ASLabel.swift

@objc func _needsDoubleUpdateConstraintsPass() -> Bool {
    return true
} 
 
override var intrinsicContentSize: CGSize {
    return attributedText?.size(forWidth: (engineBounds ?? bounds).width) ?? .zero
}

var engineBounds: CGRect? {
    let objcSelector = "_nsis_compatibleBoundsInEngine:")
    typealias CFunction = @convention(c) (AnyObject, Selector, Any) -> CGRect
     
    let impl = class_getMethodImplementation(type(of: self).self, objcSelector)
    let callableImpl = unsafeBitCast(impl, to: CFunction.self)
    
    return layoutEngine.flatMap { callableImpl(self, objcSelector, $0) }
} 
    
var layoutEngine: Any? {
    let objcSelector = "_nsli_layoutEngine:")
    typealias CFunction = @convention(c) (AnyObject, Selector) -> Any
     
    let impl = class_getMethodImplementation(type(of: self).self, objcSelector)
    let callableImpl = unsafeBitCast(impl, to: CFunction.self)
    
    return callableImpl(self, objcSelector)
}