Contradictory E0423 (constructor not visible due to private fields) when attributes are not in scope

[boxofrox]

Example at https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=0a4268fac37b445aada5d32934c465ae.

I'm upgrading a 2015 project to 2018 and ran into a wall of errors. I started with the E0423 (as seen in the example), but couldn't figure out why Rust thought this struct had private fields.

error[E0423]: expected function, found struct `Sequence`
 --> src/main.rs:7:19
  |
7 |     let payload = Sequence(data.iter());
  |                   ^^^^^^^^ constructor is not visible here due to private fields
help: possible better candidates are found in other modules, you can import them into scope
  |
1 | use ring::io::der::Tag::Sequence;
  |
1 | use serde_yaml::Value::Sequence;
  |
1 | use weedle::term::Sequence;
  |
1 | use weedle::types::NonAnyType::Sequence;

#[derive(Serialize)]
#[serde(bound(serialize = "T : Clone + Iterator, T::Item : Serialize"))]
pub struct Sequence<T>(#[serde(serialize_with = "serialize_iter")] pub T);

pub T is pub. Since I was getting nowhere with that error, I moved on to the missing serde imports, which fixed the E0423 error.

I'm reporting this, because the error is unexpected to a perpetual newbie such as myself. If Rust cannot make sense of the attributes, I would expect Rust to ignore them as if they weren't there, and recognize the pub T, so the E0423 wasn't erroneously reported.

[petrochenkov]

This is a nightly-only regression and it should be fixed by #66669.

[boxofrox]

I'm not sure I follow what a "nightly-only regression" is. The playground example reports E0423 on stable.

That aside, I thought I tested the nightly compiler on the playground example, but apparently I misclicked, because the nightly compiler doesn't report E0423. Looks like #66669 will fix this issue. My apologies for the noise.