Re: [PATCH 1/3] rust: add Aliased type

[Christian Schrefl]

Hi Boqun

On 23.01.25 6:56 PM, Boqun Feng wrote:
> On Thu, Jan 23, 2025 at 11:21:23AM +0100, Christian Schrefl wrote:
> [...]
>>>> +
>>>> +/// Stores a value that may be aliased.
>>>> +///
>>>> +/// This is similar to `Opaque<T>` but is guaranteed to contain valid data and will
>>>> +/// Call the Drop implementation of T when dropped.
>>>> +#[repr(transparent)]
>>>> +pub struct Aliased<T> {
>>>
>>> As I already mentioned [1], the name `Aliased` is more reflecting the
>>> fact that this wrapper will avoid generating the "noalias" attribute(?)
>>> on the reference/pointer to the type rather than an intuitive idea about
>>> "why or when do I need this". Moreover, I think the argument about the
>>> naming of the counterpart in unstable Rust (UnsafePinned) makes sense to
>>> me [2]: this type alone won't prevent `&mut Aliased` getting `swap`, and
>>> it has to be used with `Pin`.
>>>
>>> Therefore, I think we should use a different name, perhaps
>>> `(Always)Shared`, or just use `UnsafePinned`, or, as always, looking
>>> fowards to a better name from anybody ;-)
>>>
>>> [1]: https://lore.kernel.org/rust-for-linux/Z407egxOy7oNLpq8@boqun-archlinux/
>>> [2]: https://rust-lang.github.io/rfcs/3467-unsafe-pinned.html#naming
>>
>> I don't particularly care about the name, I mostly used aliased, because that's
>> the name that Alice originally used.
>>
>> `(Always)Shared` seems confusing to me.
>>
>> I guess we can use `UnsafePinned`, but most people won't know what that means,
> 
> Hmm.. but doesn't `Aliased` have the same effect, i.e. most people won't
> know what that means? Moreover, people who already knows `UnsafePinned`
> will still take some time to realize "`Aliased` is actually
> `UnsafePinned`

I guess I'll name it `UnsafePinned` then.

> 
>> also I'm not sure if it's a good Idea to use the same name as a (future) 
>> language type.
> 
> The benefit is that we won't re-invent the wheel since `UnsafePinned`
> already does what `Aliased` does here. If we don't have a good name, we
> should use the one that most people are already using. Honestly, at this
> point, I think we should just use the unstable feature unsafe_pinned.

I think that's not implemented in rustc yet.
At least no implementation is linked in the tracking issue:
https://github.com/rust-lang/rust/issues/125735

Once that's implemented we can use a `cfg` to disable this 
implementation on new versions that provide it.
(Assuming we use the same API)

> [...]

Cheers
Christian