E0609's "one of the expressions' fields has a field of the same name" suggestion does not consider privacy

[ash2x3zb9cy]

https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=d65d484826fe6e0d2d490ee1fa63052e
Given the following code:

mod lib {
    #[derive(Default)]
    pub struct Xyz { x: f32, y: f32, z: f32 }
    #[derive(Default)]
    pub struct Vec3(Xyz);
}

fn main() {
    let a: lib::Vec3 = Default::default();
    println!("{}", a.x);
}

The current output is:

   Compiling playground v0.0.1 (/playground)
error[E0609]: no field `x` on type `Vec3`
  --> src/main.rs:10:22
   |
10 |     println!("{}", a.x);
   |                      ^
   |
help: one of the expressions' fields has a field of the same name
   |
10 |     println!("{}", a.0.x);
   |                      ^^
help: a field with a similar name exists
   |
10 |     println!("{}", a.0);
   |                      ^

error: aborting due to previous error

For more information about this error, try `rustc --explain E0609`.
error: could not compile `playground`

To learn more, run the command again with --verbose.

The suggested fixes, a.0 and a.0.x both refer to a private field, so they do not compile..

Given the following code, having implemented the suggested change:

mod lib {
    #[derive(Default)]
    pub struct Xyz { x: f32, y: f32, z: f32 }
    #[derive(Default)]
    pub struct Vec3(Xyz);
}

fn main() {
    let a: lib::Vec3 = Default::default();
    println!("{}", a.0.x);
}

The output is, correctly:

   Compiling playground v0.0.1 (/playground)
error[E0616]: field `0` of struct `Vec3` is private
  --> src/main.rs:10:22
   |
10 |     println!("{}", a.0.x);
   |                      ^ private field

error[E0616]: field `x` of struct `Xyz` is private
  --> src/main.rs:10:24
   |
10 |     println!("{}", a.0.x);
   |                        ^ private field

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0616`.
error: could not compile `playground`

To learn more, run the command again with --verbose.

[workingjubilee]

This may be related to #64684. The diagnostics currently seem to be largely privacy-unaware.

[jyn514]

Is this actually wrong? I still think this is a helpful diagnostic, it means you know you have the option of making the field public.

[workingjubilee]

  |
5 |     println!("{}", a.x);
  |                      ^ unknown field
  |
help: one of the expressions' fields has a field of the same name
  |
5 |     println!("{}", a.0.x);
  |                      ^^

Almost the same error is emitted if the module is in another entire crate.

[ash2x3zb9cy]

The initial place I ran into this error was when the module was from another crate, yeah.

[hellow554]

I have this piece of code:

use std::collections::{HashMap, HashSet};

pub struct A {
    items: HashSet<u32>,
}
pub struct B {
    a: A,
    map: HashMap<u32, u32>,
}
impl B {
    fn new() -> Self { todo!() }
}

fn main() {
    B::new().items.contains("");
}

which errors out with this error message:

error[E0609]: no field `items` on type `B`
  --> src/main.rs:17:14
   |
17 |     B::new().items.contains("");
   |              ^^^^^ unknown field
   |
   = note: available fields are: `a`, `map`
help: one of the expressions' fields has a field of the same name
   |
17 |     B::new().a.items.contains("");
   |              ++
help: one of the expressions' fields has a field of the same name
   |
17 |     B::new().map.base.table.table.items.contains("");
   |              +++++++++++++++++++++

e.g. it shows the internals of HashMap, which is not desired.
Maybe having an in-crate suggestion is okay, but outside supress it?

[hellow554]

This regressed somewhere between 0e63af5...d4e3570

@rustbot modify labels: D-incorrect

[estebank]

Current output:

error[[E0609]](https://doc.rust-lang.org/nightly/error_codes/E0609.html): no field `x` on type `Vec3`
  --> src/main.rs:12:22
   |
12 |     println!("{}", a.x);
   |                      ^ help: a field with a similar name exists: `0`

error[[E0616]](https://doc.rust-lang.org/nightly/error_codes/E0616.html): field `0` of struct `Vec3` is private
  --> src/main.rs:16:22
   |
16 |     println!("{}", a.0.x);
   |                      ^ private field

error[[E0609]](https://doc.rust-lang.org/nightly/error_codes/E0609.html): no field `items` on type `B`
  --> src/main.rs:15:14
   |
15 |     B::new().items.contains("");
   |              ^^^^^ unknown field
   |
   = note: available fields are: `a`, `map`
help: one of the expressions' fields has a field of the same name
   |
15 |     B::new().a.items.contains("");
   |              ++

It seems like this is now correctly handled.