error[E0308]: mismatched types
  --> $DIR/hang-on-deeply-nested-dyn.rs:12:5
   |
LL |   ) -> &dyn Fn(
   |  ______-
LL | |     &dyn Fn(
LL | |         &dyn Fn(
LL | |             &dyn Fn(&dyn Fn(&dyn Fn(&dyn Fn(&dyn Fn(&dyn Fn(&dyn Fn(&dyn Fn(&dyn Fn(u32))))))))),
LL | |         ),
LL | |     ),
LL | | ) {
   | |_- expected `&dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn Fn(u32) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a))` because of return type
LL |       f
   |       ^ expected `&dyn Fn(&dyn Fn(&dyn Fn(&...)))`, found `&dyn Fn(u32)`
   |
   = note: expected reference `&dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn for<'a> Fn(&'a (dyn Fn(u32) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a)) + 'a))`
              found reference `&dyn Fn(u32)`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.