error[E0499]: cannot borrow `x` as mutable more than once at a time --> $DIR/issue-11715.rs:5:13 | LL | let y = &mut x; | ------ first mutable borrow occurs here LL | let z = &mut x; | ^^^^^^ second mutable borrow occurs here LL | z.use_mut(); LL | y.use_mut(); | - first borrow later used here error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0499`.