Ch. 17: clarify 'in order to compile'

src/ch17-01-what-is-oo.md

@@ -86,10 +86,10 @@ Because we’ve encapsulated the implementation details of the struct
 in the future. For instance, we could use a `HashSet<i32>` instead of a
 `Vec<i32>` for the `list` field. As long as the signatures of the `add`,
 `remove`, and `average` public methods stay the same, code using
-`AveragedCollection` wouldn’t need to change. If we made `list` public instead,
-this wouldn’t necessarily be the case: `HashSet<i32>` and `Vec<i32>` have
-different methods for adding and removing items, so the external code would
-likely have to change if it were modifying `list` directly.
+`AveragedCollection` wouldn’t need to change in order to compile. If we made
+`list` public instead, this wouldn’t necessarily be the case: `HashSet<i32>` and
+`Vec<i32>` have different methods for adding and removing items, so the external
+code would likely have to change if it were modifying `list` directly.
 
 If encapsulation is a required aspect for a language to be considered
 object-oriented, then Rust meets that requirement. The option to use `pub` or