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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"False positive `unreachable` when variable is set and reset inside loop","articleBody":"**Bug Report**\r\n\r\nmypy warns about the right side of a condition being unreachable when a variable is reset in an outer loop, then set again inside the inner loop.\r\n\r\n**To Reproduce**\r\n\r\n```python\r\nfrom typing import Optional\r\n\r\ntest: Optional[float] = None\r\nreveal_type(test)  # Revealed type: Union[builtins.float, None]\r\n\r\nfor i in range(10):\r\n    test = None\r\n    reveal_type(test)  # Revealed type: None (???)\r\n    for k in range(10):\r\n        if test is None or k \u003e test:\r\n           test = k\r\n```\r\n\r\n**Expected Behavior**\r\n\r\nNo error.\r\n\r\n**Actual Behavior**\r\n\r\nmypy outputs `error: Right operand of \"or\"  is never evaluated`. This is clearly because the type of `test` is re-evaluated at some point, even though it was declared with a type and no statement narrows that type.\r\n\r\nThis appears related to #7204, #8721, #8865, #13973, #14120, except it can't be solved by declaring the type of the variable before the loop in which it's updated (because that violates `no-redef`).\r\n\r\nNote: I'm not sure why anyone would want to actually do this in practice. But I thought it might provide a useful test case.\r\n\r\n**Your Environment**\r\n\r\n- Mypy version used: 1.1.1\r\n- Mypy command-line flags: --disable-error-code name-defined, plus a few others that I don't believe could possibly have any relevance.\r\n- Mypy configuration options from `mypy.ini` (and other config files): None\r\n- Python version used: 3.10.10","author":{"url":"https://github.com/adebrecht661","@type":"Person","name":"adebrecht661"},"datePublished":"2023-03-31T13:56:30.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/14987/mypy/issues/14987"}