foreach with assoc. array

[DLearner via Digitalmars-d-learn]

Hi

Please consider (1):
```
void main() {
   import std.stdio;

   int wk_Idx;

   int[2] IntArr;

   IntArr[0] = 1;
   IntArr[1] = 2;

   for (wk_Idx = 0; wk_Idx <= 1; wk_Idx = wk_Idx + 1) {

      writeln("wk_Idx = ", wk_Idx, " IntArr = ", IntArr[wk_Idx]);
   }
}
```

Now consider (2), which is (1) via assoc. array:
```
void main() {
   import std.stdio;

   int wk_Idx;

   int[int] IntArr;

   IntArr[0] = 1;
   IntArr[1] = 2;

   for (wk_Idx = 0; wk_Idx <= 1; wk_Idx = wk_Idx + 1) {

      writeln("wk_Idx = ", wk_Idx, " IntArr = ", IntArr[wk_Idx]);
   }
}
```

And finally (3) which is (2) via a foreach:
```
void main() {
   import std.stdio;

   int wk_Idx;

   int[int] IntArr;

   IntArr[0] = 1;
   IntArr[1] = 2;

   foreach (wk_Idx; IntArr.keys) {

      writeln("wk_Idx = ", wk_Idx, " IntArr = ", IntArr[wk_Idx]);
   }
}
```

(1) & (2) compile and run with the expected results.
But (3) fails with:
```
Error: variable `wk_Idx` is shadowing variable `for3.main.wk_Idx`
```
Why is this usage wrong?