Can you simplify nested Indexed types?

[Sergei Nosov]

Consider, I have the following code:

```
     auto a = [3, 6, 2, 1, 5, 4, 0];

     auto indicies = iota(3);
     auto ai = indexed(a, indicies);
     ai = indexed(ai, iota(2));

     writeln(ai);
```

Basically, my idea is to apply `indexed` to an array several 
times and have all the intermediaries saved in the same variable. 
The provided code doesn't compile with an error:

```
Error: cannot implicitly convert expression `indexed(ai, 
iota(2))` of type `Indexed!(Indexed!(int[], Result), Result)` to 
`Indexed!(int[], Result)`
```

I wonder, if there's a way to "collapse" or "simplify" the 
`Indexed!(Indexed!(int[], Result), Result)` type to just 
`Indexed!(int[], Result)` ?