error[E0502]: cannot borrow `my_stuff` as mutable because it is also borrowed as immutable --> $DIR/hashmap-lifetimes.rs:18:5 | LL | let mut it = my_stuff.iter(); | -------- immutable borrow occurs here LL | my_stuff.insert(1, 43); //~ ERROR cannot borrow | ^^^^^^^^^^^^^^^^^^^^^^ mutable borrow occurs here LL | it; | -- borrow later used here error: aborting due to previous error For more information about this error, try `rustc --explain E0502`.