anchor.diff:  
   class _HashBase implements Hash  {
   
  -  Uint8List _content;
  +  UnmodifiableUint8List _content;
   
     _HashBase(dynamic content) {
       // convert
  
positive.code:   factory Hash(dynamic content) => new _HashBase(content);
  
    /**
     * The bytes that represent the hash value.
     *
     * This returns an unmodifiable version of this hash value,
     * if you want to modify the bytes, use hash.buffer.asUint8List();
     */
    Uint8List asBytes();
  
  
negative.code:     else if(content is Uint8List)
        _content = new UnmodifiableUint8List(content);
      else if(content is TypedData)
        _content = new UnmodifiableUint8List.fromList(content.buffer.asUint8List(content.offsetInBytes, content.lengthInBytes));
      else
        _content = new UnmodifiableUint8List.fromList(content);
    }
  
    @override
    Uint8List get bytes => _content;
  
    @override
    List<int> asBytes() => bytes;
  
    @override
    BigInteger asBigInteger() => new BigInteger.fromBytes(1, asBytes());
  