boost/outcome/convert.hpp

0001 /* Says how to convert value, error and exception types
0002 (C) 2017-2024 Niall Douglas <http://www.nedproductions.biz/> (12 commits)
0003 File Created: Nov 2017
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_CONVERT_HPP
0032 #define BOOST_OUTCOME_CONVERT_HPP
0033
0034 #include "detail/basic_result_storage.hpp"
0035
0036 BOOST_OUTCOME_V2_NAMESPACE_EXPORT_BEGIN
0037
0038 namespace concepts
0039 {
0040 #if defined(__cpp_concepts)
0041 #if(defined(_MSC_VER) || defined(__clang__) || (defined(__GNUC__) && __cpp_concepts >= 201707) || BOOST_OUTCOME_FORCE_STD_BOOST_OUTCOME_C_CONCEPTS) &&                           \
0042 !BOOST_OUTCOME_FORCE_LEGACY_GCC_BOOST_OUTCOME_C_CONCEPTS
0043 #define BOOST_OUTCOME_GCC6_CONCEPT_BOOL
0044 #else
0045 #ifndef BOOST_OUTCOME_SUPPRESS_LEGACY_CONCEPTS_WARNING
0046 #warning "WARNING: Legacy GCC concepts are known to fail to compile in a number of important situations!"
0047 #endif
0048 #define BOOST_OUTCOME_GCC6_CONCEPT_BOOL bool
0049 #endif
0050   namespace detail
0051   {
0052     template <class T, class U>
0053     concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL SameHelper = std::is_same<T, U>::value;
0054     template <class T, class U>
0055     concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL same_as = detail::SameHelper<T, U> && detail::SameHelper<U, T>;
0056     template <class T, class U>
0057     concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL convertible = std::is_convertible<T, U>::value;
0058     template <class T, class U>
0059     concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL base_of = std::is_base_of<T, U>::value;
0060   }  // namespace detail
0061
0062
0063   /* The `value_or_none` concept.
0064   \requires That `U::value_type` exists and that `std::declval<U>().has_value()` returns a `bool` and `std::declval<U>().value()` exists.
0065   */
0066   template <class U>
0067   concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL value_or_none = requires(U a) {
0068     {
0069       a.has_value()
0070     } -> detail::same_as<bool>;
0071     {
0072       a.value()
0073     };
0074   };
0075   /* The `value_or_error` concept.
0076   \requires That `U::value_type` and `U::error_type` exist;
0077   that `std::declval<U>().has_value()` returns a `bool`, `std::declval<U>().value()` and  `std::declval<U>().error()` exists.
0078   */
0079   template <class U>
0080   concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL value_or_error = requires(U a) {
0081     {
0082       a.has_value()
0083     } -> detail::same_as<bool>;
0084     {
0085       a.value()
0086     };
0087     {
0088       a.error()
0089     };
0090   };
0091
0092 #else
0093   namespace detail
0094   {
0095     struct no_match
0096     {
0097     };
0098     inline no_match match_value_or_none(...);
0099     inline no_match match_value_or_error(...);
0100     BOOST_OUTCOME_TEMPLATE(class U)
0101     BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TEXPR(std::declval<U>().has_value()), BOOST_OUTCOME_TEXPR(std::declval<U>().value()))
0102     inline U match_value_or_none(U &&);
0103     BOOST_OUTCOME_TEMPLATE(class U)
0104     BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TEXPR(std::declval<U>().has_value()), BOOST_OUTCOME_TEXPR(std::declval<U>().value()), BOOST_OUTCOME_TEXPR(std::declval<U>().error()))
0105     inline U match_value_or_error(U &&);
0106
0107     template <class U>
0108     static constexpr bool value_or_none =
0109     !std::is_same<no_match, decltype(match_value_or_none(std::declval<BOOST_OUTCOME_V2_NAMESPACE::detail::devoid<U>>()))>::value;
0110     template <class U>
0111     static constexpr bool value_or_error =
0112     !std::is_same<no_match, decltype(match_value_or_error(std::declval<BOOST_OUTCOME_V2_NAMESPACE::detail::devoid<U>>()))>::value;
0113   }  // namespace detail
0114   /* The `value_or_none` concept.
