libcxx/test/std/utilities/optional/optional.object/optional.object.observe/dereference_rvalue.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 T&& optional<T>::operator*() &&;
  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     constexpr int test() && {return 7;}
  33 };
  34
  35 constexpr int
  36 test()
  37 {
  38     optional<Y> opt{Y{}};
  39     return (*std::move(opt)).test();
  40 }
  41
  42 int main(int, char**)
  43 {
  44     {
  45         optional<X> opt; ((void)opt);
  46         ASSERT_SAME_TYPE(decltype(*std::move(opt)), X&&);
  47         LIBCPP_STATIC_ASSERT(noexcept(*opt));
  48         // ASSERT_NOT_NOEXCEPT(*std::move(opt));
  49         // FIXME: This assertion fails with GCC because it can see that
  50         // (A) operator*() is constexpr, and
  51         // (B) there is no path through the function that throws.
  52         // It's arguable if this is the correct behavior for the noexcept
  53         // operator.
  54         // Regardless this function should still be noexcept(false) because
  55         // it has a narrow contract.
  56     }
  57     {
  58         optional<X> opt(X{});
  59         assert((*std::move(opt)).test() == 6);
  60     }
  61     static_assert(test() == 7, "");
  62
  63     return 0;
  64 }