1public extension DefaultStringInterpolation

1mutating func appendInterpolation(indented string: String)

1class Root {
2let children: [Root] = []
3func description: String {
4  var desc = "\(type(of: self)) {"
5  children.forEach { child in
6    desc += "\n  \(indented: child.debugDescription),"
7  }
8  if !children.isEmpty { desc += "\n" }
9  desc += "\(indented: "}")"
10  return desc
11}
12// Given classes A - E as subclasses of Root
13
14let root = Root(children: [A(children: [B(), C(children: [D()])]), E()])
15print(root.description)