{}};
 105     using S = decltype(s1); // what type did we get?
 106     static_assert(std::is_same_v<S::value_type, char32_t>, "");
 107     static_assert(std::is_same_v<S::traits_type, std::char_traits<char32_t>>, "");
 108     static_assert(std::is_same_v<S::allocator_type, explicit_allocator<char32_t>>, "");
 109     assert(s1.size() == 10);
 110     assert(s1.compare(0, s1.size(), s, s1.size()) == 0);
 111   }
 112
 113   return true;
 114 }
 115
 116 int main(int, char**) {
 117   test();
 118 #if TEST_STD_VER > 17
 119   static_assert(test());
 120 #endif
 121
 122   return 0;
 123 }