bpo-39481: Implementation for PEP 585 (#18239)
This implements things like `list[int]`,
which returns an object of type `types.GenericAlias`.
This object mostly acts as a proxy for `list`,
but has attributes `__origin__` and `__args__`
that allow recovering the parts (with values `list` and `(int,)`.
There is also an approximate notion of type variables;
e.g. `list[T]` has a `__parameters__` attribute equal to `(T,)`.
Type variables are objects of type `typing.TypeVar`.
diff --git a/Objects/tupleobject.c b/Objects/tupleobject.c
index 8a8c6ae..68163d8 100644
--- a/Objects/tupleobject.c
+++ b/Objects/tupleobject.c
@@ -832,6 +832,7 @@
TUPLE___GETNEWARGS___METHODDEF
TUPLE_INDEX_METHODDEF
TUPLE_COUNT_METHODDEF
+ {"__class_getitem__", (PyCFunction)Py_GenericAlias, METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
{NULL, NULL} /* sentinel */
};