pythoncapi
diff --git a/‎Lib/test/test_range.py‎
Lines changed: 9 additions & 0 deletions b/‎Lib/test/test_range.py‎
Lines changed: 9 additions & 0 deletions
diff --git a/‎Misc/NEWS‎
Lines changed: 3 additions & 0 deletions b/‎Misc/NEWS‎
Lines changed: 3 additions & 0 deletions
diff --git a/‎Objects/rangeobject.c‎
Lines changed: 5 additions & 5 deletions b/‎Objects/rangeobject.c‎
Lines changed: 5 additions & 5 deletions
@@ -312,6 +312,15 @@ def __index__(self):
 
         self.assertRaises(TypeError, range, IN())
 
+        # Test use of user-defined classes in slice indices.
+        self.assertEqual(list(range(10)[:I(5)]), list(range(5)))
+
+        with self.assertRaises(RuntimeError):
+            range(0, 10)[:IX()]
+
+        with self.assertRaises(TypeError):
+            range(0, 10)[:IN()]
+
     def test_count(self):
         self.assertEqual(range(3).count(-1), 0)
         self.assertEqual(range(3).count(0), 1)
 
@@ -12,6 +12,9 @@ What's New in Python 3.3.1?
 Core and Builtins
 -----------------
 
+- Issue #16402: When slicing a range, fix shadowing of exceptions from
+  __index__.
+
 - Issue #16336: fix input checking in the surrogatepass error handler.
   Patch by Serhiy Storchaka.
 
 
@@ -331,11 +331,11 @@ compute_slice_element(PyObject *obj)
         if (PyIndex_Check(obj)) {
             result = PyNumber_Index(obj);
         }
-    }
-    if (result == NULL) {
-        PyErr_SetString(PyExc_TypeError,
-                        "slice indices must be integers or "
-                        "None or have an __index__ method");
+        else {
+            PyErr_SetString(PyExc_TypeError,
+                            "slice indices must be integers or "
+                            "None or have an __index__ method");
+        }
     }
     return result;
 }
Original file line number	Diff line number	Diff line change
`@@ -331,11 +331,11 @@ compute_slice_element(PyObject *obj)`
`331`	`331`	`if (PyIndex_Check(obj)) {`
`332`	`332`	`result = PyNumber_Index(obj);`
`333`	`333`	`}`
`334`		`- }`
`335`		`- if (result == NULL) {`
`336`		`- PyErr_SetString(PyExc_TypeError,`
`337`		`- "slice indices must be integers or "`
`338`		`- "None or have an __index__ method");`
	`334`	`+ else {`
	`335`	`+ PyErr_SetString(PyExc_TypeError,`
	`336`	`+ "slice indices must be integers or "`
	`337`	`+ "None or have an __index__ method");`
	`338`	`+ }`
`339`	`339`	`}`
`340`	`340`	`return result;`
`341`	`341`	`}`