error[E0308]: mismatched types
  --> $DIR/issue-24819.rs:5:9
   |
LL |     foo(&mut v);
   |         ^^^^^^ expected struct `std::collections::HashSet`, found struct `std::vec::Vec`
   |
   = note: expected mutable reference `&mut std::collections::HashSet<u32>`
              found mutable reference `&mut std::vec::Vec<_>`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.