Handle escapes in string literals.

frog/leg/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.
 
 final int EOF_TOKEN = 0;
 
 final int KEYWORD_TOKEN = $k;
 final int IDENTIFIER_TOKEN = $a;
 final int DOUBLE_TOKEN = $d;
 final int INT_TOKEN = $i;
@@ skipping 110 matching lines @@
 
   String toString() => value.toString();
 }
 
 interface SourceString extends Hashable default StringWrapper {
   const SourceString(String string);
 
   int get length();
 
   void printOn(StringBuffer sb);
+  void printSubstringOn(StringBuffer sb, int from, int to);
+
+  int charCodeAt(int i);
+  String operator[](int index);
 
   String get stringValue();
 }
 
 class StringWrapper implements SourceString {
   final String stringValue;
 
   const StringWrapper(String this.stringValue);
 
   int hashCode() => stringValue.hashCode();
 
   bool operator ==(other) {
     return other is SourceString && toString() == other.toString();
   }
 
   int get length() => stringValue.length;
 
   void printOn(StringBuffer sb) {
     sb.add(stringValue);
   }
 
+  void printSubstringOn(StringBuffer sb, int from, int to) {
+    if (from >= to) return;
+    sb.add(stringValue.substring(from, to));
+  }
+
+  int charCodeAt(int index) => stringValue.charCodeAt(index);
+  String operator[](int index) => stringValue[index];
+
   String toString() => stringValue;
 }
 
 class BeginGroupToken extends StringToken {
   Token endGroup;
   BeginGroupToken(PrecedenceInfo info, String value, int charOffset)
     : super(info, value, charOffset);
 }
 
 class PrecedenceInfo {
@@ skipping 193 matching lines @@
 
 final PrecedenceInfo DOUBLE_INFO =
   const PrecedenceInfo(const SourceString('double'), 0, DOUBLE_TOKEN);
 
 final PrecedenceInfo STRING_INTERPOLATION_INFO =
   const PrecedenceInfo(const SourceString('\${'), 0,
                        STRING_INTERPOLATION_TOKEN);
 
 final PrecedenceInfo HEXADECIMAL_INFO =
   const PrecedenceInfo(const SourceString('hexadecimal'), 0, HEXADECIMAL_TOKEN);