Rules for type check in Swift builds? - swift

Question

I’ve wanted to speed up my build times, so one of the steps was using Other Swift Flags and
-Xfrontend -warn-long-function-bodies=100
-Xfrontend -warn-long-expression-type-checking=100
But I’m not really sure how type checks work. For example, here’s a simple func for creating random CGFloat. Type check for it is over 200ms
static func randomColorValue() -> CGFloat {
return CGFloat(Int.random(in: 0...255))/255.0
}
But on changing to something like this
static func randomColorValue() -> CGFloat {
let rnd = Int.random(in: 0...255)
let frnd = CGFloat(rnd)
let result = frnd/255.0
return result
}
or like this
static func randomColorValue() -> CGFloat {
let rnd : Int = Int.random(in: 0...255)
let frnd : CGFloat = CGFloat(rnd)
let result : CGFloat = frnd/255.0
return result
}
type check is still over 200ms.
What's wrong here? Is there any set of rules and best practices for dealing with build times?
My Mac is a bit older (2012), maybe that's the problem?
EDIT:
After turning off -warn-long-function-bodies problematic line appeared, and that is
CGFloat(rnd)
It appears that casting Int to Float, Double or CGFloat shows slowing down of 150ms.

Answer 1

Note that warn-long-function-bodies is unsupported (it was added as an experimental flag). If you remove it, I find that the expression time is often reported as twice as fast, which makes be believe that using the two measurements together is causing interference. Measurement takes time, too. warn-long-expression is a supported option.