regression: rustc incorrectly claims that enum variant is inaccessible

[camelid]

MCVE

mod list {
    pub use List::Cons;

    pub enum List<T> {
        Cons(T, Box<List<T>>),
    }
}

mod alias {
    use crate::list::List;

    pub type Foo = List<String>;
}

fn foo(l: crate::alias::Foo) {
    match l {
        Cons(hd, tl) => {}
    }
}

New error (incorrect)

error[E0531]: cannot find tuple struct or tuple variant `Cons` in this scope
  --> src/lib.rs:17:9
   |
17 |         Cons(hd, tl) => {}
   |         ^^^^ not found in this scope
   |
note: tuple variant `crate::alias::List::Cons` exists but is inaccessible
  --> src/lib.rs:5:9
   |
5  |         Cons(T, Box<List<T>>),
   |         ^^^^^^^^^^^^^^^^^^^^^ not accessible

For more information about this error, try `rustc --explain E0531`.

Old error (correct)

error[E0531]: cannot find tuple struct or tuple variant `Cons` in this scope
  --> src/lib.rs:17:9
   |
17 |         Cons(hd, tl) => {}
   |         ^^^^ not found in this scope
   |
help: consider importing this tuple variant
   |
1  | use crate::alias::List::Cons;
   |

For more information about this error, try `rustc --explain E0531`.

[camelid]

Bisected to a rollup, but I think it's very likely to be #88838. cc @FabianWolff @estebank

searched nightlies: from nightly-2021-10-01 to nightly-2021-10-19
regressed nightly: nightly-2021-10-02
searched commits: from aa7aca3 to c02371c
regressed commit: 69eb996

bisected with cargo-bisect-rustc v0.6.0

Host triple: x86_64-apple-darwin
Reproduce with:

cargo bisect-rustc --preserve --prompt --start=2021-10-01 --end=2021-10-19 -- check 

[camelid]

The old suggestion was actually incorrect because it suggested crate::alias::List::Cons, which is a private import. However, the new error is "more incorrect" IMO since it says something confusing (and incorrect).

[apiraino]

Assigning priority as discussed in the Zulip thread of the Prioritization Working Group.

@rustbot label -I-prioritize +P-medium