| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | // | ||
| 2 | // Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.com) | ||
| 3 | // Copyright (c) 2022 Dmitry Arkhipov (grisumbras@yandex.ru) | ||
| 4 | // | ||
| 5 | // Distributed under the Boost Software License, Version 1.0. (See accompanying | ||
| 6 | // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | ||
| 7 | // | ||
| 8 | // Official repository: https://github.com/boostorg/json | ||
| 9 | // | ||
| 10 | |||
| 11 | #ifndef BOOST_JSON_IMPL_CONVERSION_HPP | ||
| 12 | #define BOOST_JSON_IMPL_CONVERSION_HPP | ||
| 13 | |||
| 14 | #include <boost/json/fwd.hpp> | ||
| 15 | #include <boost/json/value.hpp> | ||
| 16 | #include <boost/json/string_view.hpp> | ||
| 17 | #include <boost/describe/enumerators.hpp> | ||
| 18 | #include <boost/describe/members.hpp> | ||
| 19 | #include <boost/describe/bases.hpp> | ||
| 20 | #include <boost/mp11/algorithm.hpp> | ||
| 21 | #include <boost/mp11/utility.hpp> | ||
| 22 | #include <boost/system/result.hpp> | ||
| 23 | |||
| 24 | #include <iterator> | ||
| 25 | #include <tuple> | ||
| 26 | #include <utility> | ||
| 27 | #ifndef BOOST_NO_CXX17_HDR_VARIANT | ||
| 28 | # include <variant> | ||
| 29 | #endif // BOOST_NO_CXX17_HDR_VARIANT | ||
| 30 | |||
| 31 | namespace boost { | ||
| 32 | namespace json { | ||
| 33 | namespace detail { | ||
| 34 | |||
| 35 | #ifdef __cpp_lib_nonmember_container_access | ||
| 36 | using std::size; | ||
| 37 | #endif | ||
| 38 | |||
| 39 | template<std::size_t I, class T> | ||
| 40 | using tuple_element_t = typename std::tuple_element<I, T>::type; | ||
| 41 | |||
| 42 | template<class T> | ||
| 43 | using iterator_type = decltype(std::begin(std::declval<T&>())); | ||
| 44 | template<class T> | ||
| 45 | using iterator_traits = std::iterator_traits< iterator_type<T> >; | ||
| 46 | |||
| 47 | template<class T> | ||
| 48 | using value_type = typename iterator_traits<T>::value_type; | ||
| 49 | template<class T> | ||
| 50 | using mapped_type = tuple_element_t< 1, value_type<T> >; | ||
| 51 | |||
| 52 | // had to make the metafunction always succeeding in order to make it work | ||
| 53 | // with msvc 14.0 | ||
| 54 | template<class T> | ||
| 55 | using key_type_helper = tuple_element_t< 0, value_type<T> >; | ||
| 56 | template<class T> | ||
| 57 | using key_type = mp11::mp_eval_or< | ||
| 58 | void, | ||
| 59 | key_type_helper, | ||
| 60 | T>; | ||
| 61 | |||
| 62 | template<class T> | ||
| 63 | using are_begin_and_end_same = std::is_same< | ||
| 64 | iterator_type<T>, | ||
| 65 | decltype(std::end(std::declval<T&>()))>; | ||
| 66 | |||
| 67 | // msvc 14.0 gets confused when std::is_same is used directly | ||
| 68 | template<class A, class B> | ||
| 69 | using is_same_msvc_140 = std::is_same<A, B>; | ||
| 70 | template<class T> | ||
| 71 | using is_its_own_value = is_same_msvc_140<value_type<T>, T>; | ||
| 72 | |||
| 73 | template<class T> | ||
| 74 | using not_its_own_value = mp11::mp_not< is_its_own_value<T> >; | ||
| 75 | |||
| 76 | template<class T> | ||
| 77 | using begin_iterator_category = typename std::iterator_traits< | ||
| 78 | iterator_type<T>>::iterator_category; | ||
| 79 | |||
| 80 | template<class T> | ||
| 81 | using has_positive_tuple_size = mp11::mp_bool< | ||
| 82 | (std::tuple_size<T>::value > 0) >; | ||
| 83 | |||
| 84 | template<class T> | ||
