linux-kernel - Re: [PATCH 1/4] rust: alloc: implement `Borrow` and `BorrowMut` for `Vec`

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Message-ID: <aD4NW2vDc9rKBDPy@tardis.local>
Date: Mon, 2 Jun 2025 13:45:15 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Benno Lossin <lossin@...nel.org>
Cc: Alexandre Courbot <acourbot@...dia.com>,
	Danilo Krummrich <dakr@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] rust: alloc: implement `Borrow` and `BorrowMut` for
 `Vec`

On Mon, Jun 02, 2025 at 10:21:12PM +0200, Benno Lossin wrote:
> On Mon Jun 2, 2025 at 5:06 PM CEST, Boqun Feng wrote:
> > On Mon, Jun 02, 2025 at 10:13:22AM +0900, Alexandre Courbot wrote:
> >> On Mon Jun 2, 2025 at 1:11 AM JST, Benno Lossin wrote:
> >> > On Sun Jun 1, 2025 at 5:00 AM CEST, Alexandre Courbot wrote:
> >> >> Implement these two common traits, which allow generic types to store
> >> >> either an owned value or a reference to it.
> >> >
> >> > I don't understand the second part of the sentence.
> >> 
> >> I want to say that Borrow allows you to do something like:
> >> 
> >>     struct Foo<B: Borrow<u32>>(B);
> >> 
> >>     // `foo1` owns its value...
> >>     let foo1 = Foo(0x12);
> >> 
> >>     let i = 0x24;
> >>     // ... but `foo2` just borrows it, subject to the lifetime of `i`.
> >>     let foo2 = Foo(&i);
> >> 
> >> And the implementations in this series also let you do:
> >> 
> >>     // `foo3`'s value is owned, but heap-allocated
> >>     let foo3 = Arc::new(KBox::new(0x56, GFP_KERNEL)?);
> >> 
> >>     let j = Arc::new(0x78, GFP_KERNEL)?;
> >>     // `foo4`'s value is shared and its lifetime runtime-managed.
> >>     let foo4 = Foo(j.clone());
> >
> > Maybe you could put these in the "# Examples" section before impl
> > blocks. E.g
> >
> > 	/// # Examples
> > 	/// ```
> > 	/// <you case above>
> > 	/// ```
> > 	impl<T, A> Borrow<[T]> for Vec<T, A> ...
> 
> Does that get rendered in the docs? If not, I don't think we should do
> it.

It does. I just tried myself, in the "Trait Implementations" section,
if you provide a doc comment for an impl block, it will show under the
"impl line" of corresponding to that impl block, including ```code```.

Regards,
Boqun

> 
> ---
> Cheers,
> Benno