allow arbitrary types in set difference #15160
Open
+9
−2
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Fixes #9004
See also: #11403
This PR allows set differences with disjoint generic types. This option was previously argued against (#9004 (comment)) because
However,
typeshedshouldn't try to act as a linter. That's the job of the type checker. There are cases when the current setup hurts, for instance when we try to doset[Literal["a", "b"]] - set[str].This should be handled on the type-checker side, for instance by warning on
set[T] - set[S]ifTandShave empty intersection (⇝ disjoint_bases https://peps.python.org/pep-0800/), which would catch the bad case described above.