| 85 | using has_unique_keys = has_positive_tuple_size<decltype( | ||
| 86 | std::declval<T&>().emplace( | ||
| 87 | std::declval<value_type<T>>()))>; | ||
| 88 | |||
| 89 | template<class T> | ||
| 90 | using has_string_type = std::is_same< | ||
| 91 | typename T::string_type, std::basic_string<typename T::value_type> >; | ||
| 92 | |||
| 93 | template<class T> | ||
| 94 | struct is_value_type_pair_helper : std::false_type | ||
| 95 | { }; | ||
| 96 | template<class T1, class T2> | ||
| 97 | struct is_value_type_pair_helper<std::pair<T1, T2>> : std::true_type | ||
| 98 | { }; | ||
| 99 | template<class T> | ||
| 100 | using is_value_type_pair = is_value_type_pair_helper<value_type<T>>; | ||
| 101 | |||
| 102 | template<class T> | ||
| 103 | using has_size_member_helper | ||
| 104 | = std::is_convertible<decltype(std::declval<T&>().size()), std::size_t>; | ||
| 105 | template<class T> | ||
| 106 | using has_size_member = mp11::mp_valid_and_true<has_size_member_helper, T>; | ||
| 107 | template<class T> | ||
| 108 | using has_free_size_helper | ||
| 109 | = std::is_convertible< | ||
| 110 | decltype(size(std::declval<T const&>())), | ||
| 111 | std::size_t>; | ||
| 112 | template<class T> | ||
| 113 | using has_free_size = mp11::mp_valid_and_true<has_free_size_helper, T>; | ||
| 114 | template<class T> | ||
| 115 | using size_implementation = mp11::mp_cond< | ||
| 116 | has_size_member<T>, mp11::mp_int<3>, | ||
| 117 | has_free_size<T>, mp11::mp_int<2>, | ||
| 118 | std::is_array<T>, mp11::mp_int<1>, | ||
| 119 | mp11::mp_true, mp11::mp_int<0>>; | ||
| 120 | |||
| 121 | template<class T> | ||
| 122 | std::size_t | ||
| 123 | 276 | try_size(T&& cont, mp11::mp_int<3>) | |
| 124 | { | ||
| 125 | 276 | return cont.size(); | |
| 126 | } | ||
| 127 | |||
| 128 | template<class T> | ||
| 129 | std::size_t | ||
| 130 | 1 | try_size(T& cont, mp11::mp_int<2>) | |
| 131 | { | ||
| 132 | 1 | return size(cont); | |
| 133 | } | ||
| 134 | |||
| 135 | template<class T, std::size_t N> | ||
| 136 | std::size_t | ||
| 137 | 1 | try_size(T(&)[N], mp11::mp_int<1>) | |
| 138 | { | ||
| 139 | 1 | return N; | |
| 140 | } | ||
| 141 | |||
| 142 | template<class T> | ||
| 143 | std::size_t | ||
| 144 | 14 | try_size(T&, mp11::mp_int<0>) | |
| 145 | { | ||
| 146 | 14 | return 0; | |
| 147 | } | ||
| 148 | |||
| 149 | template<class T> | ||
| 150 | using has_push_back_helper | ||
| 151 | = decltype(std::declval<T&>().push_back(std::declval<value_type<T>>())); | ||
| 152 | template<class T> | ||
| 153 | using has_push_back = mp11::mp_valid<has_push_back_helper, T>; | ||
| 154 | template<class T> | ||
| 155 | using inserter_implementation = mp11::mp_cond< | ||
| 156 | is_tuple_like<T>, mp11::mp_int<2>, | ||
| 157 | has_push_back<T>, mp11::mp_int<1>, | ||
| 158 | mp11::mp_true, mp11::mp_int<0>>; | ||
| 159 | |||
| 160 | template<class T> | ||
| 161 | iterator_type<T> | ||
| 162 | 62 | inserter( | |
| 163 | T& target, | ||
| 164 | mp11::mp_int<2>) | ||
| 165 | { | ||
| 166 | 62 | return target.begin(); | |
| 167 | } | ||
| 168 | |||
| 169 | template<class T> | ||
| 170 | std::back_insert_iterator<T> | ||
| 171 | 1134 | inserter( | |
| 172 | T& target, | ||
| 173 | mp11::mp_int<1>) | ||
| 174 | { | ||
| 175 | 1134 | return std::back_inserter(target); | |
| 176 | } | ||
| 177 | |||
| 178 | template<class T> | ||
