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-no-concepts
11 // UNSUPPORTED: libcpp-has-no-incomplete-ranges
12 
13 // constexpr auto begin()
14 //   requires (!(simple-view<V> &&
15 //               random_access_range<const V> && sized_range<const V>));
16 // constexpr auto begin() const
17 //   requires random_access_range<const V> && sized_range<const V>;
18 
19 #include <ranges>
20 
21 #include "test_macros.h"
22 #include "test_iterators.h"
23 #include "types.h"
24 
25 template<class T>
26 concept BeginInvocable = requires(std::ranges::drop_view<T> t) { t.begin(); };
27 
28 template <bool IsSimple>
29 struct MaybeSimpleView : std::ranges::view_base {
30   int* num_of_non_const_begin_calls;
31   int* num_of_const_begin_calls;
32 
33   constexpr int* begin() {
34     ++(*num_of_non_const_begin_calls);
35     return nullptr;
36   }
37   constexpr std::conditional_t<IsSimple, int*, const int*> begin() const {
38     ++(*num_of_const_begin_calls);
39     return nullptr;
40   }
41   constexpr int* end() const { return nullptr; }
42   constexpr size_t size() const { return 0; }
43 };
44 
45 using SimpleView = MaybeSimpleView<true>;
46 using NonSimpleView = MaybeSimpleView<false>;
47 
48 constexpr bool test() {
49   // random_access_range<const V> && sized_range<const V>
50   std::ranges::drop_view dropView1(MoveOnlyView(), 4);
51   assert(dropView1.begin() == globalBuff + 4);
52 
53   // !random_access_range<const V>
54   std::ranges::drop_view dropView2(ForwardView(), 4);
55   assert(dropView2.begin().base() == globalBuff + 4);
56 
57   // !random_access_range<const V>
58   std::ranges::drop_view dropView3(InputView(), 4);
59   assert(dropView3.begin().base() == globalBuff + 4);
60 
61   // random_access_range<const V> && sized_range<const V>
62   std::ranges::drop_view dropView4(MoveOnlyView(), 8);
63   assert(dropView4.begin() == globalBuff + 8);
64 
65   // random_access_range<const V> && sized_range<const V>
66   std::ranges::drop_view dropView5(MoveOnlyView(), 0);
67   assert(dropView5.begin() == globalBuff);
68 
69   // random_access_range<const V> && sized_range<const V>
70   const std::ranges::drop_view dropView6(MoveOnlyView(), 0);
71   assert(dropView6.begin() == globalBuff);
72 
73   // random_access_range<const V> && sized_range<const V>
74   std::ranges::drop_view dropView7(MoveOnlyView(), 10);
75   assert(dropView7.begin() == globalBuff + 8);
76 
77   CountedView view8;
78   std::ranges::drop_view dropView8(view8, 5);
79   assert(base(base(dropView8.begin())) == globalBuff + 5);
80   assert(dropView8.begin().stride_count() == 5);
81   assert(base(base(dropView8.begin())) == globalBuff + 5);
82   assert(dropView8.begin().stride_count() == 5);
83 
84   static_assert(!BeginInvocable<const ForwardView>);
85 
86   {
87     static_assert(std::ranges::random_access_range<const SimpleView>);
88     static_assert(std::ranges::sized_range<const SimpleView>);
89     LIBCPP_STATIC_ASSERT(std::ranges::__simple_view<SimpleView>);
90     int non_const_calls = 0;
91     int const_calls = 0;
92     std::ranges::drop_view dropView(SimpleView{{}, &non_const_calls, &const_calls}, 4);
93     assert(dropView.begin() == nullptr);
94     assert(non_const_calls == 0);
95     assert(const_calls == 1);
96     assert(std::as_const(dropView).begin() == nullptr);
97     assert(non_const_calls == 0);
98     assert(const_calls == 2);
99   }
100 
101   {
102     static_assert(std::ranges::random_access_range<const NonSimpleView>);
103     static_assert(std::ranges::sized_range<const NonSimpleView>);
104     LIBCPP_STATIC_ASSERT(!std::ranges::__simple_view<NonSimpleView>);
105     int non_const_calls = 0;
106     int const_calls = 0;
107     std::ranges::drop_view dropView(NonSimpleView{{}, &non_const_calls, &const_calls}, 4);
108     assert(dropView.begin() == nullptr);
109     assert(non_const_calls == 1);
110     assert(const_calls == 0);
111     assert(std::as_const(dropView).begin() == nullptr);
112     assert(non_const_calls == 1);
113     assert(const_calls == 1);
114   }
115 
116   return true;
117 }
118 
119 int main(int, char**) {
120   test();
121   static_assert(test());
122 
123   return 0;
124 }
125