Mypy reports incorrect errors when making async call

[julaudo]

Bug Report

Mypy sometimes reports incorrect errors when using async/async with
One example is when using aiofiles.open
These errors appeared when upgrading from 0.782 to 0.790

To Reproduce

The following code reproduces the errors:

import asyncio
import aiofiles


async def test_async_with() -> None:
    async with aiofiles.open('./file.txt', 'rb') as file:
        print(type(file))


async def test_async() -> None:
    file = await aiofiles.open('./file.txt', 'rb')
    print(type(file))

loop = asyncio.get_event_loop()
loop.run_until_complete(test_async_with())
loop.run_until_complete(test_async())

Expected Behavior

No error should be reported

Actual Behavior

2 errors in test_async_with:

test.py:6: error: "AsyncBufferedReader" has no attribute "__aenter__"
test.py:6: error: "AsyncBufferedReader" has no attribute "__aexit__"

1 error in test_async:
test.py:11: error: Incompatible types in "await" (actual type "AsyncBufferedReader", expected type "Awaitable[Any]")

Your Environment

• Mypy version used: 0.790
• Mypy command-line flags: None
• Mypy configuration options from mypy.ini (and other config files): None
• Python version used: 3.6.0
• Operating system and version: Windows 10

[JelleZijlstra]

This sounds like an issue with the aiofiles stubs. Could you try to reproduce this issue in a way that doesn't rely on third-party packages?

[hauntsaninja]

In particular, typeshed has since made improvements to the aiofiles stubs. Can you reproduce with mypy master?

[julaudo]

In particular, typeshed has since made improvements to the aiofiles stubs. Can you reproduce with mypy master?

You're right, mypy master does not report errors. I will be able to close the issue at next release