error[E0499]: cannot borrow `w.p.x` as mutable more than once at a time
  --> $DIR/multilevel-path.rs:23:14
   |
LL |     let mut c = || {
   |                 -- first mutable borrow occurs here
LL |         w.p.x += 20;
   |         ----- first borrow occurs due to use of `w.p.x` in closure
...
LL |     let py = &mut w.p.x;
   |              ^^^^^^^^^^ second mutable borrow occurs here
LL |
LL |     c();
   |     - first borrow later used here

error: aborting due to previous error

For more information about this error, try `rustc --explain E0499`.