1 //===----------------------------------------------------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 // <optional>
11 // UNSUPPORTED: c++98, c++03, c++11, c++14
12 // UNSUPPORTED: clang-5, apple-clang-9
13 // UNSUPPORTED: libcpp-no-deduction-guides
14 // Clang 5 will generate bad implicit deduction guides
15 // Specifically, for the copy constructor.
16
17
18 // template<class T>
19 // optional(T) -> optional<T>;
20
21
22 #include <optional>
23 #include <cassert>
24
25 struct A {};
26
main()27 int main()
28 {
29 // Test the explicit deduction guides
30 {
31 // optional(T)
32 std::optional opt(5);
33 static_assert(std::is_same_v<decltype(opt), std::optional<int>>, "");
34 assert(static_cast<bool>(opt));
35 assert(*opt == 5);
36 }
37
38 {
39 // optional(T)
40 std::optional opt(A{});
41 static_assert(std::is_same_v<decltype(opt), std::optional<A>>, "");
42 assert(static_cast<bool>(opt));
43 }
44
45 // Test the implicit deduction guides
46 {
47 // optional(optional);
48 std::optional<char> source('A');
49 std::optional opt(source);
50 static_assert(std::is_same_v<decltype(opt), std::optional<char>>, "");
51 assert(static_cast<bool>(opt) == static_cast<bool>(source));
52 assert(*opt == *source);
53 }
54 }
55