Teach set modules to correctly compute s-=s and s^=s as the empty set.

1 files changed, 13 insertions, 0 deletions

diff --git a/Lib/test/test_sets.py b/Lib/test/test_sets.py
index c5a48b1..ff834e0 100644
--- a/Lib/test/test_sets.py
+++ b/Lib/test/test_sets.py
@@ -243,6 +243,19 @@ class TestBinaryOps(unittest.TestCase):
         self.assertRaises(TypeError, cmp, a, 12)
         self.assertRaises(TypeError, cmp, "abc", a)
 
+    def test_inplace_on_self(self):
+        t = self.set.copy()
+        t |= t
+        self.assertEqual(t, self.set)
+        t &= t
+        self.assertEqual(t, self.set)
+        t -= t
+        self.assertEqual(len(t), 0)
+        t = self.set.copy()
+        t ^= t
+        self.assertEqual(len(t), 0)
+
+
 #==============================================================================
 
 class TestUpdateOps(unittest.TestCase):