Issue #23722: Initialize __class__ from type.__new__()
The __class__ cell used by zero-argument super() is now initialized from type.__new__ rather than __build_class__, so class methods relying on that will now work correctly when called from metaclass methods during class creation. Patch by Martin Teichmann.
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@ -236,7 +236,8 @@ _code_type = type(_write_atomic.__code__)
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# Python 3.6b1 3373 (add BUILD_STRING opcode #27078)
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# Python 3.6b1 3375 (add SETUP_ANNOTATIONS and STORE_ANNOTATION opcodes
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# #27985)
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# Python 3.6a1 3376 (simplify CALL_FUNCTIONs & BUILD_MAP_UNPACK_WITH_CALL)
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# Python 3.6b1 3376 (simplify CALL_FUNCTIONs & BUILD_MAP_UNPACK_WITH_CALL)
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# Python 3.6b1 3377 (set __class__ cell from type.__new__ #23722)
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#
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# MAGIC must change whenever the bytecode emitted by the compiler may no
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# longer be understood by older implementations of the eval loop (usually
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@ -245,7 +246,7 @@ _code_type = type(_write_atomic.__code__)
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# Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
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# in PC/launcher.c must also be updated.
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MAGIC_NUMBER = (3376).to_bytes(2, 'little') + b'\r\n'
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MAGIC_NUMBER = (3377).to_bytes(2, 'little') + b'\r\n'
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_RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little') # For import.c
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_PYCACHE = '__pycache__'
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@ -143,6 +143,87 @@ class TestSuper(unittest.TestCase):
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return __class__
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self.assertIs(X.f(), X)
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def test___class___new(self):
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test_class = None
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class Meta(type):
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def __new__(cls, name, bases, namespace):
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nonlocal test_class
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self = super().__new__(cls, name, bases, namespace)
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test_class = self.f()
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return self
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class A(metaclass=Meta):
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@staticmethod
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def f():
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return __class__
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self.assertIs(test_class, A)
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def test___class___delayed(self):
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test_namespace = None
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class Meta(type):
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def __new__(cls, name, bases, namespace):
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nonlocal test_namespace
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test_namespace = namespace
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return None
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class A(metaclass=Meta):
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@staticmethod
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def f():
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return __class__
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self.assertIs(A, None)
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B = type("B", (), test_namespace)
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self.assertIs(B.f(), B)
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def test___class___mro(self):
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test_class = None
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class Meta(type):
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def mro(self):
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# self.f() doesn't work yet...
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self.__dict__["f"]()
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return super().mro()
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class A(metaclass=Meta):
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def f():
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nonlocal test_class
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test_class = __class__
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self.assertIs(test_class, A)
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def test___classcell___deleted(self):
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class Meta(type):
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def __new__(cls, name, bases, namespace):
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del namespace['__classcell__']
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return super().__new__(cls, name, bases, namespace)
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class A(metaclass=Meta):
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@staticmethod
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def f():
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__class__
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with self.assertRaises(NameError):
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A.f()
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def test___classcell___reset(self):
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class Meta(type):
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def __new__(cls, name, bases, namespace):
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namespace['__classcell__'] = 0
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return super().__new__(cls, name, bases, namespace)
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class A(metaclass=Meta):
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@staticmethod
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def f():
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__class__
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with self.assertRaises(NameError):
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A.f()
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self.assertEqual(A.__classcell__, 0)
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def test_obscure_super_errors(self):
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def f():
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super()
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@ -10,6 +10,11 @@ What's New in Python 3.6.0 beta 1
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Core and Builtins
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-----------------
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- Issue #23722: The __class__ cell used by zero-argument super() is now
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initialized from type.__new__ rather than __build_class__, so class methods
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relying on that will now work correctly when called from metaclass methods
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during class creation. Patch by Martin Teichmann.
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- Issue #25221: Fix corrupted result from PyLong_FromLong(0) when Python
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is compiled with NSMALLPOSINTS = 0.
