Problem

Why does the doc test for sub under impl<T> Sub for Point2<T> work, but my attempt to implement area under impl<T> Bounds2<T> fails to compile with:

error[E0369]: binary operation `-` cannot be applied to type `Point2<T>`
  --> src/lib.rs:87:28
   |
87 |         let d = self.p_max - self.p_min;
   |                 ---------- ^ ---------- Point2<T>
   |                 |
   |                 Point2<T>
   |
   = note: an implementation of `std::ops::Sub` might be missing for `Point2<T>`