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ZeeD opened this issue Oct 3, 2019 · 2 comments
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class decorator could change type of the decorated class #7614

ZeeD opened this issue Oct 3, 2019 · 2 comments

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@ZeeD
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ZeeD commented Oct 3, 2019

Can a class decorator "change" the type of the decorated class?
My issue is with a "wrapper" class that I created, but I can replicate with even this example:

@str
class C: ...
reveal_type(C)

if I launch mypy I see

$ mypy <(echo '@str
> class C: ...
> reveal_type(C)')
/dev/fd/63:3: note: Revealed type is 'def () -> __main__.C'
$

while C, actually, has became a str!
@msullivan
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Yeah, we basically don't do any typechecking of class decorators at all. This is definitely a bug (and a duplicate of #3135) but mostly it hasn't seemed to be a problem!

I think it is somewhat unlikely we will ever understand complicated class decorator behaviors, but we could certainly do better here. I think we'd be more likely to just reject this call than to turn C into a variable of type str, though.

@ZeeD
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ZeeD commented Oct 4, 2019

Sorry for the duplicate, I couldn't find similar issues.
As I said, the "str" was just a "minimal reproducible example", my original problem was with a "wrapper class that act as a replacement".
By the way, I remember to have seen (in a private repo) code with a "singleton" decorator that basically instantiated the class

JukkaL added a commit that referenced this issue Apr 13, 2022
@JukkaL
Typeshed cherry-pick: Drop some literal types from argparse (add_argu…
9cd9741 
…ment) (#7614)
JukkaL added a commit that referenced this issue Apr 13, 2022
@JukkaL
Typeshed cherry-pick: Drop some literal types from argparse (add_argu…
1cccb0b 
…ment) (#7614) (#12576)

From python/typeshed#7614.
JukkaL added a commit that referenced this issue Apr 13, 2022
@JukkaL
Typeshed cherry-pick: Drop some literal types from argparse (add_argu…
90be28d 
…ment) (#7614) (#12576)

From python/typeshed#7614.
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@ZeeD @msullivan