__hash__ may now return long int; the final hash

value is obtained by invoking hash on the long int.
Fixes #1536021.

Doc/ref/ref3.tex

@@ -1307,6 +1307,11 @@ defines mutable objects and implements a \method{__cmp__()} or
 since the dictionary implementation requires that a key's hash value
 is immutable (if the object's hash value changes, it will be in the
 wrong hash bucket).
+
+\versionchanged[\method{__hash__()} may now also return a long
+integer object; the 32-bit integer is then derived from the hash
+of that object]{2.5}
+
 \withsubitem{(object method)}{\ttindex{__cmp__()}}
 \end{methoddesc}
 

Lib/test/test_builtin.py

@@ -640,6 +640,15 @@ class BuiltinTest(unittest.TestCase):
         def f(): pass
         self.assertRaises(TypeError, hash, [])
         self.assertRaises(TypeError, hash, {})
+        # Bug 1536021: Allow hash to return long objects
+        class X:
+            def __hash__(self):
+                return 2**100
+        self.assertEquals(type(hash(X())), int)
+        class Y(object):
+            def __hash__(self):
+                return 2**100
+        self.assertEquals(type(hash(Y())), int)
 
     def test_hex(self):
         self.assertEqual(hex(16), '0x10')

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.5 release candidate 1?
 Core and builtins
 -----------------
 
+- Bug #1536021: __hash__ may now return long int; the final hash
+  value is obtained by invoking hash on the long int.
+
 - Bug #1536786: buffer comparison could emit a RuntimeWarning.
 
 - Bug #1535165: fixed a segfault in input() and raw_input() when

Objects/classobject.c

@@ -934,11 +934,9 @@ instance_hash(PyInstanceObject *inst)
 	Py_DECREF(func);
 	if (res == NULL)
 		return -1;
-	if (PyInt_Check(res)) {
-		outcome = PyInt_AsLong(res);
-		if (outcome == -1)
-			outcome = -2;
-	}
+	if (PyInt_Check(res) || PyLong_Check(res))
+		/* This already converts a -1 result to -2. */
+		outcome = res->ob_type->tp_hash(res);
 	else {
 		PyErr_SetString(PyExc_TypeError,
 				"__hash__() should return an int");

Objects/typeobject.c

@@ -4559,7 +4559,10 @@ slot_tp_hash(PyObject *self)
 		Py_DECREF(func);
 		if (res == NULL)
 			return -1;
-		h = PyInt_AsLong(res);
+		if (PyLong_Check(res))
+			h = res->ob_type->tp_hash(res);
+		else
+			h = PyInt_AsLong(res);
 		Py_DECREF(res);
 	}
 	else {