Serhiy Storchaka <storchaka+cpyt...@gmail.com> added the comment:
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]
----------
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue44653>
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