error: mutable key type
  --> tests/ui/mut_key.rs:31:32
   |
LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Key`, which has interior mutability
   = note: ... because it contains `AtomicUsize`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability
   = note: `-D clippy::mutable-key-type` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::mutable_key_type)]`

error: mutable key type
  --> tests/ui/mut_key.rs:31:72
   |
LL | fn should_not_take_this_arg(m: &mut HashMap<Key, usize>, _n: usize) -> HashSet<Key> {
   |                                                                        ^^^^^^^^^^^^
   |
   = note: ... because it contains `Key`, which has interior mutability
   = note: ... because it contains `AtomicUsize`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:35:5
   |
LL |     let _other: HashMap<Key, bool> = HashMap::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Key`, which has interior mutability
   = note: ... because it contains `AtomicUsize`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:63:22
   |
LL | fn tuples_bad<U>(_m: &mut HashMap<(Key, U), bool>) {}
   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `(Key, U)`, which has interior mutability
   = note: ... because it contains `Key`, which has interior mutability
   = note: ... because it contains `AtomicUsize`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:76:5
   |
LL |     let _map = HashMap::<Cell<usize>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:78:5
   |
LL |     let _map = HashMap::<&mut Cell<usize>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `&mut Cell<usize>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:81:5
   |
LL |     let _map = HashMap::<Vec<Cell<usize>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Vec<Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:83:5
   |
LL |     let _map = HashMap::<BTreeMap<Cell<usize>, ()>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `BTreeMap<Cell<usize>, ()>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:85:5
   |
LL |     let _map = HashMap::<BTreeMap<(), Cell<usize>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `BTreeMap<(), Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:87:5
   |
LL |     let _map = HashMap::<BTreeSet<Cell<usize>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `BTreeSet<Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:89:5
   |
LL |     let _map = HashMap::<Option<Cell<usize>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Option<Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:91:5
   |
LL |     let _map = HashMap::<Option<Vec<Cell<usize>>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Option<Vec<Cell<usize>>>`, which has interior mutability
   = note: ... because it contains `Vec<Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:94:5
   |
LL |     let _map = HashMap::<Box<Cell<usize>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Box<Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:96:5
   |
LL |     let _map = HashMap::<Rc<Cell<usize>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Rc<Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: mutable key type
  --> tests/ui/mut_key.rs:98:5
   |
LL |     let _map = HashMap::<Arc<Cell<usize>>, usize>::new();
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: ... because it contains `Arc<Cell<usize>>`, which has interior mutability
   = note: ... because it contains `Cell<usize>`, which has interior mutability
   = note: ... because it contains `UnsafeCell<usize>`, which has interior mutability

error: aborting due to 15 previous errors