use Waker::noop instead of defining our own Waker

Author: RalfJung

tests/pass/async-fn.rs

@@ -1,4 +1,5 @@
 #![feature(never_type)]
+#![feature(noop_waker)]
 
 use std::future::Future;
 
@@ -58,17 +59,9 @@ async fn hello_world() {
 }
 
 fn run_fut<T>(fut: impl Future<Output = T>) -> T {
-    use std::sync::Arc;
-    use std::task::{Context, Poll, Wake, Waker};
+    use std::task::{Context, Poll, Waker};
 
-    struct MyWaker;
-    impl Wake for MyWaker {
-        fn wake(self: Arc<Self>) {
-            unimplemented!()
-        }
-    }
-
-    let waker = Waker::from(Arc::new(MyWaker));
+    let waker = Waker::noop();
     let mut context = Context::from_waker(&waker);
 
     let mut pinned = Box::pin(fut);

tests/pass/dyn-star.rs

@@ -1,6 +1,7 @@
 #![feature(dyn_star)]
 #![allow(incomplete_features)]
 #![feature(custom_inner_attributes)]
+#![feature(noop_waker)]
 // rustfmt destroys `dyn* Trait` syntax
 #![rustfmt::skip]
 
@@ -89,25 +90,10 @@ fn dispatch_on_pin_mut() {
     use std::pin::Pin;
     use std::task::*;
 
-    pub fn noop_waker() -> Waker {
-        let raw = RawWaker::new(std::ptr::null(), &NOOP_WAKER_VTABLE);
-
-        // SAFETY: the contracts for RawWaker and RawWakerVTable are upheld
-        unsafe { Waker::from_raw(raw) }
-    }
-
-    const NOOP_WAKER_VTABLE: RawWakerVTable = RawWakerVTable::new(noop_clone, noop, noop, noop);
-
-    unsafe fn noop_clone(_p: *const ()) -> RawWaker {
-        RawWaker::new(std::ptr::null(), &NOOP_WAKER_VTABLE)
-    }
-
-    unsafe fn noop(_p: *const ()) {}
-
     let mut fut = async_main();
 
     // Poll loop, just to test the future...
-    let waker = noop_waker();
+    let waker = Waker::noop();
     let ctx = &mut Context::from_waker(&waker);
 
     loop {

tests/pass/future-self-referential.rs

@@ -1,5 +1,6 @@
 //@revisions: stack tree
 //@[tree]compile-flags: -Zmiri-tree-borrows
+#![feature(noop_waker)]
 
 use std::future::*;
 use std::marker::PhantomPinned;
@@ -29,19 +30,6 @@ impl Future for Delay {
     }
 }
 
-fn mk_waker() -> Waker {
-    use std::sync::Arc;
-
-    struct MyWaker;
-    impl Wake for MyWaker {
-        fn wake(self: Arc<Self>) {
-            unimplemented!()
-        }
-    }
-
-    Waker::from(Arc::new(MyWaker))
-}
-
 async fn do_stuff() {
     (&mut Delay::new(1)).await;
 }
@@ -89,7 +77,7 @@ impl Future for DoStuff {
 }
 
 fn run_fut<T>(fut: impl Future<Output = T>) -> T {
-    let waker = mk_waker();
+    let waker = Waker::noop();
     let mut context = Context::from_waker(&waker);
 
     let mut pinned = pin!(fut);
@@ -102,7 +90,7 @@ fn run_fut<T>(fut: impl Future<Output = T>) -> T {
 }
 
 fn self_referential_box() {
-    let waker = mk_waker();
+    let waker = Waker::noop();
     let cx = &mut Context::from_waker(&waker);
 
     async fn my_fut() -> i32 {

tests/pass/issues/issue-miri-2068.rs

@@ -1,19 +1,13 @@
-use core::future::Future;
-use core::pin::Pin;
-use core::task::{Context, Poll};
+#![feature(noop_waker)]
 
-use std::sync::Arc;
-
-struct NopWaker;
-
-impl std::task::Wake for NopWaker {
-    fn wake(self: Arc<Self>) {}
-}
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll, Waker};
 
 pub fn fuzzing_block_on<O, F: Future<Output = O>>(fut: F) -> O {
     let mut fut = std::pin::pin!(fut);
-    let waker = std::task::Waker::from(Arc::new(NopWaker));
-    let mut context = std::task::Context::from_waker(&waker);
+    let waker = Waker::noop();
+    let mut context = Context::from_waker(&waker);
     loop {
         match fut.as_mut().poll(&mut context) {
             Poll::Ready(v) => return v,

tests/pass/move-data-across-await-point.rs

@@ -1,3 +1,4 @@
+#![feature(noop_waker)]
 use std::future::Future;
 use std::ptr;
 
@@ -53,17 +54,9 @@ fn data_moved() {
 }
 
 fn run_fut<T>(fut: impl Future<Output = T>) -> T {
-    use std::sync::Arc;
-    use std::task::{Context, Poll, Wake, Waker};
+    use std::task::{Context, Poll, Waker};
 
-    struct MyWaker;
-    impl Wake for MyWaker {
-        fn wake(self: Arc<Self>) {
-            unimplemented!()
-        }
-    }
-
-    let waker = Waker::from(Arc::new(MyWaker));
+    let waker = Waker::noop();
     let mut context = Context::from_waker(&waker);
 
     let mut pinned = Box::pin(fut);