## Summary
This PR is a more holistic fix for
https://github.com/astral-sh/ruff/issues/9534 and
https://github.com/astral-sh/ruff/issues/9159.
When we visit the AST, we track nodes that we need to visit _later_
(deferred nodes). For example, when visiting a function, we defer the
function body, since we don't want to visit the body until we've visited
the rest of the statements in the containing scope.
However, deferred nodes can themselves contain deferred nodes... For
example, a function body can contain a lambda (which contains a deferred
body). And then there are rarer cases, like a lambda inside of a type
annotation.
The aforementioned issues were fixed by reordering the deferral visits
to catch common cases. But even with those fixes, we still fail on cases
like:
```python
from __future__ import annotations
import re
from typing import cast
cast(lambda: re.match, 1)
```
Since we don't expect lambdas to appear inside of type definitions.
This PR modifies the `Checker` to keep visiting until all the deferred
stacks are empty. We _already_ do this for any one kind of deferred
node; now, we do it for _all_ of them at a level above.
## Summary
This is effectively the same problem as
https://github.com/astral-sh/ruff/pull/9175. And this just papers over
it again, though I'm gonna try a more holistic fix in a follow-up PR.
The _real_ fix here is that we need to continue to visit deferred items
until they're exhausted since, e.g., we still get this case wrong
(flagging `re` as unused):
```python
import re
cast(lambda: re.match, 1)
```
Closes https://github.com/astral-sh/ruff/issues/9534.
