no error when extending class that has polymorphic self with a non-polymorphic self
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bug
- Dominant language
- Python
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Description
from typing import TypeVar
Self = TypeVar("Self")
class A:
def foo(self: Self) -> Self:
return self
class B(A):
def foo(self) -> B: # no error
return B()
class C(B):
a = 1
T = TypeVar("T", bound=A)
def foo(a: T) -> T:
return a.foo()
print(foo(C()).a) # runtime error
https://mypy-play.net/?mypy=master&python=3.10&flags=strict&gist=26bab72984c4d8d721febf3b5c09e497
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Research direction
Reproduce the example from the mypy-play link with strict settings, then trace how mypy checks overrides involving Self and TypeVar. Add a regression test for the A/B/C example; done means the checker reports the invalid override and prevents the demonstrated unsound call from type-checking.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100