1 error[E0308]: mismatched types
2 --> $DIR/issue-24819.rs:5:9
5 | ^^^^^^ expected struct `HashSet`, found struct `Vec`
7 = note: expected mutable reference `&mut HashSet<u32>`
8 found mutable reference `&mut Vec<_>`
10 error: aborting due to previous error
12 For more information about this error, try `rustc --explain E0308`.