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
11// template<class T>
12// concept default_initializable = constructible_from<T> &&
13// requires { T{}; } &&
14// is-default-initializable<T>;
15
16#include <concepts>
17#include <cassert>
18
19#include "test_macros.h"
20
21template<class T>
22concept brace_initializable = requires { T{}; };
23
24void test() {
25 // LWG3149
26 // Changed the concept from constructible_from<T>
27 // to constructible_from<T> &&
28 // requires { T{}; } && is-default-initializable <T>
29 struct S0 { explicit S0() = default; };
30 S0 x0;
31 S0 y0{};
32 static_assert(std::constructible_from<S0>);
33 static_assert(brace_initializable<S0>);
34 LIBCPP_STATIC_ASSERT(std::__default_initializable<S0>);
35 static_assert(std::default_initializable<S0>);
36
37 struct S1 { S0 x; }; // Note: aggregate
38 S1 x1;
39 S1 y1{}; // expected-error {{chosen constructor is explicit in copy-initialization}}
40 static_assert(std::constructible_from<S1>);
41 static_assert(!brace_initializable<S1>);
42 LIBCPP_STATIC_ASSERT(std::__default_initializable<S1>);
43 static_assert(!std::default_initializable<S1>);
44
45 const int x2; // expected-error {{default initialization of an object of const type 'const int'}}
46 const int y2{};
47
48 static_assert(std::constructible_from<const int>);
49 static_assert(brace_initializable<const int>);
50 LIBCPP_STATIC_ASSERT(!std::__default_initializable<const int>);
51 static_assert(!std::default_initializable<const int>);
52
53 const int x3[1]; // expected-error-re {{default initialization of an object of const type 'const int{{[ ]*}}[1]'}}
54 const int y3[1]{};
55 static_assert(std::constructible_from<const int[1]>);
56 static_assert(brace_initializable<const int[1]>);
57 LIBCPP_STATIC_ASSERT(!std::__default_initializable<const int[1]>);
58 static_assert(!std::default_initializable<const int[1]>);
59
60 // Zero-length array extension
61 const int x4[]; // expected-error {{definition of variable with array type needs an explicit size or an initializer}}
62 const int y4[]{};
63 static_assert(!std::constructible_from<const int[]>);
64 static_assert(brace_initializable<const int[]>);
65 LIBCPP_STATIC_ASSERT(!std::__default_initializable<const int[]>);
66 static_assert(!std::default_initializable<const int[]>);
67}
68

source code of libcxx/test/std/concepts/concepts.lang/concept.default.init/default_initializable.verify.cpp