Fix issue #1237
* Make the conversion operator SFINAE correct. * Workaround a GCC bug with some traits in type_traits.hpp The first bullet-point implies that every `get`/`get_ptr` be SFINAE correct as well.
This commit is contained in:
Théo DELRIEU
parent
e4bc98d036
commit
4e52277b70
4 changed files with 146 additions and 168 deletions
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@ -425,6 +425,9 @@ using to_json_function = decltype(T::to_json(std::declval<Args>()...));
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template <typename T, typename... Args>
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using from_json_function = decltype(T::from_json(std::declval<Args>()...));
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template <typename T, typename U>
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using get_template_function = decltype(std::declval<T>().template get<U>());
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///////////////////
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// is_ functions //
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///////////////////
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@ -545,8 +548,12 @@ struct is_compatible_integer_type
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CompatibleNumberIntegerType> {};
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// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
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template<typename BasicJsonType, typename T>
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struct has_from_json
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template <typename BasicJsonType, typename T, typename = void>
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struct has_from_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_from_json<BasicJsonType, T,
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enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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@ -557,8 +564,11 @@ struct has_from_json
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// This trait checks if JSONSerializer<T>::from_json(json const&) exists
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// this overload is used for non-default-constructible user-defined-types
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template <typename BasicJsonType, typename T, typename = void>
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struct has_non_default_from_json : std::false_type {};
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template<typename BasicJsonType, typename T>
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struct has_non_default_from_json
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struct has_non_default_from_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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@ -568,8 +578,12 @@ struct has_non_default_from_json
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};
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// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
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template<typename BasicJsonType, typename T>
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struct has_to_json
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// Do not evaluate the trait when T is a basic_json type, to avoid template instantiation infinite recursion.
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template <typename BasicJsonType, typename T, typename = void>
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struct has_to_json : std::false_type {};
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template <typename BasicJsonType, typename T>
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struct has_to_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
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{
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using serializer = typename BasicJsonType::template json_serializer<T, void>;
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@ -13696,6 +13710,53 @@ class basic_json
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return JSONSerializer<ValueTypeCV>::from_json(*this);
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}
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/*!
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@brief get a pointer value (implicit)
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Implicit pointer access to the internally stored JSON value. No copies are
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made.
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@warning Writing data to the pointee of the result yields an undefined
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state.
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@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
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object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
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@ref number_unsigned_t, or @ref number_float_t. Enforced by a static
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assertion.
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@return pointer to the internally stored JSON value if the requested
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pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
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@complexity Constant.
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@liveexample{The example below shows how pointers to internal values of a
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JSON value can be requested. Note that no type conversions are made and a
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`nullptr` is returned if the value and the requested pointer type does not
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match.,get_ptr}
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@since version 1.0.0
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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auto get_ptr() noexcept -> decltype(std::declval<basic_json_t&>().get_impl_ptr(std::declval<PointerType>()))
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{
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// delegate the call to get_impl_ptr<>()
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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/*!
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@brief get a pointer value (implicit)
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@copydoc get_ptr()
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value and
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std::is_const<typename std::remove_pointer<PointerType>::type>::value, int>::type = 0>
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constexpr auto get_ptr() const noexcept -> decltype(std::declval<const basic_json_t&>().get_impl_ptr(std::declval<PointerType>()))
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{
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// delegate the call to get_impl_ptr<>() const
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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/*!
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@brief get a pointer value (explicit)
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@ -13725,7 +13786,7 @@ class basic_json
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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PointerType get() noexcept
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auto get() noexcept -> decltype(std::declval<basic_json_t&>().template get_ptr<PointerType>())
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{
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// delegate the call to get_ptr
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return get_ptr<PointerType>();
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@ -13737,89 +13798,12 @@ class basic_json
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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constexpr const PointerType get() const noexcept
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constexpr auto get() const noexcept -> decltype(std::declval<const basic_json_t&>().template get_ptr<PointerType>())
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{
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// delegate the call to get_ptr
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return get_ptr<PointerType>();
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}
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/*!
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@brief get a pointer value (implicit)
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Implicit pointer access to the internally stored JSON value. No copies are
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made.
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@warning Writing data to the pointee of the result yields an undefined
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state.
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@tparam PointerType pointer type; must be a pointer to @ref array_t, @ref
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object_t, @ref string_t, @ref boolean_t, @ref number_integer_t,
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@ref number_unsigned_t, or @ref number_float_t. Enforced by a static
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assertion.
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@return pointer to the internally stored JSON value if the requested
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pointer type @a PointerType fits to the JSON value; `nullptr` otherwise
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@complexity Constant.
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@liveexample{The example below shows how pointers to internal values of a
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JSON value can be requested. Note that no type conversions are made and a
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`nullptr` is returned if the value and the requested pointer type does not
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match.,get_ptr}
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@since version 1.0.0
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value, int>::type = 0>
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PointerType get_ptr() noexcept
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{
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// get the type of the PointerType (remove pointer and const)
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using pointee_t = typename std::remove_const<typename
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std::remove_pointer<typename
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std::remove_const<PointerType>::type>::type>::type;
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// make sure the type matches the allowed types
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static_assert(
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std::is_same<object_t, pointee_t>::value
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or std::is_same<array_t, pointee_t>::value
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or std::is_same<string_t, pointee_t>::value
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or std::is_same<boolean_t, pointee_t>::value
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or std::is_same<number_integer_t, pointee_t>::value
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or std::is_same<number_unsigned_t, pointee_t>::value
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or std::is_same<number_float_t, pointee_t>::value
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, "incompatible pointer type");
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// delegate the call to get_impl_ptr<>()
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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/*!
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@brief get a pointer value (implicit)
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@copydoc get_ptr()
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*/
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template<typename PointerType, typename std::enable_if<
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std::is_pointer<PointerType>::value and
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std::is_const<typename std::remove_pointer<PointerType>::type>::value, int>::type = 0>
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constexpr const PointerType get_ptr() const noexcept
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{
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// get the type of the PointerType (remove pointer and const)
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using pointee_t = typename std::remove_const<typename
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std::remove_pointer<typename
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std::remove_const<PointerType>::type>::type>::type;
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// make sure the type matches the allowed types
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static_assert(
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std::is_same<object_t, pointee_t>::value
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or std::is_same<array_t, pointee_t>::value
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or std::is_same<string_t, pointee_t>::value
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or std::is_same<boolean_t, pointee_t>::value
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or std::is_same<number_integer_t, pointee_t>::value
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or std::is_same<number_unsigned_t, pointee_t>::value
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or std::is_same<number_float_t, pointee_t>::value
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, "incompatible pointer type");
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// delegate the call to get_impl_ptr<>() const
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return get_impl_ptr(static_cast<PointerType>(nullptr));
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}
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/*!
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@brief get a reference value (implicit)
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@ -13901,12 +13885,14 @@ class basic_json
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not std::is_same<ValueType, detail::json_ref<basic_json>>::value and
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not std::is_same<ValueType, typename string_t::value_type>::value and
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not detail::is_basic_json<ValueType>::value
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#ifndef _MSC_VER // fix for issue #167 operator<< ambiguity under VS2015
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and not std::is_same<ValueType, std::initializer_list<typename string_t::value_type>>::value
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#if defined(JSON_HAS_CPP_17) && defined(_MSC_VER) and _MSC_VER <= 1914
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and not std::is_same<ValueType, typename std::string_view>::value
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#endif
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#endif
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and detail::is_detected<detail::get_template_function, const basic_json_t&, ValueType>::value
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, int >::type = 0 >
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operator ValueType() const
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{
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