Mypy don't narrow types of 2 variables based on its combination

Bug Report

Mypy don't narrow types of 2 variables based on its combination.

x: Literal["a", "b"] = a_or_b()
y: Literal["a", "b"] = a_or_b()

if not (x == "a" and y == "a") and x == "a":
    # At this point, the type of y should be Literal["b"],
    # but mypy reports "Union[Literal['a'], Literal['b']]"
    reveal_type(y)

Note: the above if block can be separated into 2, which is probably more likely scenario in real codebase, such that:

if x == "a" and y == "a":
    # some code...
    pass
elif x == "a":
    # At this point, the type of y should be Literal["b"],
    # but mypy reports "Union[Literal['a'], Literal['b']]"
    reveal_type(y)

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.12&gist=9d0b24fba42e824b220e087003559068

Expected Behavior

Mypy narrows the type of y to be Literal["b"]

Actual Behavior

Mypy doesn't narrow the type and reports the type of y to be "Union[Literal['a'], Literal['b']]"

Your Environment

• Mypy version used: 1.7.1
• Mypy command-line flags: none
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.12.0

Inizia con il riproduttore mypy-play collegato usando Mypy 1.7.1 e Python 3.12, quindi confronta le due forme condizionali e il relativo output di reveal_type. Il lavoro è completato quando il secondo ramo restringe y da Literal["a", "b"] a Literal["b"] senza introdurre regressioni nel comportamento esistente.