"cannot construct with struct literal syntax due to inaccessible fields" could use an explain

[QuineDot]

Given the following code:

pub mod m {
    pub struct S {
        pub visible: bool,
        private: (),
        also_private: String,
    }
}

fn main() {
    let _ = m::S {
        visible: true,
        private: (),
    };
}

The current output is:

error: cannot construct `S` with struct literal syntax due to inaccessible fields
  [--> src/main.rs:10:13
](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=9f3e3c29a1dd0db9008d9683c108b330#)   |
10 |     let _ = m::S {
   |             ^^^^

Ideally, the output should

• Explain more fully that there are private fields, perhaps via --explain
• Not occlude E0451 when some private fields are supplied (as in the above example)

In my opinion, the errors when you supply all the private fields are more understandable than those when you supply none or only some of the private fields. See also this URLO thread.

I believe the current output is a result of #87872.

[compiler-errors]

I also agree that this seems like a regression.

1. Firstly, I think that the word "inaccessible" is vague. I think "private" is pretty standard Rust terminology.
2. In both cases (where all fields are provided, and when some are missing) we sould probably continue to mention that the struct can't be constructed due to having private fields -- this is a property that holds even when we provide all the fields.
3. In the case that not all private fields are provided, but some are, we should at least point at which ones are private.

[hadrizi]

@rustbot claim

[lionellloh]

Hi @hadrizi are you still working on this?