Added regression test for issue24581.

Lib/test/test_set.py

@@ -1731,6 +1731,17 @@ class TestWeirdBugs(unittest.TestCase):
         be_bad = True
         set1.symmetric_difference_update(dict2)
 
+    def test_iter_and_mutate(self):
+        # Issue #24581
+        s = set(range(100))
+        s.clear()
+        s.update(range(100))
+        si = iter(s)
+        s.clear()
+        a = list(range(100))
+        s.update(range(100))
+        list(si)
+
 # Application tests (based on David Eppstein's graph recipes ====================================
 
 def powerset(U):