Spurious private-in-public error for impl block

[joshlf]

The following code results in a private-in-public error:

pub(crate) trait Foo {}

pub struct Bar<T>(T);

impl<T: Foo> Bar<T> {
    pub(crate) fn new(t: T) -> Bar<T> {
        Bar(t)
    }
}

error[E0445]: crate-visible trait `Foo` in public interface
 --> src/lib.rs:5:1
  |
1 |   pub(crate) trait Foo {}
  |   ---------- `Foo` declared as crate-visible
...
5 | / impl<T: Foo> Bar<T> {
6 | |     pub(crate) fn new(t: T) -> Bar<T> {
7 | |         Bar(t)
8 | |     }
9 | | }
  | |_^ can't leak crate-visible trait

This seems wrong to me; though the impl block is on a public type, none of the methods in it are public.

[petrochenkov]

This currently works as expected, but #48054 is going to change the rules once implemented, so the error will no longer be reported.

[joshlf]

OK, sounds good, thanks!