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 // <optional>
10 // UNSUPPORTED: c++98, c++03, c++11, c++14
11 // UNSUPPORTED: clang-5, apple-clang-9
12 // UNSUPPORTED: libcpp-no-deduction-guides
13 // Clang 5 will generate bad implicit deduction guides
14 //  Specifically, for the copy constructor.
15 
16 
17 // template<class T>
18 //   optional(T) -> optional<T>;
19 
20 
21 #include <optional>
22 #include <cassert>
23 
24 struct A {};
25 
26 int main(int, char**)
27 {
28 //  Test the explicit deduction guides
29     {
30 //  optional(T)
31     std::optional opt(5);
32     static_assert(std::is_same_v<decltype(opt), std::optional<int>>, "");
33     assert(static_cast<bool>(opt));
34     assert(*opt == 5);
35     }
36 
37     {
38 //  optional(T)
39     std::optional opt(A{});
40     static_assert(std::is_same_v<decltype(opt), std::optional<A>>, "");
41     assert(static_cast<bool>(opt));
42     }
43 
44 //  Test the implicit deduction guides
45     {
46 //  optional(optional);
47     std::optional<char> source('A');
48     std::optional opt(source);
49     static_assert(std::is_same_v<decltype(opt), std::optional<char>>, "");
50     assert(static_cast<bool>(opt) == static_cast<bool>(source));
51     assert(*opt == *source);
52     }
53 
54   return 0;
55 }
56