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 // UNSUPPORTED: c++03, c++11, c++14, c++17
10 
11 // constexpr decltype(auto) operator*();
12 // constexpr decltype(auto) operator*() const
13 //   requires dereferenceable<const I>;
14 
15 #include <iterator>
16 
17 #include "test_macros.h"
18 #include "test_iterators.h"
19 
20 struct InputOrOutputArchetype {
21   using difference_type = int;
22 
23   int *ptr;
24 
25   constexpr int operator*() const { return *ptr; }
26   constexpr void operator++(int) { ++ptr; }
27   constexpr InputOrOutputArchetype& operator++() { ++ptr; return *this; }
28 };
29 
30 struct NonConstDeref {
31   using difference_type = int;
32 
33   int *ptr;
34 
35   constexpr int operator*() { return *ptr; }
36   constexpr void operator++(int) { ++ptr; }
37   constexpr NonConstDeref& operator++() { ++ptr; return *this; }
38 };
39 
40 template<class T>
41 concept IsDereferenceable = requires(T& i) {
42   *i;
43 };
44 
45 constexpr bool test() {
46   int buffer[8] = {1, 2, 3, 4, 5, 6, 7, 8};
47 
48   {
49     static_assert( IsDereferenceable<std::counted_iterator<InputOrOutputArchetype>>);
50     static_assert( IsDereferenceable<const std::counted_iterator<InputOrOutputArchetype>>);
51     static_assert( IsDereferenceable<std::counted_iterator<NonConstDeref>>);
52     static_assert(!IsDereferenceable<const std::counted_iterator<NonConstDeref>>);
53   }
54 
55   {
56     std::counted_iterator iter(cpp20_input_iterator<int*>{buffer}, 8);
57     for (int i = 1; i < 9; ++i, ++iter)
58       assert(*iter == i);
59   }
60 
61   {
62     std::counted_iterator iter(forward_iterator<int*>{buffer}, 8);
63     for (int i = 1; i < 9; ++i, ++iter)
64       assert(*iter == i);
65   }
66 
67   {
68     std::counted_iterator iter(contiguous_iterator<int*>{buffer}, 8);
69     for (int i = 1; i < 9; ++i, ++iter)
70       assert(*iter == i);
71   }
72 
73   {
74     std::counted_iterator iter(InputOrOutputArchetype{buffer}, 8);
75     for (int i = 1; i < 9; ++i, ++iter)
76       assert(*iter == i);
77   }
78 
79   {
80     const std::counted_iterator iter(cpp20_input_iterator<int*>{buffer}, 8);
81     assert(*iter == 1);
82   }
83 
84   {
85     const std::counted_iterator iter(forward_iterator<int*>{buffer + 1}, 7);
86     assert(*iter == 2);
87   }
88 
89   {
90     const std::counted_iterator iter(contiguous_iterator<int*>{buffer + 2}, 6);
91     assert(*iter == 3);
92   }
93 
94   {
95     const std::counted_iterator iter(InputOrOutputArchetype{buffer + 2}, 6);
96     assert(*iter == 3);
97   }
98 
99   return true;
100 }
101 
102 int main(int, char**) {
103   test();
104   static_assert(test());
105 
106   return 0;
107 }
108