This issue was originally filed by xavier.ha...@gmail.com

What steps will reproduce the problem?
Run this dummy code on Safari iOS 6 or 7

import 'dart:html';
main() {
  List<bool> pattern = [true, false];
  int index = 0;
  
  int animate() {
    for(int i = 0; i < 1; i++) {
      int patternIndex = index.abs();
      toggle(pattern[patternIndex]);
    }
  }
  
  int i = 0;
  try {
    for(; i < 1000; i++) {
     animate();
    }
  }catch(e) {
    window.alert('$e: $i');
  }
}
toggle(bool on) { }

What is the expected output? What do you see instead?
It runs fine on all browser except iOS Safari.
It shows an alert with "RangeError: value 0: 384"

The reason is that dart2js generates code like this:
if (patternIndex >>> 0 !== patternIndex || patternIndex >= 2)
  return H.ioore(t2, patternIndex);

I had a similar issue previously on iOS when doing a >> 0: after a few hundreds executions, it starts to fail.

It clearly looks like a bug in the javascript engine of Safari, but I think dart2js could do something about it and never emmit '>> 0' code.

What version of the product are you using? On what operating system?
Editor: 1.1.0.dev_05_00 (2013-12-20)

Please provide any additional information below.