Re: [PATCH v3 1/4] rust: add num module and Integer trait

["Alexandre Courbot" <acourbot@nvidia.com>]

On Thu Nov 6, 2025 at 6:46 PM JST, Alice Ryhl wrote:
> On Thu, Nov 06, 2025 at 04:07:13PM +0900, Alexandre Courbot wrote:
>> Introduce the `num` module, which will provide numerical extensions and
>> utilities for the kernel.
>> 
>> For now, introduce the `Integer` trait, which is implemented for all
>> primitive integer types to provides their core properties to generic
>> code.
>> 
>> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
>> ---
>>  rust/kernel/lib.rs |  1 +
>>  rust/kernel/num.rs | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 77 insertions(+)
>> 
>> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
>> index 3dd7bebe7888..235d0d8b1eff 100644
>> --- a/rust/kernel/lib.rs
>> +++ b/rust/kernel/lib.rs
>> @@ -109,6 +109,7 @@
>>  pub mod mm;
>>  #[cfg(CONFIG_NET)]
>>  pub mod net;
>> +pub mod num;
>>  pub mod of;
>>  #[cfg(CONFIG_PM_OPP)]
>>  pub mod opp;
>> diff --git a/rust/kernel/num.rs b/rust/kernel/num.rs
>> new file mode 100644
>> index 000000000000..3f85e50b8632
>> --- /dev/null
>> +++ b/rust/kernel/num.rs
>> @@ -0,0 +1,76 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +
>> +//! Additional numerical features for the kernel.
>> +
>> +use core::ops;
>> +
>> +/// Designates unsigned primitive types.
>> +pub struct Unsigned(());
>> +
>> +/// Designates signed primitive types.
>> +pub struct Signed(());
>
> Since these types are not intended to be constructed, I would suggest
> using enums so that they can't be constructed:
>
> 	pub enum Unsigned {}
> 	pub enum Signed {}

Ah, of course - I thought about having a private `()` to forbid
construction outside of the module, but the empty enum prevents them
from being instantiated from the module as well! Will apply, thanks!