Function from_json

Source/external/json.hpp:4593–4600

template<typename BasicJsonType>
inline void from_json(const BasicJsonType& j, typename std::nullptr_t& n)
{
	if (JSON_HEDLEY_UNLIKELY(!j.is_null()))
	{
		JSON_THROW(type_error::create(302, concat("type must be null, but is ", j.type_name()), &j));
	}
	n = nullptr;
}

// overloads for basic_json template parameters
template < typename BasicJsonType, typename ArithmeticType,