| 179 | std::insert_iterator<T> | ||
| 180 | 104 | inserter( | |
| 181 | T& target, | ||
| 182 | mp11::mp_int<0>) | ||
| 183 | { | ||
| 184 | 104 | return std::inserter( target, target.end() ); | |
| 185 | } | ||
| 186 | |||
| 187 | using value_from_conversion = mp11::mp_true; | ||
| 188 | using value_to_conversion = mp11::mp_false; | ||
| 189 | |||
| 190 | struct user_conversion_tag { }; | ||
| 191 | struct context_conversion_tag : user_conversion_tag { }; | ||
| 192 | struct full_context_conversion_tag : context_conversion_tag { }; | ||
| 193 | struct native_conversion_tag { }; | ||
| 194 | struct value_conversion_tag : native_conversion_tag { }; | ||
| 195 | struct object_conversion_tag : native_conversion_tag { }; | ||
| 196 | struct array_conversion_tag : native_conversion_tag { }; | ||
| 197 | struct string_conversion_tag : native_conversion_tag { }; | ||
| 198 | struct bool_conversion_tag : native_conversion_tag { }; | ||
| 199 | struct number_conversion_tag : native_conversion_tag { }; | ||
| 200 | struct integral_conversion_tag : number_conversion_tag { }; | ||
| 201 | struct floating_point_conversion_tag : number_conversion_tag { }; | ||
| 202 | struct null_like_conversion_tag { }; | ||
| 203 | struct string_like_conversion_tag { }; | ||
| 204 | struct map_like_conversion_tag { }; | ||
| 205 | struct path_conversion_tag { }; | ||
| 206 | struct sequence_conversion_tag { }; | ||
| 207 | struct tuple_conversion_tag { }; | ||
| 208 | struct described_class_conversion_tag { }; | ||
| 209 | struct described_enum_conversion_tag { }; | ||
| 210 | struct variant_conversion_tag { }; | ||
| 211 | struct optional_conversion_tag { }; | ||
| 212 | struct no_conversion_tag { }; | ||
| 213 | |||
| 214 | template<class... Args> | ||
| 215 | using supports_tag_invoke = decltype(tag_invoke( std::declval<Args>()... )); | ||
| 216 | |||
| 217 | template<class T> | ||
| 218 | using has_user_conversion_from_impl = supports_tag_invoke< | ||
| 219 | value_from_tag, value&, T&& >; | ||
| 220 | template<class T> | ||
| 221 | using has_user_conversion_to_impl = supports_tag_invoke< | ||
| 222 | value_to_tag<T>, value const& >; | ||
| 223 | template<class T> | ||
| 224 | using has_nonthrowing_user_conversion_to_impl = supports_tag_invoke< | ||
| 225 | try_value_to_tag<T>, value const& >; | ||
| 226 | template< class T, class Dir > | ||
| 227 | using has_user_conversion1 = mp11::mp_if< | ||
| 228 | std::is_same<Dir, value_from_conversion>, | ||
| 229 | mp11::mp_valid<has_user_conversion_from_impl, T>, | ||
| 230 | mp11::mp_or< | ||
| 231 | mp11::mp_valid<has_user_conversion_to_impl, T>, | ||
| 232 | mp11::mp_valid<has_nonthrowing_user_conversion_to_impl, T>>>; | ||
| 233 | |||
| 234 | template< class Ctx, class T > | ||
| 235 | using has_context_conversion_from_impl = supports_tag_invoke< | ||
| 236 | value_from_tag, value&, T&&, Ctx const& >; | ||
| 237 | template< class Ctx, class T > | ||
| 238 | using has_context_conversion_to_impl = supports_tag_invoke< | ||
| 239 | value_to_tag<T>, value const&, Ctx const& >; | ||
| 240 | template< class Ctx, class T > | ||
| 241 | using has_nonthrowing_context_conversion_to_impl = supports_tag_invoke< | ||
| 242 | try_value_to_tag<T>, value const&, Ctx const& >; | ||
| 243 | template< class Ctx, class T, class Dir > | ||
| 244 | using has_user_conversion2 = mp11::mp_if< | ||
