[WSL] An array reference of an array cell should return a reference of length 1, not a slice to the end of the original array

[Robin Morisset]

```
int[3] x;
x[0] = 1;
x[1] = 3;
x[2] = 6;
thread int[] r = @x[1]; // or @(x[1])
r[1] = 5;
```
should fail, instead of resulting in x being [1;3;5].

[Myles C. Maxfield]

Migrated to https://github.com/gpuweb/WHLSL/issues/115