error[E0667]: `impl Trait` is not allowed in path parameters
  --> $DIR/issue-57979-impl-trait-in-path.rs:8:48
   |
LL | pub fn demo(_: impl Quux<(), Assoc=<() as Quux<impl Bar>>::Assoc>) { }
   |                                                ^^^^^^^^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0667`.