error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:5:28
   |
LL | const CONST_NOT_OK: Option<BTreeMap<String, ()>> = None;
   |                            ^^^^^^^^^^^^^^^^^^^^
   |
   = note: `-D clippy::zero-sized-map-values` implied by `-D warnings`
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:8:30
   |
LL | static STATIC_NOT_OK: Option<BTreeMap<String, ()>> = None;
   |                              ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:11:17
   |
LL | type NotOkMap = BTreeMap<String, ()>;
   |                 ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:15:11
   |
LL |     NotOk(BTreeMap<String, ()>),
   |           ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:20:13
   |
LL |     not_ok: BTreeMap<String, ()>,
   |             ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:22:22
   |
LL |     also_not_ok: Vec<BTreeMap<usize, ()>>,
   |                      ^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:30:30
   |
LL |     fn weird_map(&self, map: BTreeMap<usize, ()>);
   |                              ^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:38:25
   |
LL |     fn not_ok(&self) -> BTreeMap<String, ()> {
   |                         ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:55:14
   |
LL | fn test(map: BTreeMap<String, ()>, key: &str) -> BTreeMap<String, ()> {
   |              ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:55:50
   |
LL | fn test(map: BTreeMap<String, ()>, key: &str) -> BTreeMap<String, ()> {
   |                                                  ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:64:35
   |
LL |     let _: BTreeMap<String, ()> = BTreeMap::new();
   |                                   ^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:64:12
   |
LL |     let _: BTreeMap<String, ()> = BTreeMap::new();
   |            ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> $DIR/zero_sized_btreemap_values.rs:67:12
   |
LL |     let _: BTreeMap<_, _> = std::iter::empty::<(String, ())>().collect();
   |            ^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: aborting due to 13 previous errors