Auto merge of #45 - mbrubeck:into-vec, r=emilio

Add SmallVec::into_vec

Converts a SmallVec to a Vec, without reallocating if the SmallVec has already spilled onto the heap.

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/rust-smallvec/45)
<!-- Reviewable:end -->

Author: bors-servo

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "smallvec"
-version = "0.3.1"
+version = "0.3.2"
 authors = ["Simon Sapin <[email protected]>"]
 license = "MPL-2.0"
 repository = "https://github.com/servo/rust-smallvec"

lib.rs

@@ -482,6 +482,19 @@ impl<A: Array> SmallVec<A> {
             }
         }
     }
+
+    /// Convert a SmallVec to a Vec, without reallocating if the SmallVec has already spilled onto
+    /// the heap.
+    pub fn into_vec(self) -> Vec<A::Item> {
+        match self.data {
+            Inline { .. } => self.into_iter().collect(),
+            Heap { ptr, capacity } => unsafe {
+                let v = Vec::from_raw_parts(ptr, self.len, capacity);
+                mem::forget(self);
+                v
+            }
+        }
+    }
 }
 
 impl<A: Array> SmallVec<A> where A::Item: Copy {
@@ -1341,4 +1354,13 @@ pub mod tests {
         vec.shrink_to_fit();
         assert!(!vec.spilled(), "shrink_to_fit will un-spill if possible");
     }
+
+    #[test]
+    fn test_into_vec() {
+        let vec = SmallVec::<[u8; 2]>::from_iter(0..2);
+        assert_eq!(vec.into_vec(), vec![0, 1]);
+
+        let vec = SmallVec::<[u8; 2]>::from_iter(0..3);
+        assert_eq!(vec.into_vec(), vec![0, 1, 2]);
+    }
 }