Mypy does not correctly infer type of union typed variable on asignment when on same line as type declaration

[tblum]

Mypy does not correctly infer the type of in the following example
i: int | None = 42
i's type is int | None

when splitting declaration and assignment it works i.e:

i: int | None
i = 42

i's type is int

i: int | None = 42
makes for nicer code.

To Reproduce

i: int | None = 42
i = i + 1

Expected Behavior
Should be accepted by mypy

Actual Behavior

inone_test.py:2: error: Unsupported operand types for + ("None" and "int") [operator]
none_test.py:2: note: Left operand is of type "int | None"

Your Environment

• Mypy version used: 1.10.0
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.12.6

[hauntsaninja]

Duplicate of #2008

(there's consensus mypy should change this and it's a trivial change to make, but it exposes some bugs in the binder)