It took me many hours to narrow down a problem in some code to this reproducible error, which seems to me like a bug in AVM2. Can anyone shed light on why this is occurring or how to fix it?
When the value at index 1 is deleted and a value is subsequently set at index 0, the non-existent (undefined) value at index 1 will now show up in a foreach loop. I have only been able to produce this outcome with index 1 and 0 (not any other n and n-1).
Run this code:
package
{
import flash.display.Sprite;
public class Main extends Sprite
{
public function Main():void
{
var bar : Array = new Array(6);
out(bar);
//proper behavior
trace("bar[1] = 1", bar[1] = 1);
out(bar);
//proper behavior
trace("delete bar[1]", delete bar[1]);
out(bar);
//proper behavior
trace("bar[4] = 4", bar[4] = 4);
out(bar);
//for each loop will now iterate over the undefined position at index 1
trace("bar[0] = 0", bar[0] = 0);
out(bar);
trace("bar[3] = 3", bar[3] = 3);
out(bar);
}
private function out(bar:Array):void
{
trace(bar);
for each(var i : * in bar)
{
trace(i);
}
}
}
}
It will give this output:
,,,,,
bar[1] = 1 1
,1,,,,
1
delete bar[1] true
,,,,,
bar[4] = 4 4
,,,,4,
4
bar[0] = 0 0
0,,,,4,
0
undefined
4
bar[3] = 3 3
0,,,3,4,
0
undefined
4
3
