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, c++20
10
11// template<class... Args>
12// constexpr T& emplace(Args&&... args) noexcept;
13// Constraints: is_nothrow_constructible_v<T, Args...> is true.
14//
15// Effects: Equivalent to:
16// if (has_value()) {
17// destroy_at(addressof(val));
18// } else {
19// destroy_at(addressof(unex));
20// has_val = true;
21// }
22// return *construct_at(addressof(val), std::forward<Args>(args)...);
23
24#include <cassert>
25#include <concepts>
26#include <expected>
27#include <type_traits>
28#include <utility>
29
30#include "../../types.h"
31#include "test_macros.h"
32
33template <class T, class... Args>
34concept CanEmplace = requires(T t, Args&&... args) { t.emplace(std::forward<Args>(args)...); };
35
36static_assert(CanEmplace<std::expected<int, int>, int>);
37
38template <bool Noexcept>
39struct CtorFromInt {
40 CtorFromInt(int) noexcept(Noexcept);
41 CtorFromInt(int, int) noexcept(Noexcept);
42};
43
44static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int>);
45static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int, int>);
46static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int>);
47static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int, int>);
48
49constexpr bool test() {
50 // has_value
51 {
52 BothNoexcept::state oldState{};
53 BothNoexcept::state newState{};
54 std::expected<BothNoexcept, int> e(std::in_place, oldState, 5);
55 decltype(auto) x = e.emplace(newState, 10);
56 static_assert(std::same_as<decltype(x), BothNoexcept&>);
57 assert(&x == &(*e));
58
59 assert(oldState.dtorCalled);
60 assert(e.has_value());
61 assert(e.value().data_ == 10);
62 }
63
64 // !has_value
65 {
66 BothMayThrow::state oldState{};
67 std::expected<int, BothMayThrow> e(std::unexpect, oldState, 5);
68 decltype(auto) x = e.emplace(10);
69 static_assert(std::same_as<decltype(x), int&>);
70 assert(&x == &(*e));
71
72 assert(oldState.dtorCalled);
73 assert(e.has_value());
74 assert(e.value() == 10);
75 }
76
77 // TailClobberer
78 {
79 std::expected<TailClobberer<0>, bool> e(std::unexpect);
80 e.emplace();
81 assert(e.has_value());
82 }
83
84 // CheckForInvalidWrites
85 {
86 {
87 CheckForInvalidWrites<true> e;
88 e.emplace();
89 assert(e.check());
90 }
91 {
92 CheckForInvalidWrites<false> e;
93 e.emplace();
94 assert(e.check());
95 }
96 }
97
98 return true;
99}
100
101int main(int, char**) {
102 test();
103 static_assert(test());
104 return 0;
105}
106

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