linux-kernel - Re: [PATCH 2/2] rust: add `const

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Message-ID: <3f811c47-663c-4326-a7b5-cfe068e3b9d9@nvidia.com>
Date: Fri, 6 Feb 2026 15:37:45 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Gary Guo <gary@...yguo.net>, Miguel Ojeda <ojeda@...nel.org>,
 Boqun Feng <boqun@...nel.org>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, Benno Lossin <lossin@...nel.org>,
 Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>,
 Alexandre Courbot <acourbot@...dia.com>, Yury Norov <yury.norov@...il.com>,
 Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nsc@...nel.org>
Cc: linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
 linux-kbuild@...r.kernel.org
Subject: Re: [PATCH 2/2] rust: add `const_assert!` macro

On 2/6/26 2:28 PM, Gary Guo wrote:
> On Fri Feb 6, 2026 at 10:21 PM GMT, John Hubbard wrote:
>> On 2/6/26 9:12 AM, Gary Guo wrote:
>>> From: Gary Guo <gary@...yguo.net>
...
>>> +/// Assertion during constant evaluation.
>>> +///
>>> +/// This is a more powerful version of `static_assert` that can refer to generics inside functions
>>> +/// or implementation blocks. However, it also have a limitation where it can only appear in places
>>> +/// where statements can appear; for example, you cannot use it as an item in the module.
>>> +///
>>> +/// [`static_assert!`] should be preferred where possible.
>>
>> Over what? There are 3 different assertion types. If it is actually
>> possible to list a clear order of preference, then let's list all
>> 3 in order, rather than having a scattering around of "A is 
>> better than B", "C is sometimes worse than A", and then the
>> reader has to play treasure hunt to work it out. haha :)
> 
> I am trying to avoid listing all assertion macros in all assertions macros,
> that's just going to be duplications.
> 
> How about remove `#[doc(hidden)]` on `mod build_assert` and enumerate all
> assertions in the module documentation and give them rankings there?
> 

Maybe yes? In any case, let's at least clarify the preference one-liner
above. Something like:

    /// [`static_assert!`] should be preferred over [`const_assert!`]
    /// because ...

(If that's even correct. I'm a little vague on the intent still.)

thanks,
-- 
John Hubbard