error[E0308]: mismatched types --> $DIR/issue-24819.rs:5:9 | LL | foo(&mut v); | --- ^^^^^^ expected `&mut HashSet`, found `&mut Vec<_>` | | | arguments to this function are incorrect | = note: expected mutable reference `&mut HashSet` found mutable reference `&mut Vec<_>` note: function defined here --> $DIR/issue-24819.rs:10:4 | LL | fn foo(h: &mut HashSet) { | ^^^ -------------------- error: aborting due to previous error For more information about this error, try `rustc --explain E0308`.