Issue #1766304: The range.__contains__ optimization should only be

applied to ints, not to instances of subclasses of int.

Lib/test/test_range.py

@@ -97,6 +97,12 @@ class RangeTest(unittest.TestCase):
         # ..except if explicitly told so.
         self.assertTrue(int(C2()) in range(3))
 
+        # Check that the range.__contains__ optimization is only
+        # used for ints, not for instances of subclasses of int.
+        class C3(int):
+            def __eq__(self, other): return True
+        self.assertTrue(C3(11) in range(10))
+        self.assertTrue(C3(11) in list(range(10)))
 
     def test_strided_limits(self):
         r = range(0, 101, 2)

Objects/rangeobject.c

@@ -275,7 +275,7 @@ range_reduce(rangeobject *r, PyObject *args)
 
 static int
 range_contains(rangeobject *r, PyObject *ob) {
-    if (PyLong_Check(ob)) {
+    if (PyLong_CheckExact(ob) || PyBool_Check(ob)) {
         int cmp1, cmp2, cmp3;
         PyObject *tmp1 = NULL;
         PyObject *tmp2 = NULL;