## Summary
We were previously recording wrong reachability constraints for negative
branches. Instead of `[cond] AND (NOT [True])` below, we were recording
`[cond] AND (NOT ([cond] AND [True]))`, i.e. we were negating not just
the last predicate, but the `AND`-ed reachability constraint from last
clause. With this fix, we now record the correct constraints for the
example from #17723:
```py
def _(cond: bool):
if cond:
# reachability: [cond]
if True:
# reachability: [cond] AND [True]
pass
else:
# reachability: [cond] AND (NOT [True])
x
```
closes#17723
## Test Plan
* Regression test.
* Verified the ecosystem changes
4a621c2c12