error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:5:28
   |
LL | const CONST_NOT_OK: Option<BTreeMap<String, ()>> = None;
   |                            ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead
   = note: `-D clippy::zero-sized-map-values` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::zero_sized_map_values)]`

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:9:30
   |
LL | static STATIC_NOT_OK: Option<BTreeMap<String, ()>> = None;
   |                              ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:13:17
   |
LL | type NotOkMap = BTreeMap<String, ()>;
   |                 ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:18:11
   |
LL |     NotOk(BTreeMap<String, ()>),
   |           ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:24:13
   |
LL |     not_ok: BTreeMap<String, ()>,
   |             ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:26:22
   |
LL |     also_not_ok: Vec<BTreeMap<usize, ()>>,
   |                      ^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:35:30
   |
LL |     fn weird_map(&self, map: BTreeMap<usize, ()>);
   |                              ^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:44:25
   |
LL |     fn not_ok(&self) -> BTreeMap<String, ()> {
   |                         ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:62:14
   |
LL | fn test(map: BTreeMap<String, ()>, key: &str) -> BTreeMap<String, ()> {
   |              ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:62:50
   |
LL | fn test(map: BTreeMap<String, ()>, key: &str) -> BTreeMap<String, ()> {
   |                                                  ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:73:35
   |
LL |     let _: BTreeMap<String, ()> = BTreeMap::new();
   |                                   ^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:73:12
   |
LL |     let _: BTreeMap<String, ()> = BTreeMap::new();
   |            ^^^^^^^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: map with zero-sized value type
  --> tests/ui/zero_sized_btreemap_values.rs:78:12
   |
LL |     let _: BTreeMap<_, _> = std::iter::empty::<(String, ())>().collect();
   |            ^^^^^^^^^^^^^^
   |
   = help: consider using a set instead

error: aborting due to 13 previous errors