protected static function make_space_nonbreaking( $string, $narrow_space, $u ) {
		return \preg_replace(
			[
				'/\s*' . U::THIN_SPACE . '\s*/u', // @codeCoverageIgnoreStart
				'/\s*' . U::NO_BREAK_NARROW_SPACE . '\s*/u',
				"/\\s+/$u",
				'/' . self::MASKED_NARROW_SPACE . "/$u",
			],
			[
				self::MASKED_NARROW_SPACE,
				self::MASKED_NARROW_SPACE,
				U::NO_BREAK_SPACE, // @codeCoverageIgnoreEnd
				$narrow_space,
			],
			$string
		);
	}