Fix merge conflicts

11 files changed, 125 insertions, 6 deletions

diff --git a/src/liballoc/boxed.rs b/src/liballoc/boxed.rs
index 9109a730cce..41966360377 100644
--- a/src/liballoc/boxed.rs
+++ b/src/liballoc/boxed.rs
@@ -367,12 +367,19 @@ impl<T: Clone> Clone for Box<T> {
     /// ```
     /// let x = Box::new(5);
     /// let y = x.clone();
+    ///
+    /// // The value is the same
+    /// assert_eq!(x, y);
+    ///
+    /// // But they are unique objects
+    /// assert_ne!(&*x as *const i32, &*y as *const i32);
     /// ```
     #[rustfmt::skip]
     #[inline]
     fn clone(&self) -> Box<T> {
         box { (**self).clone() }
     }
+
     /// Copies `source`'s contents into `self` without creating a new allocation.
     ///
     /// # Examples
@@ -380,10 +387,15 @@ impl<T: Clone> Clone for Box<T> {
     /// ```
     /// let x = Box::new(5);
     /// let mut y = Box::new(10);
+    /// let yp: *const i32 = &*y;
     ///
     /// y.clone_from(&x);
     ///
-    /// assert_eq!(*y, 5);
+    /// // The value is the same
+    /// assert_eq!(x, y);
+    ///
+    /// // And no allocation occurred
+    /// assert_eq!(yp, &*y);
     /// ```
     #[inline]
     fn clone_from(&mut self, source: &Box<T>) {
@@ -716,6 +728,14 @@ impl<I: Iterator + ?Sized> Iterator for Box<I> {
         (**self).nth(n)
     }
 }
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<I: Iterator + Sized> Iterator for Box<I> {
+    fn last(self) -> Option<I::Item> where I: Sized {
+        (*self).last()
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<I: DoubleEndedIterator + ?Sized> DoubleEndedIterator for Box<I> {
     fn next_back(&mut self) -> Option<I::Item> {
diff --git a/src/liballoc/collections/binary_heap.rs b/src/liballoc/collections/binary_heap.rs
index c898f064fd0..9f531f5b83c 100644
--- a/src/liballoc/collections/binary_heap.rs
+++ b/src/liballoc/collections/binary_heap.rs
@@ -1035,6 +1035,11 @@ impl<'a, T> Iterator for Iter<'a, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(self) -> Option<&'a T> {
+        self.iter.last()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/liballoc/collections/btree/map.rs b/src/liballoc/collections/btree/map.rs
index 6b079fc87cc..ca35600e857 100644
--- a/src/liballoc/collections/btree/map.rs
+++ b/src/liballoc/collections/btree/map.rs
@@ -770,8 +770,8 @@ impl<K: Ord, V> BTreeMap<K, V> {
         }
 
         // First, we merge `self` and `other` into a sorted sequence in linear time.
-        let self_iter = mem::replace(self, BTreeMap::new()).into_iter();
-        let other_iter = mem::replace(other, BTreeMap::new()).into_iter();
+        let self_iter = mem::take(self).into_iter();
+        let other_iter = mem::take(other).into_iter();
         let iter = MergeIter {
             left: self_iter.peekable(),
             right: other_iter.peekable(),
@@ -1193,6 +1193,10 @@ impl<'a, K: 'a, V: 'a> Iterator for Iter<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.length, Some(self.length))
     }
+
+    fn last(mut self) -> Option<(&'a K, &'a V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "fused", since = "1.26.0")]
@@ -1253,6 +1257,10 @@ impl<'a, K: 'a, V: 'a> Iterator for IterMut<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.length, Some(self.length))
     }
+
+    fn last(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1421,6 +1429,10 @@ impl<'a, K, V> Iterator for Keys<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+
+    fn last(mut self) -> Option<&'a K> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1458,6 +1470,10 @@ impl<'a, K, V> Iterator for Values<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+
+    fn last(mut self) -> Option<&'a V> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1495,6 +1511,10 @@ impl<'a, K, V> Iterator for Range<'a, K, V> {
             unsafe { Some(self.next_unchecked()) }
         }
     }
+
+    fn last(mut self) -> Option<(&'a K, &'a V)> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "map_values_mut", since = "1.10.0")]
@@ -1508,6 +1528,10 @@ impl<'a, K, V> Iterator for ValuesMut<'a, K, V> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.inner.size_hint()
     }
+
+    fn last(mut self) -> Option<&'a mut V> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "map_values_mut", since = "1.10.0")]
@@ -1626,6 +1650,10 @@ impl<'a, K, V> Iterator for RangeMut<'a, K, V> {
             unsafe { Some(self.next_unchecked()) }
         }
     }
+
+    fn last(mut self) -> Option<(&'a K, &'a mut V)> {
+        self.next_back()
+    }
 }
 
