Shared via mypy Playground

main.py

from typing import TypeVar, Generic, Literal

Tco = TypeVar("Tco", covariant=True)

class C(Generic[Tco]):
    def __init__(self, x : Tco) -> None:
        self.x = x
    def f(self) -> Tco:
        return self.x
        
Tcon = TypeVar("Tcon", contravariant=True)

class C2(Generic[Tcon]):
    def f(self, x: Tcon) -> None:
        pass
        
class C3(Generic[Tco]):
    def __init__(self, x: Tco) -> None:
        self.x = x
        
    def f (self, x: Tco) -> None:
        pass
    
class C4(Generic[Tcon]):
    def __init__(self, x : Tcon) -> None:
        self.x = x
    def f(self) -> Tcon:
        return self.x


class X:
    pass

class Y(X):
    pass

A = TypeVar('A', bound = X)
class Tensor(Generic[A]):
    def __init__(self, a : A) -> None: ...

def fun(tensor : Tensor[A]) -> None : ...

v = X()
x = Tensor(v)
reveal_type(x)  # main.Tensor[main.X*]
fun(x)

w = Y()
x0 = Tensor(w)
reveal_type(x0)
fun(x0)

y : Tensor[X]
reveal_type(y) # main.Tensor[main.X]
fun(y)

z : Tensor[Y]
reveal_type(z)
fun(z)