Hi, Sorry it took so long to get back to you. It does run correctly if I switch it to Swift 5.

The same issue appears when using animatableData with GeometryEffect: struct ShakeEffect: GeometryEffect { var position: CGFloat var animatableData: CGFloat { get { position } set { position = newValue } } init(shakes: Int) { position = CGFloat(shakes) } func effectValue(size: CGSize) -> ProjectionTransform { return ProjectionTransform( CGAffineTransform(translationX: -30 * sin(position * 2 * .pi), y: 0)) } }

same here: struct ShakeEffect: GeometryEffect { var position: CGFloat var animatableData: CGFloat { //same error as in original post here get {position} set {position = newValue} } init(shakes: Int) { position = CGFloat(shakes) } func effectValue(size: CGSize) -> ProjectionTransform { //same error as in original post here ProjectionTransform(CGAffineTransform(translationX: -30 * sin(position * 2 * .pi), y: 0)) } }