Summary

Observed behavior:

ty correctly raises an invalid-argument-type error when using a Protocol in an isinstance() check, but doesn't raise the same error when an equivalent runtime check is done with match:

from dataclasses import dataclass
from typing import Any, Protocol


class Foo(Protocol):
    foo: str


@dataclass
class ImplFoo:
    foo: str = "bar"


def isinstance_check(input: Any) -> None:
    if isinstance(input, Foo):
        input.foo


def match_check(input: Any) -> None:
    match input:
        case Foo():
            input.foo


isinstance_check(ImplFoo())
match_check(ImplFoo())

In the above code, ty raises one error.

Expected Behavior:

ty should raise the same error on the match structure, since it raises the same runtime error. mypy misses this as well, but pyright catches it.

Version

0.0.10