`import xxx as var` does not narrow type

[spagh-eddie]

Bug Report

I would expect a variable that gets imported narrow the type.

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.11&gist=11a4883cf29edd47fd1aff15302ead30

x: str | None = None
if x is None:
    from os import sep as x
# revealed type is Optional[str]
print(x + "a")  # mypy false positive

Expected Behavior

No error.

Actual Behavior

% mypy test.py
main.py:5: error: Unsupported left operand type for + ("None")  [operator]
main.py:5: note: Left operand is of type "Optional[str]"
Found 1 error in 1 file (checked 1 source file)

% python test.py
/a

Your Environment

• Mypy version used: 1.1.1
• Mypy command-line flags: none
• Python version used: 3.11

[AlexWaygood]

Duplicate of #12965

[spagh-eddie]

Duplicate of #12965

nice! I didn't find it... I assume because searching "import" has many false positives