| 245 | std::is_same<Dir, value_from_conversion>, | ||
| 246 | mp11::mp_valid<has_context_conversion_from_impl, Ctx, T>, | ||
| 247 | mp11::mp_or< | ||
| 248 | mp11::mp_valid<has_context_conversion_to_impl, Ctx, T>, | ||
| 249 | mp11::mp_valid<has_nonthrowing_context_conversion_to_impl, Ctx, T>>>; | ||
| 250 | |||
| 251 | template< class Ctx, class T > | ||
| 252 | using has_full_context_conversion_from_impl = supports_tag_invoke< | ||
| 253 | value_from_tag, value&, T&&, Ctx const&, Ctx const& >; | ||
| 254 | template< class Ctx, class T > | ||
| 255 | using has_full_context_conversion_to_impl = supports_tag_invoke< | ||
| 256 | value_to_tag<T>, value const&, Ctx const&, Ctx const& >; | ||
| 257 | template< class Ctx, class T > | ||
| 258 | using has_nonthrowing_full_context_conversion_to_impl = supports_tag_invoke< | ||
| 259 | try_value_to_tag<T>, value const&, Ctx const&, Ctx const& >; | ||
| 260 | template< class Ctx, class T, class Dir > | ||
| 261 | using has_user_conversion3 = mp11::mp_if< | ||
| 262 | std::is_same<Dir, value_from_conversion>, | ||
| 263 | mp11::mp_valid<has_full_context_conversion_from_impl, Ctx, T>, | ||
| 264 | mp11::mp_or< | ||
| 265 | mp11::mp_valid<has_full_context_conversion_to_impl, Ctx, T>, | ||
| 266 | mp11::mp_valid< | ||
| 267 | has_nonthrowing_full_context_conversion_to_impl, Ctx, T>>>; | ||
| 268 | |||
| 269 | template< class T > | ||
| 270 | using described_non_public_members = describe::describe_members< | ||
| 271 | T, describe::mod_private | describe::mod_protected>; | ||
| 272 | template< class T > | ||
| 273 | using described_bases = describe::describe_bases< | ||
| 274 | T, describe::mod_any_access>; | ||
| 275 | |||
| 276 | #if defined(BOOST_MSVC) && BOOST_MSVC < 1920 | ||
| 277 | |||
| 278 | template< class T > | ||
| 279 | struct described_member_t_impl; | ||
| 280 | |||
| 281 | template< class T, class C > | ||
| 282 | struct described_member_t_impl<T C::*> | ||
| 283 | { | ||
| 284 | using type = T; | ||
| 285 | }; | ||
| 286 | |||
| 287 | template< class T, class D > | ||
| 288 | using described_member_t = remove_cvref< | ||
| 289 | typename described_member_t_impl< | ||
| 290 | remove_cvref<decltype(D::pointer)> >::type>; | ||
| 291 | |||
| 292 | #else | ||
| 293 | |||
| 294 | template< class T, class D > | ||
| 295 | using described_member_t = remove_cvref<decltype( | ||
| 296 | std::declval<T&>().* D::pointer )>; | ||
| 297 | |||
| 298 | #endif | ||
| 299 | |||
| 300 | template< class T > | ||
| 301 | using described_members = describe::describe_members< | ||
| 302 | T, describe::mod_any_access | describe::mod_inherited>; | ||
| 303 | |||
| 304 | // user conversion (via tag_invoke) | ||
| 305 | template< class Ctx, class T, class Dir > | ||
| 306 | using user_conversion_category = mp11::mp_cond< | ||
| 307 | has_user_conversion3<Ctx, T, Dir>, full_context_conversion_tag, | ||
| 308 | has_user_conversion2<Ctx, T, Dir>, context_conversion_tag, | ||
| 309 | has_user_conversion1<T, Dir>, user_conversion_tag>; | ||
| 310 | |||
| 311 | // native conversions (constructors and member functions of value) | ||
| 312 | template< class T > | ||
| 313 | using native_conversion_category = mp11::mp_cond< | ||
| 314 | std::is_same<T, value>, value_conversion_tag, | ||
| 315 | std::is_same<T, array>, array_conversion_tag, | ||
