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Pattern Matching with type() #5573

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KalleDK opened this issue Jul 25, 2023 · 3 comments
Closed

Pattern Matching with type() #5573

KalleDK opened this issue Jul 25, 2023 · 3 comments
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addressed in next version Issue is fixed and will appear in next published version bug Something isn't working

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@KalleDK
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KalleDK commented Jul 25, 2023

Environment data

  • Language Server version: 2023.7.31 (pyright b917b7a)
  • OS and version: WSL2 Debian
  • Python version (& distribution if applicable, e.g. Anaconda): 3.11

Code Snippet

y = str

match y:
    case type(): # <-- This line complains - Pattern will never be matched for subject type "y"
        print(8)
    case _:
        pass
@rchiodo
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rchiodo commented Jul 25, 2023

Thanks for the issue. Took me a bit to see the error. Requires turning on reportUnnecessaryComparison.

image

Seems like a core type checking issue. Transferring to Pyright.

@rchiodo rchiodo transferred this issue from microsoft/pylance-release Jul 25, 2023
@rchiodo rchiodo removed their assignment Jul 25, 2023
@erictraut erictraut added the bug Something isn't working label Jul 25, 2023
erictraut pushed a commit that referenced this issue Jul 25, 2023
@msfterictraut
Added support for type narrowing of a class pattern when the specifie…
e5c1966 
…d class is `type()` or a subtype thereof and the subject contains a `type[X]` whose metaclass potentially matches the pattern. This addresses #5573.
@erictraut erictraut mentioned this issue Jul 25, 2023
Merged
erictraut added a commit that referenced this issue Jul 25, 2023
@erictraut @msfterictraut
Added support for type narrowing of a class pattern when the specifie…
1da8c18 
…d class is `type()` or a subtype thereof and the subject contains a `type[X]` whose metaclass potentially matches the pattern. This addresses #5573. (#5576)

Co-authored-by: Eric Traut <erictr@microsoft.com>
@erictraut erictraut added the addressed in next version Issue is fixed and will appear in next published version label Jul 25, 2023
@erictraut
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Thanks for the bug report. This will be addressed in the next release.

@erictraut
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This is addressed in pyright 1.1.319, which I just published. It will also be included in a future release of pylance.

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@KalleDK @erictraut @rchiodo