Alternative approach: do not raise, just ignore the cast

Author: sobolevn

Lib/test/test_property.py

@@ -410,12 +410,11 @@ def __new__(typ, *args, **kwargs):
                 return "abcdef"
 
         p = property.__new__(pro)
-        with self.assertRaises(TypeError):
-            p.getter(lambda self: 1)  # this line was causing a crash
-        with self.assertRaises(TypeError):
-            p.setter(lambda self, val: 1)  # this line was causing a crash
-        with self.assertRaises(TypeError):
-            p.deleter(lambda self: 1)  # this line was causing a crash
+
+        # These lines were causing crashes:
+        p.getter(lambda self: 1)
+        p.setter(lambda self, val: 1)
+        p.deleter(lambda self: 1)
 
 
 class _PropertyUnreachableAttribute:

Objects/descrobject.c

@@ -1711,13 +1711,11 @@ property_copy(PyObject *old, PyObject *get, PyObject *set, PyObject *del)
     Py_DECREF(type);
     if (new == NULL)
         return NULL;
-    if (!PyObject_TypeCheck(new, &PyProperty_Type)) {
-        PyErr_Format(PyExc_TypeError, "property instance expected, got %.50s",
-                     Py_TYPE(new)->tp_name);
-        return NULL;
+    if (PyObject_TypeCheck(new, &PyProperty_Type)) {
+        Py_XSETREF(((propertyobject *) new)->prop_name,
+                   Py_XNewRef(pold->prop_name));
     }
 
-    Py_XSETREF(((propertyobject *) new)->prop_name, Py_XNewRef(pold->prop_name));
     return new;
 }