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Apply the None rule only to callable protocol members. #3938

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ilevkivskyi opened this issue Sep 9, 2017 · 0 comments
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Apply the None rule only to callable protocol members. #3938

ilevkivskyi opened this issue Sep 9, 2017 · 0 comments
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bug mypy got something wrong priority-1-normal topic-protocols

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Currently mypy applies the rule that things like __iter__ = None block protocol implementation. However, it is applied only to dunder attributes, which is too ad-hoc (also there are names like send and throw in collections.abc). It is proposed in python/typing#464 that it should be applied only to methods (callable members) which would be more consistent.
@ilevkivskyi ilevkivskyi self-assigned this Sep 9, 2017
@ilevkivskyi ilevkivskyi mentioned this issue Sep 9, 2017
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@ilevkivskyi ilevkivskyi mentioned this issue Sep 24, 2017
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gvanrossum pushed a commit that referenced this issue Sep 29, 2017
@ilevkivskyi @gvanrossum
Minor updates to protocol semantics (#3996)
b3ca169 
This updates protocol semantic according to the discussion in python/typing#464:

    None should be considered a subtype of an empty protocol
    method = None rule should apply only to callable protocol members
    issublcass() is prohibited for protocols with non-method members.

Fixes #3906
Fixes #3938
Fixes #3939
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