 impl<'a, K, V> RangeMut<'a, K, V> {
diff --git a/src/liballoc/collections/btree/set.rs b/src/liballoc/collections/btree/set.rs
index 16a96ca19b8..d3af910a82c 100644
--- a/src/liballoc/collections/btree/set.rs
+++ b/src/liballoc/collections/btree/set.rs
@@ -1019,6 +1019,9 @@ impl<'a, T> Iterator for Iter<'a, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+    fn last(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
@@ -1073,6 +1076,10 @@ impl<'a, T> Iterator for Range<'a, T> {
     fn next(&mut self) -> Option<&'a T> {
         self.iter.next().map(|(k, _)| k)
     }
+
+    fn last(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "btree_range", since = "1.17.0")]
diff --git a/src/liballoc/collections/linked_list.rs b/src/liballoc/collections/linked_list.rs
index 40a82d6feaa..db0d6e2f9b9 100644
--- a/src/liballoc/collections/linked_list.rs
+++ b/src/liballoc/collections/linked_list.rs
@@ -708,7 +708,7 @@ impl<T> LinkedList<T> {
         let len = self.len();
         assert!(at <= len, "Cannot split off at a nonexistent index");
         if at == 0 {
-            return mem::replace(self, Self::new());
+            return mem::take(self);
         } else if at == len {
             return Self::new();
         }
@@ -832,6 +832,11 @@ impl<'a, T> Iterator for Iter<'a, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.len, Some(self.len))
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -881,6 +886,11 @@ impl<'a, T> Iterator for IterMut<'a, T> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.len, Some(self.len))
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a mut T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/liballoc/collections/vec_deque.rs b/src/liballoc/collections/vec_deque.rs
index 71faf672962..573dd86b23a 100644
--- a/src/liballoc/collections/vec_deque.rs
+++ b/src/liballoc/collections/vec_deque.rs
@@ -2206,6 +2206,11 @@ impl<'a, T> Iterator for Iter<'a, T> {
         self.tail = self.head - iter.len();
         final_res
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -2319,6 +2324,11 @@ impl<'a, T> Iterator for IterMut<'a, T> {
         accum = front.iter_mut().fold(accum, &mut f);
         back.iter_mut().fold(accum, &mut f)
     }
+
+    #[inline]
+    fn last(mut self) -> Option<&'a mut T> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 5fc58c8ab5a..bfe7d12d9d0 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -112,6 +112,7 @@
 #![feature(maybe_uninit_extra, maybe_uninit_slice, maybe_uninit_array)]
 #![feature(alloc_layout_extra)]
 #![feature(try_trait)]
+#![feature(mem_take)]
 
 // Allow testing this library
 
diff --git a/src/liballoc/str.rs b/src/liballoc/str.rs
index 40104554fe5..70a93157c9e 100644
--- a/src/liballoc/str.rs
+++ b/src/liballoc/str.rs
@@ -203,7 +203,7 @@ impl ToOwned for str {
     }
 
     fn clone_into(&self, target: &mut String) {
-        let mut b = mem::replace(target, String::new()).into_bytes();
+        let mut b = mem::take(target).into_bytes();
         self.as_bytes().clone_into(&mut b);
         *target = unsafe { String::from_utf8_unchecked(b) }
     }
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 7f7722548f5..1b0d3c19692 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -2385,6 +2385,11 @@ impl Iterator for Drain<'_> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         self.iter.size_hint()
     }
+
+    #[inline]
+    fn last(mut self) -> Option<char> {
+        self.next_back()
+    }
 }
 
 #[stable(feature = "drain", since = "1.6.0")]
diff --git a/src/liballoc/tests/vec.rs b/src/liballoc/tests/vec.rs
index 5ddac673c9f..e0c724f557b 100644
--- a/src/liballoc/tests/vec.rs
+++ b/src/liballoc/tests/vec.rs
@@ -761,7 +761,6 @@ fn from_into_inner() {
     it.next().unwrap();
     let vec = it.collect::<Vec<_>>();
     assert_eq!(vec, [2, 3]);
-    #[cfg(not(miri))] // Miri does not support comparing dangling pointers
     assert!(ptr != vec.as_ptr());
 }
 
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index 92fe0834dd0..c0544d7469c 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -1367,6 +1367,40 @@ impl<T> Vec<T> {
             self.truncate(new_len);
         }
     }
+
+    /// Consumes and leaks the `Vec`, returning a mutable reference to the contents,
+    /// `&'a mut [T]`. Note that the type `T` must outlive the chosen lifetime
+    /// `'a`. If the type has only static references, or none at all, then this
+    /// may be chosen to be `'static`.
+    ///
+    /// This function is similar to the `leak` function on `Box`.
+    ///
+    /// This function is mainly useful for data that lives for the remainder of
+    /// the program's life. Dropping the returned reference will cause a memory
+    /// leak.
+    ///
+    /// # Examples
+    ///
+    /// Simple usage:
+    ///
+    /// ```
+    /// #![feature(vec_leak)]
+    ///
+    /// fn main() {
+    ///     let x = vec![1, 2, 3];
+    ///     let static_ref: &'static mut [usize] = Vec::leak(x);
+    ///     static_ref[0] += 1;
+    ///     assert_eq!(static_ref, &[2, 2, 3]);
+    /// }
+    /// ```
+    #[unstable(feature = "vec_leak", issue = "62195")]
+    #[inline]
+    pub fn leak<'a>(vec: Vec<T>) -> &'a mut [T]
+    where
+        T: 'a // Technically not needed, but kept to be explicit.
+    {
+        Box::leak(vec.into_boxed_slice())
+    }
 }
 
 impl<T: Clone> Vec<T> {