libcxx/test/std/utilities/optional/optional.object/optional.object.observe/dereference_const.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 // <optional>
  11
  12 // constexpr const T& optional<T>::operator*() const &;
  13
  14 #include <optional>
  15 #include <type_traits>
  16 #include <cassert>
  17
  18 #include "test_macros.h"
  19
  20 using std::optional;
  21
  22 struct X
  23 {
  24     constexpr int test() const& {return 3;}
  25     int test() & {return 4;}
  26     constexpr int test() const&& {return 5;}
  27     int test() && {return 6;}
  28 };
  29
  30 struct Y
  31 {
  32     int test() const {return 2;}
  33 };
  34
  35 int main(int, char**)
  36 {
  37     {
  38         const optional<X> opt; ((void)opt);
  39         ASSERT_SAME_TYPE(decltype(*opt), X const&);
  40         LIBCPP_STATIC_ASSERT(noexcept(*opt));
  41         // ASSERT_NOT_NOEXCEPT(*opt);
  42         // FIXME: This assertion fails with GCC because it can see that
  43         // (A) operator*() is constexpr, and
  44         // (B) there is no path through the function that throws.
  45         // It's arguable if this is the correct behavior for the noexcept
  46         // operator.
  47         // Regardless this function should still be noexcept(false) because
  48         // it has a narrow contract.
  49     }
  50     {
  51         constexpr optional<X> opt(X{});
  52         static_assert((*opt).test() == 3, "");
  53     }
  54     {
  55         constexpr optional<Y> opt(Y{});
  56         assert((*opt).test() == 2);
  57     }
  58
  59     return 0;
  60 }