[Python] TypeVar as dict key type hint "has no meaning in this context"

The context:


I have a dict whose keys are arbitrary types, and whose values are Callables which take a string and return an instance of the same type as the key. For example:

class Hero:
def __init__(self, name):
self.name = name


all_heroes = {
"deadpool": Hero("wade wilson"),
"wolverine": Hero("james howlett")
}

REGISTERED_CONVERTERS = {
Hero: all_heroes.get,
int: int,
}

hero_lookup = REGISTERED_CONVERTERS[Hero]
assert hero_lookup("deadpool").name == "wade wilson"

int_lookup = REGISTERED_CONVERTERS[int]
assert int_lookup("5") == 5

The Problem:


I want to properly type hint this dict of converter functions

What's not Working:


This was my first attempt:

from typing import Callable, TypeVar

T = TypeVar("T")
TypeConverter = Callable[[str], T]
REGISTERED_CONVERTERS: dict[type[T], TypeConverter] = {
int: int,
}


Pylance is happy with the T in the TypeConverter alias, but complains about the T for the dict's key:

Type variable "T" has no meaning in this context Pylance(reportGeneralTypeIssues)
(constant) T: type[T]


I thought maybe the TypeConverter alias was causing issues, so then I tried this:

T = TypeVar("T")
REGISTERED_CONVERTERS: dict[type[T], Callable[[str], T]] = {
int: int,
}


This is seemingly worse as Pylance now raises the same complaint about both Ts

What am I doing wrong, or is this a Pylance problem?

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