   }
 
   @_inlineable
+  @inline(__always)
   /// Creates an iterator over the given collection.
   public /// @testable
   init(_elements: Elements, _position: Elements.Index) {

  /// - Returns: The next element in the underlying sequence if a next element
  ///   exists; otherwise, `nil`.
  @_inlineable
  public mutating func next() -> Elements._Element? {
    if _position == _elements.endIndex { return nil }
    let element = _elements[_position]
    _elements.formIndex(after: &_position)
    return element
  }
  @_versioned
  internal let _elements: Elements
  @_versioned

> : IteratorProtocol, Sequence {

  @_inlineable
  @inline(__always)
  /// Creates an iterator over the given collection.
  public /// @testable
  init(_elements: Elements) {
