Invalid solution to contravariant type variable with upper bound

For example,

```py
class Contra[T]:
    def append(self, x: T): ...

def f[T: int](x: Contra[T]):
    ...

def _(x: Contra[str]):
    f(x) # Argument to function `f` is incorrect: Argument type `str` does not satisfy upper bound `int` of type variable `T`
```

Solving `T` to `int & str = Never` would avoid the assignability error.