Cannot Dereference Dynamically Sized (Template) Type

Test `001137` is as follows:

```Whiley
method assign<T>(&T x, &T y, T v1, T v2)
ensures *x == v1
ensures *y == v2:
    // Broken if x == y
    *x = v1
    *y = v2
```

This doesn't allow the dereference.  I think to make this work, we need some information about `T` --- namely that it is statically sized.  This is evident from the fact that it is passed as a parameter.