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@ -2285,7 +2285,7 @@ static PyObject *
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type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
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{
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PyObject *name, *bases = NULL, *orig_dict, *dict = NULL;
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PyObject *qualname, *slots = NULL, *tmp, *newslots;
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PyObject *qualname, *slots = NULL, *tmp, *newslots, *cell;
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PyTypeObject *type = NULL, *base, *tmptype, *winner;
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PyHeapTypeObject *et;
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PyMemberDef *mp;
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@ -2293,6 +2293,7 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
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int j, may_add_dict, may_add_weak, add_dict, add_weak;
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_Py_IDENTIFIER(__qualname__);
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_Py_IDENTIFIER(__slots__);
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_Py_IDENTIFIER(__classcell__);
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assert(args != NULL && PyTuple_Check(args));
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assert(kwds == NULL || PyDict_Check(kwds));
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@ -2559,7 +2560,7 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
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}
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et->ht_qualname = qualname ? qualname : et->ht_name;
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Py_INCREF(et->ht_qualname);
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if (qualname != NULL && PyDict_DelItem(dict, PyId___qualname__.object) < 0)
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if (qualname != NULL && _PyDict_DelItemId(dict, &PyId___qualname__) < 0)
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goto error;
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/* Set tp_doc to a copy of dict['__doc__'], if the latter is there
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@ -2685,6 +2686,14 @@ type_new(PyTypeObject *metatype, PyObject *args, PyObject *kwds)
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else
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type->tp_free = PyObject_Del;
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/* store type in class' cell */
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cell = _PyDict_GetItemId(dict, &PyId___classcell__);
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if (cell != NULL && PyCell_Check(cell)) {
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PyCell_Set(cell, (PyObject *) type);
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_PyDict_DelItemId(dict, &PyId___classcell__);
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PyErr_Clear();
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}
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/* Initialize the rest */
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if (PyType_Ready(type) < 0)
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goto error;
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@ -1089,7 +1089,7 @@ static PYC_MAGIC magic_values[] = {
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{ 3190, 3230, L"3.3" },
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{ 3250, 3310, L"3.4" },
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{ 3320, 3351, L"3.5" },
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{ 3360, 3375, L"3.6" },
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{ 3360, 3379, L"3.6" },
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{ 0 }
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};
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@ -54,7 +54,7 @@ _Py_IDENTIFIER(stderr);
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static PyObject *
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builtin___build_class__(PyObject *self, PyObject *args, PyObject *kwds)
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{
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PyObject *func, *name, *bases, *mkw, *meta, *winner, *prep, *ns, *cell;
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PyObject *func, *name, *bases, *mkw, *meta, *winner, *prep, *ns, *none;
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PyObject *cls = NULL;
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Py_ssize_t nargs;
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int isclass = 0; /* initialize to prevent gcc warning */
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@ -167,15 +167,13 @@ builtin___build_class__(PyObject *self, PyObject *args, PyObject *kwds)
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Py_DECREF(bases);
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return NULL;
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}
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cell = PyEval_EvalCodeEx(PyFunction_GET_CODE(func), PyFunction_GET_GLOBALS(func), ns,
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none = PyEval_EvalCodeEx(PyFunction_GET_CODE(func), PyFunction_GET_GLOBALS(func), ns,
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NULL, 0, NULL, 0, NULL, 0, NULL,
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PyFunction_GET_CLOSURE(func));
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if (cell != NULL) {
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if (none != NULL) {
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PyObject *margs[3] = {name, bases, ns};
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cls = _PyObject_FastCallDict(meta, margs, 3, mkw);
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if (cls != NULL && PyCell_Check(cell))
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PyCell_Set(cell, cls);
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Py_DECREF(cell);
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Py_DECREF(none);
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}
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Py_DECREF(ns);
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Py_DECREF(meta);
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@ -1968,7 +1968,7 @@ compiler_class(struct compiler *c, stmt_ty s)
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return 0;
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}
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if (c->u->u_ste->ste_needs_class_closure) {
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/* return the (empty) __class__ cell */
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/* store __classcell__ into class namespace */
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str = PyUnicode_InternFromString("__class__");
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if (str == NULL) {
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compiler_exit_scope(c);
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@ -1981,15 +1981,20 @@ compiler_class(struct compiler *c, stmt_ty s)
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return 0;
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}
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assert(i == 0);
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/* Return the cell where to store __class__ */
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ADDOP_I(c, LOAD_CLOSURE, i);
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str = PyUnicode_InternFromString("__classcell__");
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if (!str || !compiler_nameop(c, str, Store)) {
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Py_XDECREF(str);
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compiler_exit_scope(c);
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return 0;
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}
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Py_DECREF(str);
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}
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else {
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/* This happens when nobody references the cell. */
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assert(PyDict_Size(c->u->u_cellvars) == 0);
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/* This happens when nobody references the cell. Return None. */
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ADDOP_O(c, LOAD_CONST, Py_None, consts);
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}
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ADDOP_IN_SCOPE(c, RETURN_VALUE);
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/* create the code object */
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co = assemble(c, 1);
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}
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