Protocol inheritance and associated type specification

Protocols.swift

/*
 This Swift bug seems to be related: https://bugs.swift.org/browse/SR-2235. Seems as though
 the different ways that worked previously might have never actually been intended?
 */

protocol DataVendor {
  associatedtype Vended
  
  var data: [Vended]
  
  func data(at index: Int) -> Vended
}

// This worked in Swift 3.0
protocol StringVendor: DataVendor {
  typealias Vended = String
}

// This now seems to be required, as of Swift 3.1
protocol StringVendor: DataVendor {
  var data: [String]
  
  func data(at index: Int) -> String
}