existential-opening-2.swift

func getString(collection: Any<Collection where .Element == String>, index: Int) -> String {
	do collection openas T {
		// T is available as a type.
		// (Is this true?) T's associated types are also available, since T is opened into an explicit type.
		var collectionIndex : T.Index = input.startIndex 
		for _ = 0..<index {
			collectionIndex = collectionIndex.next(collection)
		}
		let returnValue : T.Element /* e.g. String */ = collection[collectionIndex]
		return returnValue
	}
}