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From:   "Ariel Miculas (amiculas)" <amiculas@cisco.com>
To:     Alice Ryhl <aliceryhl@google.com>
CC:     "nmi@metaspace.dk" <nmi@metaspace.dk>,
        "alex.gaynor@gmail.com" <alex.gaynor@gmail.com>,
        "benno.lossin@proton.me" <benno.lossin@proton.me>,
        "bjorn3_gh@protonmail.com" <bjorn3_gh@protonmail.com>,
        "boqun.feng@gmail.com" <boqun.feng@gmail.com>,
        "gary@garyguo.net" <gary@garyguo.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "ojeda@kernel.org" <ojeda@kernel.org>,
        "patches@lists.linux.dev" <patches@lists.linux.dev>,
        "rust-for-linux@vger.kernel.org" <rust-for-linux@vger.kernel.org>,
        "wedsonaf@gmail.com" <wedsonaf@gmail.com>
Subject: Re: [PATCH v1] rust: add improved version of
 `ForeignOwnable::borrow_mut`
Thread-Topic: [PATCH v1] rust: add improved version of
 `ForeignOwnable::borrow_mut`
Thread-Index: AQHaBz3vws48uhIkVEW6DeRCSD9Ktg==
Date:   Wed, 25 Oct 2023 12:22:35 +0000
Message-ID: <rfx55e62g3uvdwunxtfkhheyhgnfgladthezuig2gk4uaaksat@pd4pttamfff2>
References: <87msyi406u.fsf@metaspace.dk>
 <20230823103458.243871-1-aliceryhl@google.com>
In-Reply-To: <20230823103458.243871-1-aliceryhl@google.com>
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On 23/08/23 10:34AM, Alice Ryhl wrote:
> Andreas Hindborg <nmi@metaspace.dk> writes:
> >>> I am not sure this makes sense. How about splitting the trait in two,
> >>> immutable and mutable and only implementing the immutable one or Arc?
> >>
> >> I used this design based on what would make sense for a linked list. T=
he
> >> idea is that we can have two different types of cursors for a linked
> >> list: immutable and mutable. The immutable cursor lets you:
> >>
> >>  * move around the linked list
> >>  * access the values using `borrow`
> >>
> >> The mutable cursor lets you:
> >>
> >>  * move around the linked list
> >>  * delete or add items to the list
> >>  * access the values using `borrow_mut`
> >>
> >> The mutable cursor gives you extra abilities beyond the `borrow` vs
> >> `borrow_mut` distinction, so we want to provide both types of cursors
> >> even if the pointer type is Arc. To do that, we need a trait that
> >> defines what it means to have mutable access to an Arc.
> >=20
> > I don't see how that prevents this trait from being split in two?
>=20
> Well, you could split the trait, but if you make the mutable iterator
> require the `borrow_mut` trait, then you have to implement the mutable
> trait for `Arc` too if you want the mutable iterator to work with `Arc`.
>=20
> And if you're always going to implement both traits, then maybe it
> makes more sense to not split the traits?
>=20
> Alice

I see this patch present in the rust-dev branch, but not in rust-next.
Are there plans for including this patch in rust-next?

Cheers,
Ariel=