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 //   requires (!(simple-view<V> &&
14 //               random_access_range<const V> && sized_range<const V>));
15 // constexpr auto begin() const
16 //   requires random_access_range<const V> && sized_range<const V>;
17 
18 #include <ranges>
19 
20 #include "test_macros.h"
21 #include "test_iterators.h"
22 #include "types.h"
23 
24 template<class T>
25 concept BeginInvocable = requires(std::ranges::drop_view<T> t) { t.begin(); };
26 
27 template <bool IsSimple>
28 struct MaybeSimpleView : std::ranges::view_base {
29   int* num_of_non_const_begin_calls;
30   int* num_of_const_begin_calls;
31 
32   constexpr int* begin() {
33     ++(*num_of_non_const_begin_calls);
34     return nullptr;
35   }
36   constexpr std::conditional_t<IsSimple, int*, const int*> begin() const {
37     ++(*num_of_const_begin_calls);
38     return nullptr;
39   }
40   constexpr int* end() const { return nullptr; }
41   constexpr size_t size() const { return 0; }
42 };
43 
44 using SimpleView = MaybeSimpleView<true>;
45 using NonSimpleView = MaybeSimpleView<false>;
46 
47 constexpr bool test() {
48   // random_access_range<const V> && sized_range<const V>
49   std::ranges::drop_view dropView1(MoveOnlyView(), 4);
50   assert(dropView1.begin() == globalBuff + 4);
51 
52   // !random_access_range<const V>
53   std::ranges::drop_view dropView2(ForwardView(), 4);
54   assert(base(dropView2.begin()) == globalBuff + 4);
55 
56   // !random_access_range<const V>
57   std::ranges::drop_view dropView3(InputView(), 4);
58   assert(base(dropView3.begin()) == globalBuff + 4);
59 
60   // random_access_range<const V> && sized_range<const V>
61   std::ranges::drop_view dropView4(MoveOnlyView(), 8);
62   assert(dropView4.begin() == globalBuff + 8);
63 
64   // random_access_range<const V> && sized_range<const V>
65   std::ranges::drop_view dropView5(MoveOnlyView(), 0);
66   assert(dropView5.begin() == globalBuff);
67 
68   // random_access_range<const V> && sized_range<const V>
69   const std::ranges::drop_view dropView6(MoveOnlyView(), 0);
70   assert(dropView6.begin() == globalBuff);
71 
72   // random_access_range<const V> && sized_range<const V>
73   std::ranges::drop_view dropView7(MoveOnlyView(), 10);
74   assert(dropView7.begin() == globalBuff + 8);
75 
76   CountedView view8;
77   std::ranges::drop_view dropView8(view8, 5);
78   assert(base(base(dropView8.begin())) == globalBuff + 5);
79   assert(dropView8.begin().stride_count() == 5);
80   assert(base(base(dropView8.begin())) == globalBuff + 5);
81   assert(dropView8.begin().stride_count() == 5);
82 
83   static_assert(!BeginInvocable<const ForwardView>);
84 
85   {
86     static_assert(std::ranges::random_access_range<const SimpleView>);
87     static_assert(std::ranges::sized_range<const SimpleView>);
88     LIBCPP_STATIC_ASSERT(std::ranges::__simple_view<SimpleView>);
89     int non_const_calls = 0;
90     int const_calls = 0;
91     std::ranges::drop_view dropView(SimpleView{{}, &non_const_calls, &const_calls}, 4);
92     assert(dropView.begin() == nullptr);
93     assert(non_const_calls == 0);
94     assert(const_calls == 1);
95     assert(std::as_const(dropView).begin() == nullptr);
96     assert(non_const_calls == 0);
97     assert(const_calls == 2);
98   }
99 
100   {
101     static_assert(std::ranges::random_access_range<const NonSimpleView>);
102     static_assert(std::ranges::sized_range<const NonSimpleView>);
103     LIBCPP_STATIC_ASSERT(!std::ranges::__simple_view<NonSimpleView>);
104     int non_const_calls = 0;
105     int const_calls = 0;
106     std::ranges::drop_view dropView(NonSimpleView{{}, &non_const_calls, &const_calls}, 4);
107     assert(dropView.begin() == nullptr);
108     assert(non_const_calls == 1);
109     assert(const_calls == 0);
110     assert(std::as_const(dropView).begin() == nullptr);
111     assert(non_const_calls == 1);
112     assert(const_calls == 1);
113   }
114 
115   return true;
116 }
117 
118 int main(int, char**) {
119   test();
120   static_assert(test());
121 
122   return 0;
123 }
124