Metaclasses should inherit from type. #2818

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1. elazarg commented on Feb 7, 2017

   

   elazarg

   on Feb 7, 2017

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   I am for fixing it. The reason I have allowed this behavior is the documentation.

   Quote:

   The appropriate metaclass for a class definition is determined as follows:

   • if no bases and no explicit metaclass are given, then type() is used
   • if an explicit metaclass is given and it is not an instance of type(), then it is used directly as the metaclass
   • if an instance of type() is given as the explicit metaclass, or bases are defined, then the most derived metaclass is used

   End quote.

   What do you think?
2. ilevkivskyi commented on Feb 7, 2017

   

   ilevkivskyi

   on Feb 7, 2017

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   @elazarg I think the use case where metaclass is not an instance of type is quite rare, and (more importantly) this case could be difficult to typecheck. I think mypy could give an error message like: Metaclasses not inheriting from "type" are not yet supported.

   👍React with 👍1Reacted by Elazar Gershuni
3. elazarg commented on Feb 7, 2017

   

   elazarg

   on Feb 7, 2017

   Last edited by elazarg

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   I have a branch ready , but it requires multiple changes to typeshed before it can be merged.
4. JukkaL

   closed this as completedin #2820on Feb 7, 2017
5. JukkaL

   added a commit that references this issue on Feb 7, 2017

   Do not support metaclasses not inheriting from type (#2820)

   ...

   This issue will close once commit 452a64f is merged into the 'master' branch.

   452a64f