gha: fix cargofmt checks to use nightly

Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>

.github/workflows/rust.yml

@@ -146,7 +146,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
+      # We need to use nightly Rust to check the formatting.
+      - uses: dtolnay/rust-toolchain@nightly
         with:
           components: rustfmt
       - run: cargo fmt --all -- --check

src/capi/error.rs

@@ -34,7 +34,8 @@ use libc::{c_char, c_int};
 use once_cell::sync::Lazy;
 use rand::{self, Rng};
 
-// TODO: Switch this to using a slab or similar structure, possibly using a less heavy-weight lock?
+// TODO: Switch this to using a slab or similar structure, possibly using a less
+// heavy-weight lock?
 // MSRV(1.80): Use LazyLock.
 static ERROR_MAP: Lazy<Mutex<HashMap<CReturn, Error>>> = Lazy::new(|| Mutex::new(HashMap::new()));
 

src/tests/test_resolve_partial.rs

@@ -18,8 +18,11 @@
  */
 
 use crate::{
-    error::ErrorKind, flags::ResolverFlags, resolvers::PartialLookup, resolvers::ResolverBackend,
-    tests::common as tests_common, Root,
+    error::ErrorKind,
+    flags::ResolverFlags,
+    resolvers::{PartialLookup, ResolverBackend},
+    tests::common as tests_common,
+    Root,
 };
 
 use anyhow::Error;