Add ptr::offset_to

2 files changed, 5 insertions, 8 deletions

diff --git a/src/libcollections/lib.rs b/src/libcollections/lib.rs
index 72e950bc91f..2b345e3d0a5 100644
--- a/src/libcollections/lib.rs
+++ b/src/libcollections/lib.rs
@@ -61,6 +61,7 @@
 #![feature(unique)]
 #![feature(untagged_unions)]
 #![cfg_attr(test, feature(rand, test))]
+#![feature(offset_to)]
 
 #![no_std]
 
diff --git a/src/libcollections/vec.rs b/src/libcollections/vec.rs
index 56b60a3e003..f12380a9ea5 100644
--- a/src/libcollections/vec.rs
+++ b/src/libcollections/vec.rs
@@ -2073,14 +2073,10 @@ impl<T> Iterator for IntoIter<T> {
 
     #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        let diff = (self.end as usize) - (self.ptr as usize);
-        let size = mem::size_of::<T>();
-        let exact = diff /
-                    (if size == 0 {
-                         1
-                     } else {
-                         size
-                     });
+        let exact = match self.ptr.offset_to(self.end) {
+            Some(x) => x as usize,
+            None => (self.end as usize).wrapping_sub(self.ptr as usize),
+        };
         (exact, Some(exact))
     }