Pass most conformance tests for Zuban #2139
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… bound of the class
| ret2 = example4(v2, 1) | ||
| assert_type(ret2, Any) | ||
| assert_type(ret2, Any) # E[example4] | ||
| assert_type(ret2, list[Any]) # E[example4] |
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Doesn't Step 5 of https://typing.python.org/en/latest/spec/overload.html#step-5 explicitly mandate Any (not list[Any]) here?
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You are right, that it's written that way. My personal opinion is that it should be possible for type checkers to be more precise than what the spec mandates. I personally would also be supportive to allow list[int] | list[str], but I doubt any type checker would do that.
It's of course possible for me to disable this fallback logic, but I'd rather not, because I find it useful. I also don't think that it's necessary to explain in the spec that fallback types can be used. But if people don't think so, then I probably have to start a discussion about this as well (like 2-3 other cases where Zuban is more strict).
In this specific case I also doubt that it will cause interoperability issues, since anybody using the overload will work with a list output.
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Our motivation for standardizing the overload algorithm was to ensure that type checkers produce the same result when evaluating overloaded calls. Allowing variations would be run counter to this goal.
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I do think that it's good that overloads are standardized. I'm just a bit sad that this behavior is being ditched for IMO no good reason. I have changed it regardless, I don't think it's worth discussing. I did not yet create a Zuban release, so you should probably not merge yet.
Are there other issues? Happy to create a release otherwise.
…luation" Reverted because this change was not according to the spec. This reverts commit 593d74d.
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| @@ -1,12 +1,9 @@ | |||
| conformant = "Partial" | |||
| notes = """ | |||
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can remove the empty notes section (possibly in a few more files too)
| return x | ||
| stop() | ||
| ... # E?: This statement can be marked unreachable | ||
| return "whatever works" # No type error |
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For what it's worth I wouldn't mind allowing an error here; the type is clearly wrong and I don't think it's wrong for type checkers to detect that even in unreachable code.
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(No change requested though; fine to leave it as is.)
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This latest update passes most conformance tests for Zuban. I simplified the flags for
zuban checkand it also passes 2 more tests for Pyrefly.I have made several small changes to the tests. These should mostly be uncontroversial:
SelfTypeVar = TypeVar("SelfTypeVar", bound=Foo7[int]); Callable[[SelfTypevar], SelfTypeVar]instead ofCallable[[Foo7[int]], Foo7[int]]. I personally believe this should be how we infer things, since it's more precise but I don't think we have to mandate this.list[Any]instead ofAnyin an overload, if there was no match, because both of the overloads return a list and it is therefore just a slightly more precise type.__init__). There is already an error for the outer attributex, but I feel like this error should be fine.There remain 4 non-passing tests for Zuban, all of which I'm not sure the tests are doing the right thing. I will be discussing these in the typing discourse.