Use TypeIs instead of TypeGuard

Open Beginner friendly
#36 0 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
62/100
Issue type
Feature
Clarity
Clearly specified
Activity status
Stale
Tech stack
python
Domain
devtools

Research direction

Start at the isassignable API declaration and inspect its existing type-checking tests, if present. Change the return annotation to TypeIs[T], verify that negative-case narrowing behaves as expected, and document the API change as a major/breaking change.

Written by the indexing model from the issue text.

Description

enhancement

The isassignable API is currently:

def isassignable(
    value: object,
    tp: TypeForm[T]† | TypeFormString[T]‡,
    /, *, eval: bool = True
) -> TypeGuard[T]: ...

Alter it to return a TypeIs[T] instead, so that type narrowing happens as expected in the negative case, when isassignable returns False.

This change could potentially break API users, so should be marked as a major/breaking change.

Dominant language
Python
Stars
88
Forks
6
PR merge metrics
No merged PRs in 30d

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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