diff -r d86aec3f61b0 Include/longobject.h
--- a/Include/longobject.h	Sat Aug 03 17:14:50 2013 +0100
+++ b/Include/longobject.h	Sun Aug 04 11:05:46 2013 +0100
@@ -164,6 +164,12 @@
     unsigned char* bytes, size_t n,
     int little_endian, int is_signed);
 
+/* _PyLong_FromNbInt: Convert the given object to a PyLongObject
+   using the nb_int slot, if available.  Raise TypeError if either the
+   nb_int slot is not available or the result of the call to nb_int
+   returns something not of type int.
+*/
+PyAPI_FUNC(PyLongObject *)_PyLong_FromNbInt(PyObject *);
 
 /* _PyLong_Format: Convert the long to a string object with given base,
    appending a base prefix of 0[box] if base is 2, 8 or 16. */
diff -r d86aec3f61b0 Lib/test/test_index.py
--- a/Lib/test/test_index.py	Sat Aug 03 17:14:50 2013 +0100
+++ b/Lib/test/test_index.py	Sun Aug 04 11:05:46 2013 +0100
@@ -9,7 +9,7 @@
 
 class TrapInt(int):
     def __index__(self):
-        return self
+        return int(self)
 
 class BaseTestCase(unittest.TestCase):
     def setUp(self):
@@ -55,6 +55,31 @@
         self.assertRaises(TypeError, slice(self.o).indices, 0)
         self.assertRaises(TypeError, slice(self.n).indices, 0)
 
+    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, 8)
+        # 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
+
+        bad_int = BadInt()
+        with support.check_warnings(('', DeprecationWarning)):
+            operator.index(bad_int)
+
 
 class SeqTestCase:
     # This test case isn't run directly. It just defines common tests
diff -r d86aec3f61b0 Lib/test/test_int.py
--- a/Lib/test/test_int.py	Sat Aug 03 17:14:50 2013 +0100
+++ b/Lib/test/test_int.py	Sun Aug 04 11:05:46 2013 +0100
@@ -320,10 +320,6 @@
             def __int__(self):
                 return 42
 
-        class Foo3(int):
-            def __int__(self):
-                return self
-
         class Foo4(int):
             def __int__(self):
                 return 42
@@ -335,7 +331,6 @@
         self.assertEqual(int(Foo0()), 42)
         self.assertEqual(int(Foo1()), 42)
         self.assertEqual(int(Foo2()), 42)
-        self.assertEqual(int(Foo3()), 0)
         self.assertEqual(int(Foo4()), 42)
         self.assertRaises(TypeError, int, Foo5())
 
@@ -400,6 +395,49 @@
                 with self.assertRaises(TypeError):
                     int(TruncReturnsBadInt())
 
+    def test_int_subclass_with_int(self):
+        class MyInt(int):
+            def __int__(self):
+                return 42
+
+        my_int = MyInt(7)
+        self.assertEqual(my_int, 7)
+        self.assertEqual(int(my_int), 42)
+
+    def test_int_returns_int_subclass(self):
+        class BadInt:
+            def __int__(self):
+                return True
+
+        class Foo3(int):
+            def __int__(self):
+                return self
+
+        class TruncReturnsBadInt:
+            def __trunc__(self):
+                return BadInt()
+
+        class TruncReturnsIntSubclass:
+            def __trunc__(self):
+                return True
+
+        bad_int = BadInt()
+        with support.check_warnings(('', DeprecationWarning)):
+            int(bad_int)
+
+        bad_int = Foo3()
+        with support.check_warnings(('', DeprecationWarning)):
+            int(bad_int)
+
+        bad_int = TruncReturnsBadInt()
+        with support.check_warnings(('', DeprecationWarning)):
+            int(bad_int)
+
+        good_int = TruncReturnsIntSubclass()
+        n = int(good_int)
+        self.assertIs(type(n), int)
+        self.assertEqual(n, 1)
+
     def test_error_message(self):
         testlist = ('\xbd', '123\xbd', '  123 456  ')
         for s in testlist:
diff -r d86aec3f61b0 Objects/abstract.c
--- a/Objects/abstract.c	Sat Aug 03 17:14:50 2013 +0100
+++ b/Objects/abstract.c	Sun Aug 04 11:05:46 2013 +0100
@@ -1153,8 +1153,8 @@
     return type_error("bad operand type for abs(): '%.200s'", o);
 }
 
