[PATCH] rust: replace length checks with match

[Tamir Duberstein]

Use a match expression with slice patterns instead of length checks and
indexing. The result is more idiomatic, which is a better example for
future Rust code authors.

Signed-off-by: Tamir Duberstein <tam...@gmail.com>
---
scripts/rustdoc_test_gen.rs | 33 +++++++++++++++++----------------
1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/scripts/rustdoc_test_gen.rs b/scripts/rustdoc_test_gen.rs
index 1ca253594d38..a3dc251221e0 100644
--- a/scripts/rustdoc_test_gen.rs
+++ b/scripts/rustdoc_test_gen.rs
@@ -85,24 +85,25 @@ fn find_candidates(
}
}

- assert!(
- valid_paths.len() > 0,
- "No path candidates found for `{file}`. This is likely a bug in the build system, or some \
- files went away while compiling."
- );
-
- if valid_paths.len() > 1 {
- eprintln!("Several path candidates found:");
- for path in valid_paths {
- eprintln!(" {path:?}");
+ match valid_paths.as_slice() {
+ [] => panic!(
+ "No path candidates found for `{file}`. This is likely a bug in the build system, or \
+ some files went away while compiling."
+ ),
+ [valid_path] => {
+ valid_path.to_str().unwrap()
+ }
+ valid_paths => {
+ eprintln!("Several path candidates found:");
+ for path in valid_paths {
+ eprintln!(" {path:?}");
+ }
+ panic!(
+ "Several path candidates found for `{file}`, please resolve the ambiguity by \
+ renaming a file or folder."
+ );
}
- panic!(
- "Several path candidates found for `{file}`, please resolve the ambiguity by renaming \
- a file or folder."
- );
}
-
- valid_paths[0].to_str().unwrap()
}

fn main() {

---
base-commit: bfc3cd87559bc593bb32bb1482f9cae3308b6398
change-id: 20250527-idiomatic-match-slice-26a79d100e4d

Best regards,
--
Tamir Duberstein <tam...@gmail.com>

[Alice Ryhl]

On Tue, May 27, 2025 at 12:09:36PM -0400, Tamir Duberstein wrote:
> Use a match expression with slice patterns instead of length checks and
> indexing. The result is more idiomatic, which is a better example for
> future Rust code authors.
>
> Signed-off-by: Tamir Duberstein <tam...@gmail.com>

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

[kernel test robot]

Hi Tamir,

kernel test robot noticed the following build errors:

[auto build test ERROR on bfc3cd87559bc593bb32bb1482f9cae3308b6398]

url: https://github.com/intel-lab-lkp/linux/commits/Tamir-Duberstein/rust-replace-length-checks-with-match/20250528-001121
base: bfc3cd87559bc593bb32bb1482f9cae3308b6398
patch link: https://lore.kernel.org/r/20250527-idiomatic-match-slice-v1-1-34b0b1d1d58c%40gmail.com
patch subject: [PATCH] rust: replace length checks with match
config: x86_64-rhel-9.4-rust (https://download.01.org/0day-ci/archive/20250528/202505282330...@intel.com/config)
compiler: clang version 18.1.8 (https://github.com/llvm/llvm-project 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff)
rustc: rustc 1.78.0 (9b00956e5 2024-04-29)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250528/202505282330...@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <l...@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505282330...@intel.com/

All errors (new ones prefixed by >>):

PATH=/opt/cross/clang-18/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
INFO PATH=/opt/cross/rustc-1.78.0-bindgen-0.65.1/cargo/bin:/opt/cross/clang-18/bin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
/usr/bin/timeout -k 100 12h /usr/bin/make KCFLAGS= -Wno-error=return-type -Wreturn-type -funsigned-char -Wundef W=1 --keep-going LLVM=1 -j24 -C source O=/kbuild/obj/consumer/x86_64-rhel-9.4-rust ARCH=x86_64 SHELL=/bin/bash rustfmtcheck
make: Entering directory '/kbuild/src/consumer'
make[1]: Entering directory '/kbuild/obj/consumer/x86_64-rhel-9.4-rust'
>> Diff in scripts/rustdoc_test_gen.rs at line 90:

"No path candidates found for `{file}`. This is likely a bug in the build system, or \

some files went away while compiling."
),
- [valid_path] => {
- valid_path.to_str().unwrap()
- }
+ [valid_path] => valid_path.to_str().unwrap(),
valid_paths => {

eprintln!("Several path candidates found:");

for path in valid_paths {
make[2]: *** [Makefile:1826: rustfmt] Error 123
make[2]: Target 'rustfmtcheck' not remade because of errors.
make[1]: Leaving directory '/kbuild/obj/consumer/x86_64-rhel-9.4-rust'
make[1]: *** [Makefile:248: __sub-make] Error 2
make[1]: Target 'rustfmtcheck' not remade because of errors.
make: *** [Makefile:248: __sub-make] Error 2
make: Target 'rustfmtcheck' not remade because of errors.
make: Leaving directory '/kbuild/src/consumer'

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

[Tamir Duberstein]

Yep, I already noticed this. Will send v2 with proper formatting.