Compile times of with, concat & mut functions in swift4 are very high!! about swift-overture

[stephencelis]

This is mainly an issue of key paths taking longer when not qualified. Try recompiling stackView by qualifying at least one of the root types:

var stackView = with(UIStackView(), concat(
    mut(\UIStackView.axis, .vertical),
    mut(\.isLayoutMarginsRelativeArrangement, true),
    mut(\.layoutMargins, UIEdgeInsets(top: 0, left: 16, bottom: 0, right: 16)),
    mut(\.spacing, 16),
    mut(\.alignment, .center)
))

You can go so far as to qualify all root types to get a massive speedup:

var stackView = with(UIStackView(), concat(
    mut(\UIStackView.axis, .vertical),
    mut(\UIStackView.isLayoutMarginsRelativeArrangement, true),
    mut(\UIStackView.layoutMargins, UIEdgeInsets(top: 0, left: 16, bottom: 0, right: 16)),
    mut(\UIStackView.spacing, 16),
    mut(\UIStackView.alignment, .center)
))

I think this is worth filing a bug at bugs.swift.org, though, as they should be able to make some optimizations here.

[mbrandonw]

Hey @jonchui, we're going to close this out, but it's definitely an issue. One thing you could also try is to not use lazy, which tends to put a lot of pressure on the type checker. Usually the way lazy is used is not really saving too much work since most of a view's properties are probably accessed immediately.

Also filing bugs at bugs.swift.org can always help. The type checker has definitely gotten better over the years and these use cases provide great real-world examples.