red-knot: infer and display ellipsis type #13124
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chriskrycho
requested review from
carljm,
MichaReiser and
AlexWaygood
as code owners
|
| Type::EllipsisType => { | ||
| // TODO: attribute lookup on Ellipsis type | ||
| Type::Unknown | ||
| } |
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I'm not sure this needs to be its own variant in the Type enum... it's conceptually just an instance of types.EllipsisType. types.EllipsisType was only exposed on Python 3.10+, but typeshed already provides a nice little compatibility workaround for us here: https://github.com/python/typeshed/blob/f58dac1d62d33bb2255b762783d06463c40f5065/stdlib/builtins.pyi#L1849-L1865
(builtins.Ellipsis is the same object as ...)
>>> ...
Ellipsis
>>> Ellipsis
Ellipsis
>>> Ellipsis is ...
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One interesting way in which ... is special is that it's a singleton: it is the only instance of types.EllipsisType that there is, or that there could be. But that can be thought of as just a sealed type that has exactly one member, and we've yet to implement a generalised way of handling sealed types. (We'll need them to tackle enums in Python!) See #12694.
Defer to the built-in type and leave notes about where and how we ought to be resolving to `typing.EllipsisType` instead of the current output, which is `Unknown | Literal[EllipsisType]`.
Summary
Just what it says on the tin: adds basic
EllipsisTypeinference for any time...appears in the AST.Test Plan
Test that
x = ...produces exactly what we would expect.