Test and fix "__eq__" override with extern base type (tested with 'list').

Cython/Compiler/ModuleNode.py

@@ -1830,17 +1830,20 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
             code.putln("case Py_%s: {" % cmp_type)
             if cmp_method == '__eq__':
                 eq_entry = entry
-                code.putln("if (o1 == o2) return __Pyx_NewRef(Py_True);")
+                # Python itself does not do this optimisation, it seems...
+                #code.putln("if (o1 == o2) return __Pyx_NewRef(Py_True);")
             elif cmp_method == '__ne__':
                 has_ne = True
-                code.putln("if (o1 == o2) return __Pyx_NewRef(Py_False);")
+                # Python itself does not do this optimisation, it seems...
+                #code.putln("if (o1 == o2) return __Pyx_NewRef(Py_False);")
             code.putln("return %s(o1, o2);" % entry.func_cname)
             code.putln("}")
 
         if eq_entry and not has_ne and not extern_parent:
             code.putln("case Py_NE: {")
             code.putln("PyObject *ret;")
-            code.putln("if (o1 == o2) return __Pyx_NewRef(Py_False);")
+            # Python itself does not do this optimisation, it seems...
+            #code.putln("if (o1 == o2) return __Pyx_NewRef(Py_False);")
             code.putln("ret = %s(o1, o2);" % eq_entry.func_cname)
             code.putln("if (likely(ret && ret != Py_NotImplemented)) {")
             code.putln("int b = __Pyx_PyObject_IsTrue(ret); Py_DECREF(ret);")

tests/run/ext_auto_richcmp.py

@@ -424,3 +424,21 @@ class ClassLtGt(X):
             if isinstance(other, X):
                 return self.x > other.x
         return NotImplemented
+
+
+@cython.cclass
+class List(list):
+    """
+    >>> l = [1, 2, 3, 4]
+    >>> notl = List(l)
+    >>> notl == l
+    False
+    >>> notl != l     # implemented by base type
+    False
+    >>> notl == notl
+    True
+    >>> notl != notl  # implemented by base type
+    False
+    """
+    def __eq__(self, other):
+        return self is other or list(self) != list(other)