Documentation: accessing the private items of a parent module

[swatteau]

When accessing items defined in the parent module, it is tempting to write use super::*;. However, this does not allow accessing private items. For example, this fails:

fn print_hello() {
    println!("hello");
}

mod inner {
    use super::*;
    pub fn do_something() {
        print_hello(); // error: unresolved name `print_hello` [E0425]
    }
}

This is a mistake I've made several times (I suspect many others have too) and the solution is to be explicit about the item used, either with

use super::print_hello;

or

super::print_hello();

On this topic, the Rust Reference says:

Use declarations support a number of convenient shortcuts:

• ...
• Binding all paths matching a given prefix, using the asterisk wildcard syntax use a::b::*;
• ...

I find this a bit misleading because the asterisk wildcard syntax really only binds public paths matching a given prefix.

I think it would be nice to add a paragraph in the Rust Book to explain how to access private items properly and to state clearly that use super::* won't help.

[steveklabnik]

I just added one to the book. The PR may still be open, or it may have been merged in the last day or two; I'm on mobile or I'd check.

On Jan 30, 2016, 11:11 -0500, Sébastien Watteaunotifications@github.com, wrote:

When accessing items defined in the parent module, it is tempting to writeuse super::*;However, this does not allow accessing private items For example, this fails:

fnprint_hello() { println!("hello");}modinner {usesuper::*;pubfndo_something() {print_hello();// error: unresolved name print_hello [E0425]} }

This is a mistake I've made several times (I suspect many others have too) and the solution is to be explicit about the item used, either with

usesuper::print_hello;

or

super::print_hello();

On this topic, theRust Referencesays:

Use declarations support a number of convenient shortcuts:

• Binding all paths matching a given prefix, using the asterisk wildcard syntaxuse a::b::*;

I find this a bit misleading because the asterisk wildcard syntax really only bindspublicpaths matching a given prefix

I think it would be nice to add a paragraph in the Rust Book to explain how to access private items properly and to state clearly thatuse super::*won't help

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[steveklabnik]

Yes, it was #31226