error[E0596]: cannot borrow immutable borrowed content `*x` as mutable --> $DIR/borrowck-object-mutability.rs:8:5 | LL | fn borrowed_receiver(x: &Foo) { | ---- use `&mut Foo` here to make mutable LL | x.borrowed(); LL | x.borrowed_mut(); | ^ cannot borrow as mutable error[E0596]: cannot borrow immutable `Box` content `*x` as mutable --> $DIR/borrowck-object-mutability.rs:18:5 | LL | fn owned_receiver(x: Box) { | - help: make this binding mutable: `mut x` LL | x.borrowed(); LL | x.borrowed_mut(); | ^ cannot borrow as mutable error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0596`.