Auto merge of #22541 - Manishearth:rollup, r=Gankro 1.0.0-alpha.2

Continued from #22520

1 files changed, 1522 insertions, 0 deletions

diff --git a/src/libcollections/linked_list.rs b/src/libcollections/linked_list.rs
new file mode 100644
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+++ b/src/libcollections/linked_list.rs
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+// Copyright 2012-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A doubly-linked list with owned nodes.
+//!
+//! The `LinkedList` allows pushing and popping elements at either end and is thus
+//! efficiently usable as a double-ended queue.
+
+// LinkedList is constructed like a singly-linked list over the field `next`.
+// including the last link being None; each Node owns its `next` field.
+//
+// Backlinks over LinkedList::prev are raw pointers that form a full chain in
+// the reverse direction.
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use core::prelude::*;
+
+use alloc::boxed::Box;
+use core::cmp::Ordering;
+use core::default::Default;
+use core::fmt;
+use core::hash::{Hasher, Hash};
+#[cfg(stage0)]
+use core::hash::Writer;
+use core::iter::{self, FromIterator, IntoIterator};
+use core::mem;
+use core::ptr;
+
+#[deprecated(since = "1.0.0", reason = "renamed to LinkedList")]
+#[unstable(feature = "collections")]
+pub use LinkedList as DList;
+
+/// A doubly-linked list.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct LinkedList<T> {
+    length: usize,
+    list_head: Link<T>,
+    list_tail: Rawlink<Node<T>>,
+}
+
+type Link<T> = Option<Box<Node<T>>>;
+
+struct Rawlink<T> {
+    p: *mut T,
+}
+
+impl<T> Copy for Rawlink<T> {}
+unsafe impl<T:'static+Send> Send for Rawlink<T> {}
+unsafe impl<T:Send+Sync> Sync for Rawlink<T> {}
+
+struct Node<T> {
+    next: Link<T>,
+    prev: Rawlink<Node<T>>,
+    value: T,
+}
+
+/// An iterator over references to the items of a `LinkedList`.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct Iter<'a, T:'a> {
+    head: &'a Link<T>,
+    tail: Rawlink<Node<T>>,
+    nelem: usize,
+}
+
+// FIXME #19839: deriving is too aggressive on the bounds (T doesn't need to be Clone).
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T> Clone for Iter<'a, T> {
+    fn clone(&self) -> Iter<'a, T> {
+        Iter {
+            head: self.head.clone(),
+            tail: self.tail,
+            nelem: self.nelem,
+        }
+    }
+}
+
+/// An iterator over mutable references to the items of a `LinkedList`.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct IterMut<'a, T:'a> {
+    list: &'a mut LinkedList<T>,
+    head: Rawlink<Node<T>>,
+    tail: Rawlink<Node<T>>,
+    nelem: usize,
+}
+
+/// An iterator over mutable references to the items of a `LinkedList`.
+#[derive(Clone)]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct IntoIter<T> {
+    list: LinkedList<T>
+}
+
+/// Rawlink is a type like Option<T> but for holding a raw pointer
+impl<T> Rawlink<T> {
+    /// Like Option::None for Rawlink
+    fn none() -> Rawlink<T> {
+        Rawlink{p: ptr::null_mut()}
+    }
+
+    /// Like Option::Some for Rawlink
+    fn some(n: &mut T) -> Rawlink<T> {
+        Rawlink{p: n}
+    }
+
+    /// Convert the `Rawlink` into an Option value
+    fn resolve_immut<'a>(&self) -> Option<&'a T> {
+        unsafe {
+            mem::transmute(self.p.as_ref())
+        }
+    }
+
+    /// Convert the `Rawlink` into an Option value
+    fn resolve<'a>(&mut self) -> Option<&'a mut T> {
+        if self.p.is_null() {
+            None
+        } else {
+            Some(unsafe { mem::transmute(self.p) })
+        }
+    }
+
+    /// Return the `Rawlink` and replace with `Rawlink::none()`
+    fn take(&mut self) -> Rawlink<T> {
+        mem::replace(self, Rawlink::none())
+    }
+}
+
+impl<T> Clone for Rawlink<T> {
+    #[inline]
+    fn clone(&self) -> Rawlink<T> {
+        Rawlink{p: self.p}
+    }
+}
+
+impl<T> Node<T> {
+    fn new(v: T) -> Node<T> {
+        Node{value: v, next: None, prev: Rawlink::none()}
+    }
+}
+
+/// Set the .prev field on `next`, then return `Some(next)`
+fn link_with_prev<T>(mut next: Box<Node<T>>, prev: Rawlink<Node<T>>)
+                  -> Link<T> {
+    next.prev = prev;
+    Some(next)
+}
+
+// private methods
+impl<T> LinkedList<T> {
+    /// Add a Node first in the list
+    #[inline]
+    fn push_front_node(&mut self, mut new_head: Box<Node<T>>) {
+        match self.list_head {
+            None => {
+                self.list_tail = Rawlink::some(&mut *new_head);
+                self.list_head = link_with_prev(new_head, Rawlink::none());
+            }
+            Some(ref mut head) => {
+                new_head.prev = Rawlink::none();
+                head.prev = Rawlink::some(&mut *new_head);
+                mem::swap(head, &mut new_head);
+                head.next = Some(new_head);
+            }
+        }
+        self.length += 1;
+    }
+
+    /// Remove the first Node and return it, or None if the list is empty
+    #[inline]
+    fn pop_front_node(&mut self) -> Option<Box<Node<T>>> {
