Open Radar

 
Summary:
Support for `defer if ` which will call defer block only if the condition are true which including throwing some error

I think there are some cases which this feature might works for example

func createGroupFromData(data: T) -> Handler {
	guard if let queue = dispatch_queue_create() else { throws error }
	defer if throws error {
		dispatch_queue_release(queue)
	}
	guard if let file = open(fd) else { throws error }
	defer if throws error {
		close(fd)
	}

	if let handler = data.handlerWithQueue(queue, file: file) {
		return handler
	} else {
		throws error // Call the previous 2 defer blocks only if this error is thrown
	}
}

This is an @schwa ’s idea and I think it would be very useful in some case.

Regression:

Notes:
Credit to @schwa