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++03, c++11, c++14, c++17
10 // UNSUPPORTED: libcpp-no-concepts
11 
12 // template<class T>
13 //     concept default_initializable = constructible_from<T> &&
14 //     requires { T{}; } &&
15 //     is-default-initializable<T>;
16 
17 #include <concepts>
18 #include <cassert>
19 
20 #include "test_macros.h"
21 
22 template<class T>
23 concept brace_initializable = requires { T{}; };
24 
25 void test() {
26     // LWG3149
27     // Changed the concept from constructible_from<T>
28     // to constructible_from<T> &&
29     //    requires { T{}; } && is-default-initializable <T>
30     struct S0 { explicit S0() = default; };
31     S0 x0;
32     S0 y0{};
33     static_assert( std::constructible_from<S0>);
34     static_assert( brace_initializable<S0>);
35     LIBCPP_STATIC_ASSERT( std::__default_initializable<S0>);
36     static_assert( std::default_initializable<S0>);
37 
38     struct S1 { S0 x; }; // Note: aggregate
39     S1 x1;
40     S1 y1{}; // expected-error {{chosen constructor is explicit in copy-initialization}}
41     static_assert( std::constructible_from<S1>);
42     static_assert(!brace_initializable<S1>);
43     LIBCPP_STATIC_ASSERT( std::__default_initializable<S1>);
44     static_assert(!std::default_initializable<S1>);
45 
46     const int x2; // expected-error {{default initialization of an object of const type 'const int'}}
47     const int y2{};
48 
49     static_assert( std::constructible_from<const int>);
50     static_assert( brace_initializable<const int>);
51     LIBCPP_STATIC_ASSERT(!std::__default_initializable<const int>);
52     static_assert(!std::default_initializable<const int>);
53 
54     const int x3[1]; // expected-error {{default initialization of an object of const type 'const int [1]'}}
55     const int y3[1]{};
56     static_assert( std::constructible_from<const int[1]>);
57     static_assert( brace_initializable<const int[1]>);
58     LIBCPP_STATIC_ASSERT(!std::__default_initializable<const int[1]>);
59     static_assert(!std::default_initializable<const int[1]>);
60 
61     // Zero-length array extension
62     const int x4[]; // expected-error {{definition of variable with array type needs an explicit size or an initializer}}
63     const int y4[]{};
64     static_assert(!std::constructible_from<const int[]>);
65     static_assert( brace_initializable<const int[]>);
66     LIBCPP_STATIC_ASSERT(!std::__default_initializable<const int[]>);
67     static_assert(!std::default_initializable<const int[]>);
68 }
69 
70 int main(int, char**) {
71     test();
72 
73     return 0;
74 }
75