+        self.list_head.take().map(|mut front_node| {
+            self.length -= 1;
+            match front_node.next.take() {
+                Some(node) => self.list_head = link_with_prev(node, Rawlink::none()),
+                None => self.list_tail = Rawlink::none()
+            }
+            front_node
+        })
+    }
+
+    /// Add a Node last in the list
+    #[inline]
+    fn push_back_node(&mut self, mut new_tail: Box<Node<T>>) {
+        match self.list_tail.resolve() {
+            None => return self.push_front_node(new_tail),
+            Some(tail) => {
+                self.list_tail = Rawlink::some(&mut *new_tail);
+                tail.next = link_with_prev(new_tail, Rawlink::some(tail));
+            }
+        }
+        self.length += 1;
+    }
+
+    /// Remove the last Node and return it, or None if the list is empty
+    #[inline]
+    fn pop_back_node(&mut self) -> Option<Box<Node<T>>> {
+        self.list_tail.resolve().map_or(None, |tail| {
+            self.length -= 1;
+            self.list_tail = tail.prev;
+            match tail.prev.resolve() {
+                None => self.list_head.take(),
+                Some(tail_prev) => tail_prev.next.take()
+            }
+        })
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Default for LinkedList<T> {
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn default() -> LinkedList<T> { LinkedList::new() }
+}
+
+impl<T> LinkedList<T> {
+    /// Creates an empty `LinkedList`.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn new() -> LinkedList<T> {
+        LinkedList{list_head: None, list_tail: Rawlink::none(), length: 0}
+    }
+
+    /// Moves all elements from `other` to the end of the list.
+    ///
+    /// This reuses all the nodes from `other` and moves them into `self`. After
+    /// this operation, `other` becomes empty.
+    ///
+    /// This operation should compute in O(1) time and O(1) memory.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut a = LinkedList::new();
+    /// let mut b = LinkedList::new();
+    /// a.push_back(1);
+    /// a.push_back(2);
+    /// b.push_back(3);
+    /// b.push_back(4);
+    ///
+    /// a.append(&mut b);
+    ///
+    /// for e in a.iter() {
+    ///     println!("{}", e); // prints 1, then 2, then 3, then 4
+    /// }
+    /// println!("{}", b.len()); // prints 0
+    /// ```
+    pub fn append(&mut self, other: &mut LinkedList<T>) {
+        match self.list_tail.resolve() {
+            None => {
+                self.length = other.length;
+                self.list_head = other.list_head.take();
+                self.list_tail = other.list_tail.take();
+            },
+            Some(tail) => {
+                // Carefully empty `other`.
+                let o_tail = other.list_tail.take();
+                let o_length = other.length;
+                match other.list_head.take() {
+                    None => return,
+                    Some(node) => {
+                        tail.next = link_with_prev(node, self.list_tail);
+                        self.list_tail = o_tail;
+                        self.length += o_length;
+                    }
+                }
+            }
+        }
+        other.length = 0;
+    }
+
+    /// Provides a forward iterator.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn iter(&self) -> Iter<T> {
+        Iter{nelem: self.len(), head: &self.list_head, tail: self.list_tail}
+    }
+
+    /// Provides a forward iterator with mutable references.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn iter_mut(&mut self) -> IterMut<T> {
+        let head_raw = match self.list_head {
+            Some(ref mut h) => Rawlink::some(&mut **h),
+            None => Rawlink::none(),
+        };
+        IterMut{
+            nelem: self.len(),
+            head: head_raw,
+            tail: self.list_tail,
+            list: self
+        }
+    }
+
+    /// Consumes the list into an iterator yielding elements by value.
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn into_iter(self) -> IntoIter<T> {
+        IntoIter{list: self}
+    }
+
+    /// Returns `true` if the `LinkedList` is empty.
+    ///
+    /// This operation should compute in O(1) time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    /// assert!(dl.is_empty());
+    ///
+    /// dl.push_front("foo");
+    /// assert!(!dl.is_empty());
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn is_empty(&self) -> bool {
+        self.list_head.is_none()
+    }
+
+    /// Returns the length of the `LinkedList`.
+    ///
+    /// This operation should compute in O(1) time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    ///
+    /// dl.push_front(2);
+    /// assert_eq!(dl.len(), 1);
+    ///
+    /// dl.push_front(1);
+    /// assert_eq!(dl.len(), 2);
+    ///
+    /// dl.push_back(3);
+    /// assert_eq!(dl.len(), 3);
+    ///
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn len(&self) -> usize {
+        self.length
+    }
+
+    /// Removes all elements from the `LinkedList`.
