BufferedRWPair annotations #13495

Bug Report

It is typical to initialize an io.BufferedRWPair with the returns of Path.open() (in binary mode) as the arguments, and this works as expected.

BufferedRWPair(
        Path('readfrom.dat').open('rb'),
        Path('writeto.dat').open('wb')
)

To Reproduce

https://mypy-play.net/?mypy=latest&python=3.13&gist=79ee15dce5f93b8aa66a2a04c7bedcdc

Expected Behavior

Type checking should pass.

Actual Behavior

The type checking fails with:

error: Argument 1 to "BufferedRWPair" has incompatible type "BufferedReader"; expected "RawIOBase"  [arg-type]
error: Argument 2 to "BufferedRWPair" has incompatible type "BufferedWriter"; expected "RawIOBase"  [arg-type]

Your Environment

• Mypy version used: 1.15.0
• Mypy command-line flags:
• Mypy configuration options from mypy.ini (and other config files):

[tool.mypy]
strict = true

• Python version used: 3.13