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 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
11 
12 
13 // constexpr iterator_t<R> begin();
14 // constexpr sentinel_t<R> end();
15 // constexpr auto begin() const requires range<const R>;
16 // constexpr auto end() const requires range<const R>;
17 
18 #include <ranges>
19 
20 #include <array>
21 #include <cassert>
22 #include <concepts>
23 
24 #include "test_iterators.h"
25 #include "test_macros.h"
26 
27 struct Base {
28   constexpr int *begin() { return nullptr; }
29   constexpr auto end() { return sentinel_wrapper<int*>(nullptr); }
30   constexpr char *begin() const { return nullptr; }
31   constexpr auto end() const { return sentinel_wrapper<char*>(nullptr); }
32 };
33 static_assert(std::same_as<std::ranges::iterator_t<Base>, int*>);
34 static_assert(std::same_as<std::ranges::sentinel_t<Base>, sentinel_wrapper<int*>>);
35 static_assert(std::same_as<std::ranges::iterator_t<const Base>, char*>);
36 static_assert(std::same_as<std::ranges::sentinel_t<const Base>, sentinel_wrapper<char*>>);
37 
38 struct NoConst {
39   int* begin();
40   sentinel_wrapper<int*> end();
41 };
42 
43 struct DecayChecker {
44   int*& begin() const;
45   int*& end() const;
46 };
47 
48 template <class T>
49 concept HasBegin = requires (T t) {
50   t.begin();
51 };
52 
53 template <class T>
54 concept HasEnd = requires (T t) {
55   t.end();
56 };
57 
58 constexpr bool test()
59 {
60   {
61     using OwningView = std::ranges::owning_view<Base>;
62     OwningView ov;
63     std::same_as<int*> decltype(auto) b1 = static_cast<OwningView&>(ov).begin();
64     std::same_as<int*> decltype(auto) b2 = static_cast<OwningView&&>(ov).begin();
65     std::same_as<char*> decltype(auto) b3 = static_cast<const OwningView&>(ov).begin();
66     std::same_as<char*> decltype(auto) b4 = static_cast<const OwningView&&>(ov).begin();
67 
68     std::same_as<sentinel_wrapper<int*>> decltype(auto) e1 = static_cast<OwningView&>(ov).end();
69     std::same_as<sentinel_wrapper<int*>> decltype(auto) e2 = static_cast<OwningView&&>(ov).end();
70     std::same_as<sentinel_wrapper<char*>> decltype(auto) e3 = static_cast<const OwningView&>(ov).end();
71     std::same_as<sentinel_wrapper<char*>> decltype(auto) e4 = static_cast<const OwningView&&>(ov).end();
72 
73     assert(b1 == e1);
74     assert(b2 == e2);
75     assert(b3 == e3);
76     assert(b4 == e4);
77   }
78   {
79     // NoConst has non-const begin() and end(); so does the owning_view.
80     using OwningView = std::ranges::owning_view<NoConst>;
81     static_assert(HasBegin<OwningView&>);
82     static_assert(HasBegin<OwningView&&>);
83     static_assert(!HasBegin<const OwningView&>);
84     static_assert(!HasBegin<const OwningView&&>);
85     static_assert(HasEnd<OwningView&>);
86     static_assert(HasEnd<OwningView&&>);
87     static_assert(!HasEnd<const OwningView&>);
88     static_assert(!HasEnd<const OwningView&&>);
89   }
90   {
91     // DecayChecker's begin() and end() return references; make sure the owning_view decays them.
92     using OwningView = std::ranges::owning_view<DecayChecker>;
93     OwningView ov;
94     ASSERT_SAME_TYPE(decltype(ov.begin()), int*);
95     ASSERT_SAME_TYPE(decltype(ov.end()), int*);
96   }
97   {
98     // Test an empty view.
99     int a[] = {1};
100     auto ov = std::ranges::owning_view(std::ranges::subrange(a, a));
101     assert(ov.begin() == a);
102     assert(std::as_const(ov).begin() == a);
103     assert(ov.end() == a);
104     assert(std::as_const(ov).end() == a);
105   }
106   {
107     // Test a non-empty view.
108     int a[] = {1};
109     auto ov = std::ranges::owning_view(std::ranges::subrange(a, a+1));
110     assert(ov.begin() == a);
111     assert(std::as_const(ov).begin() == a);
112     assert(ov.end() == a+1);
113     assert(std::as_const(ov).end() == a+1);
114   }
115   {
116     // Test a non-view.
117     std::array<int, 2> a = {1, 2};
118     auto ov = std::ranges::owning_view(std::move(a));
119     assert(std::to_address(ov.begin()) != std::to_address(a.begin())); // because it points into the copy
120     assert(std::to_address(std::as_const(ov).begin()) != std::to_address(a.begin()));
121     assert(std::to_address(ov.end()) != std::to_address(a.end()));
122     assert(std::to_address(std::as_const(ov).end()) != std::to_address(a.end()));
123   }
124   return true;
125 }
126 
127 int main(int, char**) {
128   test();
129   static_assert(test());
130 
131   return 0;
132 }
133