+    ///
+    /// This operation should compute in O(n) time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    ///
+    /// dl.push_front(2);
+    /// dl.push_front(1);
+    /// assert_eq!(dl.len(), 2);
+    /// assert_eq!(dl.front(), Some(&1));
+    ///
+    /// dl.clear();
+    /// assert_eq!(dl.len(), 0);
+    /// assert_eq!(dl.front(), None);
+    ///
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn clear(&mut self) {
+        *self = LinkedList::new()
+    }
+
+    /// Provides a reference to the front element, or `None` if the list is
+    /// empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    /// assert_eq!(dl.front(), None);
+    ///
+    /// dl.push_front(1);
+    /// assert_eq!(dl.front(), Some(&1));
+    ///
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn front(&self) -> Option<&T> {
+        self.list_head.as_ref().map(|head| &head.value)
+    }
+
+    /// Provides a mutable reference to the front element, or `None` if the list
+    /// is empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    /// assert_eq!(dl.front(), None);
+    ///
+    /// dl.push_front(1);
+    /// assert_eq!(dl.front(), Some(&1));
+    ///
+    /// match dl.front_mut() {
+    ///     None => {},
+    ///     Some(x) => *x = 5,
+    /// }
+    /// assert_eq!(dl.front(), Some(&5));
+    ///
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn front_mut(&mut self) -> Option<&mut T> {
+        self.list_head.as_mut().map(|head| &mut head.value)
+    }
+
+    /// Provides a reference to the back element, or `None` if the list is
+    /// empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    /// assert_eq!(dl.back(), None);
+    ///
+    /// dl.push_back(1);
+    /// assert_eq!(dl.back(), Some(&1));
+    ///
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn back(&self) -> Option<&T> {
+        self.list_tail.resolve_immut().as_ref().map(|tail| &tail.value)
+    }
+
+    /// Provides a mutable reference to the back element, or `None` if the list
+    /// is empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    /// assert_eq!(dl.back(), None);
+    ///
+    /// dl.push_back(1);
+    /// assert_eq!(dl.back(), Some(&1));
+    ///
+    /// match dl.back_mut() {
+    ///     None => {},
+    ///     Some(x) => *x = 5,
+    /// }
+    /// assert_eq!(dl.back(), Some(&5));
+    ///
+    /// ```
+    #[inline]
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn back_mut(&mut self) -> Option<&mut T> {
+        self.list_tail.resolve().map(|tail| &mut tail.value)
+    }
+
+    /// Adds an element first in the list.
+    ///
+    /// This operation should compute in O(1) time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut dl = LinkedList::new();
+    ///
+    /// dl.push_front(2);
+    /// assert_eq!(dl.front().unwrap(), &2);
+    ///
+    /// dl.push_front(1);
+    /// assert_eq!(dl.front().unwrap(), &1);
+    ///
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn push_front(&mut self, elt: T) {
+        self.push_front_node(box Node::new(elt))
+    }
+
+    /// Removes the first element and returns it, or `None` if the list is
+    /// empty.
+    ///
+    /// This operation should compute in O(1) time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut d = LinkedList::new();
+    /// assert_eq!(d.pop_front(), None);
+    ///
+    /// d.push_front(1);
+    /// d.push_front(3);
+    /// assert_eq!(d.pop_front(), Some(3));
+    /// assert_eq!(d.pop_front(), Some(1));
+    /// assert_eq!(d.pop_front(), None);
+    ///
+    /// ```
+    ///
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn pop_front(&mut self) -> Option<T> {
+        self.pop_front_node().map(|box Node{value, ..}| value)
+    }
+
+    /// Appends an element to the back of a list
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut d = LinkedList::new();
+    /// d.push_back(1);
+    /// d.push_back(3);
+    /// assert_eq!(3, *d.back().unwrap());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn push_back(&mut self, elt: T) {
+        self.push_back_node(box Node::new(elt))
+    }
+
+    /// Removes the last element from a list and returns it, or `None` if
+    /// it is empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut d = LinkedList::new();
+    /// assert_eq!(d.pop_back(), None);
+    /// d.push_back(1);
+    /// d.push_back(3);
+    /// assert_eq!(d.pop_back(), Some(3));
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn pop_back(&mut self) -> Option<T> {
+        self.pop_back_node().map(|box Node{value, ..}| value)
+    }
+
+    /// Splits the list into two at the given index. Returns everything after the given index,
+    /// including the index.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `at > len`.
+    ///
+    /// This operation should compute in O(n) time.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut d = LinkedList::new();
+    ///
+    /// d.push_front(1);
+    /// d.push_front(2);
+    /// d.push_front(3);
+    ///
+    /// let mut splitted = d.split_off(2);
+    ///
+    /// assert_eq!(splitted.pop_front(), Some(1));
+    /// assert_eq!(splitted.pop_front(), None);
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn split_off(&mut self, at: usize) -> LinkedList<T> {
+        let len = self.len();
+        assert!(at <= len, "Cannot split off at a nonexistent index");
+        if at == 0 {
+            return mem::replace(self, LinkedList::new());
+        } else if at == len {
+            return LinkedList::new();
+        }
+
+        // Below, we iterate towards the `i-1`th node, either from the start or the end,
+        // depending on which would be faster.
