error[E0503]: cannot use `self.width` because it was mutably borrowed
  --> $DIR/issue-25793.rs:4:9
   |
LL |         $this.width.unwrap()
   |         ^^^^^^^^^^^ use of borrowed `*self`
...
LL |         let r = &mut *self;
   |                 ---------- borrow of `*self` occurs here
LL |         r.get_size(width!(self))
   |           -------- ------------ in this macro invocation
   |           |
   |           borrow later used by call
   |
   = note: this error originates in the macro `width` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error

For more information about this error, try `rustc --explain E0503`.