warning: trait `Private<<Self as Public>::P, <Self as Public>::R>` is more private than the item `Public`
  --> $DIR/issue-18389.rs:9:1
   |
LL | / pub trait Public: Private<
LL | |
LL | |     <Self as Public>::P,
LL | |     <Self as Public>::R
LL | | > {
   | |_^ trait `Public` is reachable at visibility `pub`
   |
note: but trait `Private<<Self as Public>::P, <Self as Public>::R>` is only usable at visibility `pub(crate)`
  --> $DIR/issue-18389.rs:6:1
   |
LL | trait Private<P, R> {
   | ^^^^^^^^^^^^^^^^^^^
   = note: `#[warn(private_bounds)]` on by default

warning: 1 warning emitted