+        let mut split_node = if at - 1 <= len - 1 - (at - 1) {
+            let mut iter = self.iter_mut();
+            // instead of skipping using .skip() (which creates a new struct),
+            // we skip manually so we can access the head field without
+            // depending on implementation details of Skip
+            for _ in 0..at - 1 {
+                iter.next();
+            }
+            iter.head
+        }  else {
+            // better off starting from the end
+            let mut iter = self.iter_mut();
+            for _ in 0..len - 1 - (at - 1) {
+                iter.next_back();
+            }
+            iter.tail
+        };
+
+        let mut splitted_list = LinkedList {
+            list_head: None,
+            list_tail: self.list_tail,
+            length: len - at
+        };
+
+        mem::swap(&mut split_node.resolve().unwrap().next, &mut splitted_list.list_head);
+        self.list_tail = split_node;
+        self.length = at;
+
+        splitted_list
+    }
+}
+
+#[unsafe_destructor]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Drop for LinkedList<T> {
+    fn drop(&mut self) {
+        // Dissolve the linked_list in backwards direction
+        // Just dropping the list_head can lead to stack exhaustion
+        // when length is >> 1_000_000
+        let mut tail = self.list_tail;
+        loop {
+            match tail.resolve() {
+                None => break,
+                Some(prev) => {
+                    prev.next.take(); // release Box<Node<T>>
+                    tail = prev.prev;
+                }
+            }
+        }
+        self.length = 0;
+        self.list_head = None;
+        self.list_tail = Rawlink::none();
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, A> Iterator for Iter<'a, A> {
+    type Item = &'a A;
+
+    #[inline]
+    fn next(&mut self) -> Option<&'a A> {
+        if self.nelem == 0 {
+            return None;
+        }
+        self.head.as_ref().map(|head| {
+            self.nelem -= 1;
+            self.head = &head.next;
+            &head.value
+        })
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.nelem, Some(self.nelem))
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, A> DoubleEndedIterator for Iter<'a, A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<&'a A> {
+        if self.nelem == 0 {
+            return None;
+        }
+        self.tail.resolve_immut().as_ref().map(|prev| {
+            self.nelem -= 1;
+            self.tail = prev.prev;
+            &prev.value
+        })
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, A> ExactSizeIterator for Iter<'a, A> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, A> Iterator for IterMut<'a, A> {
+    type Item = &'a mut A;
+    #[inline]
+    fn next(&mut self) -> Option<&'a mut A> {
+        if self.nelem == 0 {
+            return None;
+        }
+        self.head.resolve().map(|next| {
+            self.nelem -= 1;
+            self.head = match next.next {
+                Some(ref mut node) => Rawlink::some(&mut **node),
+                None => Rawlink::none(),
+            };
+            &mut next.value
+        })
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.nelem, Some(self.nelem))
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, A> DoubleEndedIterator for IterMut<'a, A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<&'a mut A> {
+        if self.nelem == 0 {
+            return None;
+        }
+        self.tail.resolve().map(|prev| {
+            self.nelem -= 1;
+            self.tail = prev.prev;
+            &mut prev.value
+        })
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, A> ExactSizeIterator for IterMut<'a, A> {}
+
+// private methods for IterMut
+impl<'a, A> IterMut<'a, A> {
+    fn insert_next_node(&mut self, mut ins_node: Box<Node<A>>) {
+        // Insert before `self.head` so that it is between the
+        // previously yielded element and self.head.
+        //
+        // The inserted node will not appear in further iteration.
+        match self.head.resolve() {
+            None => { self.list.push_back_node(ins_node); }
+            Some(node) => {
+                let prev_node = match node.prev.resolve() {
+                    None => return self.list.push_front_node(ins_node),
+                    Some(prev) => prev,
+                };
+                let node_own = prev_node.next.take().unwrap();
+                ins_node.next = link_with_prev(node_own, Rawlink::some(&mut *ins_node));
+                prev_node.next = link_with_prev(ins_node, Rawlink::some(prev_node));
+                self.list.length += 1;
+            }
+        }
+    }
+}
+
+impl<'a, A> IterMut<'a, A> {
+    /// Inserts `elt` just after the element most recently returned by `.next()`.
+    /// The inserted element does not appear in the iteration.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut list: LinkedList<_> = vec![1, 3, 4].into_iter().collect();
+    ///
+    /// {
+    ///     let mut it = list.iter_mut();
+    ///     assert_eq!(it.next().unwrap(), &1);
+    ///     // insert `2` after `1`
+    ///     it.insert_next(2);
+    /// }
+    /// {
+    ///     let vec: Vec<_> = list.into_iter().collect();
+    ///     assert_eq!(vec, vec![1, 2, 3, 4]);
+    /// }
+    /// ```
+    #[inline]
+    #[unstable(feature = "collections",
+               reason = "this is probably better handled by a cursor type -- we'll see")]
+    pub fn insert_next(&mut self, elt: A) {
+        self.insert_next_node(box Node::new(elt))
+    }
+
+    /// Provides a reference to the next element, without changing the iterator.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::collections::LinkedList;
+    ///
+    /// let mut list: LinkedList<_> = vec![1, 2, 3].into_iter().collect();
+    ///
+    /// let mut it = list.iter_mut();
+    /// assert_eq!(it.next().unwrap(), &1);
+    /// assert_eq!(it.peek_next().unwrap(), &2);
+    /// // We just peeked at 2, so it was not consumed from the iterator.
