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classification
Title: Substitution does not work after ParamSpec substitution of the user generic with a list of TypeVars
Type: behavior Stage:
Components: Library (Lib) Versions: Python 3.11, Python 3.10
process
Status: open Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: gvanrossum, kj, serhiy.storchaka
Priority: normal Keywords:

Created on 2021-08-01 11:37 by serhiy.storchaka, last changed 2022-04-11 14:59 by admin.

Messages (1)
msg398694 - (view) Author: Serhiy Storchaka (serhiy.storchaka) * (Python committer) Date: 2021-08-01 11:37
If the user generic with ParamSpec parameter substituted with a parametrised list containing TypeVar, that TypeVar cannot be substituted.

>>> from typing import *
>>> T = TypeVar("T")
>>> P = ParamSpec("P")
>>> class X(Generic[P]):
...     f: Callable[P, int]
... 
>>> Y = X[[int, T]]
>>> Y
__main__.X[(<class 'int'>, ~T)]
>>> Y[str]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/serhiy/py/cpython/Lib/typing.py", line 309, in inner
    return func(*args, **kwds)
           ^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/typing.py", line 1028, in __getitem__
    _check_generic(self, params, len(self.__parameters__))
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/serhiy/py/cpython/Lib/typing.py", line 228, in _check_generic
    raise TypeError(f"{cls} is not a generic class")
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: __main__.X[(<class 'int'>, ~T)] is not a generic class

Expected result equal to X[[int, str]].
History
Date User Action Args
2022-04-11 14:59:48adminsetgithub: 88965
2021-08-01 11:37:51serhiy.storchakacreate