-/* Return a Python Int or Long from the object item
-   Raise TypeError if the result is not an int-or-long
+/* Return a Python int from the object item.
+   Raise TypeError if the result is not an int
    or if the object cannot be interpreted as an index.
 */
 PyObject *
@@ -1163,19 +1163,36 @@
     PyObject *result = NULL;
     if (item == NULL)
         return null_error();
-    if (PyLong_Check(item)) {
+    if (PyLong_CheckExact(item)) {
         Py_INCREF(item);
         return item;
     }
     if (PyIndex_Check(item)) {
         result = item->ob_type->tp_as_number->nb_index(item);
-        if (result && !PyLong_Check(result)) {
-            PyErr_Format(PyExc_TypeError,
-                         "__index__ returned non-int "
-                         "(type %.200s)",
-                         result->ob_type->tp_name);
-            Py_DECREF(result);
-            return NULL;
+        if (result && !PyLong_CheckExact(result)) {
+            int exception_raised = 0;
+            if (!PyLong_Check(result)) {
+                PyErr_Format(PyExc_TypeError,
+                             "__index__ returned non-int "
+                             "(type %.200s)",
+                             result->ob_type->tp_name);
+                exception_raised = 1;
+            }
+            else {
+                /* Issue #17576: warn if 'result' not of exact type int. */
+                exception_raised = PyErr_WarnFormat(
+                    PyExc_DeprecationWarning,
+                    1,
+                    "__index__ returned non-int "
+                    "(type %.200s).  The ability to return an instance of "
+                    "a strict subclass of int is deprecated, and "
+                    "may be removed in a future version of Python.",
+                    result->ob_type->tp_name);
+            }
+            if (exception_raised) {
+                Py_DECREF(result);
+                return NULL;
+            }
         }
     }
     else {
@@ -1233,34 +1250,6 @@
 }
 
 
-/*
-  Returns the Integral instance converted to an int. The instance is expected
-  to be an int or have an __int__ method. Steals integral's
-  reference. error_format will be used to create the TypeError if integral
-  isn't actually an Integral instance. error_format should be a format string
-  that can accept a char* naming integral's type.
-*/
-static PyObject *
-convert_integral_to_int(PyObject *integral, const char *error_format)
-{
-    PyNumberMethods *nb;
-    if (PyLong_Check(integral))
-        return integral;
-    nb = Py_TYPE(integral)->tp_as_number;
-    if (nb->nb_int) {
-        PyObject *as_int = nb->nb_int(integral);
-        if (!as_int || PyLong_Check(as_int)) {
-            Py_DECREF(integral);
-            return as_int;
-        }
-        Py_DECREF(as_int);
-    }
-    PyErr_Format(PyExc_TypeError, error_format, Py_TYPE(integral)->tp_name);
-    Py_DECREF(integral);
-    return NULL;
-}
-
-
 /* Add a check for embedded NULL-bytes in the argument. */
 static PyObject *
 long_from_string(const char *s, Py_ssize_t len)
@@ -1297,18 +1286,8 @@
     }
     m = o->ob_type->tp_as_number;
     if (m && m->nb_int) { /* This should include subclasses of int */
-        PyObject *res = m->nb_int(o);
-        if (res && !PyLong_Check(res)) {
-            PyErr_Format(PyExc_TypeError,
-                         "__int__ returned non-int (type %.200s)",
-                         res->ob_type->tp_name);
-            Py_DECREF(res);
-            return NULL;
-        }
-        return res;
+        return (PyObject *)_PyLong_FromNbInt(o);
     }
-    if (PyLong_Check(o)) /* An int subclass without nb_int */
-        return _PyLong_Copy((PyLongObject *)o);
     trunc_func = _PyObject_LookupSpecial(o, &PyId___trunc__);
     if (trunc_func) {
         PyObject *truncated = PyEval_CallObject(trunc_func, NULL);
@@ -1318,8 +1297,17 @@
             return NULL;
         /* __trunc__ is specified to return an Integral type,
            but int() needs to return a int. */
-        int_instance = convert_integral_to_int(truncated,
-            "__trunc__ returned non-Integral (type %.200s)");
+        m = truncated->ob_type->tp_as_number;
+        if (m == NULL || m->nb_int == NULL) {
+            PyErr_Format(
+                PyExc_TypeError,
+                "__trunc__ returned non-Integral (type %.200s)",
+                truncated->ob_type->tp_name);
+            Py_DECREF(truncated);
+            return NULL;
+        }
+        int_instance = (PyObject *)_PyLong_FromNbInt(truncated);
+        Py_DECREF(truncated);
         return int_instance;
     }
     if (PyErr_Occurred())
diff -r d86aec3f61b0 Objects/longobject.c
--- a/Objects/longobject.c	Sat Aug 03 17:14:50 2013 +0100
+++ b/Objects/longobject.c	Sun Aug 04 11:05:46 2013 +0100
@@ -122,6 +122,63 @@
     return v;
 }
 
