error[E0700]: hidden type for `impl Sized` captures lifetime that does not appear in bounds
  --> $DIR/nested-rpit-hrtb-2.rs:6:57
   |
LL | fn test() -> impl for<'a> Trait<'a, Assoc = impl Sized> {}
   |                       --                    ----------  ^^
   |                       |                     |
   |                       |                     opaque type defined here
   |                       hidden type `&'a str` captures the lifetime `'a` as defined here

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0700`.