error[E0445]: private trait `Private<<Self as Public>::P, <Self as Public>::R>` in public interface
  --> $DIR/issue-18389.rs:7:1
   |
LL |   trait Private<P, R> {
   |   - `Private<<Self as Public>::P, <Self as Public>::R>` declared as private
...
LL | / pub trait Public: Private<
LL | |
LL | |     <Self as Public>::P,
LL | |     <Self as Public>::R
...  |
LL | |     fn call_inner(&self);
LL | | }
   | |_^ can't leak private trait

error: aborting due to previous error

For more information about this error, try `rustc --explain E0445`.