Author serhiy.storchaka
Recipients gvanrossum, kj, serhiy.storchaka, uriyyo
Date 2021-07-19.18:15:58
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Marked as misclassified Yes
Message-id <1626718558.46.0.93600914261.issue44653@roundup.psfhosted.org>
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There is also problem with other typing types:

>>> (int | T)[typing.List]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Each union argument must be a type, got typing.List
>>> (int | T)[typing.List[int]]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Each union argument must be a type, got typing.List[int]
>>> (int | T)[typing.Hashable]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Each union argument must be a type, got typing.Hashable
>>> (int | T)[typing.Callable[[int], str]]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: Each union argument must be a type, got typing.Callable[[int], str]
>>> (int | T)[typing.ParamSpec('P')]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
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]
History
Date User Action Args
2021-07-19 18:15:58serhiy.storchakasetrecipients: + serhiy.storchaka, gvanrossum, uriyyo, kj
2021-07-19 18:15:58serhiy.storchakasetmessageid: <1626718558.46.0.93600914261.issue44653@roundup.psfhosted.org>
2021-07-19 18:15:58serhiy.storchakalinkissue44653 messages
2021-07-19 18:15:58serhiy.storchakacreate