Pylance-release: "Awaitable[Any]" is incompatible with "Coroutine[Any, Any, Any]"

[iwoloschin]

Environment data

• Language Server version: 2020.7.3 (pyright 5004efe5)
• OS and version: macOS 10.15.6
• Python version (& distribution if applicable, e.g. Anaconda): 3.8.5 via Homebrew

Expected behaviour

Awaitable[Any] should be compatible with Coroutine[Any, Any, Any]. Or, potentially, instead of being an Awaitable[Any] an un-awaited coroutine should be Coroutine[Any, Any, Any]? For comparison, I do not believe mypy views the below code snippet as an error, though it is possible I'm using mypy incorrectly.

Details from mypy are available here: https://mypy.readthedocs.io/en/stable/more_types.html#async-and-await

Actual behaviour

Pylance throws an error:

Argument of type "Awaitable[str]" cannot be assigned to parameter "coro" of type "Coroutine[Any, Any, Any]" in function "inspector"
  "Awaitable[str]" is incompatible with "Coroutine[Any, Any, Any]"Pylance (reportGeneralTypeIssues)

Logs

I don't think logs are necessary for this issue, can provide if requested.

Code Snippet / Additional information

Here's a silly example that just does some basic introspection of a passed coroutine. It runs as-is if copied into ipython, but pylance flags with the error from above on the last line, inner(1, "test"). I don't have much experience with mypy but I do not believe it is flagging the same line as an error.

import asyncio
from typing import Any, Coroutine

async def inspector(coro: Coroutine[Any, Any, Any]):
    print(coro.cr_frame.f_locals)
    return await coro

async def inner(sleep: int, message: str) -> str:
    await asyncio.sleep(sleep)
    print(message)
    return message

async def outer():
    await inspector(inner(1, "test"))

[erictraut]

Thanks for the bug report. Currently, Pylance infers the type Awaitable[T] for an async function's return type. Mypy appears to infer the type Coroutine[Any, Any, T]. Both are arguably correct because Coroutine derives from Awaitable, but I think it's reasonable to change the behavior to match mypy in this case. This change will be in the next version of Pylance.

[jakebailey]

This didn't quite make it into 2020.7.4, but will be in the next release.

[jakebailey]

This issue has been fixed in version 2020.8.0, which we've just released. You can find the changelog here: https://github.com/microsoft/pylance-release/blob/master/CHANGELOG.md#202080-5-august-2020