Re: [PATCH] rust: pin-init: use irrefutable pattern for `stack_pin_init`

[Gary Guo]

On Tue Sep 1, 2026 at 12:58 AM BST, Miguel Ojeda wrote:
> On Fri, Aug 28, 2026 at 5:50 PM Gary Guo <gary@xxxxxxxxxx> wrote:
>>
>> From: Gary Guo <gary@xxxxxxxxxxx>
>>
>> In Rust 1.100.0, `Infallible` will become an alias of `!`. The let
>> binding in `stack_pin_init` will thus become unreachable and produce a
>> "unreachable expression" warning for subsequent match, and thus will fail
>> `-Dwarnings` build. For this macro, all we need to know is that the error
>> type is uninhabited, so replace this with a irrefutable pattern instead.
>>
>> Reported-by: Mohamad Alsadhan <mo@xxxxxxx>
>> Closes: https://github.com/Rust-for-Linux/pin-init/pull/171
>> Signed-off-by: Gary Guo <gary@xxxxxxxxxxx>
>
> Applied to `rust-fixes` -- thanks!
>
> For stable, we will need a custom backport without
> `feature(min_exhaustive_patterns)` (we could in principle enable that
> one since it is available in Rust 1.77.0, but for stable I would avoid
> it), so I wrote this tag:

We can probably just allow `unreachable_code`?

Best,
Gary

>
>     Cc: stable@xxxxxxxxxxxxxxx # Needed in 7.1.y and later (for 6.12.y
> and 6.18.y a custom one is needed).
>
>     [ The error looks like (dummy reproducer):
>
>           error: unreachable expression
>              --> rust/kernel/sync.rs:177:5
>               |
>           177 |     pin_init::stack_pin_init!(let num = 42u32);
>               |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>               |     |
>               |     unreachable expression
>               |     any code following this expression is unreachable
>               |
>               = note: `-D unreachable-code` implied by `-D warnings`
>               = help: to override `-D warnings` add `#[allow(unreachable_code)]`
>               = note: this error originates in the macro
> `pin_init::stack_pin_init` (in Nightly builds, run with -Z
> macro-backtrace for more info)
>
>         - Miguel ]
>
>     [ Reworded for typos. - Miguel ]
>
> Cheers,
> Miguel