Re: [PATCH] rust: proc-macro2: rebuild if the version text changes

[Alice Ryhl <aliceryhl@google.com>]

On Thu, Jan 22, 2026 at 06:41:35AM +0100, Miguel Ojeda wrote:
> The Rust compiler cannot use dependencies built by other versions, e.g.:
> 
>     error[E0514]: found crate `proc_macro2` compiled by an incompatible version of rustc
>      --> rust/quote/ext.rs:5:5
>       |
>     5 | use proc_macro2::{TokenStream, TokenTree};
>       |     ^^^^^^^^^^^
>       |
>       = note: the following crate versions were found:
>               crate `proc_macro2` compiled by rustc 1.92.0 (ded5c06cf 2025-12-08): ./rust/libproc_macro2.rlib
>       = help: please recompile that crate using this compiler (rustc 1.93.0 (254b59607 2026-01-19)) (consider running `cargo clean` first)
> 
> Thus trigger a rebuild if the version text changes like we do in other
> top-level cases (e.g. see commit aeb0e24abbeb ("kbuild: rust: replace
> proc macros dependency on `core.o` with the version text")).
> 
> The build errors for now are hard to trigger, since we do not yet use
> the new crates we just introduced (the use cases are coming in the next
> merge window), but they can still be seen if e.g. one manually removes
> one of the targets, so fix it already.
> 
> Fixes: 158a3b72118a ("rust: proc-macro2: enable support in kbuild")
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

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