1 error[E0499]: cannot borrow `foo` as mutable more than once at a time
2 --> $DIR/hrtb-debruijn-in-receiver.rs:27:5
5 | --- first mutable borrow occurs here
6 LL | foo.insert(); //~ ERROR cannot borrow
9 | second mutable borrow occurs here
10 | first borrow later used here
12 error: aborting due to previous error
14 For more information about this error, try `rustc --explain E0499`.