`!= (None, None)` Narrowing only in else branch

**Bug Report** `!= (None, None)` correctly narrows the else branch to `tuple[None, None]` but, doesn't narrow the union in the if branch. **To Reproduce** ```python a: tuple[int, str] | tuple[None, None] if a != (None, None): reveal_type(a) # Revealed type is "tuple[int, str] | tuple[None, None]" else: reveal_type(a) # Revealed type is "tuple[None, None]" ``` **Expected Behavior** The if branch should narrow to `tuple[int, str]` **Actual Behavior** The if branch is `tuple[int, str] | tuple[None, None]` **Your Environment** <!-- Include as many relevant details about the environment you experienced the bug in --> - Mypy version used: 2.1 - Mypy command-line flags: - Mypy configuration options from `mypy.ini` (and other config files): - Python version used: <!-- You can freely edit this text, please remove all the lines you believe are unnecessary. -->