[Python] Overloaded method invocation causes type check error

I posted a question earlier asking how to overload Python methods using generics.

The solution provided is shown below.

from __future__ import annotations
from typing import Literal, overload

class WoodData: ...
class ConcreteData: ...

class Foo[T: Literal["wood", "concrete"]]:
def __init__(self, data_type: T) -> None:
self.data_type = data_type

@overload
def get_data(self: Foo[Literal["wood"]]) -> WoodData: ...

@overload
def get_data(self: Foo[Literal["concrete"]]) -> ConcreteData: ...

def get_data(self):
if self.data_type == "wood":
return WoodData()
return ConcreteData()

foo = Foo("concrete")
x = foo.get_data()


This example works as expected, but the problem arises when we try to call get_data from a sibling class method.

For example, I add the bar method below.

from __future__ import annotations
from typing import Literal, overload

class WoodData: ...
class ConcreteData: ...

class Foo[T: Literal["wood", "concrete"]]:
def __init__(self, data_type: T) -> None:
self.data_type = data_type

@overload
def get_data(self: Foo[Literal["wood"]]) -> WoodData: ...

@overload
def get_data(self: Foo[Literal["concrete"]]) -> ConcreteData: ...

def get_data(self):
if self.data_type == "wood":
return WoodData()
return ConcreteData()

def bar(self):
self.get_data()


This gives the typing error:

Cannot access attribute "get_data" for class "Foo[T@Foo]*"
Could not bind method "get_data" because "Self@Foo[T@Foo]" is not assignable to parameter "self"
"Foo[T@Foo]*" is not assignable to "Foo[Literal['wood']]"
Type parameter "T@Foo" is covariant, but "T@Foo" is not a subtype of "Literal['wood']"
Type "Literal['wood', 'concrete']" is not assignable to type "Literal['wood']"
"Literal['concrete']" is not assignable to type "Literal['wood']"
Could not bind method "get_data" because "Self@Foo[T@Foo]" is not assignable to parameter "self"
"Foo[T@Foo]*" is not assignable to "Foo[Literal['concrete']]"
Type parameter "T@Foo" is covariant, but "T@Foo" is not a subtype of "Literal['concrete']"


How can I access the get_data function from another method without getting a typing error?

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