impl FusedStream for stream::{Empty, Pending} (#1693)

impl FusedStream for stream::{Empty, Pending}

Pending is never returning Poll::Ready.

Author: taiki-e

futures-util/src/future/pending.rs

@@ -12,7 +12,7 @@ pub struct Pending<T> {
 
 impl<T> FusedFuture for Pending<T> {
     fn is_terminated(&self) -> bool {
-        false
+        true
     }
 }
 

futures-util/src/stream/empty.rs

@@ -1,6 +1,6 @@
 use core::marker::PhantomData;
 use core::pin::Pin;
-use futures_core::stream::Stream;
+use futures_core::stream::{FusedStream, Stream};
 use futures_core::task::{Context, Poll};
 
 /// Stream for the [`empty`] function.
@@ -21,6 +21,12 @@ pub fn empty<T>() -> Empty<T> {
 
 impl<T> Unpin for Empty<T> {}
 
+impl<T> FusedStream for Empty<T> {
+    fn is_terminated(&self) -> bool {
+        true
+    }
+}
+
 impl<T> Stream for Empty<T> {
     type Item = T;
 

futures-util/src/stream/pending.rs

@@ -1,8 +1,7 @@
 use core::marker;
 use core::pin::Pin;
-
-use futures_core::{Stream, Poll};
-use futures_core::task;
+use futures_core::stream::{FusedStream, Stream};
+use futures_core::task::{Context, Poll};
 
 /// Stream for the [`pending()`] function.
 #[derive(Debug)]
@@ -18,10 +17,16 @@ pub fn pending<T>() -> Pending<T> {
     Pending { _data: marker::PhantomData }
 }
 
+impl<T> FusedStream for Pending<T> {
+    fn is_terminated(&self) -> bool {
+        true
+    }
+}
+
 impl<T> Stream for Pending<T> {
     type Item = T;
 
-    fn poll_next(self: Pin<&mut Self>, _: &mut task::Context<'_>) -> Poll<Option<Self::Item>> {
+    fn poll_next(self: Pin<&mut Self>, _: &mut Context<'_>) -> Poll<Option<Self::Item>> {
         Poll::Pending
     }
 }