error[E0521]: borrowed data escapes outside of function
  --> $DIR/hrtb-implied-2.rs:18:17
   |
LL | fn fails<I: LendingIterator, F>(iter: &mut I, f: F) -> bool
   |                                 ----  - let's call the lifetime of this reference `'1`
   |                                 |
   |                                 `iter` is a reference that is only valid in the function body
...
LL |     let _next = iter2.next();
   |                 ^^^^^^^^^^^^
   |                 |
   |                 `iter` escapes the function body here
   |                 argument requires that `'1` must outlive `'static`
   |
   = note: requirement occurs because of a mutable reference to `Eat<&mut I, F>`
   = note: mutable references are invariant over their type parameter
   = help: see <https://doc.rust-lang.org/nomicon/subtyping.html> for more information about variance
   = note: due to current limitations in the borrow checker, this implies a `'static` lifetime

error: aborting due to previous error

For more information about this error, try `rustc --explain E0521`.