Fix various CI errors

Fixes the following issues:

- Failed to build on MSRV due to Unpin bound
- Failed to build on no_std, as I didn't import Box
- Failed to build on portable-atomic, as Arc didn't implement Unpin

Cargo.toml

@@ -21,7 +21,7 @@ portable-atomic = ["portable-atomic-util", "portable_atomic_crate"]
 
 [dependencies]
 parking = { version = "2.0.0", optional = true }
-portable-atomic-util = { version = "0.1.1", default-features = false, optional = true, features = ["alloc"] }
+portable-atomic-util = { version = "0.1.2", default-features = false, optional = true, features = ["alloc"] }
 
 [dependencies.portable_atomic_crate]
 package = "portable-atomic"

src/lib.rs

@@ -80,11 +80,11 @@ mod notify;
 
 use alloc::boxed::Box;
 
+use core::borrow::Borrow;
 use core::fmt;
 use core::future::Future;
 use core::marker::PhantomPinned;
 use core::mem::ManuallyDrop;
-use core::ops::Deref;
 use core::pin::Pin;
 use core::ptr;
 use core::task::{Context, Poll, Waker};
@@ -99,7 +99,7 @@ use sync::{Arc, WithMut};
 
 pub use notify::{Additional, IntoNotification, Notification, Notify, Tag, TagWith};
 
-/// Useful trait for listeners.
+/// Useful traits for notifications.
 pub mod prelude {
     pub use crate::{IntoNotification, Notification};
 }
@@ -129,7 +129,7 @@ struct Inner<T> {
     list: sys::List<T>,
 }
 
-impl<T: Unpin> Inner<T> {
+impl<T> Inner<T> {
     fn new() -> Self {
         Self {
             notified: AtomicUsize::new(core::usize::MAX),
@@ -180,14 +180,14 @@ impl<T> fmt::Debug for Event<T> {
     }
 }
 
-impl<T: Unpin> Default for Event<T> {
+impl<T> Default for Event<T> {
     #[inline]
     fn default() -> Self {
         Self::with_tag()
     }
 }
 
-impl<T: Unpin> Event<T> {
+impl<T> Event<T> {
     /// Creates a new `Event` with a tag type.
     ///
     /// # Examples
@@ -347,7 +347,7 @@ impl<T: Unpin> Event<T> {
 
         if let Some(inner) = self.try_inner() {
             let limit = if notify.is_additional() {
-                usize::MAX
+                core::usize::MAX
             } else {
                 notify.count()
             };
@@ -600,15 +600,15 @@ impl<T> Drop for Event<T> {
 /// If a notified listener is dropped without receiving a notification, dropping will notify
 /// another active listener. Whether one *additional* listener will be notified depends on what
 /// kind of notification was delivered.
-pub struct EventListener<T: Unpin = ()>(Listener<T, Arc<Inner<T>>>);
+pub struct EventListener<T = ()>(Listener<T, Arc<Inner<T>>>);
 
-impl<T: Unpin> fmt::Debug for EventListener<T> {
+impl<T> fmt::Debug for EventListener<T> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.write_str("EventListener { .. }")
     }
 }
 
-impl<T: Unpin> EventListener<T> {
+impl<T> EventListener<T> {
     /// Create a new `EventListener` that will wait for a notification from the given [`Event`].
     pub fn new(event: &Event<T>) -> Self {
         let inner = event.inner();
@@ -762,15 +762,15 @@ impl<T: Unpin> EventListener<T> {
     }
 }
 
-impl<T: Unpin> Future for EventListener<T> {
+impl<T> Future for EventListener<T> {
     type Output = T;
 
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         self.listener().poll_internal(cx)
     }
 }
 
-struct Listener<T: Unpin, B: Deref<Target = Inner<T>> + Unpin> {
+struct Listener<T, B: Borrow<Inner<T>> + Unpin> {
     /// The reference to the original event.
     event: B,
 
@@ -781,10 +781,10 @@ struct Listener<T: Unpin, B: Deref<Target = Inner<T>> + Unpin> {
     _pin: PhantomPinned,
 }
 
-unsafe impl<T: Send + Unpin, B: Deref<Target = Inner<T>> + Unpin + Send> Send for Listener<T, B> {}
-unsafe impl<T: Send + Unpin, B: Deref<Target = Inner<T>> + Unpin + Sync> Sync for Listener<T, B> {}
+unsafe impl<T: Send, B: Borrow<Inner<T>> + Unpin + Send> Send for Listener<T, B> {}
+unsafe impl<T: Send, B: Borrow<Inner<T>> + Unpin + Sync> Sync for Listener<T, B> {}
 
-impl<T: Unpin, B: Deref<Target = Inner<T>> + Unpin> Listener<T, B> {
+impl<T, B: Borrow<Inner<T>> + Unpin> Listener<T, B> {
     /// Pin-project this listener.
     fn project(self: Pin<&mut Self>) -> (&Inner<T>, Pin<&mut Option<sys::Listener<T>>>) {
         // SAFETY: `event` is `Unpin`, and `listener`'s pin status is preserved
@@ -793,7 +793,7 @@ impl<T: Unpin, B: Deref<Target = Inner<T>> + Unpin> Listener<T, B> {
                 event, listener, ..
             } = self.get_unchecked_mut();
 
