Implementation of Collection Versions of Zip

Development Standard Library
36

I'm looking into conforming Zip2Collection to both ExpressibleByArrayLiteral and ExpressibleByDictionaryLiteral:

extension Zip2Collection: ExpressibleByArrayLiteral where
    Collection1: RangeReplaceableCollection,
    Collection2: RangeReplaceableCollection {
  public typealias ArrayLiteralElement = Element

  public init (arrayLiteral: Element...) {
    self.init()

    let arrayLiteralCount = arrayLiteral.count

    _collection1.reserveCapacity(arrayLiteralCount)
    _collection2.reserveCapacity(arrayLiteralCount)

    for (element1, element2) in arrayLiteral {
      _collection1.append(element1)
      _collection2.append(element2)
    }
  }
}

extension Zip2Collection: ExpressibleByDictionaryLiteral where
    Collection1: RangeReplaceableCollection,
    Collection2: RangeReplaceableCollection {
  public typealias Key = Collection1.Element
  public typealias Value = Collection2.Element

  public init (dictionaryLiteral elements: Element...) {
    self.init()

    let elementsCount = elements.count

    _collection1.reserveCapacity(elementsCount)
    _collection2.reserveCapacity(elementsCount)

    for (element1, element2) in elements {
      _collection1.append(element1)
      _collection2.append(element2)
    }
  }
}

If anybody sees any room for improvement here, let me know. :+1: