Implement additional traits for iter::Once/Empty

Also changed the stability feature on them.

Implement Default for iter::Once/Empty

Implement additional traits for iter::Once/Empty

Author: XMPPwocky

src/libcore/iter.rs

@@ -3031,40 +3031,95 @@ pub fn repeat<T: Clone>(elt: T) -> Repeat<T> {
 }
 
 /// An iterator that yields nothing.
-#[unstable(feature="core", reason = "new addition")]
+#[unstable(feature="iter_empty", reason = "new addition")]
 pub struct Empty<T>(marker::PhantomData<T>);
 
+#[unstable(feature="iter_empty", reason = "new addition")]
 impl<T> Iterator for Empty<T> {
     type Item = T;
 
     fn next(&mut self) -> Option<T> {
         None
     }
+    
+    fn size_hint(&self) -> (usize, Option<usize>){
+        (0, Some(0))
+    }
+}
+
+#[unstable(feature="iter_empty", reason = "new addition")]
+impl<T> DoubleEndedIterator for Empty<T> {
+    fn next_back(&mut self) -> Option<T> {
+        None
+    }
+}
+
+#[unstable(feature="iter_empty", reason = "new addition")]
+impl<T> ExactSizeIterator for Empty<T> {
+    fn len(&self) -> usize {
+        0 
+    }
+}
+
+// not #[derive] because that adds a Clone bound on T,
+// which isn't necessary.
+#[unstable(feature="iter_empty", reason = "new addition")]
+impl<T> Clone for Empty<T> {
+    fn clone(&self) -> Empty<T> {
+        Empty(marker::PhantomData)
+    }
+}
+
+// not #[derive] because that adds a Default bound on T,
+// which isn't necessary.
+#[unstable(feature="iter_empty", reason = "new addition")]
+impl<T> Default for Empty<T> {
+    fn default() -> Empty<T> {
+        Empty(marker::PhantomData)
+    }
 }
 
 /// Creates an iterator that yields nothing.
-#[unstable(feature="core", reason = "new addition")]
+#[unstable(feature="iter_empty", reason = "new addition")]
 pub fn empty<T>() -> Empty<T> {
     Empty(marker::PhantomData)
 }
 
-
 /// An iterator that yields an element exactly once.
-#[unstable(feature="core", reason = "new addition")]
+#[unstable(feature="iter_once", reason = "new addition")]
 pub struct Once<T> {
     inner: ::option::IntoIter<T>
 }
 
+#[unstable(feature="iter_once", reason = "new addition")]
 impl<T> Iterator for Once<T> {
     type Item = T;
 
     fn next(&mut self) -> Option<T> {
         self.inner.next()
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) { 
+        self.inner.size_hint()
+    }
+}
+
+#[unstable(feature="iter_once", reason = "new addition")]
+impl<T> DoubleEndedIterator for Once<T> {
+    fn next_back(&mut self) -> Option<T> {
+        self.inner.next_back()
+    }
+}
+
+#[unstable(feature="iter_once", reason = "new addition")]
+impl<T> ExactSizeIterator for Once<T> {
+    fn len(&self) -> usize {
+        self.inner.len()
+    }
 }
 
 /// Creates an iterator that yields an element exactly once.
-#[unstable(feature="core", reason = "new addition")]
+#[unstable(feature="iter_once", reason = "new addition")]
 pub fn once<T>(value: T) -> Once<T> {
     Once { inner: Some(value).into_iter() }
 }

src/libcore/lib.rs

@@ -167,6 +167,7 @@ mod core {
     pub use marker;
     pub use option;
     pub use iter;
+    pub use default;
 }
 
 #[doc(hidden)]

src/libcoretest/lib.rs

@@ -24,6 +24,8 @@
 #![feature(step_by)]
 #![feature(slice_patterns)]
 #![feature(float_from_str_radix)]
+#![feature(iter_empty)]
+#![feature(iter_once)]
 
 extern crate core;
 extern crate test;