| 316 | std::is_same<T, object>, object_conversion_tag, | ||
| 317 | std::is_same<T, string>, string_conversion_tag>; | ||
| 318 | |||
| 319 | // generic conversions | ||
| 320 | template< class T > | ||
| 321 | using generic_conversion_category = mp11::mp_cond< | ||
| 322 | std::is_same<T, bool>, bool_conversion_tag, | ||
| 323 | std::is_integral<T>, integral_conversion_tag, | ||
| 324 | std::is_floating_point<T>, floating_point_conversion_tag, | ||
| 325 | is_null_like<T>, null_like_conversion_tag, | ||
| 326 | is_string_like<T>, string_like_conversion_tag, | ||
| 327 | is_map_like<T>, map_like_conversion_tag, | ||
| 328 | is_sequence_like<T>, sequence_conversion_tag, | ||
| 329 | is_tuple_like<T>, tuple_conversion_tag, | ||
| 330 | is_described_class<T>, described_class_conversion_tag, | ||
| 331 | is_described_enum<T>, described_enum_conversion_tag, | ||
| 332 | is_variant_like<T>, variant_conversion_tag, | ||
| 333 | is_optional_like<T>, optional_conversion_tag, | ||
| 334 | is_path_like<T>, path_conversion_tag, | ||
| 335 | // failed to find a suitable implementation | ||
| 336 | mp11::mp_true, no_conversion_tag>; | ||
| 337 | |||
| 338 | template< class T > | ||
| 339 | using nested_type = typename T::type; | ||
| 340 | template< class T1, class T2 > | ||
| 341 | using conversion_category_impl_helper = mp11::mp_eval_if_not< | ||
| 342 | std::is_same<detail::no_conversion_tag, T1>, | ||
| 343 | T1, | ||
| 344 | mp11::mp_eval_or_q, T1, mp11::mp_quote<nested_type>, T2>; | ||
| 345 | template< class Ctx, class T, class Dir > | ||
| 346 | struct conversion_category_impl | ||
| 347 | { | ||
| 348 | using type = mp11::mp_fold< | ||
| 349 | mp11::mp_list< | ||
| 350 | mp11::mp_defer<user_conversion_category, Ctx, T, Dir>, | ||
| 351 | mp11::mp_defer<native_conversion_category, T>, | ||
| 352 | mp11::mp_defer<generic_conversion_category, T>>, | ||
| 353 | no_conversion_tag, | ||
| 354 | conversion_category_impl_helper>; | ||
| 355 | }; | ||
| 356 | template< class Ctx, class T, class Dir > | ||
| 357 | using conversion_category = | ||
| 358 | typename conversion_category_impl< Ctx, T, Dir >::type; | ||
| 359 | |||
| 360 | template< class T > | ||
| 361 | using any_conversion_tag = mp11::mp_not< | ||
| 362 | std::is_same< T, no_conversion_tag > >; | ||
| 363 | |||
| 364 | template< class T, class Dir, class... Ctxs > | ||
| 365 | struct conversion_category_impl< std::tuple<Ctxs...>, T, Dir > | ||
| 366 | { | ||
| 367 | using ctxs = mp11::mp_list< remove_cvref<Ctxs>... >; | ||
| 368 | using cats = mp11::mp_list< | ||
| 369 | conversion_category<remove_cvref<Ctxs>, T, Dir>... >; | ||
| 370 | |||
| 371 | template< class I > | ||
| 372 | using exists = mp11::mp_less< I, mp11::mp_size<cats> >; | ||
| 373 | |||
| 374 | using context2 = mp11::mp_find< cats, full_context_conversion_tag >; | ||
| 375 | using context1 = mp11::mp_find< cats, context_conversion_tag >; | ||
| 376 | using context0 = mp11::mp_find< cats, user_conversion_tag >; | ||
| 377 | using index = mp11::mp_cond< | ||
| 378 | exists<context2>, context2, | ||
| 379 | exists<context1>, context1, | ||
| 380 | exists<context0>, context0, | ||
| 381 | mp11::mp_true, mp11::mp_find_if< cats, any_conversion_tag > >; | ||
| 382 | using type = mp11::mp_eval_or< | ||
| 383 | no_conversion_tag, | ||
| 384 | mp11::mp_at, cats, index >; | ||
