rust/tests/ui/privacy/issue-30079.rs

struct SemiPriv;

mod m1 {
    struct Priv;
    impl crate::SemiPriv {
        pub fn f(_: Priv) {} //~ WARN type `m1::Priv` is more private than the item `m1::<impl SemiPriv>::f`
    }

    impl Priv {
        pub fn f(_: Priv) {} // ok
    }
}

mod m2 {
    struct Priv;
    impl std::ops::Deref for crate::SemiPriv {
        type Target = Priv; //~ ERROR private type `m2::Priv` in public interface
        fn deref(&self) -> &Self::Target { unimplemented!() }
    }

    impl std::ops::Deref for Priv {
        type Target = Priv; // ok
        fn deref(&self) -> &Self::Target { unimplemented!() }
    }
}

trait SemiPrivTrait {
    type Assoc;
}

mod m3 {
    struct Priv;
    impl crate::SemiPrivTrait for () {
        type Assoc = Priv; //~ ERROR private type `m3::Priv` in public interface
    }
}

fn main() {}