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typecheck failure with parameterized iterator #11375
Description
mypy-bug.py
from typing import *
import asyncio
T = TypeVar('T')
class Foo(Generic[T]):
def __iter__(self) -> Iterator[Awaitable[T]]:
return iter([])
async def bar(foo:Foo[T]):
# No error
await asyncio.gather(*iter(foo))
# mypy says:
# No overload variant of "gather" matches argument type "Foo[T]"
await asyncio.gather(*foo)
async def baz(foo:Foo):
# also no error
await asyncio.gather(*foo)To Reproduce
➜ mypy mypy-bug.py
mypy-bug.py:17: error: No overload variant of "gather" matches argument type "Foo[T]"
mypy-bug.py:17: note: Possible overload variants:
mypy-bug.py:17: note: def gather(coro_or_future1: Union[Future[Any], Generator[Any, None, Any], Awaitable[Any]], coro_or_future2: Union[Future[Any], Generator[Any, None, Any], Awaitable[Any]], coro_or_future3: Union[Future[Any], Generator[Any, None, Any], Awaitable[Any]], coro_or_future4: Union[Future[Any], Generator[Any, None, Any], Awaitable[Any]], coro_or_future5: Union[Future[Any], Generator[Any, None, Any], Awaitable[Any]], coro_or_future6: Union[Future[Any], Generator[Any, None, Any], Awaitable[Any]], *coros_or_futures: Union[Future[Any], Generator[Any, None, Any], Awaitable[Any]], loop: Optional[AbstractEventLoop] = ..., return_exceptions: bool = ...) -> Future[List[Any]]
mypy-bug.py:17: note: def [_T1] gather(coro_or_future1: Union[Future[_T1], Generator[Any, None, _T1], Awaitable[_T1]], *, loop: Optional[AbstractEventLoop] = ..., return_exceptions: Literal[False] = ...) -> Future[Tuple[_T1]]
mypy-bug.py:17: note: <9 more similar overloads not shown, out of 11 total overloads>
Found 1 error in 1 file (checked 1 source file)
Expected Behavior
The second gather call should typecheck just like the first one, as using *foo is essentially the same as *iter(foo).
Note also that the type variable is required to reproduce the bug.
Actual Behavior
Mypy prints an error
Your Environment
- Mypy version used: mypy 0.812, also reproduces with mypy-0.910
- Mypy command-line flags: none
- Mypy configuration options from
mypy.ini(and other config files): none - Python version used: Python 3.8.9
- Operating system and version: macOS 12.1
Activity
sobolevn commentedon Oct 22, 2021
It can probably be fixed by #11151