| 385 | }; | ||
| 386 | |||
| 387 | struct no_context | ||
| 388 | {}; | ||
| 389 | |||
| 390 | template <class T, class Dir> | ||
| 391 | using can_convert = mp11::mp_not< | ||
| 392 | std::is_same< | ||
| 393 | detail::conversion_category<no_context, T, Dir>, | ||
| 394 | detail::no_conversion_tag>>; | ||
| 395 | |||
| 396 | template<class Impl1, class Impl2> | ||
| 397 | using conversion_round_trips_helper = mp11::mp_or< | ||
| 398 | std::is_same<Impl1, Impl2>, | ||
| 399 | std::is_base_of<user_conversion_tag, Impl1>, | ||
| 400 | std::is_base_of<user_conversion_tag, Impl2>>; | ||
| 401 | template< class Ctx, class T, class Dir > | ||
| 402 | using conversion_round_trips = conversion_round_trips_helper< | ||
| 403 | conversion_category<Ctx, T, Dir>, | ||
| 404 | conversion_category<Ctx, T, mp11::mp_not<Dir>>>; | ||
| 405 | |||
| 406 | template< class T1, class T2 > | ||
| 407 | struct copy_cref_helper | ||
| 408 | { | ||
| 409 | using type = remove_cvref<T2>; | ||
| 410 | }; | ||
| 411 | template< class T1, class T2 > | ||
| 412 | using copy_cref = typename copy_cref_helper< T1, T2 >::type; | ||
| 413 | |||
| 414 | template< class T1, class T2 > | ||
| 415 | struct copy_cref_helper<T1 const, T2> | ||
| 416 | { | ||
| 417 | using type = remove_cvref<T2> const; | ||
| 418 | }; | ||
| 419 | template< class T1, class T2 > | ||
| 420 | struct copy_cref_helper<T1&, T2> | ||
| 421 | { | ||
| 422 | using type = copy_cref<T1, T2>&; | ||
| 423 | }; | ||
| 424 | template< class T1, class T2 > | ||
| 425 | struct copy_cref_helper<T1&&, T2> | ||
| 426 | { | ||
| 427 | using type = copy_cref<T1, T2>&&; | ||
| 428 | }; | ||
| 429 | |||
| 430 | template< class Rng, class Traits > | ||
| 431 | using forwarded_value_helper = mp11::mp_if< | ||
| 432 | std::is_convertible< | ||
| 433 | typename Traits::reference, | ||
| 434 | copy_cref<Rng, typename Traits::value_type> >, | ||
| 435 | copy_cref<Rng, typename Traits::value_type>, | ||
| 436 | typename Traits::value_type >; | ||
| 437 | |||
| 438 | template< class Rng > | ||
| 439 | using forwarded_value = forwarded_value_helper< | ||
| 440 | Rng, iterator_traits< Rng > >; | ||
| 441 | |||
| 442 | template< class Ctx, class T, class Dir > | ||
| 443 | struct supported_context | ||
| 444 | { | ||
| 445 | using type = Ctx; | ||
| 446 | |||
| 447 | static | ||
| 448 | type const& | ||
| 449 | 60 | get( Ctx const& ctx ) noexcept | |
| 450 | { | ||
| 451 | 60 | return ctx; | |
| 452 | } | ||
| 453 | }; | ||
| 454 | |||
| 455 | template< class T, class Dir, class... Ctxs > | ||
| 456 | struct supported_context< std::tuple<Ctxs...>, T, Dir > | ||
| 457 | { | ||
| 458 | using Ctx = std::tuple<Ctxs...>; | ||
| 459 | using impl = conversion_category_impl<Ctx, T, Dir>; | ||
| 460 | using index = typename impl::index; | ||
| 461 | using next_supported = supported_context< | ||
| 462 | mp11::mp_at< typename impl::ctxs, index >, T, Dir >; | ||
| 463 | using type = typename next_supported::type; | ||
| 464 | |||
| 465 | static | ||
| 466 | type const& | ||
| 467 | 19 | get( Ctx const& ctx ) noexcept | |
| 468 | { | ||
| 469 | 19 | return next_supported::get( std::get<index::value>( ctx ) ); | |
| 470 | } | ||
| 471 | }; | ||
| 472 | |||
| 473 | template< class T > | ||
| 474 | using value_result_type = typename std::decay< | ||
| 475 | decltype( std::declval<T&>().value() )>::type; | ||
