Re: [PATCH v11 1/4] rust: types: Add Ownable/Owned types

[Benno Lossin]

On Tue Aug 19, 2025 at 11:00 AM CEST, Andreas Hindborg wrote:
> "Oliver Mangold" <oliver.mangold@xxxxx> writes:
>> You mean of `Ownable`, when `OwnableMut` is removed? Yes. A good question
>> in that context is, what it actually means to have an `&mut Opaque<T>`
>> where `T` is `Unpin`. If that implies being allowed to obtain an `&mut T`,
>> it would we easy, I guess.
>
> You should not be able to get a `&mut T` from a `&mut Opaque<T>`.
> `Opaque` opts out of invariants that normally hold for rust references.

Yes, that function mustn't exist.

>> But what I am wondering is, if we actually want to start using `Pin`
>> at all. Isn't `Opaque` currently used about everywhere pinning is needed?
>
> `Opaque` is `!Unpin`, but pinning guarantees does not come into effect
> until we produce a `Pin<Opaque<T>>`.

`Pin<Opaque<T>>` isn't really a thing. You still need a pointer
indirection, so `Pin<P>` where `P: DerefMut<Target = Opaque<T>>` so for
example `Pin<Box<Opaque<T>>>`.

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Cheers,
Benno