Exclude the same special attributes from Protocol as CPython

mypy/nodes.py

@@ -2801,6 +2801,25 @@ def accept(self, visitor: ExpressionVisitor[T]) -> T:
         return visitor.visit_temp_node(self)
 
 
+# Special attributes not collected as protocol members by Python 3.12
+# See typing._SPECIAL_NAMES
+EXCLUDED_PROTOCOL_ATTRIBUTES: Final = frozenset(
+    {
+        "__abstractmethods__",
+        "__annotations__",
+        "__dict__",
+        "__doc__",
+        "__init__",
+        "__module__",
+        "__new__",
+        "__slots__",
+        "__subclasshook__",
+        "__weakref__",
+        "__class_getitem__",  # Since Python 3.9
+    }
+)
+
+
 class TypeInfo(SymbolNode):
     """The type structure of a single class.
 
@@ -3115,6 +3134,8 @@ def protocol_members(self) -> list[str]:
                     if isinstance(node.node, (TypeAlias, TypeVarExpr, MypyFile)):
                         # These are auxiliary definitions (and type aliases are prohibited).
                         continue
+                    if name in EXCLUDED_PROTOCOL_ATTRIBUTES:
+                        continue
                     members.add(name)
         return sorted(list(members))
 

test-data/unit/check-protocols.test

@@ -2789,6 +2789,70 @@ class A(Protocol):
 
 [builtins fixtures/tuple.pyi]
 
+[case testProtocolSlotsIsNotProtocolMember]
+# https://github.com/python/mypy/issues/11884
+from typing import Protocol
+
+class Foo(Protocol):
+    __slots__ = ()
+class NoSlots:
+    pass
+class EmptySlots:
+    __slots__ = ()
+class TupleSlots:
+    __slots__ = ('x', 'y')
+class StringSlots:
+    __slots__ = 'x y'
+class InitSlots:
+    __slots__ = ('x',)
+    def __init__(self) -> None:
+        self.x = None
+def foo(f: Foo):
+    pass
+
+# All should pass:
+foo(NoSlots())
+foo(EmptySlots())
+foo(TupleSlots())
+foo(StringSlots())
+foo(InitSlots())
+[builtins fixtures/tuple.pyi]
+
+[case testProtocolSlotsAndRuntimeCheckable]
+from typing import Protocol, runtime_checkable
+
+@runtime_checkable
+class Foo(Protocol):
+    __slots__ = ()
+class Bar:
+    pass
+issubclass(Bar, Foo)  # Used to be an error, when `__slots__` counted as a protocol member
+[builtins fixtures/isinstance.pyi]
+[typing fixtures/typing-full.pyi]
+
+
+[case testProtocolWithClassGetItem]
+# https://github.com/python/mypy/issues/11886
+from typing import Any, Iterable, Protocol, Union
+
+class B:
+    ...
+
+class C:
+    def __class_getitem__(cls, __item: Any) -> Any:
+        ...
+
+class SupportsClassGetItem(Protocol):
+    __slots__: Union[str, Iterable[str]] = ()
+    def __class_getitem__(cls, __item: Any) -> Any:
+        ...
+
+b1: SupportsClassGetItem = B()
+c1: SupportsClassGetItem = C()
+[builtins fixtures/tuple.pyi]
+[typing fixtures/typing-full.pyi]
+
+
 [case testNoneVsProtocol]
 # mypy: strict-optional
 from typing_extensions import Protocol