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[syntax-errors] Extend __debug__ write check to attribute targets - #27908
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Sacrimento
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MichaReiser
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CPython forbids assigning to or deleting `__debug__` when accessed as an attribute (`x.__debug__`). Attribute assignment is a `SyntaxError` on all supported versions, but attribute deletion only became one in Python 3.14. This change extends `WriteToDebugKind::Delete` with a `removed_in` field so the diagnostic message reports the version-specific removal, and factors the shared `Store`/`Del` dispatch used by both the `Name` and `Attribute` checks into a single `write_to_debug` helper. Closes part of astral-sh#17412.
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MichaReiser
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Thank you! I made a few simplifications in line with my review comments, but this looked good to me overall.
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Summary
Ruff currently flags assigning to or deleting
__debug__when it's a bare name (__debug__ = False,del __debug__), but not when it's an attribute target (x.__debug__ = False,del x.__debug__).CPython forbids both assigning to
x.__debug__(SyntaxErroron every supported Python version) and deletingx.__debug__only became aSyntaxErrorin Python 3.14.This PR extends the existing
__debug__check toExpr::Attributetargets, gated on the target Python version for the deletion case.Part of #17412.
Test Plan
Added inline test_err/test_ok fixtures alongside the new
Expr::AttributecheckCross-checked the version gating logic and errors against real CPython 3.12/3.13/3.14.