+    /// assert_eq!(it.next().unwrap(), &2);
+    /// ```
+    #[inline]
+    #[unstable(feature = "collections",
+               reason = "this is probably better handled by a cursor type -- we'll see")]
+    pub fn peek_next(&mut self) -> Option<&mut A> {
+        if self.nelem == 0 {
+            return None
+        }
+        self.head.resolve().map(|head| &mut head.value)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A> Iterator for IntoIter<A> {
+    type Item = A;
+
+    #[inline]
+    fn next(&mut self) -> Option<A> { self.list.pop_front() }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.list.length, Some(self.list.length))
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A> DoubleEndedIterator for IntoIter<A> {
+    #[inline]
+    fn next_back(&mut self) -> Option<A> { self.list.pop_back() }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A> FromIterator<A> for LinkedList<A> {
+    fn from_iter<T: IntoIterator<Item=A>>(iter: T) -> LinkedList<A> {
+        let mut ret = DList::new();
+        ret.extend(iter);
+        ret
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> IntoIterator for LinkedList<T> {
+    type Item = T;
+    type IntoIter = IntoIter<T>;
+
+    fn into_iter(self) -> IntoIter<T> {
+        self.into_iter()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, T> IntoIterator for &'a LinkedList<T> {
+    type Item = &'a T;
+    type IntoIter = Iter<'a, T>;
+
+    fn into_iter(self) -> Iter<'a, T> {
+        self.iter()
+    }
+}
+
+impl<'a, T> IntoIterator for &'a mut LinkedList<T> {
+    type Item = &'a mut T;
+    type IntoIter = IterMut<'a, T>;
+
+    fn into_iter(mut self) -> IterMut<'a, T> {
+        self.iter_mut()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A> Extend<A> for LinkedList<A> {
+    fn extend<T: IntoIterator<Item=A>>(&mut self, iter: T) {
+        for elt in iter { self.push_back(elt); }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A: PartialEq> PartialEq for LinkedList<A> {
+    fn eq(&self, other: &LinkedList<A>) -> bool {
+        self.len() == other.len() &&
+            iter::order::eq(self.iter(), other.iter())
+    }
+
+    fn ne(&self, other: &LinkedList<A>) -> bool {
+        self.len() != other.len() ||
+            iter::order::ne(self.iter(), other.iter())
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A: Eq> Eq for LinkedList<A> {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A: PartialOrd> PartialOrd for LinkedList<A> {
+    fn partial_cmp(&self, other: &LinkedList<A>) -> Option<Ordering> {
+        iter::order::partial_cmp(self.iter(), other.iter())
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A: Ord> Ord for LinkedList<A> {
+    #[inline]
+    fn cmp(&self, other: &LinkedList<A>) -> Ordering {
+        iter::order::cmp(self.iter(), other.iter())
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A: Clone> Clone for LinkedList<A> {
+    fn clone(&self) -> LinkedList<A> {
+        self.iter().cloned().collect()
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<A: fmt::Debug> fmt::Debug for LinkedList<A> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        try!(write!(f, "LinkedList ["));
+
+        for (i, e) in self.iter().enumerate() {
+            if i != 0 { try!(write!(f, ", ")); }
+            try!(write!(f, "{:?}", *e));
+        }
+
+        write!(f, "]")
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(stage0)]
+impl<S: Writer + Hasher, A: Hash<S>> Hash<S> for LinkedList<A> {
+    fn hash(&self, state: &mut S) {
+        self.len().hash(state);
+        for elt in self {
+            elt.hash(state);
+        }
+    }
+}
+#[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(not(stage0))]
+impl<A: Hash> Hash for LinkedList<A> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.len().hash(state);
+        for elt in self {
+            elt.hash(state);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use prelude::*;
+    use std::rand;
+    use std::hash::{self, SipHasher};
+    use std::thread;
+    use test::Bencher;
+    use test;
+
+    use super::{LinkedList, Node};
+
+    pub fn check_links<T>(list: &LinkedList<T>) {
+        let mut len = 0;
+        let mut last_ptr: Option<&Node<T>> = None;
+        let mut node_ptr: &Node<T>;
+        match list.list_head {
+            None => { assert_eq!(0, list.length); return }
+            Some(ref node) => node_ptr = &**node,
+        }
+        loop {
+            match (last_ptr, node_ptr.prev.resolve_immut()) {
+                (None   , None      ) => {}
+                (None   , _         ) => panic!("prev link for list_head"),
+                (Some(p), Some(pptr)) => {
+                    assert_eq!(p as *const Node<T>, pptr as *const Node<T>);
+                }
+                _ => panic!("prev link is none, not good"),
+            }
+            match node_ptr.next {
+                Some(ref next) => {
+                    last_ptr = Some(node_ptr);
+                    node_ptr = &**next;
+                    len += 1;
+                }
+                None => {
+                    len += 1;
+                    break;
