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 // constexpr auto begin();
13 // constexpr auto begin() const
14 //    requires input_­range<const V> &&
15 //             is_reference_v<range_reference_t<const V>>;
16 
17 #include <cassert>
18 #include <ranges>
19 
20 #include "types.h"
21 
22 struct NonSimpleParentView : std::ranges::view_base {
23   ChildView* begin() { return nullptr; }
24   const ChildView* begin() const;
25   const ChildView* end() const;
26 };
27 
28 struct SimpleParentView : std::ranges::view_base {
29   const ChildView* begin() const;
30   const ChildView* end() const;
31 };
32 
33 struct ConstNotRange : std::ranges::view_base {
34   const ChildView* begin();
35   const ChildView* end();
36 };
37 static_assert(std::ranges::range<ConstNotRange>);
38 static_assert(!std::ranges::range<const ConstNotRange>);
39 
40 template <class T>
41 concept HasConstBegin = requires(const T& t) { t.begin(); };
42 
43 constexpr bool test() {
44   int buffer[4][4] = {{1111, 2222, 3333, 4444}, {555, 666, 777, 888}, {99, 1010, 1111, 1212}, {13, 14, 15, 16}};
45 
46   {
47     ChildView children[4] = {ChildView(buffer[0]), ChildView(buffer[1]), ChildView(buffer[2]), ChildView(buffer[3])};
48     auto jv = std::ranges::join_view(ParentView{children});
49     assert(*jv.begin() == 1111);
50   }
51 
52   {
53     CopyableChild children[4] = {CopyableChild(buffer[0], 4), CopyableChild(buffer[1], 0), CopyableChild(buffer[2], 1),
54                                  CopyableChild(buffer[3], 0)};
55     auto jv = std::ranges::join_view(ParentView{children});
56     assert(*jv.begin() == 1111);
57   }
58 
59   // Parent is empty.
60   {
61     CopyableChild children[4] = {CopyableChild(buffer[0]), CopyableChild(buffer[1]), CopyableChild(buffer[2]),
62                                  CopyableChild(buffer[3])};
63     std::ranges::join_view jv(ParentView(children, 0));
64     assert(jv.begin() == jv.end());
65   }
66 
67   // Parent size is one.
68   {
69     CopyableChild children[1] = {CopyableChild(buffer[0])};
70     std::ranges::join_view jv(ParentView(children, 1));
71     assert(*jv.begin() == 1111);
72   }
73 
74   // Parent and child size is one.
75   {
76     CopyableChild children[1] = {CopyableChild(buffer[0], 1)};
77     std::ranges::join_view jv(ParentView(children, 1));
78     assert(*jv.begin() == 1111);
79   }
80 
81   // Parent size is one child is empty
82   {
83     CopyableChild children[1] = {CopyableChild(buffer[0], 0)};
84     std::ranges::join_view jv(ParentView(children, 1));
85     assert(jv.begin() == jv.end());
86   }
87 
88   // Has all empty children.
89   {
90     CopyableChild children[4] = {CopyableChild(buffer[0], 0), CopyableChild(buffer[1], 0), CopyableChild(buffer[2], 0),
91                                  CopyableChild(buffer[3], 0)};
92     auto jv = std::ranges::join_view(ParentView{children});
93     assert(jv.begin() == jv.end());
94   }
95 
96   // First child is empty, others are not.
97   {
98     CopyableChild children[4] = {CopyableChild(buffer[0], 4), CopyableChild(buffer[1], 0), CopyableChild(buffer[2], 0),
99                                  CopyableChild(buffer[3], 0)};
100     auto jv = std::ranges::join_view(ParentView{children});
101     assert(*jv.begin() == 1111);
102   }
103 
104   // Last child is empty, others are not.
105   {
106     CopyableChild children[4] = {CopyableChild(buffer[0], 4), CopyableChild(buffer[1], 4), CopyableChild(buffer[2], 4),
107                                  CopyableChild(buffer[3], 0)};
108     auto jv = std::ranges::join_view(ParentView{children});
109     assert(*jv.begin() == 1111);
110   }
111 
112   {
113     std::ranges::join_view jv(buffer);
114     assert(*jv.begin() == 1111);
115   }
116 
117   {
118     const std::ranges::join_view jv(buffer);
119     assert(*jv.begin() == 1111);
120     static_assert(HasConstBegin<decltype(jv)>);
121   }
122 
123   // !input_­range<const V>
124   {
125     std::ranges::join_view jv{ConstNotRange{}};
126     static_assert(!HasConstBegin<decltype(jv)>);
127   }
128 
129   // !is_reference_v<range_reference_t<const V>>
130   {
131     auto innerRValueRange = std::views::iota(0, 5) | std::views::transform([](int) { return ChildView{}; });
132     static_assert(!std::is_reference_v<std::ranges::range_reference_t<const decltype(innerRValueRange)>>);
133     std::ranges::join_view jv{innerRValueRange};
134     static_assert(!HasConstBegin<decltype(jv)>);
135   }
136 
137   // !simple-view<V>
138   {
139     std::ranges::join_view<NonSimpleParentView> jv;
140     static_assert(!std::same_as<decltype(jv.begin()), decltype(std::as_const(jv).begin())>);
141   }
142 
143   // simple-view<V> && is_reference_v<range_reference_t<V>>;
144   {
145     std::ranges::join_view<SimpleParentView> jv;
146     static_assert(std::same_as<decltype(jv.begin()), decltype(std::as_const(jv).begin())>);
147   }
148 
149   return true;
150 }
151 
152 int main(int, char**) {
153   test();
154   static_assert(test());
155 
156   return 0;
157 }
158