private function determine_scalar( $type ) {
		$synonyms = array(
			'int' => 'integer',
			'float' => 'double',
			'bool' => 'boolean',
		);

		if ( array_key_exists( $type, $synonyms ) ) {
			$type = $synonyms[ $type ];
		}

		return in_array( $type, array( 'string', 'integer', 'double', 'boolean' ) ) ?
			$type :
			null;
	}