linux-kernel - Re: [PATCH 5/7] rust: sync: allow type of `self` to be `ArcBorrow<T>`

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Message-ID: <20221231194414.3f66d8af.gary@garyguo.net>
Date:   Sat, 31 Dec 2022 19:44:14 +0000
From:   Gary Guo <gary@...yguo.net>
To:     Wedson Almeida Filho <wedsonaf@...il.com>
Cc:     rust-for-linux@...r.kernel.org, Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/7] rust: sync: allow type of `self` to be
 `ArcBorrow<T>`

On Wed, 28 Dec 2022 06:03:44 +0000
Wedson Almeida Filho <wedsonaf@...il.com> wrote:

> This allows associated functions whose `self` argument has
> `ArcBorrow<T>` as their type. This, in turn, allows callers to use the
> dot syntax to make calls.
> 
> Signed-off-by: Wedson Almeida Filho <wedsonaf@...il.com>

Reviewed-by: Gary Guo <gary@...yguo.net>

> ---
>  rust/kernel/sync/arc.rs | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index f68bfc02c81a..84f31c85a513 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -255,11 +255,34 @@ impl<T: ?Sized> Drop for Arc<T> {
>  /// // Assert that both `obj` and `cloned` point to the same underlying object.
>  /// assert!(core::ptr::eq(&*obj, &*cloned));
>  /// ```
> +///
> +/// Using `ArcBorrow<T>` as the type of `self`:
> +///
> +/// ```
> +/// use crate::sync::{Arc, ArcBorrow};
> +///
> +/// struct Example {
> +///     a: u32,
> +///     b: u32,
> +/// }
> +///
> +/// impl Example {
> +///     fn use_reference(self: ArcBorrow<'_, Self>) {
> +///         // ...
> +///     }
> +/// }
> +///
> +/// let obj = Arc::try_new(Example { a: 10, b: 20 })?;
> +/// obj.as_arc_borrow().use_reference();
> +/// ```
>  pub struct ArcBorrow<'a, T: ?Sized + 'a> {
>      inner: NonNull<ArcInner<T>>,
>      _p: PhantomData<&'a ()>,
>  }
>  
> +// This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
> +impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
> +
>  impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
>      fn clone(&self) -> Self {
>          *self