auto merge of #19060 : Gankro/rust/super-cloned, r=aturon

Edit: whoops, didn't mean to hit post.

Anyway, this is something I tried to do when I first implemented cloned, but couldn't figure out. Somewhere between then and the PR actually landing, we got Deref of references, so now this works! :tada: 

Also turns out the test for the functionality was never marked as a #[test]. Oops!

Also added a Cloned iterator adaptor. If this isn't desirable, it can be taken out of the PR (seperate commits).

2 files changed, 45 insertions, 4 deletions

diff --git a/src/libcore/iter.rs b/src/libcore/iter.rs
index 93d8d7d6e48..3b62c8da1eb 100644
--- a/src/libcore/iter.rs
+++ b/src/libcore/iter.rs
@@ -65,9 +65,10 @@ use cmp;
 use cmp::Ord;
 use mem;
 use num::{ToPrimitive, Int};
-use ops::Add;
+use ops::{Add, Deref};
 use option::{Option, Some, None};
 use uint;
+
 #[deprecated = "renamed to Extend"] pub use self::Extend as Extendable;
 
 /// Conversion from an `Iterator`
@@ -1021,6 +1022,44 @@ impl<T: Clone> MinMaxResult<T> {
     }
 }
 
+/// A trait for iterators that contain cloneable elements
+pub trait CloneIteratorExt<A> {
+    /// Creates an iterator that clones the elements it yields. Useful for converting an
+    /// Iterator<&T> to an Iterator<T>.
+    fn cloned(self) -> Cloned<Self>;
+}
+
+
+impl<A: Clone, D: Deref<A>, I: Iterator<D>> CloneIteratorExt<A> for I {
+    fn cloned(self) -> Cloned<I> {
+        Cloned { it: self }
+    }
+}
+
+/// An iterator that clones the elements of an underlying iterator
+pub struct Cloned<I> {
+    it: I,
+}
+
+impl<A: Clone, D: Deref<A>, I: Iterator<D>> Iterator<A> for Cloned<I> {
+    fn next(&mut self) -> Option<A> {
+        self.it.next().cloned()
+    }
+
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        self.it.size_hint()
+    }
+}
+
+impl<A: Clone, D: Deref<A>, I: DoubleEndedIterator<D>>
+        DoubleEndedIterator<A> for Cloned<I> {
+    fn next_back(&mut self) -> Option<A> {
+        self.it.next_back().cloned()
+    }
+}
+
+impl<A: Clone, D: Deref<A>, I: ExactSize<D>> ExactSize<A> for Cloned<I> {}
+
 /// A trait for iterators that are cloneable.
 pub trait CloneableIterator {
     /// Repeats an iterator endlessly
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 5b1590518f8..19938973037 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -153,6 +153,7 @@ use result::{Result, Ok, Err};
 use slice;
 use slice::AsSlice;
 use clone::Clone;
+use ops::Deref;
 
 // Note that this is not a lang item per se, but it has a hidden dependency on
 // `Iterator`, which is one. The compiler assumes that the `next` method of
@@ -694,11 +695,12 @@ impl<T> Option<T> {
     }
 }
 
-impl<'a, T: Clone> Option<&'a T> {
-    /// Maps an Option<&T> to an Option<T> by cloning the contents of the Option<&T>.
+impl<'a, T: Clone, D: Deref<T>> Option<D> {
+    /// Maps an Option<D> to an Option<T> by dereffing and cloning the contents of the Option.
+    /// Useful for converting an Option<&T> to an Option<T>.
     #[unstable = "recently added as part of collections reform"]
     pub fn cloned(self) -> Option<T> {
-        self.map(|t| t.clone())
+        self.map(|t| t.deref().clone())
     }
 }