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
10
11 // <utility>
12
13 // template <class T1, class T2> struct pair
14
15 // template<class U, class V> pair& operator=(pair<U, V>&& p);
16
17 #include <utility>
18 #include <memory>
19 #include <cassert>
20
21 #include "test_macros.h"
22 #include "archetypes.h"
23
24 struct Derived : ConstexprTestTypes::MoveOnly {
25 Derived() = default;
DerivedDerived26 TEST_CONSTEXPR_CXX20 Derived(ConstexprTestTypes::MoveOnly&&) {}
27 };
28 struct CountAssign {
29 int copied = 0;
30 int moved = 0;
31 TEST_CONSTEXPR_CXX20 CountAssign() = default;
CountAssignCountAssign32 TEST_CONSTEXPR_CXX20 CountAssign(const int) {}
operator =CountAssign33 TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign const&) {
34 ++copied;
35 return *this;
36 }
operator =CountAssign37 TEST_CONSTEXPR_CXX20 CountAssign& operator=(CountAssign&&) {
38 ++moved;
39 return *this;
40 }
41 };
42
43 struct CopyAssignableInt {
operator =CopyAssignableInt44 CopyAssignableInt& operator=(int&) { return *this; }
45 };
46
47 struct NotAssignable {
48 NotAssignable& operator=(NotAssignable const&) = delete;
49 NotAssignable& operator=(NotAssignable&&) = delete;
50 };
51
52 struct MoveAssignable {
53 MoveAssignable& operator=(MoveAssignable const&) = delete;
54 MoveAssignable& operator=(MoveAssignable&&) = default;
55 };
56
57 struct CopyAssignable {
58 CopyAssignable& operator=(CopyAssignable const&) = default;
59 CopyAssignable& operator=(CopyAssignable&&) = delete;
60 };
61
test()62 TEST_CONSTEXPR_CXX20 bool test() {
63 {
64 typedef std::pair<Derived, short> P1;
65 typedef std::pair<ConstexprTestTypes::MoveOnly, long> P2;
66 P1 p1(Derived(), static_cast<short>(4));
67 P2 p2;
68 p2 = std::move(p1);
69 assert(p2.second == 4);
70 }
71 {
72 using P = std::pair<int, CountAssign>;
73 using T = std::pair<long, CountAssign>;
74 T t(42, -42);
75 P p(101, 101);
76 p = std::move(t);
77 assert(p.first == 42);
78 assert(p.second.moved == 1);
79 assert(p.second.copied == 0);
80 assert(t.second.moved == 0);
81 assert(t.second.copied == 0);
82 }
83 { // test const requirement
84 using T = std::pair<CopyAssignableInt, CopyAssignableInt>;
85 using P = std::pair<int, int>;
86 static_assert(!std::is_assignable<T&, P&&>::value, "");
87 static_assert(!std::is_assignable<P&, T&&>::value, "");
88 }
89 {
90 // Make sure we can't move-assign from a pair containing a reference
91 // if that type isn't copy-constructible (since otherwise we'd be
92 // stealing the object through the reference).
93 using P1 = std::pair<MoveAssignable, long>;
94 using P2 = std::pair<MoveAssignable&, int>;
95 static_assert(!std::is_assignable<P1&, P2&&>::value, "");
96
97 // ... but this should work since we're going to steal out of the
98 // incoming rvalue reference.
99 using P3 = std::pair<MoveAssignable, long>;
100 using P4 = std::pair<MoveAssignable&&, int>;
101 static_assert(std::is_assignable<P3&, P4&&>::value, "");
102 }
103 {
104 // We assign through the reference and don't move out of the incoming ref,
105 // so this doesn't work (but would if the type were CopyAssignable).
106 {
107 using P1 = std::pair<MoveAssignable&, long>;
108 using P2 = std::pair<MoveAssignable&, int>;
109 static_assert(!std::is_assignable<P1&, P2&&>::value, "");
110 }
111
112 // ... works if it's CopyAssignable
113 {
114 using P1 = std::pair<CopyAssignable&, long>;
115 using P2 = std::pair<CopyAssignable&, int>;
116 static_assert(std::is_assignable<P1&, P2&&>::value, "");
117 }
118
119 // For rvalue-references, we can move-assign if the type is MoveAssignable,
120 // or CopyAssignable (since in the worst case the move will decay into a copy).
121 {
122 using P1 = std::pair<MoveAssignable&&, long>;
123 using P2 = std::pair<MoveAssignable&&, int>;
124 static_assert(std::is_assignable<P1&, P2&&>::value, "");
125
126 using P3 = std::pair<CopyAssignable&&, long>;
127 using P4 = std::pair<CopyAssignable&&, int>;
128 static_assert(std::is_assignable<P3&, P4&&>::value, "");
129 }
130
131 // In all cases, we can't move-assign if the types are not assignable,
132 // since we assign through the reference.
133 {
134 using P1 = std::pair<NotAssignable&, long>;
135 using P2 = std::pair<NotAssignable&, int>;
136 static_assert(!std::is_assignable<P1&, P2&&>::value, "");
137
138 using P3 = std::pair<NotAssignable&&, long>;
139 using P4 = std::pair<NotAssignable&&, int>;
140 static_assert(!std::is_assignable<P3&, P4&&>::value, "");
141 }
142 }
143 return true;
144 }
145
main(int,char **)146 int main(int, char**) {
147 test();
148 #if TEST_STD_VER >= 20
149 static_assert(test());
150 #endif
151
152 return 0;
153 }
154