Summary

This PR is a more holistic fix for #9534 and #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:

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.