Swift has the slowest compiler I have ever had the misfortune of using. The dev iteration cycle was unbearable for me in a Swift project the I inherited.
SwiftUI and Previews sort-of address this now but it's not really ready yet, Swift compiler is still slow as molasses though and SwiftUI itself seems to bring the compiler to it's knees sometimes (on a brand new M1 Mini). It will flat out stop type checking anything that it deems to complex so you end changing code to appeal the compiler sometimes.
