feat: Implement From<Unparker> for Waker

This allows Wakers to be created in an allocation-free manner.

.github/workflows/ci.yml

@@ -54,7 +54,7 @@ jobs:
       matrix:
         # When updating this, the reminder to update the minimum supported
         # Rust version in Cargo.toml.
-        rust: ['1.39']
+        rust: ['1.51']
     steps:
       - uses: actions/checkout@v4
       - name: Install Rust

Cargo.toml

@@ -9,7 +9,7 @@ authors = [
   "The Rust Project Developers",
 ]
 edition = "2018"
-rust-version = "1.39"
+rust-version = "1.51"
 description = "Thread parking and unparking"
 license = "Apache-2.0 OR MIT"
 repository = "https://github.com/smol-rs/parking"

src/lib.rs

@@ -47,6 +47,8 @@ use loom::sync;
 use std::cell::Cell;
 use std::fmt;
 use std::marker::PhantomData;
+use std::sync::Arc;
+use std::task::{Wake, Waker};
 use std::time::Duration;
 
 #[cfg(not(all(loom, feature = "loom")))]
@@ -54,7 +56,7 @@ use std::time::Instant;
 
 use sync::atomic::AtomicUsize;
 use sync::atomic::Ordering::SeqCst;
-use sync::{Arc, Condvar, Mutex};
+use sync::{Condvar, Mutex};
 
 /// Creates a parker and an associated unparker.
 ///
@@ -304,6 +306,12 @@ impl Clone for Unparker {
     }
 }
 
+impl From<Unparker> for Waker {
+    fn from(up: Unparker) -> Self {
+        Waker::from(up.inner)
+    }
+}
+
 const EMPTY: usize = 0;
 const PARKED: usize = 1;
 const NOTIFIED: usize = 2;
@@ -416,3 +424,15 @@ impl Inner {
         true
     }
 }
+
+impl Wake for Inner {
+    #[inline]
+    fn wake(self: Arc<Self>) {
+        self.unpark();
+    }
+
+    #[inline]
+    fn wake_by_ref(self: &Arc<Self>) {
+        self.unpark();
+    }
+}