error[E0599]: the method `filterx` exists for struct `Map<Repeat, {closure@hrtb-doesnt-borrow-self-1.rs:115:27}>`, but its trait bounds were not satisfied
  --> $DIR/hrtb-doesnt-borrow-self-1.rs:116:22
   |
LL | pub struct Map<S, F> {
   | -------------------- method `filterx` not found for this struct because it doesn't satisfy `_: StreamExt`
...
LL |     let filter = map.filterx(|x: &_| true);
   |                      ^^^^^^^ method cannot be called due to unsatisfied trait bounds
   |
note: the following trait bounds were not satisfied:
      `&'a mut &Map<Repeat, {closure@$DIR/hrtb-doesnt-borrow-self-1.rs:115:27: 115:34}>: Stream`
      `&'a mut &mut Map<Repeat, {closure@$DIR/hrtb-doesnt-borrow-self-1.rs:115:27: 115:34}>: Stream`
      `&'a mut Map<Repeat, {closure@$DIR/hrtb-doesnt-borrow-self-1.rs:115:27: 115:34}>: Stream`
  --> $DIR/hrtb-doesnt-borrow-self-1.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 `filterx`, perhaps you need to implement it
  --> $DIR/hrtb-doesnt-borrow-self-1.rs:66:1
   |
LL | pub trait StreamExt
   | ^^^^^^^^^^^^^^^^^^^

error: aborting due to 1 previous error

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