Conformance test: make dataclass_hash.py not rely on `typing.Hashable`?

I noticed that the conformance test currently enforces a hashability check on dataclasses:
https://github.com/python/typing/blame/6d5c186ea3f45dd80dcad9f172479b270e54966a/conformance/tests/dataclasses_hash.py

If we take the annotation of typing.Hashable and the annotation of object literally, then no type errors should be reported on that file, as typing.Hashable is a protocol that requires a def __hash__(self) -> int method, and object satisfies that protocol regardless of whether the dataclass transform creates its own __hash__ method or not.

I understand that the issue of deciding whether an object is hashable or not in type checkers is a tricky business and there was a lot of pre-existing discussions/proposals around it. This makes me wonder if it's worth doing a dedicated "hashability" section in the spec, and use separate conformance tests to establish how typing.Hashable assignability should be handled. My understanding is that the pre-existing dataclass hash tests is intended to just test about whether the __hash__ method is nullified or not under the dataclass transform, but by testing it via typing.Hashable it kinds of indirectly dictate hashable assignment behaviors as a side effect.

Concretely, what I had in mind was a refactor to dataclasses_hash.py, where we change the current assertions of the form

# This should generate an error because DC1 isn't hashable.
v: Hashable = DC(0)

into something like this:

assert_type(DC(0).__hash__, NoneType)  # OK

The new version does not depend on how typing.Hashable gets defined in typeshed, and it (arguably) aligns more directly with the intention of the tests. But I am unsure about how controversial this proposal would be and hence want to get some feedback on it first.

conformance/tests/dataclasses_hash.py から始め、その Hashable ベースの assertions を、issue に記載されている dataclass の hash 動作と比較します。参照されている typing.Hashable と object のアノテーションを読み、その後、既存の conformance の期待事項を確認します。完了条件は、test が typeshed の Hashable 定義に依存せず、dataclass hash の結果を直接チェックすることです。