Fix borrow so it fails in 2018 edition Fixes #1141

Author: gurgalex

src/scope/borrow.md

@@ -30,14 +30,13 @@ fn main() {
     borrow_i32(&stacked_i32);
 
     {
-        // Take a reference to the data contained inside the box
-        let _ref_to_i32: &i32 = &boxed_i32;
-
         // Error!
-        // Can't destroy `boxed_i32` while the inner value is borrowed.
+        // Can't destroy `boxed_i32` while the inner value is borrowed later in scope.
         eat_box_i32(boxed_i32);
         // FIXME ^ Comment out this line
 
+        // Take a reference to the data contained inside the box
+        let _ref_to_i32: &i32 = &boxed_i32;
         // `_ref_to_i32` goes out of scope and is no longer borrowed.
     }