From 7e0148d7cb75b5e96282a8f5d7af58528d60ce86 Mon Sep 17 00:00:00 2001
From: sobolevn <mail@sobolevn.me>
Date: Sun, 2 Jan 2022 16:13:32 +0300
Subject: [PATCH 1/2] Do not count `__slots__` as a protocol member, refs
 #11884

---
 mypy/nodes.py                       |  3 ++-
 test-data/unit/check-protocols.test | 36 +++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/mypy/nodes.py b/mypy/nodes.py
index 78a018f94a78..0e7d44ac5010 100644
--- a/mypy/nodes.py
+++ b/mypy/nodes.py
@@ -2667,7 +2667,8 @@ def protocol_members(self) -> List[str]:
         for base in self.mro[:-1]:  # we skip "object" since everyone implements it
             if base.is_protocol:
                 for name in base.names:
-                    members.add(name)
+                    if name != '__slots__':  # `__slots__` is not a protocol member
+                        members.add(name)
         return sorted(list(members))
 
     def __getitem__(self, name: str) -> 'SymbolTableNode':
diff --git a/test-data/unit/check-protocols.test b/test-data/unit/check-protocols.test
index 6768263e9832..d787d40687e6 100644
--- a/test-data/unit/check-protocols.test
+++ b/test-data/unit/check-protocols.test
@@ -2693,6 +2693,42 @@ class A(Protocol):
 
 [builtins fixtures/tuple.pyi]
 
+[case testProrocolSlotsIsNotProtocolMember]
+# 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'
+def foo(f: Foo):
+    pass
+
+# All should pass:
+foo(NoSlots())
+foo(EmptySlots())
+foo(TupleSlots())
+foo(StringSlots())
+[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 testNoneVsProtocol]
 # mypy: strict-optional
 from typing_extensions import Protocol

From 26a950de229b27276a56d62c2426e3b541630d9f Mon Sep 17 00:00:00 2001
From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Date: Sat, 7 May 2022 16:14:55 -0700
Subject: [PATCH 2/2] Update test-data/unit/check-protocols.test

---
 test-data/unit/check-protocols.test | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test-data/unit/check-protocols.test b/test-data/unit/check-protocols.test
index d787d40687e6..e239b9a69ab8 100644
--- a/test-data/unit/check-protocols.test
+++ b/test-data/unit/check-protocols.test
@@ -2693,7 +2693,7 @@ class A(Protocol):
 
 [builtins fixtures/tuple.pyi]
 
-[case testProrocolSlotsIsNotProtocolMember]
+[case testProtocolSlotsIsNotProtocolMember]
 # https://github.com/python/mypy/issues/11884
 from typing import Protocol