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Union of a type and the typing module function #88808

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Union of a type and the typing module function#88808
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3.10 (EOL)end of life3.11only security fixesinterpreter-core(Objects, Python, Grammar, and Parser dirs)

Description

@serhiy-storchaka
serhiy-storchaka
opened on Jul 15, 2021
BPO 44642
Nosy @gvanrossum, @serhiy-storchaka, @sobolevn, @Fidget-Spinner

Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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GitHub fields:

assignee = None
closed_at = <Date 2022-01-23.07:25:17.626>
created_at = <Date 2021-07-15.07:58:18.901>
labels = ['interpreter-core', '3.10', '3.11']
title = 'Union of a type and the typing module function'
updated_at = <Date 2022-01-23.07:25:17.625>
user = 'https://github.com/serhiy-storchaka'

bugs.python.org fields:

activity = <Date 2022-01-23.07:25:17.625>
actor = 'sobolevn'
assignee = 'none'
closed = True
closed_date = <Date 2022-01-23.07:25:17.626>
closer = 'sobolevn'
components = ['Interpreter Core']
creation = <Date 2021-07-15.07:58:18.901>
creator = 'serhiy.storchaka'
dependencies = []
files = []
hgrepos = []
issue_num = 44642
keywords = []
message_count = 8.0
messages = ['397528', '397558', '397569', '397570', '397632', '411298', '411330', '411351']
nosy_count = 4.0
nosy_names = ['gvanrossum', 'serhiy.storchaka', 'sobolevn', 'kj']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue44642'
versions = ['Python 3.10', 'Python 3.11']

Activity

  1. serhiy-storchaka commented on Jul 15, 2021

    @serhiy-storchaka
    serhiy-storchaka
    on Jul 15, 2021
    MemberAuthor

    The union type accepts any function from the typing module:

    >>> import typing
>>> int | typing.cast
int | typing.cast
>>> int | typing.get_type_hints
int | typing.get_type_hints

    It is a consequence of too lenient check for the typing.NewType() result (which does not work at all with PR 9951).

  2. serhiy-storchaka
    added
    3.10 (EOL)end of life
    3.11only security fixes
    interpreter-core(Objects, Python, Grammar, and Parser dirs)
    on Jul 15, 2021

  3. gvanrossum commented on Jul 15, 2021

    @gvanrossum
    gvanrossum
    on Jul 15, 2021
    Member

    Is it worth being picky about this? The internal data structures are safe. A static checker will complain. What more do you need?

  4. serhiy-storchaka commented on Jul 15, 2021

    @serhiy-storchaka
    serhiy-storchaka
    on Jul 15, 2021
    MemberAuthor

    It is only reminder that our test for NewType is arbitrary. And it is not compatible with PR 9951. Possible solutions are:

    1. Make NewType a class and add more strict test. Pro -- we can make arbitrary repr, contra -- it has small negative effect on performance. See bpo-34963.

    2. Remove the test for NewType at all and allow or-ing types and arbitrary functions.

    3. Introduce a special attribute to distinguish unionable objects. It will make the code of unionobject.c simpler.

    I lean towards option 1 (not excluding 3). Small performance losses seem inevitable.

  5. Fidget-Spinner commented on Jul 15, 2021

    @Fidget-Spinner
    Fidget-Spinner
    on Jul 15, 2021
    Member

    @serhiy

    1. Make NewType a class and add more strict test.

    See also: bpo-44353 (https://bugs.python.org/issue44353). We had some discussion there about converting to class but it ended in a deadlock.

  6. gvanrossum commented on Jul 16, 2021

    @gvanrossum
    gvanrossum
    on Jul 16, 2021
    Member

    I think making NewType into a class isn't a good idea, it would be too slow. But I like bpo-34963 (PR 9951).

    So then let's do some variation on (3) -- unionable things would include all types (of course), typevars, and things that have a special attribute. We could then set that special attribute on the function returned by NewType (like PR 9951 already does for __name__ and __qualname__).

    What to call it? Maybe "__unionable__"?

  7. sobolevn commented on Jan 22, 2022

    @sobolevn
    sobolevn
    on Jan 22, 2022
    Member

    It does not happen anymore on main (3.11):

    Python 3.11.0a4+ (heads/main-dirty:ef3ef6fa43, Jan 20 2022, 20:48:25) [Clang 11.0.0 (clang-1100.0.33.16)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import typing

>>> int | typing.cast
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'function'

>>> int | typing.get_type_hints
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'function'

  8. gvanrossum commented on Jan 23, 2022

    @gvanrossum
    gvanrossum
    on Jan 23, 2022
    Member

    Do you recommend to just close this as "fixed"?

  9. sobolevn commented on Jan 23, 2022

    @sobolevn
    sobolevn
    on Jan 23, 2022
    Member

    Looks like it was fixed indeed, NewType is now a class. And I cannot reproduce it even on 3.10:

    Python 3.10.0 (default, Nov  1 2021, 10:24:06) [Clang 11.0.0 (clang-1100.0.33.16)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import typing

>>> int | typing.cast
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'function'

>>> int | typing.get_type_hints
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'function'
  10. sobolevn
    closed this as completedon Jan 23, 2022
  11. ezio-melotti
    transferred this issue fromon Apr 10, 2022
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