error: mutable key type --> $DIR/mut_key.rs:27:32 | LL | fn should_not_take_this_arg(m: &mut HashMap, _n: usize) -> HashSet { | ^^^^^^^^^^^^^^^^^^^^^^^^ | = note: `#[deny(clippy::mutable_key_type)]` on by default error: mutable key type --> $DIR/mut_key.rs:27:72 | LL | fn should_not_take_this_arg(m: &mut HashMap, _n: usize) -> HashSet { | ^^^^^^^^^^^^ error: mutable key type --> $DIR/mut_key.rs:28:5 | LL | let _other: HashMap = HashMap::new(); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: mutable key type --> $DIR/mut_key.rs:47:22 | LL | fn tuples_bad(_m: &mut HashMap<(Key, U), bool>) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ error: aborting due to 4 previous errors