0115   \requires That `U::value_type` exists and that `std::declval<U>().has_value()` returns a `bool` and `std::declval<U>().value()` exists.
0116   */
0117   template <class U> static constexpr bool value_or_none = detail::value_or_none<U>;
0118   /* The `value_or_error` concept.
0119   \requires That `U::value_type` and `U::error_type` exist;
0120   that `std::declval<U>().has_value()` returns a `bool`, `std::declval<U>().value()` and  `std::declval<U>().error()` exists.
0121   */
0122   template <class U> static constexpr bool value_or_error = detail::value_or_error<U>;
0123 #endif
0124 }  // namespace concepts
0125
0126 namespace convert
0127 {
0128 #if BOOST_OUTCOME_ENABLE_LEGACY_SUPPORT_FOR < 220
0129 #if defined(__cpp_concepts)
0130   template <class U>
0131   concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL ValueOrNone = concepts::value_or_none<U>;
0132   template <class U>
0133   concept BOOST_OUTCOME_GCC6_CONCEPT_BOOL ValueOrError = concepts::value_or_error<U>;
0134 #else
0135   template <class U> static constexpr bool ValueOrNone = concepts::value_or_none<U>;
0136   template <class U> static constexpr bool ValueOrError = concepts::value_or_error<U>;
0137 #endif
0138 #endif
0139
0140   namespace detail
0141   {
0142     template <class T, class X> struct make_type
0143     {
0144       template <class U> static constexpr T value(U &&v) { return T{in_place_type<typename T::value_type>, static_cast<U &&>(v).value()}; }
0145       template <class U> static constexpr T error(U &&v) { return T{in_place_type<typename T::error_type>, static_cast<U &&>(v).error()}; }
0146       static constexpr T error() { return T{in_place_type<typename T::error_type>}; }
0147     };
0148     template <class T> struct make_type<T, void>
0149     {
0150       template <class U> static constexpr T value(U && /*unused*/) { return T{in_place_type<typename T::value_type>}; }
0151       template <class U> static constexpr T error(U && /*unused*/) { return T{in_place_type<typename T::error_type>}; }
0152       static constexpr T error() { return T{in_place_type<typename T::error_type>}; }
0153     };
0154   }  // namespace detail
0155
0156   /*! AWAITING HUGO JSON CONVERSION TOOL
0157 type definition  value_or_error. Potential doc page: NOT FOUND
0158 */
0159   template <class T, class U> struct value_or_error
0160   {
0161     static constexpr bool enable_result_inputs = false;
0162     static constexpr bool enable_outcome_inputs = false;
0163     BOOST_OUTCOME_TEMPLATE(class X)
0164     BOOST_OUTCOME_TREQUIRES(
0165     BOOST_OUTCOME_TPRED(std::is_same<U, std::decay_t<X>>::value                                                                                       //
0166                   &&concepts::value_or_error<U>                                                                                                 //
0167                   && (std::is_void<typename std::decay_t<X>::value_type>::value ||
0168                       BOOST_OUTCOME_V2_NAMESPACE::detail::is_explicitly_constructible<typename T::value_type, typename std::decay_t<X>::value_type>)  //
0169                   &&(std::is_void<typename std::decay_t<X>::error_type>::value ||
0170                      BOOST_OUTCOME_V2_NAMESPACE::detail::is_explicitly_constructible<typename T::error_type, typename std::decay_t<X>::error_type>) ))
0171     constexpr T operator()(X &&v)
0172     {
0173       return v.has_value() ? detail::make_type<T, typename T::value_type>::value(static_cast<X &&>(v)) :
0174                              detail::make_type<T, typename U::error_type>::error(static_cast<X &&>(v));
0175     }
0176   };
0177 }  // namespace convert
0178
0179 BOOST_OUTCOME_V2_NAMESPACE_END
0180
0181 #endif