+                }
+            }
+        }
+        assert_eq!(len, list.length);
+    }
+
+    #[test]
+    fn test_basic() {
+        let mut m = LinkedList::new();
+        assert_eq!(m.pop_front(), None);
+        assert_eq!(m.pop_back(), None);
+        assert_eq!(m.pop_front(), None);
+        m.push_front(box 1);
+        assert_eq!(m.pop_front(), Some(box 1));
+        m.push_back(box 2);
+        m.push_back(box 3);
+        assert_eq!(m.len(), 2);
+        assert_eq!(m.pop_front(), Some(box 2));
+        assert_eq!(m.pop_front(), Some(box 3));
+        assert_eq!(m.len(), 0);
+        assert_eq!(m.pop_front(), None);
+        m.push_back(box 1);
+        m.push_back(box 3);
+        m.push_back(box 5);
+        m.push_back(box 7);
+        assert_eq!(m.pop_front(), Some(box 1));
+
+        let mut n = LinkedList::new();
+        n.push_front(2);
+        n.push_front(3);
+        {
+            assert_eq!(n.front().unwrap(), &3);
+            let x = n.front_mut().unwrap();
+            assert_eq!(*x, 3);
+            *x = 0;
+        }
+        {
+            assert_eq!(n.back().unwrap(), &2);
+            let y = n.back_mut().unwrap();
+            assert_eq!(*y, 2);
+            *y = 1;
+        }
+        assert_eq!(n.pop_front(), Some(0));
+        assert_eq!(n.pop_front(), Some(1));
+    }
+
+    #[cfg(test)]
+    fn generate_test() -> LinkedList<i32> {
+        list_from(&[0,1,2,3,4,5,6])
+    }
+
+    #[cfg(test)]
+    fn list_from<T: Clone>(v: &[T]) -> LinkedList<T> {
+        v.iter().cloned().collect()
+    }
+
+    #[test]
+    fn test_append() {
+        // Empty to empty
+        {
+            let mut m = LinkedList::<i32>::new();
+            let mut n = LinkedList::new();
+            m.append(&mut n);
+            check_links(&m);
+            assert_eq!(m.len(), 0);
+            assert_eq!(n.len(), 0);
+        }
+        // Non-empty to empty
+        {
+            let mut m = LinkedList::new();
+            let mut n = LinkedList::new();
+            n.push_back(2);
+            m.append(&mut n);
+            check_links(&m);
+            assert_eq!(m.len(), 1);
+            assert_eq!(m.pop_back(), Some(2));
+            assert_eq!(n.len(), 0);
+            check_links(&m);
+        }
+        // Empty to non-empty
+        {
+            let mut m = LinkedList::new();
+            let mut n = LinkedList::new();
+            m.push_back(2);
+            m.append(&mut n);
+            check_links(&m);
+            assert_eq!(m.len(), 1);
+            assert_eq!(m.pop_back(), Some(2));
+            check_links(&m);
+        }
+
+        // Non-empty to non-empty
+        let v = vec![1,2,3,4,5];
+        let u = vec![9,8,1,2,3,4,5];
+        let mut m = list_from(&v);
+        let mut n = list_from(&u);
+        m.append(&mut n);
+        check_links(&m);
+        let mut sum = v;
+        sum.push_all(&u);
+        assert_eq!(sum.len(), m.len());
+        for elt in sum {
+            assert_eq!(m.pop_front(), Some(elt))
+        }
+        assert_eq!(n.len(), 0);
+        // let's make sure it's working properly, since we
+        // did some direct changes to private members
+        n.push_back(3);
+        assert_eq!(n.len(), 1);
+        assert_eq!(n.pop_front(), Some(3));
+        check_links(&n);
+    }
+
+    #[test]
+    fn test_split_off() {
+        // singleton
+        {
+            let mut m = LinkedList::new();
+            m.push_back(1);
+
+            let p = m.split_off(0);
+            assert_eq!(m.len(), 0);
+            assert_eq!(p.len(), 1);
+            assert_eq!(p.back(), Some(&1));
+            assert_eq!(p.front(), Some(&1));
+        }
+
+        // not singleton, forwards
+        {
+            let u = vec![1,2,3,4,5];
+            let mut m = list_from(&u);
+            let mut n = m.split_off(2);
+            assert_eq!(m.len(), 2);
+            assert_eq!(n.len(), 3);
+            for elt in 1..3 {
+                assert_eq!(m.pop_front(), Some(elt));
+            }
+            for elt in 3..6 {
+                assert_eq!(n.pop_front(), Some(elt));
+            }
+        }
+        // not singleton, backwards
+        {
+            let u = vec![1,2,3,4,5];
+            let mut m = list_from(&u);
+            let mut n = m.split_off(4);
+            assert_eq!(m.len(), 4);
+            assert_eq!(n.len(), 1);
+            for elt in 1..5 {
+                assert_eq!(m.pop_front(), Some(elt));
+            }
+            for elt in 5..6 {
+                assert_eq!(n.pop_front(), Some(elt));
+            }
+        }
+
+        // no-op on the last index
+        {
+            let mut m = LinkedList::new();
+            m.push_back(1);
+
+            let p = m.split_off(1);
+            assert_eq!(m.len(), 1);
+            assert_eq!(p.len(), 0);
+            assert_eq!(m.back(), Some(&1));
+            assert_eq!(m.front(), Some(&1));
+        }
+
+    }
+
+    #[test]
+    fn test_iterator() {
+        let m = generate_test();
+        for (i, elt) in m.iter().enumerate() {
+            assert_eq!(i as i32, *elt);
+        }
+        let mut n = LinkedList::new();
