Undefine __hash__ when __eq__ is overriden

Author: msimacek

graalpython/com.oracle.graal.python.test/src/tests/unittest_tags/test_class.txt

@@ -2,6 +2,7 @@
 *graalpython.lib-python.3.test.test_class.ClassTests.testBinaryOps
 *graalpython.lib-python.3.test.test_class.ClassTests.testForExceptionsRaisedInInstanceGetattr2
 *graalpython.lib-python.3.test.test_class.ClassTests.testGetSetAndDel
+*graalpython.lib-python.3.test.test_class.ClassTests.testHashStuff
 *graalpython.lib-python.3.test.test_class.ClassTests.testInit
 *graalpython.lib-python.3.test.test_class.ClassTests.testListAndDictOps
 *graalpython.lib-python.3.test.test_class.ClassTests.testMisc

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/BuiltinConstructors.java

@@ -71,6 +71,8 @@
 import static com.oracle.graal.python.nodes.SpecialAttributeNames.__WEAKREF__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.DECODE;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__COMPLEX__;
+import static com.oracle.graal.python.nodes.SpecialMethodNames.__EQ__;
+import static com.oracle.graal.python.nodes.SpecialMethodNames.__HASH__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__INDEX__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__INT__;
 import static com.oracle.graal.python.nodes.SpecialMethodNames.__REPR__;
@@ -2332,6 +2334,16 @@ private PythonClass typeMetaclass(VirtualFrame frame, String name, PTuple bases,
                 }
             }
 
+            // CPython masks the __hash__ method with None when __eq__ is overriden, but __hash__ is
+            // not
+            Object hashMethod = nslib.getItem(namespace.getDictStorage(), __HASH__);
+            if (hashMethod == null) {
+                Object eqMethod = nslib.getItem(namespace.getDictStorage(), __EQ__);
+                if (eqMethod != null) {
+                    pythonClass.setAttribute(__HASH__, PNone.NONE);
+                }
+            }
+
             boolean addDict = false;
             if (slots == null) {
                 // takes care of checking if we may_add_dict and adds it if needed