[issue44653] Parameter substitution in the union type does not work with typing.Union

[Guido van Rossum]

Guido van Rossum  added the comment:

Thanks for taking over here, Ł!

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Łukasz Langa]

Łukasz Langa  added the comment:

Thanks Serhiy for the report and the fix, and Ken for reviews.

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stage: patch review -> resolved
status: open -> closed

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Łukasz Langa]

Łukasz Langa  added the comment:


New changeset 21db59fc75b6ebb01bf120a8e5930fe032174f73 by Miss Islington (bot) 
in branch '3.10':
bpo-44653: Support typing types in parameter substitution in the union type. 
(GH-27247) (#27296)
https://github.com/python/cpython/commit/21db59fc75b6ebb01bf120a8e5930fe032174f73


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[issue44653] Parameter substitution in the union type does not work with typing.Union

[miss-islington]

Change by miss-islington :


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nosy: +miss-islington
nosy_count: 5.0 -> 6.0
pull_requests: +25839
pull_request: https://github.com/python/cpython/pull/27296

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Łukasz Langa]

Łukasz Langa  added the comment:


New changeset 2e3744d50b6e30ea24351e55b4352dcc58fd469e by Serhiy Storchaka in 
branch 'main':
bpo-44653: Support typing types in parameter substitution in the union type. 
(GH-27247)
https://github.com/python/cpython/commit/2e3744d50b6e30ea24351e55b4352dcc58fd469e


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nosy: +lukasz.langa

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Guido van Rossum]

Guido van Rossum  added the comment:

I need someone else to own this, sorry.

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Serhiy Storchaka]

Serhiy Storchaka  added the comment:

There is also problem with other typing types:

>>> (int | T)[typing.List]
Traceback (most recent call last):
  File "", line 1, in 
TypeError: Each union argument must be a type, got typing.List
>>> (int | T)[typing.List[int]]
Traceback (most recent call last):
  File "", line 1, in 
TypeError: Each union argument must be a type, got typing.List[int]
>>> (int | T)[typing.Hashable]
Traceback (most recent call last):
  File "", line 1, in 
TypeError: Each union argument must be a type, got typing.Hashable
>>> (int | T)[typing.Callable[[int], str]]
Traceback (most recent call last):
  File "", line 1, in 
TypeError: Each union argument must be a type, got typing.Callable[[int], str]
>>> (int | T)[typing.ParamSpec('P')]
Traceback (most recent call last):
  File "", line 1, in 
TypeError: Each union argument must be a type, got ~P

Despite the fact that they support the | operator.

We can add one by one special support of different types supporting the | 
operator (ParamSpec, _GenericAlias, _CallableGenericAlias, _UnionGenericAlias, 
_LiteralGenericAlias, _ConcatenateGenericAlias, _AnnotatedAlias, 
_SpecialGenericAlias, _CallableType, _TupleType), but it is cumbersome and 
errorprone. We will need to synchronize code of unionobject.c with typing every 
time we add new kind of types.

PR 27247 uses more general approach. It calls the | operator for arguments 
after substitution. So all types which support the | operator are now 
automatically supported. But the result of parameter substitution can now be 
typing.Union instead of types.Union.

>>> import typing
>>> import collections.abc
>>> T = typing.TypeVar('T')
>>> (int | T)[list]
int | list
>>> (int | T)[typing.List]
typing.Union[int, typing.List]
>>> (int | T)[list[int]]
int | list[int]
>>> (int | T)[typing.List[int]]
typing.Union[int, typing.List[int]]
>>> (int | T)[collections.abc.Hashable]
int | collections.abc.Hashable
>>> (int | T)[typing.Hashable]
typing.Union[int, typing.Hashable]
>>> (int | T)[collections.abc.Sequence[int]]
int | collections.abc.Sequence[int]
>>> (int | T)[typing.Sequence[int]]
typing.Union[int, typing.Sequence[int]]
>>> (int | T)[collections.abc.Callable[[int], str]]
int | collections.abc.Callable[[int], str]
>>> (int | T)[typing.Callable[[int], str]]
typing.Union[int, typing.Callable[[int], str]]
>>> (int | T)[typing.TypeVar('S')]
int | ~S
>>> (int | T)[typing.ParamSpec('P')]
typing.Union[int, ~P]
>>> (int | T)[str | list]
int | str | list
>>> (int | T)[typing.Union[str, list]]
typing.Union[int, str, list]

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Serhiy Storchaka]

Change by Serhiy Storchaka :


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pull_requests: +25795
pull_request: https://github.com/python/cpython/pull/27247

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Ken Jin]

Ken Jin  added the comment:

@Serhiy, this doesn't just affect typing.Union, it seems that the rest of the 
typing types don't substitute:

>>> (int | T)[typing.List[str]]
Traceback (most recent call last):
  File "", line 1, in 
TypeError: Each union arg must be a type, got typing.List[str]

We should probably loosen the check during the union_getitem substitution -- no 
need to raise the TypeError or check for is_union, just blindly replace the 
TypeVar. We already do this for types.GenericAlias:

>>> list[T][1]
list[1]

Or if you want to continue checking, maybe checking for PyCallable_Check(obj) 
in substitution is enough - typing internally accepts callable(o) too:

https://github.com/python/cpython/blob/3.10/Lib/typing.py#L146

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Serhiy Storchaka]

Change by Serhiy Storchaka :


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pull_request: https://github.com/python/cpython/pull/27232

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Serhiy Storchaka]

Change by Serhiy Storchaka :


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pull_requests:  -25757

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Yurii Karabas]

Change by Yurii Karabas <1998uri...@gmail.com>:


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pull_request: https://github.com/python/cpython/pull/26980

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Serhiy Storchaka]

Change by Serhiy Storchaka :


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pull_requests:  -25745

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Yurii Karabas]

Change by Yurii Karabas <1998uri...@gmail.com>:


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keywords: +patch
nosy: +uriyyo
nosy_count: 3.0 -> 4.0
pull_requests: +25745
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/26980

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[issue44653] Parameter substitution in the union type does not work with typing.Union

[Serhiy Storchaka]

New submission from Serhiy Storchaka :

>>> import typing
>>> T = typing.TypeVar('T')
>>> (int | T)[typing.Union[str, list]]
NotImplemented

See also issue44633. But in this case the expected result is int | str | list 
or typing.Union[init, str, list].

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components: Interpreter Core
messages: 397624
nosy: gvanrossum, kj, serhiy.storchaka
priority: normal
severity: normal
status: open
title: Parameter substitution in the union type does not work with typing.Union
type: behavior
versions: Python 3.10, Python 3.11

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