Many type fixes.

lib/compiler/implementation/scanner/byte_strings.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * An abstract string representation.
  */
 class ByteString implements SourceString {
   final List<int> bytes;
   final int offset;
@@ skipping 29 matching lines @@
       code += 19 * code + bytes[i];
     }
     return code;
   }
 
   printOn(StringBuffer sb) {
     sb.add(slowToString());
   }
 
   bool isEmpty() => length == 0;
+  bool isPrivate() => !isEmpty() && bytes[offset] === $_;
+
+  String get stringValue() => null;
 }
 
 /**
  * A string that consists purely of 7bit ASCII characters.
  */
 class AsciiString extends ByteString {
   final String charset = "ASCII";
 
   AsciiString(List<int> bytes, int offset, int length)
     : super(bytes, offset, length);
@@ skipping 72 matching lines @@
  * A ByteString-valued token.
  */
 class ByteStringToken extends Token {
   final ByteString value;
 
   ByteStringToken(PrecedenceInfo info, ByteString this.value, int charOffset)
     : super(info, charOffset);
 
   String toString() => value.toString();
 }