Improve decoding of JS TypeError.

dart/sdk/lib/_internal/lib/string_helper.dart

 // Copyright (c) 2012, 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.
 
 part of _js_helper;
 
 class StringMatch implements Match {
   const StringMatch(int this.start,
                     String this.str,
                     String this.pattern);
@@ skipping 59 matching lines @@
 }
 
 stringReplaceJS(receiver, replacer, to) {
   // The JavaScript String.replace method recognizes replacement
   // patterns in the replacement string. Dart does not have that
   // behavior.
   to = JS('String', r'#.replace("$", "$$$$")', to);
   return JS('String', r'#.replace(#, #)', receiver, replacer, to);
 }
 
+const String ESCAPE_REGEXP = r'[[\]{}()*+?.\\^$|]';
+
 stringReplaceAllUnchecked(receiver, from, to) {
   checkString(to);
   if (from is String) {
     if (from == "") {
       if (receiver == "") {
         return to;
       } else {
         StringBuffer result = new StringBuffer();
         int length = receiver.length;
         result.write(to);
         for (int i = 0; i < length; i++) {
           result.write(receiver[i]);
           result.write(to);
         }
         return result.toString();
       }
     } else {
-      var quoter = JS('', "new RegExp(#, 'g')", r'[[\]{}()*+?.\\^$|]');
+      var quoter = JS('', "new RegExp(#, 'g')", ESCAPE_REGEXP);
       var quoted = JS('String', r'#.replace(#, "\\$&")', from, quoter);
       var replacer = JS('', "new RegExp(#, 'g')", quoted);
       return stringReplaceJS(receiver, replacer, to);
     }
   } else if (from is JSSyntaxRegExp) {
     var re = regExpGetGlobalNative(from);
     return stringReplaceJS(receiver, re, to);
   } else {
     checkNull(from);
     // TODO(floitsch): implement generic String.replace (with patterns).
@@ skipping 84 matching lines @@
   } else {
     checkNull(from);
     // TODO(floitsch): implement generic String.replace (with patterns).
     throw "String.replace(Pattern) UNIMPLEMENTED";
   }
 }
 
 stringJoinUnchecked(array, separator) {
   return JS('String', r'#.join(#)', array, separator);
 }