error[E0503]: cannot use `*y.pointer` because it was mutably borrowed
  --> $DIR/issue-45697.rs:20:9
   |
LL |         let z = copy_borrowed_ptr(&mut y);
   |                                   ------ borrow of `y` occurs here
LL |         *y.pointer += 1;
   |         ^^^^^^^^^^^^^^^ use of borrowed `y`
...
LL |         *z.pointer += 1;
   |         --------------- borrow later used here

error[E0506]: cannot assign to `*y.pointer` because it is borrowed
  --> $DIR/issue-45697.rs:20:9
   |
LL |         let z = copy_borrowed_ptr(&mut y);
   |                                   ------ borrow of `*y.pointer` occurs here
LL |         *y.pointer += 1;
   |         ^^^^^^^^^^^^^^^ assignment to borrowed `*y.pointer` occurs here
...
LL |         *z.pointer += 1;
   |         --------------- borrow later used here

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0503, E0506.
For more information about an error, try `rustc --explain E0503`.