New submission from Serhiy Storchaka <storchaka+cpyt...@gmail.com>:
While trying to replace typing._GenericAlias with GenericAlias I have found
that the latter does not support nested type variables.
>>> from typing import *
>>> T = TypeVar('T')
>>> X = List[List[T]]
>>> X.__parameters__
(~T,)
>>> X[int]
typing.List[typing.List[int]]
>>> Y = list[list[T]]
>>> Y.__parameters__
()
>>> Y[int]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: There are no type variables left in list[list[~T]]
----------
components: Interpreter Core
messages: 367433
nosy: gvanrossum, levkivskyi, serhiy.storchaka
priority: normal
severity: normal
status: open
title: GenericAlias does not support nested type variables
type: behavior
versions: Python 3.9
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue40408>
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