untyped defs on derived classes

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#3,903 23 comments 20 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
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
devtools

Research direction

Start by reproducing the A/B example and trace how mypy assigns Any to arguments and return values on untyped overrides. Done means an untyped method on a derived class inherits the corresponding annotations from its parent, with reveal_type(a) reporting str in the example.

Written by the indexing model from the issue text.

Description

feature priority-1-normal

Currently all arguments and return values on untyped defs are set to Any.

It would be nice, if arguments and return values on derived classes would take the type annotations from the parent class. For example:

class A:
    def foo(self, a: str) -> None: pass


class B(A):
    def foo(self, a):
        reveal_type(a)

In this example the revealed type is Any but I would expect it to be str.

Of cause, if the entire project has type annotations, than this would not be an issue, but when you add type annotations on a big project and start with the base classes, it would be nice, if you could benefit from that.

Dominant language
Python
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Avg merge
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Merged PRs (30d)
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