mypy doesn't correctly infer Self attributes on subclasses #15529
Description
Bug Report
When using the Self special form to annotate class attributes, mypy doesn't correctly infer the bound type in subclasses methods.
class A:
_ref: Self
class B(A):
def func(self):
self._ref # should be inferred as `B`To Reproduce
Here's a little more elaborate example:
from typing import Self, TypeGuard, Protocol
from typing_extensions import reveal_type
class Node:
_original: Self | None
_x: int
def __init__(self, x: int) -> None:
self._original = None
self._x = x
@property
def isClone(self) -> bool:
return self._original is not None
@property
def x(self) -> int:
if self._original is not None:
return self._original.x
return self._x
def clone(self: Self) -> Self:
cls = type(self)
cloned = cls.__new__(cls)
cloned._original = self
return cloned
class Node2D(Node):
_y: int
def __init__(self, x: int, y: int) -> None:
super().__init__(x)
self._y = y
@property
def y(self) -> int:
if self._original is not None:
reveal_type(self._original)
return self._original.y
return self._y
n2 = Node2D(10, 20)
n2c = n2.clone()
reveal_type(n2c)
reveal_type(n2c._original)
https://mypy-play.net/?mypy=latest&python=3.11&gist=c7f02b59664a088d305ea951810abc9c
Expected Behavior
When an attribute annotated as Self is referenced in a method of a subclass, the type is correctly inferred as the subclass type.
Actual Behavior
The attribute seems to be inferred as an unbound type Self'0 when referenced from the method, but it gets correctly inferred as the subclass type when referenced in the global scope.
main.py:39: note: Revealed type is "Self`0"
main.py:40: error: "Self" has no attribute "y" [attr-defined]
main.py:47: note: Revealed type is "__main__.Node2D"
main.py:48: note: Revealed type is "Union[__main__.Node2D, None]"