1 files changed, 43 insertions, 23 deletions
diff --git a/Lib/test/test_index.py b/Lib/test/test_index.py
index 7a94af1..8785711 100644
--- a/Lib/test/test_index.py
+++ b/Lib/test/test_index.py
@@ -9,7 +9,7 @@ class newstyle:
 
 class TrapInt(int):
     def __index__(self):
-        return self
+        return int(self)
 
 class BaseTestCase(unittest.TestCase):
     def setUp(self):
@@ -55,8 +55,41 @@ class BaseTestCase(unittest.TestCase):
         self.assertRaises(TypeError, slice(self.o).indices, 0)
         self.assertRaises(TypeError, slice(self.n).indices, 0)
 
-
-class SeqTestCase(unittest.TestCase):
+    def test_int_subclass_with_index(self):
+        # __index__ should be used when computing indices, even for int
+        # subclasses.  See issue #17576.
+        class MyInt(int):
+            def __index__(self):
+                return int(self) + 1
+
+        my_int = MyInt(7)
+        direct_index = my_int.__index__()
+        operator_index = operator.index(my_int)
+        self.assertEqual(direct_index, 8)
+        self.assertEqual(operator_index, 7)
+        # Both results should be of exact type int.
+        self.assertIs(type(direct_index), int)
+        #self.assertIs(type(operator_index), int)
+
+    def test_index_returns_int_subclass(self):
+        class BadInt:
+            def __index__(self):
+                return True
+
+        class BadInt2(int):
+            def __index__(self):
+                return True
+
+        bad_int = BadInt()
+        n = operator.index(bad_int)
+        self.assertEqual(n, 1)
+
+        bad_int = BadInt2()
+        n = operator.index(bad_int)
+        self.assertEqual(n, 0)
+
+
+class SeqTestCase:
     # This test case isn't run directly. It just defines common tests
     # to the different sequence types below
     def setUp(self):
@@ -126,7 +159,7 @@ class SeqTestCase(unittest.TestCase):
         self.assertRaises(TypeError, sliceobj, self.n, self)
 
 
-class ListTestCase(SeqTestCase):
+class ListTestCase(SeqTestCase, unittest.TestCase):
     seq = [0,10,20,30,40,50]
 
     def test_setdelitem(self):
@@ -182,19 +215,19 @@ class NewSeq:
         return self._list[index]
 
 
-class TupleTestCase(SeqTestCase):
+class TupleTestCase(SeqTestCase, unittest.TestCase):
     seq = (0,10,20,30,40,50)
 
-class ByteArrayTestCase(SeqTestCase):
+class ByteArrayTestCase(SeqTestCase, unittest.TestCase):
     seq = bytearray(b"this is a test")
 
-class BytesTestCase(SeqTestCase):
+class BytesTestCase(SeqTestCase, unittest.TestCase):
     seq = b"this is a test"
 
-class StringTestCase(SeqTestCase):
+class StringTestCase(SeqTestCase, unittest.TestCase):
     seq = "this is a test"
 
-class NewSeqTestCase(SeqTestCase):
+class NewSeqTestCase(SeqTestCase, unittest.TestCase):
     seq = NewSeq((0,10,20,30,40,50))
 
 
@@ -237,18 +270,5 @@ class OverflowTestCase(unittest.TestCase):
         self.assertRaises(OverflowError, lambda: "a" * self.neg)
 
 
-def test_main():
-    support.run_unittest(
-        BaseTestCase,
-        ListTestCase,
-        TupleTestCase,
-        BytesTestCase,
-        ByteArrayTestCase,
-        StringTestCase,
-        NewSeqTestCase,
-        RangeTestCase,
-        OverflowTestCase,
-    )
-
 if __name__ == "__main__":
-    test_main()
+    unittest.main()