1 error[E0499]: cannot borrow `foo` as mutable more than once at a time
2 --> $DIR/hrtb-debruijn-in-receiver.rs:17:5
5 | --- first mutable borrow occurs here
6 LL | foo.insert(); //~ ERROR cannot borrow
7 | ^^^ second mutable borrow occurs here
9 | - first borrow ends here
11 error: aborting due to previous error
13 For more information about this error, try `rustc --explain E0499`.