error: mutable key type
  --> $DIR/mut_key.rs:29:32
   |
LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: `#[deny(clippy::mutable_key_type)]` on by default

error: mutable key type
  --> $DIR/mut_key.rs:29:72
   |
LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
   |                                                                        ^^^^^^^^^^^^

error: mutable key type
  --> $DIR/mut_key.rs:30:5
   |
LL |     let _other: HashMap<Key, bool> = HashMap::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: mutable key type
  --> $DIR/mut_key.rs:49:22
   |
LL | fn tuples_bad<U>(_m: &mut HashMap<(Key, U), bool>) {}
   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 4 previous errors