linux-kernel - Re: [PATCH 1/2] rust: add BitInt integer wrapping type

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Message-ID: <aQi7e6VgFsqpq1Rn@yury>
Date: Mon, 3 Nov 2025 09:26:03 -0500
From: Yury Norov <yury.norov@...il.com>
To: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc: Alexandre Courbot <acourbot@...dia.com>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Danilo Krummrich <dakr@...nel.org>, Miguel Ojeda <ojeda@...nel.org>,
	Joel Fernandes <joelagnelf@...dia.com>,
	Jesung Yang <y.j3ms.n@...il.com>, Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <lossin@...nel.org>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Trevor Gross <tmgross@...ch.edu>, linux-kernel@...r.kernel.org,
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 1/2] rust: add BitInt integer wrapping type

On Mon, Nov 03, 2025 at 03:10:01PM +0100, Miguel Ojeda wrote:
> On Mon, Nov 3, 2025 at 3:17 AM Yury Norov <yury.norov@...il.com> wrote:
> >
> > Rust _must_ do the same thing to at least be arithmetically
> > compatible to the big brother.
> 
> No, Rust doesn't need to do anything of the sort, sorry.
> 
> The point here is not to copy what C does, but to improve on it.
> 
> In particular, we definitely do not want to have anything like integer
> promotions and arithmetic conversions from C.

This is exactly what the patch does:

  +/// let v = BitInt::<u8, 4>::from_expr(15);
  +///
  +/// // Common operations are supported against the backing type.
  +/// assert_eq!(v + 5, 20);
  +/// assert_eq!(v / 3, 5);