time: implement FusedStream for IntervalStream (#7854)

tokio-stream/src/wrappers/interval.rs

@@ -1,4 +1,5 @@
 use crate::Stream;
+use futures_core::stream::FusedStream;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 use tokio::time::{Instant, Interval};
@@ -57,6 +58,12 @@ impl Stream for IntervalStream {
     }
 }
 
+impl FusedStream for IntervalStream {
+    fn is_terminated(&self) -> bool {
+        false
+    }
+}
+
 impl AsRef<Interval> for IntervalStream {
     fn as_ref(&self) -> &Interval {
         &self.inner

tokio-stream/tests/stream_fuse.rs

@@ -48,3 +48,15 @@ async fn basic_usage() {
     assert_eq!(stream.next().await, None);
     assert_eq!(stream.size_hint(), (0, Some(0)));
 }
+
+#[tokio::test]
+#[cfg(feature = "time")]
+async fn interval_stream_is_never_terminated() {
+    use futures_core::stream::FusedStream;
+    use tokio_stream::wrappers::IntervalStream;
+
+    let interval = tokio::time::interval(std::time::Duration::from_millis(1));
+    let stream = IntervalStream::new(interval);
+
+    assert!(!stream.is_terminated());
+}