Re: [PATCH] rust: alloc: allow different error types in `KBox::pin_slice`

["Danilo Krummrich" <dakr@kernel.org>]

On Sat Feb 14, 2026 at 3:40 PM CET, Benno Lossin wrote:
> On Sat Feb 14, 2026 at 3:17 PM CET, Danilo Krummrich wrote:
>> On Sat Feb 14, 2026 at 2:28 PM CET, Andreas Hindborg wrote:
>>> @@ -333,24 +333,31 @@ pub fn pin(x: T, flags: Flags) -> Result<Pin<Box<T, A>>, AllocError>
>>>      /// assert_eq!(s[3].d.lock().a, 20);
>>>      /// # Ok::<(), Error>(())
>>>      /// ```
>>> -    pub fn pin_slice<Func, Item, E>(
>>> +    pub fn pin_slice<Func, Item, E, E2>(
>>>          mut init: Func,
>>>          len: usize,
>>>          flags: Flags,
>>>      ) -> Result<Pin<Box<[T], A>>, E>
>>>      where
>>>          Func: FnMut(usize) -> Item,
>>> -        Item: PinInit<T, E>,
>>> -        E: From<AllocError>,
>>
>> I think we should keep this bound and just add:
>
> The `Into` trait bounds are the idiomatic ones for functions consuming
> things. See https://doc.rust-lang.org/std/convert/trait.Into.html:
>
>     Prefer using Into over From when specifying trait bounds on a
>     generic function to ensure that types that only implement Into can
>     be used as well.

Yeah, but isn't this only because of [1], which does not apply to the kernel
because our minimum compiler version is 1.78 anyways?

I.e. are there any cases where we can't implement From in the kernel and have to
fall back to Into?

[1] https://doc.rust-lang.org/std/convert/trait.Into.html#implementing-into-for-conversions-to-external-types-in-old-versions-of-rust