Add PEP 800 (disjoint bases)#2262
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JelleZijlstra merged 1 commit intopython:mainfrom Apr 17, 2026
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carljm
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Apr 16, 2026
JelleZijlstra
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Apr 16, 2026
| Line 123: Expected 1 errors | ||
| """ | ||
| output = """ | ||
| directives_disjoint_base.py:69:7: error[instance-layout-conflict] Class will raise `TypeError` at runtime due to incompatible bases: Bases `Left` and `Right` cannot be combined in multiple inheritance |
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hm, this error is actually inaccurate; there's no runtime error if the class is just marked with @disjoint_base at runtime.
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I think the error is correct for the intended use of disjoint_base, though. I'm not sure it would be preferable to adjust the error message to account for misuse on classes that aren't actually disjoint bases.
srittau
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topic: typing spec
davidhalter
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Apr 16, 2026
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Accepted here: https://discuss.python.org/t/pep-800-solid-bases-in-the-type-system/99910/41