Stop using the Hashable interface.

lib/compiler/implementation/scanner/token.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.
 
 const int EOF_TOKEN = 0;
 
 const int KEYWORD_TOKEN = $k;
 const int IDENTIFIER_TOKEN = $a;
 const int BAD_INPUT_TOKEN = $X;
 const int DOUBLE_TOKEN = $d;
@@ skipping 159 matching lines @@
     : this.fromSource(info, new SourceString(value), charOffset);
 
   StringToken.fromSource(PrecedenceInfo info, this.value, int charOffset)
     : super(info, charOffset);
 
   String toString() => "StringToken(${value.slowToString()})";
 
   String slowToString() => value.slowToString();
 }
 
-interface SourceString extends Hashable, Iterable<int> default StringWrapper {
+interface SourceString extends Iterable<int> default StringWrapper {
   const SourceString(String string);
 
   void printOn(StringBuffer sb);
 
   /** Gives a [SourceString] that is not including the [initial] first and
    * [terminal] last characters. This is only intended to be used to remove
    * quotes from string literals (including an initial '@' for raw strings).
    */
   SourceString copyWithoutQuotes(int initial, int terminal);
 
@@ skipping 304 matching lines @@
 
 const PrecedenceInfo HEXADECIMAL_INFO =
   const PrecedenceInfo(const SourceString('hexadecimal'), 0, HEXADECIMAL_TOKEN);
 
 const PrecedenceInfo COMMENT_INFO =
   const PrecedenceInfo(const SourceString('comment'), 0, COMMENT_TOKEN);
 
 // For reporting lexical errors.
 const PrecedenceInfo ERROR_INFO =
   const PrecedenceInfo(const SourceString('?'), 0, UNKNOWN_TOKEN);