[issue43512] Bug in isinstance(instance, cls) with cls being a protocol? (PEP 544)

[Guido van Rossum]

Guido van Rossum <guido at python.org> added the comment:

Yeah, the runtime isinstance() checking is not required to give the right answer. Also, I believe one of the rules is "if you inherit from a protocol you are deemed to implement it". For methods, abstract methods can (but needn't) be used to indicate mandatory features. For attributes, there is no guarantee.

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resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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<https://bugs.python.org/issue43512>
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