[PATCH] rust: replace length checks with match

[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 <tamird@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 <tamird@gmail.com>

Re: [PATCH] rust: replace length checks with match

[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 <tamird@gmail.com>

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

Re: [PATCH] rust: replace length checks with match

[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.oOHtt60s-lkp@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.oOHtt60s-lkp@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 <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202505282330.oOHtt60s-lkp@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

Re: [PATCH] rust: replace length checks with match

[Tamir Duberstein]

On Wed, May 28, 2025 at 11:58 AM kernel test robot <lkp@intel.com> wrote:
>
> 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.oOHtt60s-lkp@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.oOHtt60s-lkp@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 <lkp@intel.com>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202505282330.oOHtt60s-lkp@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'

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