[3.9] Revert "[3.9] bpo-38908: Fix issue when non runtime_protocol does not raise TypeError (GH-26067)" (GH-26077)

Reverts #26075 Automerge-Triggered-By: GH:gvanrossum

Author: Fidget-Spinner

Lib/test/test_typing.py

@@ -1422,14 +1422,6 @@ class CustomProtocol(TestCase, Protocol):
  class CustomContextManager(typing.ContextManager, Protocol):
  pass
 
- def test_non_runtime_protocol_isinstance_check(self):
- class P(Protocol):
- x: int
-
- with self.assertRaisesRegex(TypeError, "@runtime_checkable"):
- isinstance(1, P)
-
-
 class GenericTests(BaseTestCase):
 
  def test_basics(self):

Lib/typing.py

@@ -1079,14 +1079,14 @@ def _no_init(self, *args, **kwargs):
  raise TypeError('Protocols cannot be instantiated')
 
 
-def _allow_reckless_class_checks(depth=3):
+def _allow_reckless_class_cheks():
  """Allow instance and class checks for special stdlib modules.
 
  The abc and functools modules indiscriminately call isinstance() and
  issubclass() on the whole MRO of a user class, which may contain protocols.
  """
  try:
- return sys._getframe(depth).f_globals['__name__'] in ['abc', 'functools']
+ return sys._getframe(3).f_globals['__name__'] in ['abc', 'functools']
  except (AttributeError, ValueError): # For platforms without _getframe().
  return True
 
@@ -1106,14 +1106,6 @@ class _ProtocolMeta(ABCMeta):
  def __instancecheck__(cls, instance):
  # We need this method for situations where attributes are
  # assigned in __init__.
- if (
- getattr(cls, '_is_protocol', False) and
- not getattr(cls, '_is_runtime_protocol', False) and
- not _allow_reckless_class_checks(depth=2)
- ):
- raise TypeError("Instance and class checks can only be used with"
- " @runtime_checkable protocols")
-
  if ((not getattr(cls, '_is_protocol', False) or
  _is_callable_members_only(cls)) and
  issubclass(instance.__class__, cls)):
@@ -1176,12 +1168,12 @@ def _proto_hook(other):
 
  # First, perform various sanity checks.
  if not getattr(cls, '_is_runtime_protocol', False):
- if _allow_reckless_class_checks():
+ if _allow_reckless_class_cheks():
  return NotImplemented
  raise TypeError("Instance and class checks can only be used with"
  " @runtime_checkable protocols")
  if not _is_callable_members_only(cls):
- if _allow_reckless_class_checks():
+ if _allow_reckless_class_cheks():
  return NotImplemented
  raise TypeError("Protocols with non-method members"
  " don't support issubclass()")