1//===----------------------------------------------------------------------===//
2// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
3// See https://llvm.org/LICENSE.txt for license information.
4// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
5//
6//===----------------------------------------------------------------------===//
7
8// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20
9
10// template<class... Args>
11// constexpr T& emplace(Args&&... args) noexcept;
12// Constraints: is_nothrow_constructible_v<T, Args...> is true.
13//
14// Effects: Equivalent to:
15// if (has_value()) {
16// destroy_at(addressof(val));
17// } else {
18// destroy_at(addressof(unex));
19// has_val = true;
20// }
21// return *construct_at(addressof(val), std::forward<Args>(args)...);
22
23#include <cassert>
24#include <concepts>
25#include <expected>
26#include <type_traits>
27#include <utility>
28
29#include "../../types.h"
30#include "test_macros.h"
31
32template <class T, class... Args>
33concept CanEmplace = requires(T t, Args&&... args) { t.emplace(std::forward<Args>(args)...); };
34
35static_assert(CanEmplace<std::expected<int, int>, int>);
36
37template <bool Noexcept>
38struct CtorFromInt {
39 CtorFromInt(int) noexcept(Noexcept);
40 CtorFromInt(int, int) noexcept(Noexcept);
41};
42
43static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int>);
44static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int, int>);
45static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int>);
46static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int, int>);
47
48constexpr bool test() {
49 // has_value
50 {
51 BothNoexcept::state oldState{};
52 BothNoexcept::state newState{};
53 std::expected<BothNoexcept, int> e(std::in_place, oldState, 5);
54 decltype(auto) x = e.emplace(newState, 10);
55 static_assert(std::same_as<decltype(x), BothNoexcept&>);
56 assert(&x == &(*e));
57
58 assert(oldState.dtorCalled);
59 assert(e.has_value());
60 assert(e.value().data_ == 10);
61 }
62
63 // !has_value
64 {
65 BothMayThrow::state oldState{};
66 std::expected<int, BothMayThrow> e(std::unexpect, oldState, 5);
67 decltype(auto) x = e.emplace(10);
68 static_assert(std::same_as<decltype(x), int&>);
69 assert(&x == &(*e));
70
71 assert(oldState.dtorCalled);
72 assert(e.has_value());
73 assert(e.value() == 10);
74 }
75
76 // TailClobberer
77 {
78 std::expected<TailClobberer<0>, bool> e(std::unexpect);
79 e.emplace();
80 assert(e.has_value());
81 }
82
83 // CheckForInvalidWrites
84 {
85 {
86 CheckForInvalidWrites<true> e;
87 e.emplace();
88 assert(e.check());
89 }
90 {
91 CheckForInvalidWrites<false> e;
92 e.emplace();
93 assert(e.check());
94 }
95 }
96
97 return true;
98}
99
100int main(int, char**) {
101 test();
102 static_assert(test());
103 return 0;
104}
105

source code of libcxx/test/std/utilities/expected/expected.expected/assign/emplace.pass.cpp