Fix List item_type validation rejecting subclasses with a custom metaclass

param/parameters.py

@@ -3731,7 +3731,7 @@ def _validate_item_type(self, val, item_type, is_instance):
             if is_instance and not isinstance(v, item_type):
                 err_kind = "instances"
                 obj_display = lambda v: type(v)
-            elif not is_instance and (type(v) is not type or not issubclass(v, item_type)):
+            elif not is_instance and (not isinstance(v, type) or not issubclass(v, item_type)):
                 err_kind = "subclasses"
             if err_kind:
                 raise TypeError(

tests/testlist.py

@@ -1,3 +1,4 @@
+import abc
 import re
 import unittest
 
@@ -16,6 +17,7 @@ class Obj: pass
 class SubObj1(Obj): pass
 class SubObj2(Obj): pass
 class DiffObj: pass
+class SubObjMeta(Obj, metaclass=abc.ABCMeta): pass
 
 class TestListParameters(unittest.TestCase):
 
@@ -109,6 +111,12 @@ def test_set_object_wrong_is_instance_type(self):
         ):
             p.o = [DiffObj]
 
+    def test_set_object_subclass_custom_metaclass(self):
+        # A subclass defined with a custom metaclass should be accepted.
+        p = self.P()
+        p.o = [SubObjMeta]
+        assert p.o == [SubObjMeta]
+
     def test_set_object_wrong_type(self):
         p = self.P()
         with pytest.raises(