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Error initializing Union of Lists with an empty list #2164

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Error initializing Union of Lists with an empty list#2164
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priority-2-lowtopic-union-types

Description

@elazarg
elazarg
opened on Sep 21, 2016

The following test case

[case testUnionListInit]
from typing import Union, List
a = []  # type: Union[List[int], List[str]]
[builtins fixtures/list.pyi]

Results in

Expected:
Actual:
  main:2: error: Incompatible types in assignment (expression has type List[None], variable has type "Union[List[int], List[str]]") (diff)

This came up during PR #2154, but I think is an independent issue.

Activity

  1. elazarg
    changed the title [-]Error [/-] [+]Error initializing Union of Lists with an empty list[/+] on Sep 21, 2016

  2. elazarg commented on Sep 21, 2016

    @elazarg
    elazarg
    on Sep 21, 2016
    ContributorAuthor

    Perhaps related to binder.py#L189?

  3. gvanrossum commented on Sep 21, 2016

    @gvanrossum
    gvanrossum
    on Sep 21, 2016
    Member

    Doesn't sound like a very important issue, the example has questionable value. (I'm not saying it's not a bug -- just that I don't think it's urgent to fix it.)

  4. gvanrossum
    added this to the milestone on Sep 21, 2016
  5. gvanrossum
    added
    priority-2-low
    on Jan 6, 2017
  6. JukkaL
    added
    topic-union-types
    on Jan 18, 2017
  7. gvanrossum
    removed this from the milestone on Mar 29, 2017

  8. JukkaL commented on Mar 29, 2019

    @JukkaL
    JukkaL
    on Mar 29, 2019
    Collaborator

    Closing in favor of duplicate #6463 (the latter issue has a slight more interesting example).

  9. JukkaL
    closed this as completedon Mar 29, 2019
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