Auto merge of servo#151 - ehuss:grow-same-size, r=jdm

Fix using `grow` to the same size.

Using `grow` on a spilled SmallVec to the current capacity would free the backing storage when it shouldn't.

Fixes servo#148

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Author: bors-servo

lib.rs

@@ -665,6 +665,8 @@ impl<A: Array> SmallVec<A> {
                 if unspilled {
                     return;
                 }
+            } else {
+                return;
             }
             deallocate(ptr, cap);
         }
@@ -2341,4 +2343,18 @@ mod tests {
         v.extend(it);
         assert_eq!(v[..], ['a']);
     }
+
+    #[test]
+    fn grow_spilled_same_size() {
+        let mut v: SmallVec<[u8; 2]> = SmallVec::new();
+        v.push(0);
+        v.push(1);
+        v.push(2);
+        assert!(v.spilled());
+        assert_eq!(v.capacity(), 4);
+        // grow with the same capacity
+        v.grow(4);
+        assert_eq!(v.capacity(), 4);
+        assert_eq!(v[..], [0, 1, 2]);
+    }
 }