Incorrect signature for builtins.object.__dir__

[johanvdhaegen]

Pytype requires an object's __dir__ method to return list[str], while Iterable[str] should be sufficient, according to the Python datamodel and typeshed's builtins.pyi.

The issue seems to be in pytype/stubs/builtins/builtins.pytd

For example, pytype incorrectly flags an error in the following test fragment:

from collections.abc import Iterable

class Foo:

  def __dir__(self) -> Iterable[str]:
    return super().__dir__()

Result:

test.py:5:3: error: in Foo: Overriding method signature mismatch [signature-mismatch]
  Base signature: 'def builtins.object.__dir__(self) -> list[str]'.
  Subclass signature: 'def Foo.__dir__(self) -> Iterable[str]'.
  Return type mismatch.

  def __dir__(self) -> Iterable[str]:
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    return super().__dir__()
~~~~~~~~~~~~~~~~~~~~~~~~~~~~