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 
34 template <class T, class... Args>
35 concept CanEmplace = requires(T t, Args&&... args) { t.emplace(std::forward<Args>(args)...); };
36 
37 static_assert(CanEmplace<std::expected<int, int>, int>);
38 
39 template <bool Noexcept>
40 struct CtorFromInitializerList {
41   CtorFromInitializerList(std::initializer_list<int>&) noexcept(Noexcept);
42   CtorFromInitializerList(std::initializer_list<int>&, int) noexcept(Noexcept);
43 };
44 
45 static_assert(CanEmplace<std::expected<CtorFromInitializerList<true>, int>, std::initializer_list<int>&>);
46 static_assert(!CanEmplace<std::expected<CtorFromInitializerList<false>, int>, std::initializer_list<int>&>);
47 static_assert(CanEmplace<std::expected<CtorFromInitializerList<true>, int>, std::initializer_list<int>&, int>);
48 static_assert(!CanEmplace<std::expected<CtorFromInitializerList<false>, int>, std::initializer_list<int>&, int>);
49 
50 struct 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 
57 constexpr 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 
96 int main(int, char**) {
97   test();
98   static_assert(test());
99   return 0;
100 }
101