Method value

src/toml.hpp:5392–5506

	template <typename T>
	TOML_NODISCARD
	inline optional<T> node::value() const noexcept(impl::value_retrieval_is_nothrow<T>)
	{
		using namespace impl;

		static_assert(!is_wide_string<T> || TOML_ENABLE_WINDOWS_COMPAT,
					  "Retrieving values as wide-character strings with node::value() is only "
					  "supported on Windows with TOML_ENABLE_WINDOWS_COMPAT enabled.");
		static_assert((is_native<T> || can_represent_native<T> || can_partially_represent_native<T>)&&!is_cvref<T>,
					  TOML_SA_VALUE_FUNC_MESSAGE("return type of node::value()"));

		// when asking for strings, dates, times and date_times there's no 'fuzzy' conversion
		// semantics to be mindful of so the exact retrieval is enough.
		if constexpr (is_natively_one_of<T, std::string, time, date, date_time>)
		{
			if (type() == node_type_of<T>)
				return { this->get_value_exact<T>() };
			else
				return {};
		}

		// everything else requires a bit of logicking.
		else
		{
			switch (type())
			{
				// int -> *
				case node_type::integer:
				{
					// int -> int
					if constexpr (is_natively_one_of<T, int64_t>)
					{
						if constexpr (is_native<T> || can_represent_native<T>)
							return static_cast<T>(*ref_cast<int64_t>());
						else
							return node_integer_cast<T>(*ref_cast<int64_t>());
					}

					// int -> float
					else if constexpr (is_natively_one_of<T, double>)
					{
						const int64_t val = *ref_cast<int64_t>();
						if constexpr (std::numeric_limits<T>::digits < 64)
						{
							constexpr auto largest_whole_float = (int64_t{ 1 } << std::numeric_limits<T>::digits);
							if (val < -largest_whole_float || val > largest_whole_float)
								return {};
						}
						return static_cast<T>(val);
					}

					// int -> bool
					else if constexpr (is_natively_one_of<T, bool>)
						return static_cast<bool>(*ref_cast<int64_t>());

					// int -> anything else
					else
						return {};