linux-kernel - Re: [PATCH v2 1/2] rust: add BitInt integer wrapping type

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Message-ID: <aQiBTOj1jl4xM3pJ@google.com>
Date: Mon, 3 Nov 2025 10:17:48 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Alexandre Courbot <acourbot@...dia.com>
Cc: Danilo Krummrich <dakr@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, 
	Joel Fernandes <joelagnelf@...dia.com>, Yury Norov <yury.norov@...il.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 v2 1/2] rust: add BitInt integer wrapping type

On Sun, Nov 02, 2025 at 11:24:42PM +0900, Alexandre Courbot wrote:
> Add the `BitInt` type, which is an integer on which the number of bits
> allowed to be used is restricted, capping its maximal value below that
> of primitive type is wraps.
> 
> This is useful to e.g. enforce guarantees when working with bit fields.
> 
> Alongside this type, provide many `From` and `TryFrom` implementations
> are to reduce friction when using with regular integer types. Proxy
> implementations of common integer traits are also provided.
> 
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>

> +                // Statically assert that `VALUE` fits within the set number of bits.
> +                const {
> +                    build_assert!(fits_within!(VALUE, $type, NUM_BITS));
> +                }

Since it's in a const block, this can just be an assert!.

Alice