Combining reachability constraints does not seem to work as expected. Consider the following example where we fail to see that print(x) is unreachable:

def _(cond: bool):
    if cond:
        if True:
            pass
        else:
            print(x)  # should not be reachable, i.e. not emit an error

https://types.ruff.rs/cc26b966-0df2-4111-8448-2a1d15d95586