+        assert_eq!(n.iter().next(), None);
+        n.push_front(4);
+        let mut it = n.iter();
+        assert_eq!(it.size_hint(), (1, Some(1)));
+        assert_eq!(it.next().unwrap(), &4);
+        assert_eq!(it.size_hint(), (0, Some(0)));
+        assert_eq!(it.next(), None);
+    }
+
+    #[test]
+    fn test_iterator_clone() {
+        let mut n = LinkedList::new();
+        n.push_back(2);
+        n.push_back(3);
+        n.push_back(4);
+        let mut it = n.iter();
+        it.next();
+        let mut jt = it.clone();
+        assert_eq!(it.next(), jt.next());
+        assert_eq!(it.next_back(), jt.next_back());
+        assert_eq!(it.next(), jt.next());
+    }
+
+    #[test]
+    fn test_iterator_double_end() {
+        let mut n = LinkedList::new();
+        assert_eq!(n.iter().next(), None);
+        n.push_front(4);
+        n.push_front(5);
+        n.push_front(6);
+        let mut it = n.iter();
+        assert_eq!(it.size_hint(), (3, Some(3)));
+        assert_eq!(it.next().unwrap(), &6);
+        assert_eq!(it.size_hint(), (2, Some(2)));
+        assert_eq!(it.next_back().unwrap(), &4);
+        assert_eq!(it.size_hint(), (1, Some(1)));
+        assert_eq!(it.next_back().unwrap(), &5);
+        assert_eq!(it.next_back(), None);
+        assert_eq!(it.next(), None);
+    }
+
+    #[test]
+    fn test_rev_iter() {
+        let m = generate_test();
+        for (i, elt) in m.iter().rev().enumerate() {
+            assert_eq!((6 - i) as i32, *elt);
+        }
+        let mut n = LinkedList::new();
+        assert_eq!(n.iter().rev().next(), None);
+        n.push_front(4);
+        let mut it = n.iter().rev();
+        assert_eq!(it.size_hint(), (1, Some(1)));
+        assert_eq!(it.next().unwrap(), &4);
+        assert_eq!(it.size_hint(), (0, Some(0)));
+        assert_eq!(it.next(), None);
+    }
+
+    #[test]
+    fn test_mut_iter() {
+        let mut m = generate_test();
+        let mut len = m.len();
+        for (i, elt) in m.iter_mut().enumerate() {
+            assert_eq!(i as i32, *elt);
+            len -= 1;
+        }
+        assert_eq!(len, 0);
+        let mut n = LinkedList::new();
+        assert!(n.iter_mut().next().is_none());
+        n.push_front(4);
+        n.push_back(5);
+        let mut it = n.iter_mut();
+        assert_eq!(it.size_hint(), (2, Some(2)));
+        assert!(it.next().is_some());
+        assert!(it.next().is_some());
+        assert_eq!(it.size_hint(), (0, Some(0)));
+        assert!(it.next().is_none());
+    }
+
+    #[test]
+    fn test_iterator_mut_double_end() {
+        let mut n = LinkedList::new();
+        assert!(n.iter_mut().next_back().is_none());
+        n.push_front(4);
+        n.push_front(5);
+        n.push_front(6);
+        let mut it = n.iter_mut();
+        assert_eq!(it.size_hint(), (3, Some(3)));
+        assert_eq!(*it.next().unwrap(), 6);
+        assert_eq!(it.size_hint(), (2, Some(2)));
+        assert_eq!(*it.next_back().unwrap(), 4);
+        assert_eq!(it.size_hint(), (1, Some(1)));
+        assert_eq!(*it.next_back().unwrap(), 5);
+        assert!(it.next_back().is_none());
+        assert!(it.next().is_none());
+    }
+
+    #[test]
+    fn test_insert_prev() {
+        let mut m = list_from(&[0,2,4,6,8]);
+        let len = m.len();
+        {
+            let mut it = m.iter_mut();
+            it.insert_next(-2);
+            loop {
+                match it.next() {
+                    None => break,
+                    Some(elt) => {
+                        it.insert_next(*elt + 1);
+                        match it.peek_next() {
+                            Some(x) => assert_eq!(*x, *elt + 2),
+                            None => assert_eq!(8, *elt),
+                        }
+                    }
+                }
+            }
+            it.insert_next(0);
+            it.insert_next(1);
+        }
+        check_links(&m);
+        assert_eq!(m.len(), 3 + len * 2);
+        assert_eq!(m.into_iter().collect::<Vec<_>>(), vec![-2,0,1,2,3,4,5,6,7,8,9,0,1]);
+    }
+
+    #[test]
+    fn test_mut_rev_iter() {
+        let mut m = generate_test();
+        for (i, elt) in m.iter_mut().rev().enumerate() {
+            assert_eq!((6 - i) as i32, *elt);
+        }
+        let mut n = LinkedList::new();
+        assert!(n.iter_mut().rev().next().is_none());
+        n.push_front(4);
+        let mut it = n.iter_mut().rev();
+        assert!(it.next().is_some());
+        assert!(it.next().is_none());
+    }
+
+    #[test]
+    fn test_send() {
+        let n = list_from(&[1,2,3]);
+        thread::spawn(move || {
+            check_links(&n);
+            let a: &[_] = &[&1,&2,&3];
+            assert_eq!(a, n.iter().collect::<Vec<_>>());
+        }).join().ok().unwrap();
+    }
+
+    #[test]
+    fn test_eq() {
+        let mut n = list_from(&[]);
+        let mut m = list_from(&[]);
+        assert!(n == m);
+        n.push_front(1);
+        assert!(n != m);
+        m.push_back(1);
+        assert!(n == m);
+
+        let n = list_from(&[2,3,4]);
+        let m = list_from(&[1,2,3]);
+        assert!(n != m);
+    }
+
+    #[test]
