No need for a custom impl for FromIter for DoubleEndedStream

src/stream/double_ended_stream/from_iter.rs

@@ -1,57 +0,0 @@
-use crate::stream::Stream;
-
-use std::pin::Pin;
-use std::task::{Context, Poll};
-use crate::stream::DoubleEndedStream;
-
-/// A double-ended stream that was created from iterator.
-///
-/// This stream is created by the [`from_iter`] function.
-/// See it documentation for more.
-///
-/// [`from_iter`]: fn.from_iter.html
-#[derive(Debug)]
-pub struct FromIter<T> {
-    inner: Vec<T>,
-}
-
-/// Converts an iterator into a double-ended stream.
-///
-/// # Examples
-///
-/// ```
-/// # async_std::task::block_on(async {
-/// #
-/// use async_std::stream::double_ended_stream::{self, DoubleEndedStream};
-///
-/// let mut s = double_ended_stream::from_iter(vec![0, 1, 2, 3]);
-///
-/// assert_eq!(s.next_back().await, Some(3));
-/// assert_eq!(s.next_back().await, Some(2));
-/// assert_eq!(s.next_back().await, Some(1));
-/// assert_eq!(s.next_back().await, Some(0));
-/// assert_eq!(s.next_back().await, None);
-/// #
-/// # })
-/// ```
-pub fn from_iter<I: IntoIterator>(iter: I) -> FromIter<I::Item> {
-    FromIter { inner: iter.into_iter().collect() }
-}
-
-impl<T> Unpin for FromIter<T> {}
-
-impl<T> Stream for FromIter<T> {
-    type Item = T;
-    fn poll_next(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        if self.inner.len() > 0 {
-            return Poll::Ready(Some(self.inner.remove(0)));
-        }
-        return Poll::Ready(None);
-    }
-}
-
-impl<T> DoubleEndedStream for FromIter<T> {
-    fn poll_next_back(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
-        Poll::Ready(self.inner.pop())
-    }
-}

src/stream/double_ended_stream/mod.rs

@@ -3,14 +3,12 @@ use crate::stream::Stream;
 use std::pin::Pin;
 use std::task::{Context, Poll};
 
-mod from_iter;
 mod next_back;
 mod nth_back;
 mod rfind;
 mod rfold;
 mod try_rfold;
 
-pub use from_iter::{from_iter, FromIter};
 use next_back::NextBackFuture;
 use nth_back::NthBackFuture;
 use rfind::RFindFuture;

src/stream/from_iter.rs

@@ -3,6 +3,8 @@ use std::pin::Pin;
 use pin_project_lite::pin_project;
 
 use crate::stream::Stream;
+#[cfg(feature = "unstable")]
+use crate::stream::double_ended_stream::DoubleEndedStream;
 use crate::task::{Context, Poll};
 
 pin_project! {
@@ -51,3 +53,10 @@ impl<I: Iterator> Stream for FromIter<I> {
         Poll::Ready(self.iter.next())
     }
 }
+
+#[cfg(feature = "unstable")]
+impl<T: DoubleEndedIterator> DoubleEndedStream for FromIter<T> {
+    fn poll_next_back(mut self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<Option<T::Item>> {
+        Poll::Ready(self.iter.next_back())
+    }
+}