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++98, c++03, c++11, c++14
10 // <optional>
11 
12 // struct nullopt_t{see below};
13 // inline constexpr nullopt_t nullopt(unspecified);
14 
15 // [optional.nullopt]/2:
16 //   Type nullopt_t shall not have a default constructor or an initializer-list
17 //   constructor, and shall not be an aggregate.
18 
19 #include <optional>
20 #include <type_traits>
21 
22 using std::nullopt_t;
23 using std::nullopt;
24 
25 constexpr bool test()
26 {
27     nullopt_t foo{nullopt};
28     (void)foo;
29     return true;
30 }
31 
32 int main(int, char**)
33 {
34     static_assert(std::is_empty_v<nullopt_t>);
35     static_assert(!std::is_default_constructible_v<nullopt_t>);
36 
37     static_assert(std::is_same_v<const nullopt_t, decltype(nullopt)>);
38     static_assert(test());
39 
40   return 0;
41 }
42