+    fn test_hash() {
+      let mut x = LinkedList::new();
+      let mut y = LinkedList::new();
+
+      assert!(hash::hash::<_, SipHasher>(&x) == hash::hash::<_, SipHasher>(&y));
+
+      x.push_back(1);
+      x.push_back(2);
+      x.push_back(3);
+
+      y.push_front(3);
+      y.push_front(2);
+      y.push_front(1);
+
+      assert!(hash::hash::<_, SipHasher>(&x) == hash::hash::<_, SipHasher>(&y));
+    }
+
+    #[test]
+    fn test_ord() {
+        let n = list_from(&[]);
+        let m = list_from(&[1,2,3]);
+        assert!(n < m);
+        assert!(m > n);
+        assert!(n <= n);
+        assert!(n >= n);
+    }
+
+    #[test]
+    fn test_ord_nan() {
+        let nan = 0.0f64/0.0;
+        let n = list_from(&[nan]);
+        let m = list_from(&[nan]);
+        assert!(!(n < m));
+        assert!(!(n > m));
+        assert!(!(n <= m));
+        assert!(!(n >= m));
+
+        let n = list_from(&[nan]);
+        let one = list_from(&[1.0f64]);
+        assert!(!(n < one));
+        assert!(!(n > one));
+        assert!(!(n <= one));
+        assert!(!(n >= one));
+
+        let u = list_from(&[1.0f64,2.0,nan]);
+        let v = list_from(&[1.0f64,2.0,3.0]);
+        assert!(!(u < v));
+        assert!(!(u > v));
+        assert!(!(u <= v));
+        assert!(!(u >= v));
+
+        let s = list_from(&[1.0f64,2.0,4.0,2.0]);
+        let t = list_from(&[1.0f64,2.0,3.0,2.0]);
+        assert!(!(s < t));
+        assert!(s > one);
+        assert!(!(s <= one));
+        assert!(s >= one);
+    }
+
+    #[test]
+    fn test_fuzz() {
+        for _ in 0..25 {
+            fuzz_test(3);
+            fuzz_test(16);
+            fuzz_test(189);
+        }
+    }
+
+    #[test]
+    fn test_show() {
+        let list: LinkedList<_> = (0..10).collect();
+        assert_eq!(format!("{:?}", list), "LinkedList [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]");
+
+        let list: LinkedList<_> = vec!["just", "one", "test", "more"].iter().cloned().collect();
+        assert_eq!(format!("{:?}", list), "LinkedList [\"just\", \"one\", \"test\", \"more\"]");
+    }
+
+    #[cfg(test)]
+    fn fuzz_test(sz: i32) {
+        let mut m: LinkedList<_> = LinkedList::new();
+        let mut v = vec![];
+        for i in 0..sz {
+            check_links(&m);
+            let r: u8 = rand::random();
+            match r % 6 {
+                0 => {
+                    m.pop_back();
+                    v.pop();
+                }
+                1 => {
+                    if !v.is_empty() {
+                        m.pop_front();
+                        v.remove(0);
+                    }
+                }
+                2 | 4 =>  {
+                    m.push_front(-i);
+                    v.insert(0, -i);
+                }
+                3 | 5 | _ => {
+                    m.push_back(i);
+                    v.push(i);
+                }
+            }
+        }
+
+        check_links(&m);
+
+        let mut i = 0;
+        for (a, &b) in m.into_iter().zip(v.iter()) {
+            i += 1;
+            assert_eq!(a, b);
+        }
+        assert_eq!(i, v.len());
+    }
+
+    #[bench]
+    fn bench_collect_into(b: &mut test::Bencher) {
+        let v = &[0; 64];
+        b.iter(|| {
+            let _: LinkedList<_> = v.iter().cloned().collect();
+        })
+    }
+
+    #[bench]
+    fn bench_push_front(b: &mut test::Bencher) {
+        let mut m: LinkedList<_> = LinkedList::new();
+        b.iter(|| {
+            m.push_front(0);
+        })
+    }
+
+    #[bench]
+    fn bench_push_back(b: &mut test::Bencher) {
+        let mut m: LinkedList<_> = LinkedList::new();
+        b.iter(|| {
+            m.push_back(0);
+        })
+    }
+
+    #[bench]
+    fn bench_push_back_pop_back(b: &mut test::Bencher) {
+        let mut m: LinkedList<_> = LinkedList::new();
+        b.iter(|| {
+            m.push_back(0);
+            m.pop_back();
+        })
+    }
+
+    #[bench]
+    fn bench_push_front_pop_front(b: &mut test::Bencher) {
+        let mut m: LinkedList<_> = LinkedList::new();
+        b.iter(|| {
+            m.push_front(0);
+            m.pop_front();
+        })
+    }
+
+    #[bench]
+    fn bench_iter(b: &mut test::Bencher) {
+        let v = &[0; 128];
+        let m: LinkedList<_> = v.iter().cloned().collect();
+        b.iter(|| {
+            assert!(m.iter().count() == 128);
+        })
+    }
+    #[bench]
+    fn bench_iter_mut(b: &mut test::Bencher) {
+        let v = &[0; 128];
+        let mut m: LinkedList<_> = v.iter().cloned().collect();
+        b.iter(|| {
+            assert!(m.iter_mut().count() == 128);
+        })
+    }
+    #[bench]
+    fn bench_iter_rev(b: &mut test::Bencher) {
+        let v = &[0; 128];
+        let m: LinkedList<_> = v.iter().cloned().collect();
+        b.iter(|| {
+            assert!(m.iter().rev().count() == 128);
+        })
+    }
+    #[bench]
+    fn bench_iter_mut_rev(b: &mut test::Bencher) {
+        let v = &[0; 128];
+        let mut m: LinkedList<_> = v.iter().cloned().collect();
+        b.iter(|| {
+            assert!(m.iter_mut().rev().count() == 128);
+        })
+    }
+}