error[E0499]: cannot borrow `b` as mutable more than once at a time --> $DIR/mut-cant-alias.rs:9:20 | LL | let b1 = &mut *b; | - first mutable borrow occurs here LL | let b2 = &mut *b; | ^ second mutable borrow occurs here LL | b1.use_mut(); | -- first borrow later used here error: aborting due to previous error For more information about this error, try `rustc --explain E0499`.