+/* _PyLong_FromNbInt: Convert the given object to a PyLongObject
+   using the nb_int slot, if available.  Raise TypeError if either the
+   nb_int slot is not available or the result of the call to nb_int
+   returns something not of type int.
+*/
+PyLongObject *
+_PyLong_FromNbInt(PyObject *integral)
+{
+    PyNumberMethods *nb;
+    PyObject *result;
+
+    /* Fast path for the case that we already have an int. */
+    if (PyLong_CheckExact(integral)) {
+        Py_INCREF(integral);
+        return (PyLongObject *)integral;
+    }
+
+    nb = Py_TYPE(integral)->tp_as_number;
+    if (nb == NULL || nb->nb_int == NULL) {
+        PyErr_Format(PyExc_TypeError,
+                     "an integer is required (got type %.200s)",
+                     Py_TYPE(integral)->tp_name);
+        return NULL;
+    }
+
+    /* Convert using the nb_int slot, which should return something
+       of exact type int. */
+    result = nb->nb_int(integral);
+    if (result && !PyLong_CheckExact(result)) {
+        int exception_raised = 0;
+        if (!PyLong_Check(result)) {
+            PyErr_Format(PyExc_TypeError,
+                         "__int__ returned non-int "
+                         "(type %.200s)",
+                         result->ob_type->tp_name);
+            exception_raised = 1;
+        }
+        else {
+            /* Issue #17576: warn if 'result' not of exact type int. */
+            exception_raised = PyErr_WarnFormat(
+                PyExc_DeprecationWarning,
+                1,
+                "__int__ returned non-int "
+                "(type %.200s).  The ability to return an instance of "
+                "a strict subclass of int is deprecated, and "
+                "may be removed in a future version of Python.",
+                result->ob_type->tp_name);
+        }
+        if (exception_raised) {
+            Py_DECREF(result);
+            return NULL;
+        }
+    }
+    return (PyLongObject *)result;
+}
+
+
 /* Allocate a new long int object with size digits.
    Return NULL and set exception if we run out of memory. */
 
@@ -345,7 +402,6 @@
     long res;
     Py_ssize_t i;
     int sign;
-    int do_decref = 0; /* if nb_int was called */
 
     *overflow = 0;
     if (vv == NULL) {
@@ -353,28 +409,11 @@
         return -1;
     }
 
-    if (!PyLong_Check(vv)) {
-        PyNumberMethods *nb;
-        nb = vv->ob_type->tp_as_number;
-        if (nb == NULL || nb->nb_int == NULL) {
-            PyErr_SetString(PyExc_TypeError,
-                            "an integer is required");
-            return -1;
-        }
-        vv = (*nb->nb_int) (vv);
-        if (vv == NULL)
-            return -1;
-        do_decref = 1;
-        if (!PyLong_Check(vv)) {
-            Py_DECREF(vv);
-            PyErr_SetString(PyExc_TypeError,
-                            "nb_int should return int object");
-            return -1;
-        }
-    }
+    v = _PyLong_FromNbInt(vv);
+    if (v == NULL)
+        return -1;
 
     res = -1;
-    v = (PyLongObject *)vv;
     i = Py_SIZE(v);
 
     switch (i) {
@@ -417,9 +456,7 @@
         }
     }
   exit:
-    if (do_decref) {
-        Py_DECREF(vv);
-    }
+    Py_DECREF(v);
     return res;
 }
 
@@ -636,36 +673,21 @@
 unsigned long
 PyLong_AsUnsignedLongMask(register PyObject *op)
 {
-    PyNumberMethods *nb;
     PyLongObject *lo;
     unsigned long val;
 
-    if (op && PyLong_Check(op))
-        return _PyLong_AsUnsignedLongMask(op);
-
-    if (op == NULL || (nb = op->ob_type->tp_as_number) == NULL ||
-        nb->nb_int == NULL) {
-        PyErr_SetString(PyExc_TypeError, "an integer is required");
+    if (op == NULL) {
+        PyErr_BadInternalCall();
         return (unsigned long)-1;
     }
 
-    lo = (PyLongObject*) (*nb->nb_int) (op);
+    lo = _PyLong_FromNbInt(op);
     if (lo == NULL)
         return (unsigned long)-1;
-    if (PyLong_Check(lo)) {
-        val = _PyLong_AsUnsignedLongMask((PyObject *)lo);
-        Py_DECREF(lo);
-        if (PyErr_Occurred())
-            return (unsigned long)-1;
-        return val;
-    }
-    else
-    {
-        Py_DECREF(lo);
-        PyErr_SetString(PyExc_TypeError,
-                        "nb_int should return int object");
-        return (unsigned long)-1;
-    }
+
+    val = _PyLong_AsUnsignedLongMask((PyObject *)lo);
+    Py_DECREF(lo);
+    return val;
 }
 