-            (&*event, Pin::new_unchecked(listener))
+            ((*event).borrow(), Pin::new_unchecked(listener))
         }
     }
 
@@ -910,7 +910,7 @@ impl<T: Unpin, B: Deref<Target = Inner<T>> + Unpin> Listener<T, B> {
     }
 }
 
-impl<T: Unpin, B: Deref<Target = Inner<T>> + Unpin> Drop for Listener<T, B> {
+impl<T, B: Borrow<Inner<T>> + Unpin> Drop for Listener<T, B> {
     fn drop(&mut self) {
         // If we're being dropped, we need to remove ourself from the list.
         let (inner, listener) = unsafe { Pin::new_unchecked(self).project() };
@@ -949,6 +949,7 @@ impl<T> State<T> {
     }
 
     /// If this state was notified, return the tag associated with the notification.
+    #[allow(unused)]
     fn notified(self) -> Option<T> {
         match self {
             Self::Notified { tag, .. } => Some(tag),

src/no_std.rs

@@ -31,9 +31,10 @@ use core::num::NonZeroUsize;
 use core::ops;
 use core::pin::Pin;
 
+use alloc::boxed::Box;
 use alloc::vec::Vec;
 
-impl<T: Unpin> crate::Inner<T> {
+impl<T> crate::Inner<T> {
     /// Locks the list.
     fn try_lock(&self) -> Option<ListGuard<'_, T>> {
         self.list.inner.try_lock().map(|guard| ListGuard {
@@ -218,7 +219,7 @@ pub(crate) struct List<T> {
     queue: Queue<T>,
 }
 
-impl<T: Unpin> List<T> {
+impl<T> List<T> {
     pub(super) fn new() -> List<T> {
         List {
             inner: Mutex::new(ListenerSlab::new()),
@@ -228,15 +229,15 @@ impl<T: Unpin> List<T> {
 }
 
 /// The guard returned by [`Inner::lock`].
-pub(crate) struct ListGuard<'a, T: Unpin> {
+pub(crate) struct ListGuard<'a, T> {
     /// Reference to the inner state.
     pub(crate) inner: &'a crate::Inner<T>,
 
     /// The locked list.
     pub(crate) guard: Option<MutexGuard<'a, ListenerSlab<T>>>,
 }
 
-impl<T: Unpin> ListGuard<'_, T> {
+impl<T> ListGuard<'_, T> {
     #[cold]
     fn process_nodes_slow(
         &mut self,
@@ -254,21 +255,21 @@ impl<T: Unpin> ListGuard<'_, T> {
     }
 }
 
-impl<T: Unpin> ops::Deref for ListGuard<'_, T> {
+impl<T> ops::Deref for ListGuard<'_, T> {
     type Target = ListenerSlab<T>;
 
     fn deref(&self) -> &Self::Target {
         self.guard.as_ref().unwrap()
     }
 }
 
-impl<T: Unpin> ops::DerefMut for ListGuard<'_, T> {
+impl<T> ops::DerefMut for ListGuard<'_, T> {
     fn deref_mut(&mut self) -> &mut Self::Target {
         self.guard.as_mut().unwrap()
     }
 }
 
-impl<T: Unpin> Drop for ListGuard<'_, T> {
+impl<T> Drop for ListGuard<'_, T> {
     fn drop(&mut self) {
         let Self { inner, guard } = self;
         let mut list = guard.take().unwrap();
@@ -443,7 +444,7 @@ pub(crate) struct ListenerSlab<T> {
     first_empty: NonZeroUsize,
 }
 
-impl<T: Unpin> ListenerSlab<T> {
+impl<T> ListenerSlab<T> {
     /// Create a new, empty list.
     pub(crate) fn new() -> Self {
         Self {
@@ -665,6 +666,8 @@ pub(crate) enum Listener<T> {
     _EatLifetime(PhantomData<T>),
 }
 
+impl<T> Unpin for Listener<T> {}
+
 impl<T> PartialEq for Listener<T> {
     fn eq(&self, other: &Self) -> bool {
         match (self, other) {

src/no_std/node.rs

@@ -52,7 +52,7 @@ pub(crate) struct TaskWaiting {
     entry_id: AtomicUsize,
 }
 
-impl<T: Unpin> Node<T> {
+impl<T> Node<T> {
     pub(crate) fn listener() -> (Self, Arc<TaskWaiting>) {
         // Create a new `TaskWaiting` structure.
         let task_waiting = Arc::new(TaskWaiting {

src/notify.rs

@@ -323,8 +323,8 @@ macro_rules! impl_for_numeric_types {
             type Tag = ();
             type Notify = Notify;
 
+            #[allow(unused_comparisons)]
             fn into_notification(self) -> Self::Notify {
-                #[allow(unused_comparisons)]
                 if self < 0 {
                     panic!("negative notification count");
                 }