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Fix issue #1237

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* 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 2018-09-12 17:01:27 +02:00
parent e4bc98d036
commit 4e52277b70
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GPG key ID: A5A505438C20539A
4 changed files with 146 additions and 168 deletions
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24
include/nlohmann/detail/meta/type_traits.hpp
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@ -65,6 +65,9 @@ using to_json_function = decltype(T::to_json(std::declval<Args>()...));
template <typename T, typename... Args>
using from_json_function = decltype(T::from_json(std::declval<Args>()...));
template <typename T, typename U>
using get_template_function = decltype(std::declval<T>().template get<U>());
///////////////////
// is_ functions //
///////////////////
@ -185,8 +188,12 @@ struct is_compatible_integer_type
CompatibleNumberIntegerType> {};
// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
template<typename BasicJsonType, typename T>
struct has_from_json
template <typename BasicJsonType, typename T, typename = void>
struct has_from_json : std::false_type {};
template <typename BasicJsonType, typename T>
struct has_from_json<BasicJsonType, T,
enable_if_t<not is_basic_json<T>::value>>
{
using serializer = typename BasicJsonType::template json_serializer<T, void>;
@ -197,8 +204,11 @@ struct has_from_json
// This trait checks if JSONSerializer<T>::from_json(json const&) exists
// this overload is used for non-default-constructible user-defined-types
template <typename BasicJsonType, typename T, typename = void>
struct has_non_default_from_json : std::false_type {};
template<typename BasicJsonType, typename T>
struct has_non_default_from_json
struct has_non_default_from_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
{
using serializer = typename BasicJsonType::template json_serializer<T, void>;
@ -208,8 +218,12 @@ struct has_non_default_from_json
};
// This trait checks if BasicJsonType::json_serializer<T>::to_json exists
template<typename BasicJsonType, typename T>
struct has_to_json
// Do not evaluate the trait when T is a basic_json type, to avoid template instantiation infinite recursion.
template <typename BasicJsonType, typename T, typename = void>
struct has_to_json : std::false_type {};
template <typename BasicJsonType, typename T>
struct has_to_json<BasicJsonType, T, enable_if_t<not is_basic_json<T>::value>>
{
using serializer = typename BasicJsonType::template json_serializer<T, void>;