 int
@@ -1172,35 +1194,26 @@
         PyErr_BadInternalCall();
         return -1;
     }
-    if (!PyLong_Check(vv)) {
-        PyNumberMethods *nb;
-        PyObject *io;
-        if ((nb = vv->ob_type->tp_as_number) == NULL ||
-            nb->nb_int == NULL) {
-            PyErr_SetString(PyExc_TypeError, "an integer is required");
-            return -1;
-        }
-        io = (*nb->nb_int) (vv);
-        if (io == NULL)
-            return -1;
-        if (PyLong_Check(io)) {
-            bytes = PyLong_AsLongLong(io);
-            Py_DECREF(io);
-            return bytes;
-        }
-        Py_DECREF(io);
-        PyErr_SetString(PyExc_TypeError, "integer conversion failed");
+    v = _PyLong_FromNbInt(vv);
+    if (v == NULL)
         return -1;
-    }
-
-    v = (PyLongObject*)vv;
+
+    res = 0;
     switch(Py_SIZE(v)) {
-    case -1: return -(sdigit)v->ob_digit[0];
-    case 0: return 0;
-    case 1: return v->ob_digit[0];
-    }
-    res = _PyLong_AsByteArray((PyLongObject *)vv, (unsigned char *)&bytes,
-                              SIZEOF_LONG_LONG, PY_LITTLE_ENDIAN, 1);
+    case -1:
+        bytes = -(sdigit)v->ob_digit[0];
+        break;
+    case 0:
+        bytes = 0;
+        break;
+    case 1:
+        bytes = v->ob_digit[0];
+        break;
+    default:
+        res = _PyLong_AsByteArray((PyLongObject *)v, (unsigned char *)&bytes,
+                                  SIZEOF_LONG_LONG, PY_LITTLE_ENDIAN, 1);
+    }
+    Py_DECREF(v);
 
     /* Plan 9 can't handle PY_LONG_LONG in ? : expressions */
     if (res < 0)
@@ -1280,36 +1293,16 @@
 unsigned PY_LONG_LONG
 PyLong_AsUnsignedLongLongMask(register PyObject *op)
 {
-    PyNumberMethods *nb;
     PyLongObject *lo;
     unsigned PY_LONG_LONG val;
 
-    if (op && PyLong_Check(op))
-        return _PyLong_AsUnsignedLongLongMask(op);
-
-    if (op == NULL || (nb = op->ob_type->tp_as_number) == NULL ||
-        nb->nb_int == NULL) {
-        PyErr_SetString(PyExc_TypeError, "an integer is required");
-        return (unsigned PY_LONG_LONG)-1;
-    }
-
-    lo = (PyLongObject*) (*nb->nb_int) (op);
+    lo = _PyLong_FromNbInt(op);
     if (lo == NULL)
         return (unsigned PY_LONG_LONG)-1;
-    if (PyLong_Check(lo)) {
-        val = _PyLong_AsUnsignedLongLongMask((PyObject *)lo);
-        Py_DECREF(lo);
-        if (PyErr_Occurred())
-            return (unsigned PY_LONG_LONG)-1;
-        return val;
-    }
-    else
-    {
-        Py_DECREF(lo);
-        PyErr_SetString(PyExc_TypeError,
-                        "nb_int should return int object");
-        return (unsigned PY_LONG_LONG)-1;
-    }
+
+    val = _PyLong_AsUnsignedLongLongMask((PyObject *)lo);
+    Py_DECREF(lo);
+    return val;
 }
 
 /* Get a C long long int from a long int object or any object that has an
@@ -1331,7 +1324,6 @@
     PY_LONG_LONG res;
     Py_ssize_t i;
     int sign;
-    int do_decref = 0; /* if nb_int was called */
 
     *overflow = 0;
     if (vv == NULL) {
@@ -1339,28 +1331,11 @@
         return -1;
     }
 
-    if (!PyLong_Check(vv)) {
-        PyNumberMethods *nb;
-        nb = vv->ob_type->tp_as_number;
-        if (nb == NULL || nb->nb_int == NULL) {
-            PyErr_SetString(PyExc_TypeError,
-                            "an integer is required");
-            return -1;
-        }
-        vv = (*nb->nb_int) (vv);
-        if (vv == NULL)
-            return -1;
-        do_decref = 1;
-        if (!PyLong_Check(vv)) {
-            Py_DECREF(vv);
-            PyErr_SetString(PyExc_TypeError,
-                            "nb_int should return int object");
-            return -1;
-        }
-    }
+    v = _PyLong_FromNbInt(vv);
+    if (v == NULL)
+        return -1;
 
     res = -1;
-    v = (PyLongObject *)vv;
     i = Py_SIZE(v);
 
     switch (i) {
@@ -1403,9 +1378,7 @@
         }
     }
   exit:
-    if (do_decref) {
-        Py_DECREF(vv);
-    }
+    Py_DECREF(vv);
     return res;
 }