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Merge pull request #919 from theodelrieu/fix/sfinae_for_incomplete_types

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fix sfinae on basic_json UDT constructor
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Niels Lohmann 2018-01-23 07:32:06 +01:00 • committed by GitHub
commit f5c4e9f3a1
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4 changed files with 83 additions and 20 deletions
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26
develop/detail/meta.hpp
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@ -96,6 +96,14 @@ template<> struct priority_tag<0> {};
// has_/is_ functions //
////////////////////////
// source: https://stackoverflow.com/a/37193089/4116453
template <typename T, typename = void>
struct is_complete_type : std::false_type {};
template <typename T>
struct is_complete_type<T, decltype(void(sizeof(T)))> : std::true_type {};
NLOHMANN_JSON_HAS_HELPER(mapped_type);
NLOHMANN_JSON_HAS_HELPER(key_type);
NLOHMANN_JSON_HAS_HELPER(value_type);
@ -171,7 +179,6 @@ struct is_compatible_integer_type
RealIntegerType, CompatibleNumberIntegerType > ::value;
};
// trait checking if JSONSerializer<T>::from_json(json const&, udt&) exists
template<typename BasicJsonType, typename T>
struct has_from_json
@ -221,6 +228,23 @@ struct has_to_json
std::declval<typename BasicJsonType::template json_serializer<T, void>>()))>::value;
};
template <typename BasicJsonType, typename CompatibleCompleteType>
struct is_compatible_complete_type
{
static constexpr bool value =
not std::is_base_of<std::istream, CompatibleCompleteType>::value and
not std::is_same<BasicJsonType, CompatibleCompleteType>::value and
not is_basic_json_nested_type<BasicJsonType, CompatibleCompleteType>::value and
has_to_json<BasicJsonType, CompatibleCompleteType>::value;
};
template <typename BasicJsonType, typename CompatibleType>
struct is_compatible_type
: conjunction<is_complete_type<CompatibleType>,
is_compatible_complete_type<BasicJsonType, CompatibleType>>
{
};
// taken from ranges-v3
template<typename T>
struct static_const