Fix crash with function redefinition #14064
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test-data/unit/check-functions.test
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| # weirdly, needs to be an empty tuple. empty lists and various other special assignments | ||
| # don't trigger the bug | ||
| cond = () | ||
| if cond: |
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A simpler test would be just if False: The problem is that mypy considers if branch unreachable, and therefore doesn't type check it, and therefore the original definition doesn't get its type inferred (and stays None).
I think a better solution is to simply not show any error in this case:
- It will be more consistent with not showing error in unreachable code
- Technically, there is no redefinition, only one definition is ever executed.
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Note however, this will be inconsistent with foo: int = 1, where user will get an error, even if the first definition is unreachable, but IMO this is OK.
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Btw it is a wider problem, some code may be semantically reachable (because types of expressions in branches are not known), but not type checked, because during type-checking expression type is inferred as something false-y. A possible option to explore in the future (not now) is to still actually type check unreachable code, only for the purpose of type inference, but don't show any errors there. |
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
Fixes #14027 (issue was surfaced by #13509)