           break refillBuffer
         }
         // Buffering mode.
-        // Fill buffer back to 4 bytes (or as many as are left in the generator).
+        // Fill buffer back to 4 bytes (or as many as are left in the iterator).
         _sanityCheck(_bitsInBuffer < 32)
         repeat {
           if let codeUnit = next.next() {

  /// Because of buffering, it is impossible to find the corresponding position
  /// in the iterator for a given returned `UnicodeScalar` or an error.
  ///
  /// - Parameter next: A generator of code units to be decoded.  Repeated
  ///   calls to this method on the same instance should always pass the same
  ///   generator and the generator or copies thereof should not be used for
  ///   anything else between calls.  Failing to do so will yield unspecified
  ///   results.
  public mutating func decode<

  /// Because of buffering, it is impossible to find the corresponding position
  /// in the iterator for a given returned `UnicodeScalar` or an error.
  ///
  /// - Parameter next: An iterator of code units to be decoded.  Repeated
  ///   calls to this method on the same instance should always pass the same
  ///   iterator and the iterator or copies thereof should not be used for
  ///   anything else between calls.  Failing to do so will yield unspecified
  ///   results.
  public mutating func decode<
