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ilevkivskyiilevkivskyi
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Fix isinstance() with generic protocol subclasses after subscripting (#669)
Fixes #656 The problem is if a generic class inherits from a protocol, then `GenericMeta.__subclasscheck__()` gets overridden with `_ProtocolMeta.__subclasscheck__()` that calls the former via `super()`, thus causing an extra frame.
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Lines changed: 32 additions & 8 deletions

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‎python2/test_typing.py‎

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Original file line numberDiff line numberDiff line change
@@ -749,6 +749,27 @@ def __init__(self, x):
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self.assertIsInstance(C(1), P)
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self.assertIsInstance(C(1), PG)
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def test_protocol_checks_after_subscript(self):
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class P(Protocol[T]): pass
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class C(P[T]): pass
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class Old1: pass
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class New1(object): pass
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class Old2: pass
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class New2(object): pass
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CA = C[Any] # noqa
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self.assertNotIsInstance(Old1(), C)
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self.assertNotIsInstance(New1(), C)
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self.assertNotIsSubclass(Old2, C)
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self.assertNotIsSubclass(New2, C)
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class D1(C[Any]): pass
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class D2(C[Any]): pass
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CI = C[int] # noqa
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self.assertIsInstance(D1(), C)
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self.assertIsSubclass(D2, C)
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def test_protocols_support_register(self):
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@runtime_checkable
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class P(Protocol):

‎python2/typing.py‎

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Original file line numberDiff line numberDiff line change
@@ -1393,14 +1393,17 @@ def __getitem__(self, params):
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def __subclasscheck__(self, cls):
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if self.__origin__ is not None:
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# This should only be modules within the standard
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# library. singledispatch is the only exception, because
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# it's a Python 2 backport of functools.singledispatch.
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if sys._getframe(1).f_globals['__name__'] not in ['abc', 'functools',
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'singledispatch']:
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raise TypeError("Parameterized generics cannot be used with class "
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"or instance checks")
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return False
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# These should only be modules within the standard library.
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# singledispatch is an exception, because it's a Python 2 backport
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# of functools.singledispatch.
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whitelist = ['abc', 'functools', 'singledispatch']
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if (sys._getframe(1).f_globals['__name__'] in whitelist or
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# The second frame is needed for the case where we came
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# from _ProtocolMeta.__subclasscheck__.
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sys._getframe(2).f_globals['__name__'] in whitelist):
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return False
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raise TypeError("Parameterized generics cannot be used with class "
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"or instance checks")
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if self is Generic:
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raise TypeError("Class %r cannot be used with class "
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"or instance checks" % self)

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