fail_to_compile_observers.hpp 4.3 KB

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  1. /* Policies for result and outcome
  2. (C) 2018-2019 Niall Douglas <http://www.nedproductions.biz/> (4 commits)
  3. File Created: Sep 2018
  4. Boost Software License - Version 1.0 - August 17th, 2003
  5. Permission is hereby granted, free of charge, to any person or organization
  6. obtaining a copy of the software and accompanying documentation covered by
  7. this license (the "Software") to use, reproduce, display, distribute,
  8. execute, and transmit the Software, and to prepare derivative works of the
  9. Software, and to permit third-parties to whom the Software is furnished to
  10. do so, all subject to the following:
  11. The copyright notices in the Software and this entire statement, including
  12. the above license grant, this restriction and the following disclaimer,
  13. must be included in all copies of the Software, in whole or in part, and
  14. all derivative works of the Software, unless such copies or derivative
  15. works are solely in the form of machine-executable object code generated by
  16. a source language processor.
  17. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18. IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19. FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
  20. SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
  21. FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
  22. ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  23. DEALINGS IN THE SOFTWARE.
  24. */
  25. #ifndef BOOST_OUTCOME_POLICY_FAIL_TO_COMPILE_OBSERVERS_HPP
  26. #define BOOST_OUTCOME_POLICY_FAIL_TO_COMPILE_OBSERVERS_HPP
  27. #include "base.hpp"
  28. BOOST_OUTCOME_V2_NAMESPACE_EXPORT_BEGIN
  29. #define BOOST_OUTCOME_FAIL_TO_COMPILE_OBSERVERS_MESSAGE \
  30. "Attempt to wide observe value, error or " \
  31. "exception for a basic_result/basic_outcome given an EC or EP type which is not void, and for whom " \
  32. "trait::is_error_code_available<EC>, trait::is_exception_ptr_available<EC>, and trait::is_exception_ptr_available<EP> " \
  33. "are all false. Please specify a NoValuePolicy to tell basic_result/basic_outcome what to do, or else use " \
  34. "a more specific convenience type alias such as unchecked<T, E> to indicate you want the wide " \
  35. "observers to be narrow, or checked<T, E> to indicate you always want an exception throw etc."
  36. namespace policy
  37. {
  38. struct fail_to_compile_observers : base
  39. {
  40. 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); }
  41. 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); }
  42. 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); }
  43. };
  44. } // namespace policy
  45. #undef BOOST_OUTCOME_FAIL_TO_COMPILE_OBSERVERS_MESSAGE
  46. BOOST_OUTCOME_V2_NAMESPACE_END
  47. #endif