Generic inner classes sees type variable from outer class

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#3,144 9 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 running the Python reproducer in the issue and read the linked PEP 484 scoping rules. Trace how mypy handles type variables in methods of nested generic classes; done means the method f annotation is rejected consistently with the annotations on x and y.

Written by the indexing model from the issue text.

Description

priority-2-low topic-type-variables 
T = TypeVar('T')
class Outer(Generic[T]):
    class Inner:
        x: T  # E: Invalid type "test.T" (correct)
        def f(self, x: T) -> T: ... # ok (incorrect)
        def g(self) -> None:
            y: T  # E: Invalid type "test.T" (correct)

Source

Dominant language
Python
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Merged PRs (30d)
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