Why does a simple Swift arithmetic operation compile so slow?

Question

In an attempt to optimize the build time of my app I've added the following to my OTHER_SWIFT_FLAGS:

OTHER_SWIFT_FLAGS = 
-Xfrontend -warn-long-expression-type-checking=75
-Xfrontend -warn-long-function-bodies=75

I got a warnings for this specific type checking being slow, and I cannot figure out if I can help the compiler in some way here.

var delay: TimeInterval = TimeInterval(index) * 0.05

Any suggestions what can be done to speed up the compile time for such basic arithmetic operations up?

I'm running Xcode 11.5 with Swift 5

Also tried explicitly casting the number to TimeInterval, which shouldn't be needed as all numbers are Doubles by default.

Answer 1

The compiler performs type checks. If you have a long expression, it takes time. Sometimes when the expression is too long, you even get an error as:

The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions

try something like

var delay: TimeInterval = TimeInterval(index) * TimeInterval(0.05)