 extension
  Unicode.UTF8.ForwardDecoder : _UTF8Decoder {
   public typealias Encoding = Unicode.UTF8
-  
-  public static var replacement : Encoding.EncodedScalar {
-    return Encoding.EncodedScalar(_storage: 0xbdbfef, _bitCount: 24)
-  }
   
   public // @testable
   func _parseMultipleCodeUnits() -> (isValid: Bool, bitCount: UInt8) {

    where EncodedScalar.Iterator.Element == CodeUnit

  /// The replacement character U+FFFD as represented in this encoding
  static var encodedReplacementScalar : EncodedScalar { get }

  /// Returns true if `x` only appears in this encoding as the representation of
  /// a complete scalar value.

  
  public struct ForwardDecoder {
    public typealias Buffer = _UIntBuffer<UInt32, UInt16>
    public init() { buffer = Buffer() }
    public var buffer: Buffer
  }
  
  public struct ReverseDecoder {
    public typealias Buffer = _UIntBuffer<UInt32, UInt16>
    public init() { buffer = Buffer() }
    public var buffer: Buffer
  }
