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 Err = E>
11// constexpr explicit unexpected(Err&& e);
12//
13// Constraints:
14// - is_same_v<remove_cvref_t<Err>, unexpected> is false; and
15// - is_same_v<remove_cvref_t<Err>, in_place_t> is false; and
16// - is_constructible_v<E, Err> is true.
17//
18// Effects: Direct-non-list-initializes unex with std::forward<Err>(e).
19// Throws: Any exception thrown by the initialization of unex.
20
21#include <cassert>
22#include <concepts>
23#include <expected>
24#include <utility>
25
26#include "test_macros.h"
27
28// Test Constraints:
29static_assert(std::constructible_from<std::unexpected<int>, int>);
30
31// is_same_v<remove_cvref_t<Err>, unexpected>
32struct CstrFromUnexpected {
33 CstrFromUnexpected(CstrFromUnexpected const&) = delete;
34 CstrFromUnexpected(std::unexpected<CstrFromUnexpected> const&);
35};
36static_assert(!std::constructible_from<std::unexpected<CstrFromUnexpected>, std::unexpected<CstrFromUnexpected>>);
37
38// is_same_v<remove_cvref_t<Err>, in_place_t>
39struct CstrFromInplace {
40 CstrFromInplace(std::in_place_t);
41};
42static_assert(!std::constructible_from<std::unexpected<CstrFromInplace>, std::in_place_t>);
43
44// !is_constructible_v<E, Err>
45struct Foo {};
46static_assert(!std::constructible_from<std::unexpected<Foo>, int>);
47
48// test explicit
49static_assert(std::convertible_to<int, int>);
50static_assert(!std::convertible_to<int, std::unexpected<int>>);
51
52struct Error {
53 int i;
54 constexpr Error(int ii) : i(ii) {}
55 constexpr Error(const Error& other) : i(other.i) {}
56 constexpr Error(Error&& other) : i(other.i) { other.i = 0; }
57 Error(std::initializer_list<Error>) { assert(false); }
58};
59
60constexpr bool test() {
61 // lvalue
62 {
63 Error e(5);
64 std::unexpected<Error> unex(e);
65 assert(unex.error().i == 5);
66 assert(e.i == 5);
67 }
68
69 // rvalue
70 {
71 Error e(5);
72 std::unexpected<Error> unex(std::move(e));
73 assert(unex.error().i == 5);
74 assert(e.i == 0);
75 }
76
77 // Direct-non-list-initializes: does not trigger initializer_list overload
78 {
79 Error e(5);
80 [[maybe_unused]] std::unexpected<Error> unex(e);
81 }
82
83 // Test default template argument.
84 // Without it, the template parameter cannot be deduced from an initializer list
85 {
86 struct Bar {
87 int i;
88 int j;
89 constexpr Bar(int ii, int jj) : i(ii), j(jj) {}
90 };
91 std::unexpected<Bar> ue({5, 6});
92 assert(ue.error().i == 5);
93 assert(ue.error().j == 6);
94 }
95
96 return true;
97}
98
99void testException() {
100#ifndef TEST_HAS_NO_EXCEPTIONS
101 struct Except {};
102
103 struct Throwing {
104 Throwing() = default;
105 Throwing(const Throwing&) { throw Except{}; }
106 };
107
108 Throwing t;
109 try {
110 std::unexpected<Throwing> u(t);
111 assert(false);
112 } catch (Except) {
113 }
114#endif // TEST_HAS_NO_EXCEPTIONS
115}
116
117int main(int, char**) {
118 test();
119 static_assert(test());
120 testException();
121 return 0;
122}
123

source code of libcxx/test/std/utilities/expected/expected.unexpected/ctor/ctor.error.pass.cpp