private_bounds: false positive on inherent impl with no public items

Code

#![allow(unused)]
struct Type<T>(T);
mod a {
    trait Trait {}
    impl<T: Trait> super::Type<T> {}
}

Current output

warning: trait `Trait` is more private than the item `a::<impl Type<T>>`
 --> src/lib.rs:5:5
  |
5 |     impl<T: Trait> super::Type<T> {}
  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ implementation `a::<impl Type<T>>` is reachable at visibility `pub(crate)`
  |
note: but trait `Trait` is only usable at visibility `pub(self)`
 --> src/lib.rs:4:5
  |
4 |     trait Trait {}
  |     ^^^^^^^^^^^
  = note: `#[warn(private_bounds)]` on by default

Desired output

No warning

Rationale and extra context

No items inside the impl exist that leak private details, and the mere existence of the impl shouldn't be an issue. Same warning appears if the impl is non-empty.

I think the warning should be on individual items inside the impl rather than the impl itself.

Other cases

Rust Version

rustc 1.88.0-nightly (1799887bb 2025-03-29)
binary: rustc
commit-hash: 1799887bb281d1ab49287750f1950b8c738c6b77
commit-date: 2025-03-29
host: x86_64-unknown-linux-gnu
release: 1.88.0-nightly
LLVM version: 20.1.1

Anything else?

No response

Reproduce the false positive with rustc 1.88.0-nightly using the Rust snippet provided in the issue. No repository file or test is named, so trace the private_bounds lint from this reproduction; the fix is complete when the empty impl emits no warning and a regression test covers the behavior.