error[E0499]: cannot borrow `map` as mutable more than once at a time
  --> tests/state/map-multiple-entries.rs:12:14
   |
11 |     let e1 = map.entry(0u8);
   |              --- first mutable borrow occurs here
12 |     let e2 = map.entry(1u8);
   |              ^^^ second mutable borrow occurs here
13 |     // Use them, so we are certain that their lifetimes overlap.
14 |     e1.or_insert(1);
   |     -- first borrow later used here