chore: fix dead code warnings (#6423)

benches/sync_mpsc.rs

@@ -4,7 +4,7 @@ use criterion::measurement::WallTime;
 use criterion::{black_box, criterion_group, criterion_main, BenchmarkGroup, Criterion};
 
 #[derive(Debug, Copy, Clone)]
-struct Medium([usize; 64]);
+struct Medium(#[allow(dead_code)] [usize; 64]);
 impl Default for Medium {
     fn default() -> Self {
         Medium([0; 64])
@@ -12,7 +12,7 @@ impl Default for Medium {
 }
 
 #[derive(Debug, Copy, Clone)]
-struct Large([Medium; 64]);
+struct Large(#[allow(dead_code)] [Medium; 64]);
 impl Default for Large {
     fn default() -> Self {
         Large([Medium::default(); 64])

tokio/src/sync/tests/notify.rs

@@ -52,7 +52,7 @@ fn notify_waiters_handles_panicking_waker() {
 
     let notify = Arc::new(Notify::new());
 
-    struct PanickingWaker(Arc<Notify>);
+    struct PanickingWaker(#[allow(dead_code)] Arc<Notify>);
 
     impl ArcWake for PanickingWaker {
         fn wake_by_ref(_arc_self: &Arc<Self>) {

tokio/src/sync/tests/semaphore_batch.rs

@@ -268,7 +268,7 @@ fn release_permits_at_drop() {
 
     let sem = Arc::new(Semaphore::new(1));
 
-    struct ReleaseOnDrop(Option<OwnedSemaphorePermit>);
+    struct ReleaseOnDrop(#[allow(dead_code)] Option<OwnedSemaphorePermit>);
 
     impl ArcWake for ReleaseOnDrop {
         fn wake_by_ref(_arc_self: &Arc<Self>) {}

tokio/src/util/markers.rs

@@ -1,8 +1,8 @@
 /// Marker for types that are `Sync` but not `Send`
-pub(crate) struct SyncNotSend(*mut ());
+pub(crate) struct SyncNotSend(#[allow(dead_code)] *mut ());
 
 unsafe impl Sync for SyncNotSend {}
 
 cfg_rt! {
-    pub(crate) struct NotSendOrSync(*mut ());
+    pub(crate) struct NotSendOrSync(#[allow(dead_code)] *mut ());
 }