Repository navigation
Order dependent bug in fine-grained generic alias handling #4903
Description
Renaming b to d in testAliasFineInitGenericMod produces the following test, which fails, producing no errors:
[case testAliasFineInitGenericMod2]
import c
[file a.py]
from typing import Generic, TypeVar
T = TypeVar('T')
S = TypeVar('S')
class A(Generic[T, S]):
def __init__(self, x: T) -> None:
pass
[file a.py.2]
from typing import Generic, TypeVar
T = TypeVar('T')
S = TypeVar('S')
class A(Generic[T, S]):
def __init__(self, x: S) -> None:
pass
[file d.py]
import a
B = a.A[int, str]
[file c.py]
from d import B
B(int())
[out]
==
c.py:2: error: Argument 1 has incompatible type "int"; expected "str"
Activity
ilevkivskyi commentedon Apr 13, 2018
Thanks for finding this!
I actually was afraid this will trigger at some point. The problem is that from the point of view of the snapshot diff, after update
Bpoints to exactly the same type. A possible solution is to include signatures of__init__and__new__in alias snapshot, but this may cause some unnecessary re-checks, because aliases are rarely used in runtime context. (On the positive side some existing deps will become redundant if we do this). @JukkaL what do you think? This seems to me similar to the problem of@abstractmethodwhere performance and correctness are also not on the same side.msullivan commentedon Apr 13, 2018
Would it be possible to create dependencies like:
?
ilevkivskyi commentedon Apr 22, 2018
I will take a look at this. There might be something more subtle happening.
JukkaL commentedon Nov 1, 2018
This was fixed by #5221.