PEP 646: Update draft #1856
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PEP 646: Update draft #1856
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This is the more-or-less final version now. I'll do one last read-through to confirm everything's consistent, then post in typing-sig to confirm it's ready for the Steering Committee. Semantic changes: * Remove support for type variable tuples in `Union`. Apparently the implementation would be tricky in Pyre because of special-casing around `Union`. That could be evidence that it would be tricky in Mypy and pytype. Since we don't have a specific use-case in mind, I think this is fine. * Support concatenation in `Callable`. Pradeep pointed ou that `ParamSpec` doesn't cover all potential use-cases because it doesn't support concatenating suffixes (in turn because `ParamSpec`s can contain keyword arguments, and concatenation is positional). Readability changes: * Remove the section on a full `Array` example. We've moved the important thing here - an explicit confirmation that `Array` can be generic in both datatype and shape - to the beginning of the PEP to make it more obvious. We've removed the `Ndim` thing after someone pointed out that e.g. `Ndim[Literal[2]]` would be incompatible with `Shape[Any, Any]`; I just don't think it's going to work. All that's left is the aliases, which we've moved into the Aliases section itself. Other changes: * Fill out Backwards Compatibility section. * Reference initial CPython implementation.
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This is the more-or-less final version now. I'll do one last read-through to confirm everything's consistent, then post in typing-sig to confirm it's ready for the Steering Committee.
Semantic changes:
Union. Apparently the implementation would be tricky in Pyre because of special-casing aroundUnion. That could be evidence that it would be tricky in Mypy and pytype. Since we don't have a specific use-case in mind, I think this is fine.Callable. Pradeep pointed ou thatParamSpecdoesn't cover all potential use-cases because it doesn't support concatenating suffixes (in turn becauseParamSpecs can contain keyword arguments, and concatenation is positional).Readability changes:
Arrayexample. We've moved the important thing here - an explicit confirmation thatArraycan be generic in both datatype and shape - to the beginning of the PEP to make it more obvious. We've removed theNdimthing after someone pointed out that e.g.Ndim[Literal[2]]would be incompatible withShape[Any, Any]; I just don't think it's going to work. All that's left is the aliases, which we've moved into the Aliases section itself.Other changes: