parameter specification/type variable tuple variance by KotlinIsland · Pull Request #2215 · python/typing
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I don't think using ... here is sound. Because it is both assignable-to and assignable-from any paramspec, it means that a case like the ContravariantParamSpec test will wrongly infer the paramspec as covariant (because lower is assignable to upper) before it even checks the contravariant direction.
I don't think there is any way to make the variance-inference algorithm described here correct and support inference of ParamSpec variance, without introducing the new concept of a "top signature".
(I'm also not sure how much value there is in including this particular variance-inference algorithm in the spec. I think it describes pyright's algorithm. I know that ty and pyrefly do not use this algorithm. I don't know about mypy or zuban.)