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 // <tuple>
10 
11 // template <class... Types> class tuple;
12 
13 // template <class... UTypes>
14 //   tuple& operator=(tuple<UTypes...>&& u);
15 
16 // UNSUPPORTED: c++03
17 
18 #include <tuple>
19 #include <string>
20 #include <memory>
21 #include <utility>
22 #include <cassert>
23 
24 #include "test_macros.h"
25 
26 struct B {
27     int id_;
BB28     explicit B(int i = 0) : id_(i) {}
~BB29     virtual ~B() {}
30 };
31 
32 struct D : B {
DD33     explicit D(int i) : B(i) {}
34 };
35 
36 struct E {
37   constexpr E() = default;
operator =E38   TEST_CONSTEXPR_CXX14 E& operator=(int) {
39       return *this;
40   }
41 };
42 
43 struct NothrowMoveAssignable {
operator =NothrowMoveAssignable44     NothrowMoveAssignable& operator=(NothrowMoveAssignable&&) noexcept { return *this; }
45 };
46 
47 struct PotentiallyThrowingMoveAssignable {
operator =PotentiallyThrowingMoveAssignable48     PotentiallyThrowingMoveAssignable& operator=(PotentiallyThrowingMoveAssignable&&) { return *this; }
49 };
50 
51 struct NonAssignable {
52   NonAssignable& operator=(NonAssignable const&) = delete;
53   NonAssignable& operator=(NonAssignable&&) = delete;
54 };
55 
56 struct MoveAssignable {
57   MoveAssignable& operator=(MoveAssignable const&) = delete;
58   MoveAssignable& operator=(MoveAssignable&&) = default;
59 };
60 
61 struct CopyAssignable {
62   CopyAssignable& operator=(CopyAssignable const&) = default;
63   CopyAssignable& operator=(CopyAssignable&&) = delete;
64 };
65 
66 struct TrackMove
67 {
TrackMoveTrackMove68     TrackMove() : value(0), moved_from(false) { }
TrackMoveTrackMove69     explicit TrackMove(int v) : value(v), moved_from(false) { }
TrackMoveTrackMove70     TrackMove(TrackMove const& other) : value(other.value), moved_from(false) { }
TrackMoveTrackMove71     TrackMove(TrackMove&& other) : value(other.value), moved_from(false) {
72         other.moved_from = true;
73     }
operator =TrackMove74     TrackMove& operator=(TrackMove const& other) {
75         value = other.value;
76         moved_from = false;
77         return *this;
78     }
operator =TrackMove79     TrackMove& operator=(TrackMove&& other) {
80         value = other.value;
81         moved_from = false;
82         other.moved_from = true;
83         return *this;
84     }
85 
86     int value;
87     bool moved_from;
88 };
89 
90 TEST_CONSTEXPR_CXX20
test()91 bool test()
92 {
93     {
94         typedef std::tuple<long> T0;
95         typedef std::tuple<long long> T1;
96         T0 t0(2);
97         T1 t1;
98         t1 = std::move(t0);
99         assert(std::get<0>(t1) == 2);
100     }
101     {
102         typedef std::tuple<long, char> T0;
103         typedef std::tuple<long long, int> T1;
104         T0 t0(2, 'a');
105         T1 t1;
106         t1 = std::move(t0);
107         assert(std::get<0>(t1) == 2);
108         assert(std::get<1>(t1) == int('a'));
109     }
110     {
111         // Test that tuple evaluates correctly applies an lvalue reference
112         // before evaluating is_assignable (i.e. 'is_assignable<int&, int&&>')
113         // instead of evaluating 'is_assignable<int&&, int&&>' which is false.
