Unexpected error related to item visibility

[pedromfedricci]

Hi, I've been experimenting with this crate and came across this error. I couldn't tell if it's a bug here or just an underlying problem with the unfinished feature itself.

Here is a small reproduction:

#![allow(incomplete_features)]
#![feature(generic_const_exprs)]
use const_guards::guard;

// `guard` doesn't like either pub(crate) or pub(super) in this completely unrelated item.
// By removing the visibility, or just setting it to `pub`, it compiles fine then. 
pub struct Unrelated(pub(crate) ());

#[guard(<const U: u8> { U > 10 })]
pub struct Struct<const U: u8>;

The unexpected error is:

error[E0446]: private type `fn() -> bool {_Struct_guard::<U>}` in public interface

I know this sorts of problems are expected with incomplete features, I just figured this could be interesting to you.
Ty.