Incorrect "possibly_undefined_name" with walrus operator

[JelleZijlstra]

% cat ~/Desktop/walrus.py 
from typing_extensions import assert_type


def f() -> int:
    return 3


def g(cond: bool) -> None:
    if cond and (x := f()):
        assert_type(x, int)
% python -m pyanalyze ~/Desktop/walrus.py  -e possibly_undefined_name

x may be used uninitialized (code: possibly_undefined_name)
In /Users/jelle/Desktop/walrus.py at line 10
   7: 
   8: def g(cond: bool) -> None:
   9:     if cond and (x := f()):
  10:         assert_type(x, int)
                          ^

Type is Union[Any[error], int] (expected int) (code: inference_failure)
In /Users/jelle/Desktop/walrus.py at line 10
   7: 
   8: def g(cond: bool) -> None:
   9:     if cond and (x := f()):
  10:         assert_type(x, int)
              ^