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AnyStr.startswith(AnyStr) fails due to bytes not matching Buffer protocol #5452
Description
Describe the Bug
from typing import *
def func(a: AnyStr, b: AnyStr) -> bool:
return a.startswith(b)Python: 3.12
When creating a function as above, pyrefly fails to resolve the .startswith() call, claiming bytes doesn't satisfy Buffer.
This should resolve correctly, as AnyStr is bound to the same type for a and b, and str.startswith accepts strings and bytes.startswith accepts bytes
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rchen152 commentedon Nov 5, 2026
@shahhamdihassan are you still working on this one?
shahhamdihassan commentedon Nov 5, 2026
Yes, still on it! The fix is going up for review today, with you and Steven as reviewers. I'll post here once it lands.
Test an AnyStr method call whose argument is also AnyStr
Accept a constrained TypeVar where its constraint is accepted in a bo…
shahhamdihassan commentedon Nov 9, 2026
The fix for this has landed, so
AnyStrmethods likestartswithandsplitnow accept anAnyStrargument when the receiver is alsoAnyStr. It'll be in the next release. Thanks for the clear report!