error[E0657]: `impl Trait` cannot capture higher-ranked lifetime from outer `impl Trait`
  --> $DIR/impl-fn-hrtb-bounds-2.rs:7:27
   |
LL | fn a() -> impl Fn(&u8) -> impl Debug {
   |                           ^^^^^^^^^^ `impl Trait` implicitly captures all lifetimes in scope
   |
note: lifetime declared here
  --> $DIR/impl-fn-hrtb-bounds-2.rs:7:19
   |
LL | fn a() -> impl Fn(&u8) -> impl Debug {
   |                   ^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0657`.