Funny, seems I have old news: Rust adopted D-like module
visibility.
https://doc.rust-lang.org/reference/visibility-and-privacy.html
pub(in path), pub(crate), pub(super), and pub(self)
In addition to public and private, Rust allows users to declare
an item as visible only within a given scope. The rules for pub
restrictions are as follows:
pub(in path) makes an item visible within the provided path. path
must be an ancestor module of the item whose visibility is being
declared.
pub(crate) makes an item visible within the current crate.
pub(super) makes an item visible to the parent module. This is
equivalent to pub(in super).
pub(self) makes an item visible to the current module. This is
equivalent to pub(in self) or not using pub at all.
