New submission from Serhiy Storchaka <storchaka+cpyt...@gmail.com>:
Substitution of ParamSpec in Concatenate produces weird results:
>>> import typing
>>> P = typing.ParamSpec('P')
>>> typing.Concatenate[str, P][int]
typing.Concatenate[str, int]
>>> typing.Concatenate[str, P][[int]]
typing.Concatenate[str, (<class 'int'>,)]
>>> typing.Concatenate[str, P][typing.Concatenate[int, P]]
typing.Concatenate[str, typing.Concatenate[int, ~P]]
But all these results are invalid:
>>> typing.Concatenate[str, int]
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 400, in __getitem__
return self._getitem(self, parameters)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/serhiy/py/cpython/Lib/typing.py", line 595, in Concatenate
raise TypeError("The last parameter to Concatenate should be a "
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: The last parameter to Concatenate should be a ParamSpec variable.
>>> typing.Concatenate[str, (int,)]
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 400, in __getitem__
return self._getitem(self, parameters)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/serhiy/py/cpython/Lib/typing.py", line 595, in Concatenate
raise TypeError("The last parameter to Concatenate should be a "
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: The last parameter to Concatenate should be a ParamSpec variable.
>>> typing.Concatenate[str, [int]]
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 400, in __getitem__
return self._getitem(self, parameters)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/serhiy/py/cpython/Lib/typing.py", line 595, in Concatenate
raise TypeError("The last parameter to Concatenate should be a "
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: The last parameter to Concatenate should be a ParamSpec variable.
>>> typing.Concatenate[str, typing.Concatenate[int, P]]
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 400, in __getitem__
return self._getitem(self, parameters)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/serhiy/py/cpython/Lib/typing.py", line 595, in Concatenate
raise TypeError("The last parameter to Concatenate should be a "
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
TypeError: The last parameter to Concatenate should be a ParamSpec variable.
I expect that
1. The last parameter to Concatenate can be a Concatenate. Inner Concatenate
should merge with the external one:
Concatenate[str, Concatenate[int, P]] -> Concatenate[str, int, P]
Concatenate[str, P][Concatenate[int, P]] -> Concatenate[str, int, P]
2. The last parameter to Concatenate can be a list of types. The result should
be a list of types.
Concatenate[str, [int, dict]] -> [str, int, dict]
Concatenate[str, P][[int, dict]] -> [str, int, dict]
3. The last parameter to Concatenate can be an ellipsis.
Concatenate[str, ...]
Concatenate[str, P][...] -> Concatenate[str, ...]
----------
components: Library (Lib)
messages: 398632
nosy: gvanrossum, kj, serhiy.storchaka
priority: normal
severity: normal
status: open
title: Substitution of ParamSpec in Concatenate
versions: Python 3.10, Python 3.11
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue44791>
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