mypy 1.8.0 regression: Incorrectly flags unreachable with re.match() result

[amykyta3]

Bug Report

It seems that v1.8.0 regressed in how it handles type checking with returned match objects from Python's regex stdlib.
It now flags unreachable code when checking on the truthyness of a regex match return value.

This was not the case in v1.7.x

To Reproduce

import re
import sys

if re.match(r"\d*", sys.argv[1]):
    print("a")
else:
    print("b") # mypy 1.8.0 incorrectly flags as unreachable

Results in:

tst.py:7: error: Statement is unreachable [unreachable]
Found 1 error in 1 file (checked 1 source file)

Changing the line to explicitly cast it as a boolean avoids this:

if bool(re.match(r"\d*", sys.argv[1])):

or:

if re.match(r"\d*", sys.argv[1]) is not None:

This seems to be related to the config setting of strict_optional = False

Expected Behavior

I would not expect any unreachable lines in this example.

Actual Behavior

mypy 1.8.0 reports an unreachable violation.

Your Environment

• Mypy version used: 1.8.0
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files):

[mypy]
warn_unreachable = True
strict_optional = False

• Python version used: Python 3.10.12

[hauntsaninja]

Duplicate of #16718