regression: visibility qualifiers are not permitted

[Mark-Simulacrum]

• https://crater-reports.s3.amazonaws.com/beta-1.77-3/beta-2024-02-18/reg/amadeus-core-0.4.3/log.txt
  • https://crater-reports.s3.amazonaws.com/beta-1.77-3/beta-2024-02-18/reg/amadeus-aws-0.4.3/log.txt
  • https://crater-reports.s3.amazonaws.com/beta-1.77-3/beta-2024-02-18/reg/amadeus-commoncrawl-0.4.3/log.txt
  • https://crater-reports.s3.amazonaws.com/beta-1.77-3/beta-2024-02-18/reg/amadeus-parquet-0.4.3/log.txt
  • https://crater-reports.s3.amazonaws.com/beta-1.77-3/beta-2024-02-18/reg/amadeus-postgres-0.4.3/log.txt
  • https://crater-reports.s3.amazonaws.com/beta-1.77-3/beta-2024-02-18/reg/amadeus-serde-0.4.3/log.txt
  • https://crater-reports.s3.amazonaws.com/beta-1.77-3/beta-2024-02-18/reg/amadeus-types-0.4.3/log.txt

[INFO] [stdout] error[E0449]: visibility qualifiers are not permitted here
[INFO] [stdout]    --> src/par_stream.rs:647:16
[INFO] [stdout]     |
[INFO] [stdout] 647 |                   pool.spawn(FnOnce!(move |pool: &P::ThreadPool| {
[INFO] [stdout]     |  ____________________________^
[INFO] [stdout] 648 | |                     let mut process_tasks = tasks.into_iter();
[INFO] [stdout] 649 | |
[INFO] [stdout] 650 | |                     let mut tasks = (0..pool.threads()).map(|_| Vec::new()).collect::<Vec<_>>();
[INFO] [stdout] ...   |
[INFO] [stdout] 719 | |                     }
[INFO] [stdout] 720 | |                 }))
[INFO] [stdout]     | |__________________^
[INFO] [stdout]     |
[INFO] [stdout]     = note: trait items always share the visibility of their trait
[INFO] [stdout]     = note: this error originates in the macro `FnOnce` (in Nightly builds, run with -Z macro-backtrace for more info)

[lukas-code]

minimized: (playground)

trait Foo {
    fn foo() {
        pub struct Bar;
        impl Bar {
            pub fn bar() {}
        }
    }
}

bisects to #119505 cc @fmease

@rustbot label -E-needs-bisection -E-needs-mcve S-has-mcve A-visibility

[fmease]

I already have a PR fixing this, namely #120698. I'd like to improve the approach though, that's why it's waiting on author atm.

I've been aware of this regression (cc #119924) but I should definitely prioritize the PR then.

[apiraino]

WG-prioritization assigning priority (Zulip discussion)

Thanks @fmease and @compiler-errors for jumping on this!

@rustbot label -I-prioritize +P-critical

[fmease]

Downgrading the priority as discussed here.

[fmease]

Fixed by #122004.
Backported in #122524.
Closing as completed.