`possibly-undefined` false positive with `global` statement inside `if`

Bug Report

The optional possibly-undefined error gives a false positive on this code with a global statement inside an if branch. At runtime, Python treats global as applying unconditionally for the entire function scope, but mypy seems to think it only applies to the branch.

To Reproduce

# mypy: enable-error-code="possibly-undefined"

g = 1

def f(b: bool) -> None:
    if b:
        global g
        g = 2

    print(g)  # error: Name "g" may be undefined  [possibly-undefined]

Playground

Expected Behavior

No error.

Actual Behavior

main.py:10: error: Name "g" may be undefined  [possibly-undefined]
Found 1 error in 1 file (checked 1 source file)

Your Environment

• Mypy version used: 1.4.1
• Mypy command-line flags: --enable-error-code=possibly-undefined
• Mypy configuration options from mypy.ini (and other config files): none
• Python version used: 3.10.12

Reproduce the report with the provided Python snippet and the possibly-undefined error code, then trace how mypy handles the global statement inside the if branch. Done means the example produces no false-positive error for g after the branch, while genuine possibly-undefined cases remain diagnosed.