 
 /// A set of unique elements.
 struct Set<Element : Hashable> {
-	var _dictionary: Dictionary<Element, Void> = [:]
+	var _dictionary: Dictionary<Element, Unit> = [:]
 	
 	init<S : Sequence where S.GeneratorType.Element == Element>(_ sequence: S) {
 		extend(sequence)

///
/// Does not actually conform to Collection because that crashes the compiler.
extension Set {
	typealias IndexType = DictionaryIndex<Element, Void>
	var startIndex: IndexType { return _dictionary.startIndex }
	var endIndex: IndexType { return _dictionary.endIndex }
	

	}
	
	mutating func insert(element: Element) {
		_dictionary[element] = Unit()
	}
	
	mutating func remove(element: Element) {
