outcome/policy/fail_to_compile_observers.hpp

0001 /* Policies for result and outcome
0002 (C) 2018-2023 Niall Douglas <http://www.nedproductions.biz/> (4 commits)
0003 File Created: Sep 2018
0004
0005
0006 Boost Software License - Version 1.0 - August 17th, 2003
0007
0008 Permission is hereby granted, free of charge, to any person or organization
0009 obtaining a copy of the software and accompanying documentation covered by
0010 this license (the "Software") to use, reproduce, display, distribute,
0011 execute, and transmit the Software, and to prepare derivative works of the
0012 Software, and to permit third-parties to whom the Software is furnished to
0013 do so, all subject to the following:
0014
0015 The copyright notices in the Software and this entire statement, including
0016 the above license grant, this restriction and the following disclaimer,
0017 must be included in all copies of the Software, in whole or in part, and
0018 all derivative works of the Software, unless such copies or derivative
0019 works are solely in the form of machine-executable object code generated by
0020 a source language processor.
0021
0022 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
0023 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
0024 FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
0025 SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
0026 FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
0027 ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
0028 DEALINGS IN THE SOFTWARE.
0029 */
0030
0031 #ifndef BOOST_OUTCOME_POLICY_FAIL_TO_COMPILE_OBSERVERS_HPP
0032 #define BOOST_OUTCOME_POLICY_FAIL_TO_COMPILE_OBSERVERS_HPP
0033
0034 #include "base.hpp"
0035
0036 BOOST_OUTCOME_V2_NAMESPACE_EXPORT_BEGIN
0037
0038 #define BOOST_OUTCOME_FAIL_TO_COMPILE_OBSERVERS_MESSAGE                                                                                                                                                                                                                                                                              \
0039   "Attempt to wide observe value, error or "                                                                                                                                                                                                                                                                                   \
0040   "exception for a basic_result/basic_outcome given an EC or EP type which is not void, and for whom "                                                                                                                                                                                                                         \
0041   "trait::is_error_code_available<EC>, trait::is_exception_ptr_available<EC>, and trait::is_exception_ptr_available<EP> "                                                                                                                                                                                                      \
0042   "are all false. Please specify a NoValuePolicy to tell basic_result/basic_outcome what to do, or else use "                                                                                                                                                                                                                  \
0043   "a more specific convenience type alias such as unchecked<T, E> to indicate you want the wide "                                                                                                                                                                                                                              \
0044   "observers to be narrow, or checked<T, E> to indicate you always want an exception throw etc."
0045
0046 namespace policy
0047 {
0048   struct fail_to_compile_observers : base
0049   {
0050     template <class Impl> static constexpr void wide_value_check(Impl && /* unused */) { static_assert(!std::is_same<Impl, Impl>::value, BOOST_OUTCOME_FAIL_TO_COMPILE_OBSERVERS_MESSAGE); }
0051     template <class Impl> static constexpr void wide_error_check(Impl && /* unused */) { static_assert(!std::is_same<Impl, Impl>::value, BOOST_OUTCOME_FAIL_TO_COMPILE_OBSERVERS_MESSAGE); }
0052     template <class Impl> static constexpr void wide_exception_check(Impl && /* unused */) { static_assert(!std::is_same<Impl, Impl>::value, BOOST_OUTCOME_FAIL_TO_COMPILE_OBSERVERS_MESSAGE); }
0053   };
0054 }  // namespace policy
0055
0056 #undef BOOST_OUTCOME_FAIL_TO_COMPILE_OBSERVERS_MESSAGE
0057
0058 BOOST_OUTCOME_V2_NAMESPACE_END
0059
0060 #endif