Recursive sequence type of Sequence[NotAString] should not accept str #819
Description
This is a (p)repost from python/mypy#18184, which also applies here:
The false negative can be reproduced with:
from collections.abc import Sequence
from typing import TypeAlias
class Scalar: ...
Vector: TypeAlias = Sequence[Scalar]
Tensor: TypeAlias = Vector | Sequence["Tensor"]
accepted_vector: Vector = [Scalar()] # true negative
rejected_vector: Vector = "duck" # true positive: ducks aren't vectors
accepted_tensor: Tensor = [[[Scalar()]]] # true negative
rejected_tensor1: Tensor = object() # true positive: objects aren't tensors
rejected_tensor2: Tensor = "duck" # false negative: ducks are tensors...?alternative example:
class Increment[T]: # covariant
def current(self, /) -> T: ... # type: ignore[empty-body]
type Infinity = Increment[Infinity]
type Zero = Increment[None]
type Integer = Zero | Increment[Integer]
def int2inf(integer: Integer, /) -> Infinity:
return integer # rejected => ok
def inf2int(infinity: Infinity, /) -> Integer:
return infinity # accepted => wut