libcxx/test/std/utilities/optional/optional.object/optional.object.observe/op_arrow_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 };
  26
  27 struct Y
  28 {
  29     int test() const noexcept {return 2;}
  30 };
  31
  32 struct Z
  33 {
  34     const Z* operator&() const;
  35     constexpr int test() const {return 1;}
  36 };
  37
  38 int main(int, char**)
  39 {
  40     {
  41         const std::optional<X> opt; ((void)opt);
  42         ASSERT_SAME_TYPE(decltype(opt.operator->()), X const*);
  43         // ASSERT_NOT_NOEXCEPT(opt.operator->());
  44         // FIXME: This assertion fails with GCC because it can see that
  45         // (A) operator->() is constexpr, and
  46         // (B) there is no path through the function that throws.
  47         // It's arguable if this is the correct behavior for the noexcept
  48         // operator.
  49         // Regardless this function should still be noexcept(false) because
  50         // it has a narrow contract.
  51     }
  52     {
  53         constexpr optional<X> opt(X{});
  54         static_assert(opt->test() == 3, "");
  55     }
  56     {
  57         constexpr optional<Y> opt(Y{});
  58         assert(opt->test() == 2);
  59     }
  60     {
  61         constexpr optional<Z> opt(Z{});
  62         static_assert(opt->test() == 1, "");
  63     }
  64
  65     return 0;
  66 }