feat: add forget method to semaphore guards

src/semaphore.rs

@@ -1,5 +1,6 @@
 use core::fmt;
 use core::pin::Pin;
+use core::ptr::addr_of_mut;
 use core::sync::atomic::{AtomicUsize, Ordering};
 use core::task::Poll;
 
@@ -337,6 +338,14 @@ impl EventListenerFuture for AcquireArcInner {
 #[derive(Debug)]
 pub struct SemaphoreGuard<'a>(&'a Semaphore);
 
+impl SemaphoreGuard<'_> {
+    /// Drops the guard _without_ releasing the acquired permit.
+    #[inline]
+    pub fn forget(self) {
+        let _ = core::mem::ManuallyDrop::new(self);
+    }
+}
+
 impl Drop for SemaphoreGuard<'_> {
     fn drop(&mut self) {
         self.0.count.fetch_add(1, Ordering::AcqRel);
@@ -349,6 +358,19 @@ impl Drop for SemaphoreGuard<'_> {
 #[derive(Debug)]
 pub struct SemaphoreGuardArc(Arc<Semaphore>);
 
+impl SemaphoreGuardArc {
+    /// Drops the guard _without_ releasing the acquired permit.
+    /// (Will still decrement the `Arc` reference count.)
+    #[inline]
+    pub fn forget(self) {
+        let mut manual = core::mem::ManuallyDrop::new(self);
+
+        // Drop the inner `Arc` in order to decrement the reference count.
+        // SAFETY: `manual` not used after this
+        let _arc = unsafe { addr_of_mut!(manual.0).read() };
+    }
+}
+
 impl Drop for SemaphoreGuardArc {
     fn drop(&mut self) {
         self.0.count.fetch_add(1, Ordering::AcqRel);