[Python] How is an instance attribute of the same type as the instance type-hinted?

I am trying to assign a variable to an instance of a class such that the variable is of the same type. I want to use the instance itself in the construction of the variable. In order to be compatible with inheritance, I want to type hint it as Self rather than the class.

The following works:

class Foo:

var: "Foo"

def bar(self) -> None:
self.var = self


However, var is marked as being of type Foo rather than Self. What I want is:

from typing import Self

class Foo:

var: Self

def bar(self) -> None:
self.var = self


In this case, mypy gives me the following message:

error: Incompatible types in assignment (expression has type "Foo", variable has type "Self") [assignment]


Clearly, self is not regarded as being of type Self but only of type Foo.

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