[Python] Pyright false positive when implementing a protocol [duplicate]

This MRE illustrates my problem:

from dataclasses import dataclass
from typing import Protocol


class Child(Protocol):
val: float

class Parent(Protocol):
sub: Child

@dataclass
class Child1(Child):
val: float

@dataclass
class Parent1(Parent):
sub: Child1 # <- Pyright complains here


To my eyes, the Parent1-class appears as a valid implementation of the Parent-protocol. I plan to use this a lot.

mypy approves this while pyright does not. The latter complains:

"sub" overrides symbol of same name in class "Parent"
Variable is mutable so its type is invariant
Override type "Child1" is not the same as base type "Child" (reportIncompatibleVariableOverride)


I do not understand. What has mutability to do with it? Playing around with frozen=True does not change anything, And why does mypy comply?

Can I do something about it? Adjust the code or pacify pyright somehow?

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