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

   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
  21 template<class T>
  22 concept brace_initializable = requires { T{}; };
  23
  24 void 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 }