Fix #5569: Fix a crash in unused-private-member when type(self) used in bound methods

ChangeLog

@@ -35,6 +35,11 @@ Release date: TBA
   Closes #4798
   Closes #5081
 
+* Fix a crash in ``unused-private-member`` checker when analyzing code using
+  ``type(self)`` in bound methods.
+
+  Closes #5569
+
 * Pyreverse - add output in mermaidjs format
 
 * ``used-before-assignment`` now considers that assignments in a try block

doc/whatsnew/2.13.rst

@@ -74,6 +74,11 @@ Other Changes
 
   Closes #4716
 
+* Fix a crash in ``unused-private-member`` checker when analyzing code using
+  ``type(self)`` in bound methods.
+
+  Closes #5569
+
 * Fix crash in ``unnecessary-dict-index-lookup`` checker if the output of
   ``items()`` is assigned to a 1-tuple.
 

pylint/checkers/classes/class_checker.py

@@ -970,6 +970,9 @@ def _check_unused_private_attributes(self, node: nodes.ClassDef) -> None:
                 if attribute.attrname != assign_attr.attrname:
                     continue
 
+                if self._is_type_self_call(attribute.expr):
+                    continue
+
                 if (
                     assign_attr.expr.name
                     in {
@@ -2034,11 +2037,19 @@ def _is_mandatory_method_param(self, node):
 
         Name is `self` for method, `cls` for classmethod and `mcs` for metaclass.
         """
-        return (
-            self._first_attrs
-            and isinstance(node, nodes.Name)
-            and node.name == self._first_attrs[-1]
-        )
+        if self._first_attrs:
+            first_attr = self._first_attrs[-1]
+        else:
+            # It's possible the function was already unregistered.
+            closest_func = utils.get_node_first_ancestor_of_type(
+                node, nodes.FunctionDef
+            )
+            if closest_func is None:
+                return False
+            if not closest_func.args.args:
+                return False
+            first_attr = closest_func.args.args[0].name
+        return isinstance(node, nodes.Name) and node.name == first_attr
 
 
 def _ancestors_to_call(klass_node, method="__init__"):

tests/functional/u/unused/unused_private_member.py

@@ -309,3 +309,13 @@ class Foo:
 
     def method(self):
         print(self.__class__.__ham)
+
+
+class TypeSelfCallInMethod:
+    """Regression test for issue 5569"""
+    @classmethod
+    def b(cls) -> None:
+        cls.__a = ''  # [unused-private-member]
+
+    def a(self):
+        return type(self).__a

tests/functional/u/unused/unused_private_member.txt

@@ -17,3 +17,4 @@ unused-private-member:243:12:243:50:FalsePositive4681.__init__:Unused private me
 unused-private-member:274:4:275:26:FalsePositive4849.__unused_private_method:Unused private member `FalsePositive4849.__unused_private_method()`:UNDEFINED
 unused-private-member:291:4:294:44:Pony.__init_defaults:Unused private member `Pony.__init_defaults(self)`:UNDEFINED
 unused-private-member:296:4:298:20:Pony.__get_fur_color:Unused private member `Pony.__get_fur_color(self)`:UNDEFINED
+unused-private-member:318:8:318:15:TypeSelfCallInMethod.b:Unused private member `TypeSelfCallInMethod.__a`:UNDEFINED