kaskade.swift

@dynamicMemberLookup
struct Identified<Value> {
  let value: Value
  let id: String

  subscript<T>(dynamicMember keyPath: KeyPath<Value, T>) -> T {
    value[keyPath: keyPath]
  }
}

@dynamicMemberLookup
struct Timestamped<Value> {
  let value: Value
  let timestamp: Date

  subscript<T>(dynamicMember keyPath: KeyPath<Value, T>) -> T {
    value[keyPath: keyPath]
  }
}

typealias Complete<T> = Timestamped<Identified<T>>

func complete(_ entry: Complete<User>) {
    // ...
}

struct User {
  let name: String
  let age: UInt8
}

let user = User(name: "Ian", age: 33)
let identified = Identified(value: user, id: UUID().uuidString)
let timestamped = Timestamped(value: identified, timestamp: .init())

timestamped.timestamp // "Apr 4, 2023 at 8:42 AM"
timestamped.id // "66D63DA4-93E1-473A-8893-6A30767FFA8F"
timestamped.name // "Ian"
timestamped.age // 33

complete(timestamped) // ✅
complete(user) // ❌
complete(identified) // ❌