diff options
Diffstat (limited to 'boost/outcome/convert.hpp')
| -rw-r--r-- | boost/outcome/convert.hpp | 128 |
1 files changed, 128 insertions, 0 deletions
diff --git a/boost/outcome/convert.hpp b/boost/outcome/convert.hpp new file mode 100644 index 0000000000..26cd6cc623 --- /dev/null +++ b/boost/outcome/convert.hpp @@ -0,0 +1,128 @@ +/* Says how to convert value, error and exception types +(C) 2017-2019 Niall Douglas <http://www.nedproductions.biz/> (59 commits) +File Created: Nov 2017 + + +Boost Software License - Version 1.0 - August 17th, 2003 + +Permission is hereby granted, free of charge, to any person or organization +obtaining a copy of the software and accompanying documentation covered by +this license (the "Software") to use, reproduce, display, distribute, +execute, and transmit the Software, and to prepare derivative works of the +Software, and to permit third-parties to whom the Software is furnished to +do so, all subject to the following: + +The copyright notices in the Software and this entire statement, including +the above license grant, this restriction and the following disclaimer, +must be included in all copies of the Software, in whole or in part, and +all derivative works of the Software, unless such copies or derivative +works are solely in the form of machine-executable object code generated by +a source language processor. + +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT +SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE +FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, +ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER +DEALINGS IN THE SOFTWARE. +*/ + +#ifndef BOOST_OUTCOME_CONVERT_HPP +#define BOOST_OUTCOME_CONVERT_HPP + +#include "detail/basic_result_storage.hpp" + +BOOST_OUTCOME_V2_NAMESPACE_EXPORT_BEGIN + +namespace convert +{ +#if defined(__cpp_concepts) + /* The `ValueOrNone` concept. + \requires That `U::value_type` exists and that `std::declval<U>().has_value()` returns a `bool` and `std::declval<U>().value()` exists. + */ + template <class U> concept bool ValueOrNone = requires(U a) + { + { + a.has_value() + } + ->bool; + {a.value()}; + }; + /* The `ValueOrError` concept. + \requires That `U::value_type` and `U::error_type` exist; + that `std::declval<U>().has_value()` returns a `bool`, `std::declval<U>().value()` and `std::declval<U>().error()` exists. + */ + template <class U> concept bool ValueOrError = requires(U a) + { + { + a.has_value() + } + ->bool; + {a.value()}; + {a.error()}; + }; +#else + namespace detail + { + struct no_match + { + }; + inline no_match match_value_or_none(...); + inline no_match match_value_or_error(...); + BOOST_OUTCOME_TEMPLATE(class U) + BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TEXPR(std::declval<U>().has_value()), BOOST_OUTCOME_TEXPR(std::declval<U>().value())) + inline U match_value_or_none(U &&); + BOOST_OUTCOME_TEMPLATE(class U) + 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())) + inline U match_value_or_error(U &&); + + template <class U> static constexpr bool ValueOrNone = !std::is_same<no_match, decltype(match_value_or_none(std::declval<BOOST_OUTCOME_V2_NAMESPACE::detail::devoid<U>>()))>::value; + template <class U> static constexpr bool ValueOrError = !std::is_same<no_match, decltype(match_value_or_error(std::declval<BOOST_OUTCOME_V2_NAMESPACE::detail::devoid<U>>()))>::value; + } // namespace detail + /* The `ValueOrNone` concept. + \requires That `U::value_type` exists and that `std::declval<U>().has_value()` returns a `bool` and `std::declval<U>().value()` exists. + */ + template <class U> static constexpr bool ValueOrNone = detail::ValueOrNone<U>; + /* The `ValueOrError` concept. + \requires That `U::value_type` and `U::error_type` exist; + that `std::declval<U>().has_value()` returns a `bool`, `std::declval<U>().value()` and `std::declval<U>().error()` exists. + */ + template <class U> static constexpr bool ValueOrError = detail::ValueOrError<U>; +#endif + + namespace detail + { + template <class T, class X> struct make_type + { + template <class U> static constexpr T value(U &&v) { return T{in_place_type<typename T::value_type>, static_cast<U &&>(v).value()}; } + template <class U> static constexpr T error(U &&v) { return T{in_place_type<typename T::error_type>, static_cast<U &&>(v).error()}; } + static constexpr T error() { return T{in_place_type<typename T::error_type>}; } + }; + template <class T> struct make_type<T, void> + { + template <class U> static constexpr T value(U && /*unused*/) { return T{in_place_type<typename T::value_type>}; } + template <class U> static constexpr T error(U && /*unused*/) { return T{in_place_type<typename T::error_type>}; } + static constexpr T error() { return T{in_place_type<typename T::error_type>}; } + }; + } // namespace detail + + /*! AWAITING HUGO JSON CONVERSION TOOL +type definition value_or_error. Potential doc page: NOT FOUND +*/ + template <class T, class U> struct value_or_error + { + static constexpr bool enable_result_inputs = false; + static constexpr bool enable_outcome_inputs = false; + BOOST_OUTCOME_TEMPLATE(class X) + BOOST_OUTCOME_TREQUIRES(BOOST_OUTCOME_TPRED(std::is_same<U, std::decay_t<X>>::value // + &&ValueOrError<U> // + && (std::is_void<typename std::decay_t<X>::value_type>::value || BOOST_OUTCOME_V2_NAMESPACE::detail::is_explicitly_constructible<typename T::value_type, typename std::decay_t<X>::value_type>) // + &&(std::is_void<typename std::decay_t<X>::error_type>::value || BOOST_OUTCOME_V2_NAMESPACE::detail::is_explicitly_constructible<typename T::error_type, typename std::decay_t<X>::error_type>) )) + constexpr T operator()(X &&v) { return v.has_value() ? detail::make_type<T, typename T::value_type>::value(static_cast<X &&>(v)) : detail::make_type<T, typename U::error_type>::error(static_cast<X &&>(v)); } + }; +} // namespace convert + +BOOST_OUTCOME_V2_NAMESPACE_END + +#endif |