Semantics of typing.Self not understood in child classes #2122
Description
Summary
When attempting to override a method of a parent class with -> Self in a child class, calls to the parent's method are considered invalid.
from typing_extensions import Self, override
class Parent:
@classmethod
def new(cls) -> Self:
return cls()
class Child(Parent):
@classmethod
@override
def new(cls) -> Self:
return super().new()The following code reports:
❯ ty check foo.py
error[invalid-return-type]: Return type does not match returned value
--> foo.py:12:21
|
10 | @classmethod
11 | @override
12 | def new(cls) -> Self:
| ---- Expected `Self@new` because of return type
13 | return super().new()
| ^^^^^^^^^^^^^ expected `Self@new`, found `Child`
|
info: rule `invalid-return-type` is enabled by default
Found 1 diagnostic
Running the same file through pyright and mypy yields no errors.
Version
ty 0.0.4 (c1e6188 2025-12-18)