python / python/mypy

Recognize list of constant values as a list of str.

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#13,767 2 comments 1 reaction 0 assignees View on GitHub

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feature topic-literal-types
Dominant language
Python
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Description

Feature
I wish mypy is recognized list of constant values as a list of literal types.

Pitch
There are example code.

from typing import Literal, Dict
values: Dict[Literal["from", "to", "cc"], str] = {}

# key should be recognized Literal["from","to", "cc"] instead of str
for key in ["from", "to", "cc"]: 
    values[key] = key # Now, this line will be error in order to recognize key as a str.

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Research direction

No files, tests, or entry points are identified in the issue. Start by locating mypy's handling of list literals and Literal type inference, then determine the expected behavior for the example; done means the loop type-checks with the intended Literal types and relevant regression coverage exists.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
devtools
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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