[[Borrow checker]]

It is not THE left hand side of an assignment but anything that is valid to put there. But they can appear anywhere from what it looks like.

It includes:
- variables `a`
- dereferences of places `*a`
- Array accesses of places `a[0]`
- Fields of places `a.0`
- Any combination of the above

The borrow checker expects a place to have certain permissions depending on the operation.