attribute failure when unpacking from tuple and wait_for #15569
Description
Bug Report
The following snippet:
from dataclasses import dataclass
from asyncio import wait_for
@dataclass
class A:
i: int | None = None
async def bar()->tuple[int, int]:
return (0,0)
async def foo()->int:
a = A()
a.i, _0 = await wait_for(bar(), timeout=5)
return a.i
fails with the error: error: Incompatible return value type (got "int | None", expected "int") [return-value]
note that this snippet works (where bar returns a straight value):
from dataclasses import dataclass
from asyncio import wait_for
@dataclass
class A:
i: int | None = None
async def bar()->int:
return 0
async def foo()->int:
a = A()
a.i = await wait_for(bar(), timeout=5)
return a.i
as does this (without wait_for):
from dataclasses import dataclass
from asyncio import wait_for
@dataclass
class A:
i: int | None = None
async def bar()->tuple[int, int]:
return (0,0)
async def foo()->int:
a = A()
a.i, _0 = await bar()
return a.i
or this (where bar returns a list):
from dataclasses import dataclass
from asyncio import wait_for
@dataclass
class A:
i: int | None = None
async def bar()->list[int]:
return [0,0]
async def foo()->int:
a = A()
a.i, _0 = await wait_for(bar(), timeout=5)
return a.i
or this (setting a variable instead of attribute):
from asyncio import wait_for
async def bar()->tuple[int, int]:
return (0,0)
async def foo()->int:
a_i = None
a_i, _0 = await wait_for(bar(), timeout=5)
return a_i
To Reproduce
run https://mypy-play.net/?mypy=latest&python=3.11&flags=local-partial-types&gist=5046bb7c065a2594953c9e876bdfd29e
Expected Behavior
the snippet should pass just as though the call was made without wait_for
Actual Behavior
the snippet fails with:
main.py:14: error: Incompatible return value type (got "int | None", expected "int") [return-value]
Found 1 error in 1 file (checked 1 source file)