False bad-specialization when a generic Protocol is used as a bound on a 2-param class inherited across modules #5449

Describe the bug

A type parameter bounded by a generic Protocol (F: SupportsSave[Any]) rejects a valid argument
when the class has two type parameters and inherits from a generic base defined in another module.
The error message shows the bound as SupportsSave (no type argument), as if SupportsSave[Any]
lost its argument:

ERROR views.py:16:17-37: `EventForm` is not assignable to upper bound `SupportsSave` of type variable `F` [bad-specialization]

Repro

lib.py:

from typing import Any, Protocol


class Model: ...


class SupportsSave[T: Model](Protocol):
    def save(self) -> T: ...


class BaseView[M, F: SupportsSave[Any]]: ...

views.py:

from typing import Any

from lib import BaseView, Model, SupportsSave


class Event(Model): ...


class EventForm:
    def save(self) -> Event: ...


class View[M, F: SupportsSave[Any]](BaseView[M, F]): ...


class EventView(View[str, EventForm]): ...  # false positive here

pyproject.toml:

[tool.pyrefly]

(Empty section; without a config, the basic preset hides the error.)

Narrowing

The error goes away if any of these change:

• everything is in a single module;
• the classes have a single type parameter;
• the bound is a non-generic Protocol.

Using old-style TypeVar(bound=...), a string bound, or SupportsSave[Model] instead of
SupportsSave[Any] does not change anything. pyright accepts the code, and so does ty.

Version

pyrefly 1.4.0 (latest release) and main 8003f9b3d (2026-10-29), Python 3.14 (same on 3.15).