| 476 | |||
| 477 | template< class T > | ||
| 478 | using can_reset = decltype( std::declval<T&>().reset() ); | ||
| 479 | |||
| 480 | template< class T > | ||
| 481 | using has_valueless_by_exception = | ||
| 482 | decltype( std::declval<T const&>().valueless_by_exception() ); | ||
| 483 | |||
| 484 | } // namespace detail | ||
| 485 | |||
| 486 | template <class T> | ||
| 487 | struct result_for<T, value> | ||
| 488 | { | ||
| 489 | using type = system::result< detail::remove_cvref<T> >; | ||
| 490 | }; | ||
| 491 | |||
| 492 | template<class T> | ||
| 493 | struct is_string_like | ||
| 494 | : std::is_convertible<T, string_view> | ||
| 495 | { }; | ||
| 496 | |||
| 497 | template<class T> | ||
| 498 | struct is_path_like | ||
| 499 | : mp11::mp_all< | ||
| 500 | mp11::mp_valid_and_true<detail::is_its_own_value, T>, | ||
| 501 | mp11::mp_valid_and_true<detail::has_string_type, T>> | ||
| 502 | { }; | ||
| 503 | template<class T> | ||
| 504 | struct is_sequence_like | ||
| 505 | : mp11::mp_all< | ||
| 506 | mp11::mp_valid_and_true<detail::are_begin_and_end_same, T>, | ||
| 507 | mp11::mp_valid_and_true<detail::not_its_own_value, T>, | ||
| 508 | mp11::mp_valid<detail::begin_iterator_category, T>> | ||
| 509 | { }; | ||
| 510 | |||
| 511 | template<class T> | ||
| 512 | struct is_map_like | ||
| 513 | : mp11::mp_all< | ||
| 514 | is_sequence_like<T>, | ||
| 515 | mp11::mp_valid_and_true<detail::is_value_type_pair, T>, | ||
| 516 | is_string_like<detail::key_type<T>>, | ||
| 517 | mp11::mp_valid_and_true<detail::has_unique_keys, T>> | ||
| 518 | { }; | ||
| 519 | |||
| 520 | template<class T> | ||
| 521 | struct is_tuple_like | ||
| 522 | : mp11::mp_valid_and_true<detail::has_positive_tuple_size, T> | ||
| 523 | { }; | ||
| 524 | |||
| 525 | template<> | ||
| 526 | struct is_null_like<std::nullptr_t> | ||
| 527 | : std::true_type | ||
| 528 | { }; | ||
| 529 | |||
| 530 | #ifndef BOOST_NO_CXX17_HDR_VARIANT | ||
| 531 | template<> | ||
| 532 | struct is_null_like<std::monostate> | ||
| 533 | : std::true_type | ||
| 534 | { }; | ||
| 535 | #endif // BOOST_NO_CXX17_HDR_VARIANT | ||
| 536 | |||
| 537 | template<class T> | ||
| 538 | struct is_described_class | ||
| 539 | : mp11::mp_and< | ||
| 540 | describe::has_describe_members<T>, | ||
| 541 | mp11::mp_not< std::is_union<T> >, | ||
| 542 | mp11::mp_empty< | ||
| 543 | mp11::mp_eval_or< | ||
| 544 | mp11::mp_list<>, detail::described_non_public_members, T>>, | ||
| 545 | mp11::mp_empty< | ||
| 546 | mp11::mp_eval_or<mp11::mp_list<>, detail::described_bases, T>>> | ||
| 547 | { }; | ||
| 548 | |||
| 549 | template<class T> | ||
| 550 | struct is_described_enum | ||
| 551 | : describe::has_describe_enumerators<T> | ||
| 552 | { }; | ||
| 553 | |||
| 554 | template<class T> | ||
| 555 | struct is_variant_like : mp11::mp_valid<detail::has_valueless_by_exception, T> | ||
| 556 | { }; | ||
| 557 | |||
| 558 | template<class T> | ||
| 559 | struct is_optional_like | ||
| 560 | : mp11::mp_and< | ||
| 561 | mp11::mp_not<std::is_void< | ||
| 562 | mp11::mp_eval_or<void, detail::value_result_type, T>>>, | ||
| 563 | mp11::mp_valid<detail::can_reset, T>> | ||
| 564 | { }; | ||
| 565 | |||
| 566 | } // namespace json | ||
| 567 | } // namespace boost | ||
| 568 | |||
| 569 | #endif // BOOST_JSON_IMPL_CONVERSION_HPP | ||
| 570 |