zip silently returns Any because of loose join with star types

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#3,370 7 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
compilers

Research direction

Start by reproducing the provided zip(*y) example in mypy and inspect the type-checking path for calls involving star-expanded arguments and imprecise tuple types. Done means this precisely typed example no longer silently reveals Any; add or update a regression test if the relevant test location is identified during investigation.

Written by the indexing model from the issue text.

Description

bug priority-1-normal 
y: List[Tuple[int]]
reveal_type(zip(*y))  # Revealed type is 'Any'

I think this is a bug since we should never silently infer Any from a precisely typed call.

Dominant language
Python
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Merged PRs (30d)
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