False positive of protocol conforming when Self is used in a base protocol

[Azureblade3808]

Describe the bug
When a protocol is inheriting another protocol, and the base protocol uses Self in some way, conforming to the derived protocol sometimes fails unexpectedly.

To Reproduce
See sample code.

Expected behavior
Both assignments in the last should type-check.

Screenshots or Code

from __future__ import annotations

from typing import Generic, Protocol, TypeVar
from typing_extensions import Self

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

class P0(Protocol[_V_co]):
    def f0(self, /) -> Self: ...
    def f1(self, /) -> _V_co: ...

class P1(P0[_V_co], Protocol[_V_co]):
    pass

class C(Generic[_V_co]):
    def f0(self, /) -> Self:
        raise NotImplementedError
    def f1(self, /) -> _V_co:
        raise NotImplementedError

a: P0[str] = C[str]()  # pass
b: P1[str] = C[str]()  # fail

VS Code extension or command-line
Pylance v2023.4.21 Pre-Release

Additional context
If C explicitly inherits P1[_V_co], no error is reported.

Mypy playground: https://mypy-play.net/?mypy=latest&python=3.10&gist=a26280d31899e845ae73aecf9068bafa

EDIT

A derived class is not needed to repro.

[erictraut]

Thanks for the bug report and great repro steps.

This will be addressed in the next release.

[erictraut]

This is addressed in pyright 1.1.306, which I just published. It will also be included in a future release of pylance.

[Azureblade3808]

Still works incorrectly over some cases in Pylance v2023.5.11 (Pyright 1.1.306).

from __future__ import annotations

from typing import Protocol, TypeVar
from typing_extensions import Self

_V_t = TypeVar("_V_t")
_V_co = TypeVar("_V_co")

class SetLike(Protocol[_V_co]):
    def __and__(self, right: Self, /) -> SetLike[_V_co]: ...
    # Other methods are omitted.

class MutableSetLike1(SetLike[_V_t], Protocol[_V_t]):
    def add(self, o: _V_t, /) -> None: ...
    # Other methods are omitted.
    
class MutableSetLike2(Protocol[_V_t]):
    def __and__(self, right: Self, /) -> SetLike[_V_t]: ...
    def add(self, o: _V_t, /) -> None: ...
    # Other methods are omitted.

SOME_SET: set[str] = {"A", "B", "C"}

a: SetLike[str] = SOME_SET
b: MutableSetLike1[str] = SOME_SET
c: MutableSetLike2[str] = SOME_SET

In the sample above, MutableSetLike1 and MutableSetLike2 should work equally, but the results are different.

Mypy playground: https://mypy-play.net/?mypy=latest&python=3.10&gist=d68e3371c260e7b333d059194b1b9774

[erictraut]

@Azureblade3808, this issue is closed. If you want to report a new bug, please open a new issue.