114         int x = 42;
115         int y = 43;
116         std::tuple<int&&, E> t(std::move(x), E{});
117         std::tuple<int&&, int> t2(std::move(y), 44);
118         t = std::move(t2);
119         assert(std::get<0>(t) == 43);
120         assert(&std::get<0>(t) == &x);
121     }
122 
123     return true;
124 }
125 
main(int,char **)126 int main(int, char**)
127 {
128     test();
129 #if TEST_STD_VER >= 20
130     static_assert(test());
131 #endif
132 
133     {
134         typedef std::tuple<long, char, D> T0;
135         typedef std::tuple<long long, int, B> T1;
136         T0 t0(2, 'a', D(3));
137         T1 t1;
138         t1 = std::move(t0);
139         assert(std::get<0>(t1) == 2);
140         assert(std::get<1>(t1) == int('a'));
141         assert(std::get<2>(t1).id_ == 3);
142     }
143     {
144         D d(3);
145         D d2(2);
146         typedef std::tuple<long, char, D&> T0;
147         typedef std::tuple<long long, int, B&> T1;
148         T0 t0(2, 'a', d2);
149         T1 t1(1, 'b', d);
150         t1 = std::move(t0);
151         assert(std::get<0>(t1) == 2);
152         assert(std::get<1>(t1) == int('a'));
153         assert(std::get<2>(t1).id_ == 2);
154     }
155     {
156         typedef std::tuple<long, char, std::unique_ptr<D>> T0;
157         typedef std::tuple<long long, int, std::unique_ptr<B>> T1;
158         T0 t0(2, 'a', std::unique_ptr<D>(new D(3)));
159         T1 t1;
160         t1 = std::move(t0);
161         assert(std::get<0>(t1) == 2);
162         assert(std::get<1>(t1) == int('a'));
163         assert(std::get<2>(t1)->id_ == 3);
164     }
165 
166     {
167         using T = std::tuple<int, NonAssignable>;
168         using U = std::tuple<NonAssignable, int>;
169         static_assert(!std::is_assignable<T&, U&&>::value, "");
170         static_assert(!std::is_assignable<U&, T&&>::value, "");
171     }
172     {
173         typedef std::tuple<NothrowMoveAssignable, long> T0;
174         typedef std::tuple<NothrowMoveAssignable, int> T1;
175         static_assert(std::is_nothrow_assignable<T0&, T1&&>::value, "");
176     }
177     {
178         typedef std::tuple<PotentiallyThrowingMoveAssignable, long> T0;
179         typedef std::tuple<PotentiallyThrowingMoveAssignable, int> T1;
180         static_assert(std::is_assignable<T0&, T1&&>::value, "");
181         static_assert(!std::is_nothrow_assignable<T0&, T1&&>::value, "");
182     }
183     {
184         // We assign through the reference and don't move out of the incoming ref,
185         // so this doesn't work (but would if the type were CopyAssignable).
186         {
187             using T1 = std::tuple<MoveAssignable&, long>;
188             using T2 = std::tuple<MoveAssignable&, int>;
189             static_assert(!std::is_assignable<T1&, T2&&>::value, "");
190         }
191 
192         // ... works if it's CopyAssignable
193         {
194             using T1 = std::tuple<CopyAssignable&, long>;
195             using T2 = std::tuple<CopyAssignable&, int>;
196             static_assert(std::is_assignable<T1&, T2&&>::value, "");
197         }
198 
199         // For rvalue-references, we can move-assign if the type is MoveAssignable
200         // or CopyAssignable (since in the worst case the move will decay into a copy).
201         {
202             using T1 = std::tuple<MoveAssignable&&, long>;
203             using T2 = std::tuple<MoveAssignable&&, int>;
204             static_assert(std::is_assignable<T1&, T2&&>::value, "");
205 
206             using T3 = std::tuple<CopyAssignable&&, long>;
207             using T4 = std::tuple<CopyAssignable&&, int>;
208             static_assert(std::is_assignable<T3&, T4&&>::value, "");
209         }
210 
211         // In all cases, we can't move-assign if the types are not assignable,
212         // since we assign through the reference.
213         {
214             using T1 = std::tuple<NonAssignable&, long>;
215             using T2 = std::tuple<NonAssignable&, int>;
216             static_assert(!std::is_assignable<T1&, T2&&>::value, "");
217 
218             using T3 = std::tuple<NonAssignable&&, long>;
219             using T4 = std::tuple<NonAssignable&&, int>;
220             static_assert(!std::is_assignable<T3&, T4&&>::value, "");
221         }
222     }
223     {
224         // Make sure that we don't incorrectly move out of the source's reference.
225         using Dest = std::tuple<TrackMove, long>;
226         using Source = std::tuple<TrackMove&, int>;
227         TrackMove track{3};
228         Source src(track, 4);
229         assert(!track.moved_from);
230 
231         Dest dst;
232         dst = std::move(src); // here we should make a copy
233         assert(!track.moved_from);
234         assert(std::get<0>(dst).value == 3);
235     }
236     {
237         // But we do move out of the source's reference if it's a rvalue ref
238         using Dest = std::tuple<TrackMove, long>;
239         using Source = std::tuple<TrackMove&&, int>;
240         TrackMove track{3};
241         Source src(std::move(track), 4);
242         assert(!track.moved_from); // we just took a reference
243 
244         Dest dst;
245         dst = std::move(src);
246         assert(track.moved_from);
247         assert(std::get<0>(dst).value == 3);
248     }
249     {
250         // If the source holds a value, then we move out of it too
251         using Dest = std::tuple<TrackMove, long>;
252         using Source = std::tuple<TrackMove, int>;
253         Source src(TrackMove{3}, 4);
254         Dest dst;
255         dst = std::move(src);
256         assert(std::get<0>(src).moved_from);
257         assert(std::get<0>(dst).value == 3);
258     }
259 
260     return 0;
261 }
262