   }
 }
 
+extension SequenceType {
+  final public func _customContainsEquatableElement(
+    element: Generator.Element
+  ) -> Bool? {
+    return nil
+  }
+}
+
 public struct _CopyToNativeArrayBuffer {}
 public func _copyToNativeArrayBuffer<Args>(args: Args)
   -> (_CopyToNativeArrayBuffer, Args)

  func generate() -> Generator
}

extension _SequenceDefaultsType {
  /// Return a value less than or equal to the number of elements in
  /// `self`, **nondestructively**.
  ///
  /// - Complexity: O(N)
  final public func underestimateCount() -> Int {
    return 0
  }

  final public func _customContainsEquatableElement(
    element: Generator.Element
  ) -> Bool? {
    return nil
  }
}
/// This protocol is an implementation detail of `SequenceType`; do
/// not use it directly.
///


  /// Copy a Sequence into an array.
  func ~> (source:Self, ptr:(_InitializeTo, UnsafeMutablePointer<Generator.Element>))
}

extension SequenceType {
  /// Return a value less than or equal to the number of elements in
  /// `self`, **nondestructively**.
  ///
  /// - Complexity: O(N)
  final public func underestimateCount() -> Int {
    return 0
  }
}

extension SequenceType {
