Missing field error in initializer for struct with inaccessible fields

[gheoan]

Given the following code:

// in file a.rs
#![crate_type = "lib"]

pub struct X {  
  pub f: u32, // remove the field f to get a different error message
  pub(crate) g: u32,
}

// this is to prevent a warning that g is not used
impl X {
  pub fn value(self) -> u32 { self.g }
}

// in file b.rs
#![crate_type = "bin"]

extern crate a;

fn main() {
  let x = a::X {};
  x.value();
}

Using rustc a.rs followed by rustc -L . b.rs, the current output is:

error[E0063]: missing fields `f` and `g` in initializer of `X`
 --> b.rs:6:11
  |
6 |   let x = a::X {};
  |           ^^^^ missing `f` and `g`

Ideally the output should look like:

error: cannot construct `X` with struct literal syntax due to inaccessible fields
 --> b.rs:6:11
  |
6 |   let x = a::X {};
  |           ^^^^

The rationale is the same as for #76077. Following the suggestion provided by the compiler will lead to another error. This can be frustrating with structs that have a large number of fields or fields with complex types, since the effort of adding those fields to the struct literal is in vain.

By removing the field f from the struct, the compiler is reporting that X cannot be constructed, as expected.

Tested on both rustc 1.56.0-nightly (574d37568 2021-08-07) and rustc 1.52.0-nightly (4a8b6f708 2021-03-11).

[TheWastl]

I guess this also applies to patterns:

pub mod foo {
    #[derive(Default)]
    pub struct Foo {
        pub x: i32,
        y: i32,
    }
}

fn main() {
    let foo::Foo {} = foo::Foo::default();
}

Playground link

Error:

error[E0027]: pattern does not mention fields `x`, `y`
  --> src/main.rs:10:9
   |
10 |     let foo::Foo {} = foo::Foo::default();
   |         ^^^^^^^^^^^ missing fields `x`, `y`
   |
help: include the missing fields in the pattern
   |
10 |     let foo::Foo { x, y } = foo::Foo::default();
   |                  ^^^^^^^^
help: if you don't care about these missing fields, you can explicitly ignore them
   |
10 |     let foo::Foo { .. } = foo::Foo::default();
   |                  ^^^^^^

For more information about this error, try `rustc --explain E0027`.

Possibly change to something along these lines:

error[E0027]: pattern does not mention field `x` and inaccessible fields
  --> src/main.rs:10:9
   |
10 |     let foo::Foo {} = foo::Foo::default();
   |         ^^^^^^^^^^^ missing field `x` and inaccessible fields
   |
help: include the missing fields and ignore the inaccessible fields in the pattern
   |
10 |     let foo::Foo { x, .. } = foo::Foo::default();
   |                  ^^^^^^^^^
help: if you don't care about these missing fields, you can explicitly ignore them
   |
10 |     let foo::Foo { .. } = foo::Foo::default();
   |                  ^^^^^^

For more information about this error, try `rustc --explain E0027`.

[TheWastl]

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