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 
12 // constexpr const T& optional<T>::value() const;
13 
14 #include <experimental/optional>
15 #include <type_traits>
16 #include <cassert>
17 
18 #if _LIBCPP_STD_VER > 11
19 
20 using std::experimental::optional;
21 using std::experimental::in_place_t;
22 using std::experimental::in_place;
23 using std::experimental::bad_optional_access;
24 
25 struct X
26 {
27     X() = default;
28     X(const X&) = delete;
testX29    constexpr int test() const {return 3;}
testX30     int test() {return 4;}
31 };
32 
33 #endif  // _LIBCPP_STD_VER > 11
34 
main()35 int main()
36 {
37 #if _LIBCPP_STD_VER > 11
38     {
39         constexpr optional<X> opt(in_place);
40         static_assert(opt.value().test() == 3, "");
41     }
42     {
43         const optional<X> opt(in_place);
44         assert(opt.value().test() == 3);
45     }
46     {
47         const optional<X> opt;
48         try
49         {
50             opt.value();
51             assert(false);
52         }
53         catch (const bad_optional_access&)
54         {
55         }
56     }
57 #endif  // _LIBCPP_STD_VER > 11
58 }
59