chore: fix up dead code warnings with loom

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

src/mpsc/async_impl.rs

@@ -78,6 +78,7 @@ feature! {
 /// }
 /// ```
 /// [`split`]: StaticChannel::split
+#[cfg_attr(all(loom, test), allow(dead_code))]
 pub struct StaticChannel<T, const CAPACITY: usize> {
     core: ChannelCore<Waker>,
     slots: [Slot<T>; CAPACITY],

src/mpsc/sync.rs

@@ -77,6 +77,7 @@ pub struct Receiver<T> {
 ///
 /// [async]: crate::mpsc::StaticChannel
 /// [`split`]: StaticChannel::split
+#[cfg_attr(all(loom, test), allow(dead_code))]
 pub struct StaticChannel<T, const CAPACITY: usize> {
     core: ChannelCore<Thread>,
     slots: [Slot<T>; CAPACITY],

src/mpsc/tests/mpsc_async.rs

@@ -1,7 +1,6 @@
 use super::*;
 use crate::{
     loom::{self, alloc::Track, future, thread},
-    ThingBuf,
 };
 
 #[test]

src/mpsc/tests/mpsc_sync.rs

@@ -1,8 +1,5 @@
 use super::*;
-use crate::{
-    loom::{self, alloc::Track, thread},
-    ThingBuf,
-};
+use crate::loom::{self, alloc::Track, thread};
 
 #[test]
 // This test currently fails because `loom` implements the wrong semantics for

src/wait/queue.rs

@@ -3,10 +3,7 @@ use crate::{
         atomic::{AtomicUsize, Ordering::*},
         cell::UnsafeCell,
     },
-    util::{
-        mutex::{self, Mutex},
-        CachePadded,
-    },
+    util::{mutex::Mutex, CachePadded},
     wait::{Notify, WaitResult},
 };
 
@@ -172,7 +169,7 @@ impl<T> WaitQueue<T> {
     pub(crate) const fn new() -> Self {
         Self {
             state: CachePadded(AtomicUsize::new(EMPTY)),
-            list: mutex::const_mutex(List::new()),
+            list: crate::util::mutex::const_mutex(List::new()),
         }
     }
 }