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bpo-42010: Prevent generic types from being indexed #22667

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bpo-42010: Prevent generic types from being indexed #22667

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7c793a4
throw error when indexing type object
Fidget-Spinner Oct 12, 2020
26f06f0
Add news
Fidget-Spinner Oct 12, 2020
4ba2a6c
Use subtests
Fidget-Spinner Oct 12, 2020
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8 changes: 8 additions & 0 deletions Lib/test/test_genericalias.py
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Expand Up @@ -293,5 +293,13 @@ def test_dir(self):
for generic_alias_property in ("__origin__", "__args__", "__parameters__"):
self.assertIn(generic_alias_property, dir_of_gen_alias)

def test_indexing(self):
stmts = ['list[0]', 'list[0.0]', 'list[True]', 'list[1 + 3j]']
for stmt in stmts:
with self.subTest(stmt=stmt):
with self.assertRaises(TypeError):
eval(stmt)


if __name__ == "__main__":
unittest.main()
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core and Builtins/2020-10-12-15-58-48.bpo-42010.1anqDP.rst
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@@ -0,0 +1,2 @@
Throw :exc:`TypeError` when attempting to index a generic type. For example,
``list[1]``.
6 changes: 6 additions & 0 deletions Objects/abstract.c
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Expand Up @@ -187,6 +187,12 @@ PyObject_GetItem(PyObject *o, PyObject *key)
if ((PyTypeObject*)o == &PyType_Type) {
return Py_GenericAlias(o, key);
}
// To deny things like list[1], list[0.8], list[True], list[3 + 3j]
if (PyLong_CheckExact(key) || PyFloat_CheckExact(key)
|| PyBool_Check(key) || PyComplex_CheckExact(key)){
return type_error("generic type parameter must be a type, "
"not '%.200s'", key);
}

if (_PyObject_LookupAttrId(o, &PyId___class_getitem__, &meth) < 0) {
return NULL;
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