Fix a crash in the unsupported-membership-test checker involving tuple unpacking

ChangeLog

@@ -214,6 +214,11 @@ What's New in Pylint 2.13.6?
 ============================
 Release date: TBA
 
+* Fix a crash in the ``unsupported-membership-test`` checker when assigning
+  multiple constants to class attributes including ``__iter__`` via unpacking.
+
+  Closes #6366
+
 * Asterisks are no longer required in Sphinx and Google style parameter documentation
   for ``missing-param-doc`` and are parsed correctly.
 

doc/whatsnew/2.13.rst

@@ -587,6 +587,11 @@ Other Changes
 
   Closes #5803
 
+* Fix a crash in the ``unsupported-membership-test`` checker when assigning
+  multiple constants to class attributes including ``__iter__`` via unpacking.
+
+  Closes #6366
+
 * Fix false positive for ``used-before-assignment`` for assignments taking place via
   nonlocal declarations after an earlier type annotation.
 

pylint/checkers/utils.py

@@ -1068,8 +1068,19 @@ def _supports_protocol_method(value: nodes.NodeNG, attr: str) -> bool:
         return False
 
     first = attributes[0]
+
+    # Return False if a constant is assigned
     if isinstance(first, nodes.AssignName):
-        if isinstance(first.parent.value, nodes.Const):
+        this_assign_parent = get_node_first_ancestor_of_type(
+            first, (nodes.Assign, nodes.NamedExpr)
+        )
+        if this_assign_parent is None:  # pragma: no cover
+            # Cannot imagine this being None, but return True to avoid false positives
+            return True
+        if isinstance(this_assign_parent.value, nodes.BaseContainer):
+            if all(isinstance(n, nodes.Const) for n in this_assign_parent.value.elts):
+                return False
+        if isinstance(this_assign_parent.value, nodes.Const):
             return False
     return True
 

tests/functional/n/none_dunder_protocols.py

@@ -25,10 +25,21 @@ class NonContainerClass(metaclass=MetaContainer):
     __iter__ = None
 
 
+class MultipleAssignmentNonesClass(metaclass=MetaContainer):
+    __len__, __iter__ = [None, None]
+
+
+class MultipleAssignmentLambdasClass(metaclass=MetaContainer):
+    """https://github.com/PyCQA/pylint/issues/6366"""
+    __len__, __iter__ = [lambda x: x] * 2
+
+
 def test():
     1 in NonIterableClass  # [unsupported-membership-test]
     1 in OldNonIterableClass  # [unsupported-membership-test]
     1 in NonContainerClass # [unsupported-membership-test]
     1 in NonIterableClass()  # [unsupported-membership-test]
     1 in OldNonIterableClass()  # [unsupported-membership-test]
     1 in NonContainerClass()  # [unsupported-membership-test]
+    1 in MultipleAssignmentNonesClass()  # [unsupported-membership-test]
+    1 in MultipleAssignmentLambdasClass()

tests/functional/n/none_dunder_protocols.txt

@@ -1,6 +1,7 @@
-unsupported-membership-test:29:9:29:25:test:Value 'NonIterableClass' doesn't support membership test:UNDEFINED
-unsupported-membership-test:30:9:30:28:test:Value 'OldNonIterableClass' doesn't support membership test:UNDEFINED
-unsupported-membership-test:31:9:31:26:test:Value 'NonContainerClass' doesn't support membership test:UNDEFINED
-unsupported-membership-test:32:9:32:27:test:Value 'NonIterableClass()' doesn't support membership test:UNDEFINED
-unsupported-membership-test:33:9:33:30:test:Value 'OldNonIterableClass()' doesn't support membership test:UNDEFINED
-unsupported-membership-test:34:9:34:28:test:Value 'NonContainerClass()' doesn't support membership test:UNDEFINED
+unsupported-membership-test:38:9:38:25:test:Value 'NonIterableClass' doesn't support membership test:UNDEFINED
+unsupported-membership-test:39:9:39:28:test:Value 'OldNonIterableClass' doesn't support membership test:UNDEFINED
+unsupported-membership-test:40:9:40:26:test:Value 'NonContainerClass' doesn't support membership test:UNDEFINED
+unsupported-membership-test:41:9:41:27:test:Value 'NonIterableClass()' doesn't support membership test:UNDEFINED
+unsupported-membership-test:42:9:42:30:test:Value 'OldNonIterableClass()' doesn't support membership test:UNDEFINED
+unsupported-membership-test:43:9:43:28:test:Value 'NonContainerClass()' doesn't support membership test:UNDEFINED
+unsupported-membership-test:44:9:44:39:test:Value 'MultipleAssignmentNonesClass()' doesn't support membership test:UNDEFINED

tests/functional/n/none_dunder_protocols_py38.py

@@ -0,0 +1,12 @@
+# pylint: disable=missing-docstring,too-few-public-methods,expression-not-assigned
+class MetaContainer(type):
+    __contains__ = None
+
+
+class NamedExpressionClass(metaclass=MetaContainer):
+    if (__iter__ := lambda x: x):
+        pass
+
+
+def test():
+    1 in NamedExpressionClass()

tests/functional/n/none_dunder_protocols_py38.rc

@@ -0,0 +1,2 @@
+[testoptions]
+min_pyver=3.8