Closed
Description
Consider the following code:
from typing import Sized
isinstance(1, Sized)This works well and returns False, as expected.
However, if I create a new protocol that subclass Sized:
from typing_extensions import Protocol
class MySized(Protocol, Sized):
pass
isinstance(1, Sized)This now raises the following exception:
TypeError Traceback (most recent call last)
<ipython-input-5-2516c5c4af5f> in <module>
----> 1 isinstance(1, Sized)
.../lib/python3.8/typing.py in __instancecheck__(self, obj)
764
765 def __instancecheck__(self, obj):
--> 766 return self.__subclasscheck__(type(obj))
767
768 def __subclasscheck__(self, cls):
.../lib/python3.8/typing.py in __subclasscheck__(self, cls)
769 if self._special:
770 if not isinstance(cls, _GenericAlias):
--> 771 return issubclass(cls, self.__origin__)
772 if cls._special:
773 return issubclass(cls.__origin__, self.__origin__)
.../lib/python3.8/abc.py in __subclasscheck__(cls, subclass)
100 def __subclasscheck__(cls, subclass):
101 """Override for issubclass(subclass, cls)."""
--> 102 return _abc_subclasscheck(cls, subclass)
103
104 def _dump_registry(cls, file=None):
.../lib/python3.8/site-packages/typing_extensions.py in __subclasscheck__(cls, other)
581 "Protocols with non-method members don't support issubclass()"
582 )
--> 583 return super().__subclasscheck__(other)
584
585 def __instancecheck__(cls, instance):
.../lib/python3.8/abc.py in __subclasscheck__(cls, subclass)
100 def __subclasscheck__(cls, subclass):
101 """Override for issubclass(subclass, cls)."""
--> 102 return _abc_subclasscheck(cls, subclass)
103
104 def _dump_registry(cls, file=None):
.../lib/python3.8/site-packages/typing_extensions.py in _proto_hook(cls, other)
637 if _allow_reckless_class_checks():
638 return NotImplemented
--> 639 raise TypeError("Instance and class checks can only be used with"
640 " @runtime_checkable protocols")
641
TypeError: Instance and class checks can only be used with @runtime_checkable protocolsThis non-local behavior did not happen in prior versions, and has caused problems in my code (GAA-UAM/scikit-fda#540).