Avoid unnecessary setattr lookups, ignore object.__setattr__

mypy/subtypes.py

@@ -1581,7 +1581,6 @@ def get_member_flags(name: str, itype: Instance, class_obj: bool = False) -> set
     """
     info = itype.type
     method = info.get_method(name)
-    setattr_meth = info.get_method("__setattr__")
     if method:
         if isinstance(method, Decorator):
             if method.var.is_staticmethod or method.var.is_classmethod:
@@ -1592,7 +1591,11 @@ def get_member_flags(name: str, itype: Instance, class_obj: bool = False) -> set
             assert isinstance(method, OverloadedFuncDef)
             dec = method.items[0]
             assert isinstance(dec, Decorator)
-            if dec.var.is_settable_property or setattr_meth:
+            if (
+                dec.var.is_settable_property
+                or (setattr_meth := info.get_method("__setattr__"))
+                and (setattr_meth.info.fullname != "builtins.object")
+            ):
                 flags = {IS_VAR, IS_SETTABLE}
                 if dec.var.setter_type is not None:
                     flags.add(IS_EXPLICIT_SETTER)
@@ -1602,7 +1605,9 @@ def get_member_flags(name: str, itype: Instance, class_obj: bool = False) -> set
         return set()  # Just a regular method
     node = info.get(name)
     if not node:
-        if setattr_meth:
+        if (setattr_meth := info.get_method("__setattr__")) and (
+            setattr_meth.info.fullname != "builtins.object"
+        ):
             return {IS_SETTABLE}
         if itype.extra_attrs and name in itype.extra_attrs.attrs:
             flags = set()

test-data/unit/check-protocols.test

@@ -1228,6 +1228,32 @@ x = C(42)
 y = CF(42)  # E: Incompatible types in assignment (expression has type "CF", variable has type "P") \
             # N: Protocol member P.x expected settable variable, got read-only attribute
 
+[case testDeletablePropertyProtocolWithSetattr]
+from typing import Protocol
+
+class P(Protocol):
+    attr: int
+
+class Deletable:
+    @property
+    def attr(self) -> int:
+        return 1
+    @attr.deleter
+    def attr(self) -> None:
+        pass
+
+class Settable(Deletable):
+    def __setattr__(self, name: str, value: int) -> None:
+        pass
+
+def consume(value: P) -> None:
+    pass
+
+consume(Deletable())  # E: Argument 1 to "consume" has incompatible type "Deletable"; expected "P" \
+                      # N: Protocol member P.attr expected settable variable, got read-only attribute
+consume(Settable())
+[builtins fixtures/property.pyi]
+
 [case testStaticAndClassMethodsInProtocols]
 from typing import Protocol, Type, TypeVar