Method parse_integer

src/toml.hpp:14252–14401

		template <uint64_t base>
		TOML_NODISCARD
		TOML_NEVER_INLINE
		int64_t parse_integer()
		{
			return_if_error({});
			assert_not_eof();
			using traits = parse_integer_traits<base>;
			push_parse_scope(traits::scope_qualifier);

			[[maybe_unused]] int64_t sign = 1;
			if constexpr (traits::is_signed)
			{
				sign = *cp == U'-' ? -1 : 1;
				if (is_match(*cp, U'+', U'-'))
					advance_and_return_if_error_or_eof({});
			}

			if constexpr (base == 10)
			{
				if (!traits::is_digit(*cp))
					set_error_and_return_default("expected expected digit or sign, saw '"sv, to_sv(*cp), "'"sv);
			}
			else
			{
				// '0'
				if (*cp != U'0')
					set_error_and_return_default("expected '0', saw '"sv, to_sv(*cp), "'"sv);
				advance_and_return_if_error_or_eof({});

				// 'b', 'o', 'x'
				if (*cp != traits::prefix_codepoint)
					set_error_and_return_default("expected '"sv, traits::prefix, "', saw '"sv, to_sv(*cp), "'"sv);
				advance_and_return_if_error_or_eof({});

				if (!traits::is_digit(*cp))
					set_error_and_return_default("expected digit, saw '"sv, to_sv(*cp), "'"sv);
			}

			// consume digits
			char digits[utf8_buffered_reader::max_history_length];
			size_t length			   = {};
			const utf8_codepoint* prev = {};
			while (!is_eof() && !is_value_terminator(*cp))
			{
				if (*cp == U'_')
				{
					if (!prev || !traits::is_digit(*prev))
						set_error_and_return_default("underscores may only follow digits"sv);

					prev = cp;
					advance_and_return_if_error_or_eof({});
					continue;
				}
				else if TOML_UNLIKELY(prev && *prev == U'_' && !traits::is_digit(*cp))
					set_error_and_return_default("underscores must be followed by digits"sv);
				else if TOML_UNLIKELY(!traits::is_digit(*cp))
					set_error_and_return_default("expected digit, saw '"sv, to_sv(*cp), "'"sv);
				else if TOML_UNLIKELY(length == sizeof(digits))