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Title: [1.15 regression] (Temporary) false positive for reachability with unannotated partial type · Issue #18606 · python/mypy · GitHub

Open Graph Title: [1.15 regression] (Temporary) false positive for reachability with unannotated partial type · Issue #18606 · python/mypy

X Title: [1.15 regression] (Temporary) false positive for reachability with unannotated partial type · Issue #18606 · python/mypy

Description: Sort of a weird / minor case, but with mypy 1.15 λ cat e.py def merge_debugs(debugs: list[int | None]) -> None: metadata = None for debug in debugs: if debug is not None: if metadata is None: metadata = {} λ mypy e.py --warn-unreachable ...

Open Graph Description: Sort of a weird / minor case, but with mypy 1.15 λ cat e.py def merge_debugs(debugs: list[int | None]) -> None: metadata = None for debug in debugs: if debug is not None: if metadata is None: metad...

X Description: Sort of a weird / minor case, but with mypy 1.15 λ cat e.py def merge_debugs(debugs: list[int | None]) -> None: metadata = None for debug in debugs: if debug is not None: if metadata is None: me...

Opengraph URL: https://github.com/python/mypy/issues/18606

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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[1.15 regression] (Temporary) false positive for reachability with unannotated partial type","articleBody":"Sort of a weird / minor case, but with mypy 1.15\n```\nλ cat e.py\ndef merge_debugs(debugs: list[int | None]) -\u003e None:\n    metadata = None\n    for debug in debugs:\n        if debug is not None:\n            if metadata is None:\n                metadata = {}\n\nλ mypy  e.py --warn-unreachable\ne.py:6: error: Need type annotation for \"metadata\" (hint: \"metadata: dict[\u003ctype\u003e, \u003ctype\u003e] = ...\")  [var-annotated]\ne.py:6: error: Statement is unreachable  [unreachable]\nFound 2 errors in 1 file (checked 1 source file)\n```\nIf you add an annotation to `metadata` (standalone or with the assignment) the unreachable warning goes away","author":{"url":"https://github.com/hauntsaninja","@type":"Person","name":"hauntsaninja"},"datePublished":"2025-02-05T05:30:29.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/18606/mypy/issues/18606"}

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