Finer-grained privacy control

[aturon]

Rust has a reasonable default meaning of pub and private items, but for larger projects it would be extremely useful to have finer-grained control -- especially "public to crate, private to world".

[aturon]

cc @carllerche

[Valloric]

"public to crate, private to world"

So something like C#'s internal access modifier?

[kud1ing]

So something like C#'s internal access modifier?

Also reminds me of Swift's internal, but C# was probably first.

[aturon]

Something like internal would be nice, but I think @nikomatsakis has some ideas about a more expressive notion of pub that takes a path parameter (and subsumes internal).

[nodakai]

+1, but I hope we can avoid a mess like in Java:

Modifier	Class	Package	Subclass	World
public	Y	Y	Y	Y
protected	Y	Y	Y	N
no modifier	Y	Y	N	N
private	Y	N	N	N

• https://docs.oracle.com/javase/tutorial/java/javaOO/accesscontrol.html

Also, I wonder if something like "protected" trait methods might be useful. They are visible, across crates, only to implementations of other trait methods of the same/child trait.

[Stebalien]

Triage: Fixed by #1422

[steveklabnik]

Yup!