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INTERNAL ERROR (AssertionError in check_multi_assignment_from_tuple) with asyncio.gather tuple-unpack into previously-bound variable #21802
Description
Crash Report
INTERNAL ERROR (AssertionError in check_multi_assignment_from_tuple) when tuple-unpacking the result of await asyncio.gather(...) into a variable that was previously bound to an incompatible type.
Traceback
Traceback (most recent call last):
File "mypy/checker.py", line 765, in accept
File "mypy/nodes.py", line 1909, in accept
File "mypy/checker.py", line 3367, in visit_assignment_stmt
File "mypy/checker.py", line 3419, in check_assignment
File "mypy/checker.py", line 4182, in check_assignment_to_multiple_lvalues
File "mypy/checker.py", line 4260, in check_multi_assignment
File "mypy/checker.py", line 4411, in check_multi_assignment_from_tuple
AssertionError
To Reproduce
import asyncio
from collections.abc import Iterable
async def bar() -> Iterable[int]:
return ()
async def foo(a: list[int]) -> None:
b = a
_, b = await asyncio.gather(bar(), bar())Your Environment
- Mypy version used: 2.3.0 (compiled: yes)
- Python version used: 3.14.0
Activity
correctmost commentedon Aug 3, 2026
This looks similar to #19920