libcxx/test/std/utilities/variant/variant.variant/variant.ctor/default.pass.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
  10
  11 // XFAIL: availability-bad_variant_access-missing && !no-exceptions
  12
  13 // <variant>
  14
  15 // template <class ...Types> class variant;
  16
  17 // constexpr variant() noexcept(see below);
  18
  19 #include <cassert>
  20 #include <type_traits>
  21 #include <variant>
  22
  23 #include "test_macros.h"
  24 #include "variant_test_helpers.h"
  25
  26 struct NonDefaultConstructible {
  27   constexpr NonDefaultConstructible(int) {}
  28 };
  29
  30 struct NotNoexcept {
  31   NotNoexcept() noexcept(false) {}
  32 };
  33
  34 #ifndef TEST_HAS_NO_EXCEPTIONS
  35 struct DefaultCtorThrows {
  36   DefaultCtorThrows() { throw 42; }
  37 };
  38 #endif
  39
  40 void test_default_ctor_sfinae() {
  41   {
  42     using V = std::variant<std::monostate, int>;
  43     static_assert(std::is_default_constructible<V>::value, "");
  44   }
  45   {
  46     using V = std::variant<NonDefaultConstructible, int>;
  47     static_assert(!std::is_default_constructible<V>::value, "");
  48   }
  49 #if !defined(TEST_VARIANT_HAS_NO_REFERENCES)
  50   {
  51     using V = std::variant<int &, int>;
  52     static_assert(!std::is_default_constructible<V>::value, "");
  53   }
  54 #endif
  55 }
  56
  57 void test_default_ctor_noexcept() {
  58   {
  59     using V = std::variant<int>;
  60     static_assert(std::is_nothrow_default_constructible<V>::value, "");
  61   }
  62   {
  63     using V = std::variant<NotNoexcept>;
  64     static_assert(!std::is_nothrow_default_constructible<V>::value, "");
  65   }
  66 }
  67
  68 void test_default_ctor_throws() {
  69 #ifndef TEST_HAS_NO_EXCEPTIONS
  70   using V = std::variant<DefaultCtorThrows, int>;
  71   try {
  72     V v;
  73     assert(false);
  74   } catch (const int &ex) {
  75     assert(ex == 42);
  76   } catch (...) {
  77     assert(false);
  78   }
  79 #endif
  80 }
  81
  82 void test_default_ctor_basic() {
  83   {
  84     std::variant<int> v;
  85     assert(v.index() == 0);
  86     assert(std::get<0>(v) == 0);
  87   }
  88   {
  89     std::variant<int, long> v;
  90     assert(v.index() == 0);
  91     assert(std::get<0>(v) == 0);
  92   }
  93   {
  94     std::variant<int, NonDefaultConstructible> v;
  95     assert(v.index() == 0);
  96     assert(std::get<0>(v) == 0);
  97   }
  98   {
  99     using V = std::variant<int, long>;
 100     constexpr V v;
 101     static_assert(v.index() == 0, "");
 102     static_assert(std::get<0>(v) == 0, "");
 103   }
 104   {
 105     using V = std::variant<int, long>;
 106     constexpr V v;
 107     static_assert(v.index() == 0, "");
 108     static_assert(std::get<0>(v) == 0, "");
 109   }
 110   {
 111     using V = std::variant<int, NonDefaultConstructible>;
 112     constexpr V v;
 113     static_assert(v.index() == 0, "");
 114     static_assert(std::get<0>(v) == 0, "");
 115   }
 116 }
 117
 118 int main(int, char**) {
 119   test_default_ctor_basic();
 120   test_default_ctor_sfinae();
 121   test_default_ctor_noexcept();
 122   test_default_ctor_throws();
 123
 124   return 0;
 125 }