AutoLayoutBuilderResultBuilder.swift

@resultBuilder
public enum AutoLayoutBuilder {
    public static func buildBlock(_ components: Constrainable...) -> [NSLayoutConstraint] {
        components.flatMap(\.constraints)
    }
}

extension UIView {
    @discardableResult public func addSubview<View: UIView>(_ view: View, @AutoLayoutBuilder with makeConstraints: (View) -> [Constrainable]) -> [NSLayoutConstraint] {
        view.translatesAutoresizingMaskIntoConstraints = false
        addSubview(view)
        let constraints = makeConstraints(view).flatMap(\.constraints)
        NSLayoutConstraint.activate(constraints)
        return constraints
    }
}