Optimize int.parse with a radix.

runtime/lib/string_patch.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.
 
 patch class String {
   /* patch */ factory String.fromCharCodes(Iterable<int> charCodes,
                                            [int start = 0, int end]) {
     return _StringBase.createFromCharCodes(charCodes, start, end);
   }
 
@@ skipping 39 matching lines @@
 
   int get hashCode native "String_getHashCode";
 
   /**
    *  Create the most efficient string representation for specified
    *  [codePoints].
    */
   static String createFromCharCodes(Iterable<int> charCodes,
                                     int start, int end) {
     if (charCodes == null) throw new ArgumentError(charCodes);
+    if (start < 0) throw new RangeError.value(start);
     // TODO(srdjan): Also skip copying of wide typed arrays.
     final ccid = ClassID.getID(charCodes);
     bool isOneByteString = false;
     if ((ccid != ClassID.cidArray) &&
         (ccid != ClassID.cidGrowableObjectArray) &&
         (ccid != ClassID.cidImmutableArray)) {
       if ((charCodes is Uint8List) || (charCodes is Int8List)) {
         isOneByteString = true;
       } else {
         charCodes = new List.from(charCodes, growable: false);
       }
     }
-    int codeCount = charCodes.length;
-    if (start < 0 || start > codeCount) {
-      throw new RangeError.range(start, 0, codeCount);
+    if ((end == null) || (end > charCodes.length)) {
+      end = charCodes.length;
     }
-    if (end == null) {
-      end = codeCount;
-    } else if (end < start || end > codeCount) {
-      throw new RangeError.range(end, start, codeCount);
-    }
+    if (end <= start) return "";
     final len = end - start;
     if (!isOneByteString) {
       for (int i = start; i < end; i++) {
         int e = charCodes[i];
         if (e is! _Smi) throw new ArgumentError(e);
         // Is e Latin1?
         if ((e < 0) || (e > 0xFF)) {
           return _createFromCodePoints(charCodes, start, end);
         }
       }
@@ skipping 944 matching lines @@
 class _CodeUnits extends Object with ListMixin<int>,
                                      UnmodifiableListMixin<int> {
   /** The string that this is the code units of. */
   String _string;
 
   _CodeUnits(this._string);
 
   int get length => _string.length;
   int operator[](int i) => _string.codeUnitAt(i);
 }