__new__ is supposed to become a staticmethod

This seems to not matter very much, but it means that
Cls.__new__ is a the original function, instead of an
unbound instance method.

src/runtime/descr.cpp

@@ -673,6 +673,10 @@ void BoxedWrapperObject::gcHandler(GCVisitor* v, Box* _o) {
     v->visit(&o->obj);
 }
 
+extern "C" PyObject* PyStaticMethod_New(PyObject* callable) noexcept {
+    return new BoxedStaticmethod(callable);
+}
+
 void setupDescr() {
     member_descriptor_cls->giveAttr("__get__", new BoxedFunction(boxRTFunction((void*)memberGet, UNKNOWN, 3)));
     member_descriptor_cls->freeze();

src/runtime/objmodel.cpp

@@ -5426,6 +5426,18 @@ Box* _typeNew(BoxedClass* metatype, BoxedString* name, BoxedTuple* bases, BoxedD
     }
     basic_size = cur_offset;
 
+    // from cpython:
+    /* Special-case __new__: if it's a plain function,
+               make it a static function */
+    Box* tmp = PyDict_GetItemString(attr_dict, "__new__");
+    if (tmp != NULL && PyFunction_Check(tmp)) {
+        tmp = PyStaticMethod_New(tmp);
+        if (tmp == NULL)
+            throwCAPIException();
+        PyDict_SetItemString(attr_dict, "__new__", tmp);
+        Py_DECREF(tmp);
+    }
+
     size_t total_slots = final_slot_names.size()
                          + (base->tp_flags & Py_TPFLAGS_HEAPTYPE ? static_cast<BoxedHeapClass*>(base)->nslots() : 0);
     BoxedHeapClass* made = BoxedHeapClass::create(metatype, base, NULL, attrs_offset, weaklist_offset, basic_size, true,

test/tests/defaults_changing.py

@@ -57,3 +57,17 @@ class MyTuple(tuple):
 f.func_defaults = MyTuple((1, 2))
 print type(f.__defaults__)
 f()
+
+
+class C(object):
+    def __new__(cls, arg):
+        print arg
+        return object.__new__(cls)
+
+    def foo(self, arg):
+        print arg
+
+print type(C.__new__), type(C.__dict__['__new__'])
+
+C.__new__.__defaults__ = (1,)
+print type(C())