error[E0599]: the method `countx` exists for struct `Filter<Map<Repeat, fn(&u64) -> &u64 {identity::<u64>}>, {closure@hrtb-doesnt-borrow-self-2.rs:111:30}>`, but its trait bounds were not satisfied
  --> $DIR/hrtb-doesnt-borrow-self-2.rs:112:24
   |
LL | pub struct Filter<S, F> {
   | ----------------------- method `countx` not found for this struct because it doesn't satisfy `_: StreamExt`
...
LL |     let count = filter.countx();
   |                        ^^^^^^ method cannot be called due to unsatisfied trait bounds
   |
note: the following trait bounds were not satisfied:
      `&'a mut &Filter<Map<Repeat, for<'a> fn(&'a u64) -> &'a u64 {identity::<u64>}>, {closure@$DIR/hrtb-doesnt-borrow-self-2.rs:111:30: 111:37}>: Stream`
      `&'a mut &mut Filter<Map<Repeat, for<'a> fn(&'a u64) -> &'a u64 {identity::<u64>}>, {closure@$DIR/hrtb-doesnt-borrow-self-2.rs:111:30: 111:37}>: Stream`
      `&'a mut Filter<Map<Repeat, for<'a> fn(&'a u64) -> &'a u64 {identity::<u64>}>, {closure@$DIR/hrtb-doesnt-borrow-self-2.rs:111:30: 111:37}>: Stream`
  --> $DIR/hrtb-doesnt-borrow-self-2.rs:98:50
   |
LL | impl<T> StreamExt for T where for<'a> &'a mut T: Stream {}
   |         ---------     -                          ^^^^^^ unsatisfied trait bound introduced here
   = help: items from traits can only be used if the trait is implemented and in scope
note: `StreamExt` defines an item `countx`, perhaps you need to implement it
  --> $DIR/hrtb-doesnt-borrow-self-2.rs:66:1
   |
LL | pub trait StreamExt
   | ^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0599`.