Recursion doesn't play nicely with unions

I tried modelling a tree with recursive entries, but if try to model this:

```haskell
type TreeEntryQ = Union "TreeEntryQ" '[FileQ, RecTreeQ, SymlinkQ]
```

I get:

```
    • Invalid TypeIndex. Must be Object but got: RecTreeQ
```

because `RecTreeQ` is a `newtype`