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 U, class... Args>
12// constexpr T& emplace(initializer_list<U> il, Args&&... args) noexcept;
13// Constraints: is_nothrow_constructible_v<T, initializer_list<U>&, 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), il, std::forward<Args>(args)...);
23
24#include <algorithm>
25#include <cassert>
26#include <concepts>
27#include <expected>
28#include <type_traits>
29#include <utility>
30
31#include "../../types.h"
32#include "test_macros.h"
33
34template <class T, class... Args>
35concept CanEmplace = requires(T t, Args&&... args) { t.emplace(std::forward<Args>(args)...); };
36
37static_assert(CanEmplace<std::expected<int, int>, int>);
38
39template <bool Noexcept>
40struct CtorFromInitializerList {
41 CtorFromInitializerList(std::initializer_list<int>&) noexcept(Noexcept);
42 CtorFromInitializerList(std::initializer_list<int>&, int) noexcept(Noexcept);
43};
44
45static_assert(CanEmplace<std::expected<CtorFromInitializerList<true>, int>, std::initializer_list<int>&>);
46static_assert(!CanEmplace<std::expected<CtorFromInitializerList<false>, int>, std::initializer_list<int>&>);
47static_assert(CanEmplace<std::expected<CtorFromInitializerList<true>, int>, std::initializer_list<int>&, int>);
48static_assert(!CanEmplace<std::expected<CtorFromInitializerList<false>, int>, std::initializer_list<int>&, int>);
49
50struct Data {
51 std::initializer_list<int> il;
52 int i;
53
54 constexpr Data(std::initializer_list<int>& l, int ii) noexcept : il(l), i(ii) {}
55};
56
57constexpr bool test() {
58 // has_value
59 {
60 auto list1 = {1, 2, 3};
61 auto list2 = {4, 5, 6};
62 std::expected<Data, int> e(std::in_place, list1, 5);
63 decltype(auto) x = e.emplace(list2, 10);
64 static_assert(std::same_as<decltype(x), Data&>);
65 assert(&x == &(*e));
66
67 assert(e.has_value());
68 assert(std::ranges::equal(e.value().il, list2));
69 assert(e.value().i == 10);
70 }
71
72 // !has_value
73 {
74 auto list = {4, 5, 6};
75 std::expected<Data, int> e(std::unexpect, 5);
76 decltype(auto) x = e.emplace(list, 10);
77 static_assert(std::same_as<decltype(x), Data&>);
78 assert(&x == &(*e));
79
80 assert(e.has_value());
81 assert(std::ranges::equal(e.value().il, list));
82 assert(e.value().i == 10);
83 }
84
85 // TailClobberer
86 {
87 std::expected<TailClobberer<0>, bool> e(std::unexpect);
88 auto list = {4, 5, 6};
89 e.emplace(list);
90 assert(e.has_value());
91 }
92
93 return true;
94}
95
96int main(int, char**) {
97 test();
98 static_assert(test());
99 return 0;
100}
101

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