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// constexpr void emplace() noexcept;
12//
13// Effects: If has_value() is false, destroys unex and sets has_val to true.
14
15#include <cassert>
16#include <concepts>
17#include <expected>
18#include <type_traits>
19#include <utility>
20
21#include "../../types.h"
22#include "test_macros.h"
23
24template <class T>
25concept EmplaceNoexcept =
26 requires(T t) {
27 { t.emplace() } noexcept;
28 };
29static_assert(!EmplaceNoexcept<int>);
30
31static_assert(EmplaceNoexcept<std::expected<void, int>>);
32
33constexpr bool test() {
34 // has_value
35 {
36 std::expected<void, int> e;
37 e.emplace();
38 assert(e.has_value());
39 }
40
41 // !has_value
42 {
43 Traced::state state{};
44 std::expected<int, Traced> e(std::unexpect, state, 5);
45 e.emplace();
46
47 assert(state.dtorCalled);
48 assert(e.has_value());
49 }
50
51 return true;
52}
53
54int main(int, char**) {
55 test();
56 static_assert(test());
57 return 0;
58}
59

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