error[E0308]: mismatched types --> $DIR/coerce-mut.rs:5:7 | LL | f(&x); | - ^^ types differ in mutability | | | arguments to this function are incorrect | = note: expected mutable reference `&mut i32` found reference `&{integer}` note: function defined here --> $DIR/coerce-mut.rs:1:4 | LL | fn f(x: &mut i32) {} | ^ ----------- error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0308`.