Also check for BTreeMap with zero-sized value type

Author: korrat

clippy_lints/src/zero_sized_map_values.rs

@@ -139,7 +139,7 @@ impl ZeroSizedMapValues {
         }
 
         if_chain! {
-                if match_type(cx, ty, &paths::HASHMAP);
+                if match_type(cx, ty, &paths::HASHMAP) || match_type(cx, ty, &paths::BTREEMAP);
                 if let Adt(_, ref substs) = ty.kind();
                 let ty = substs.type_at(1);
                 if let Ok(layout) = cx.layout_of(ty);

tests/ui/zero_sized_map_values.stderr

@@ -24,18 +24,18 @@ LL |     fn weird_map(&self, map: HashMap<usize, ()>);
    = help: consider using a set instead
 
 error: map with zero-sized value type
-  --> $DIR/zero_sized_map_values.rs:31:14
+  --> $DIR/zero_sized_map_values.rs:31:24
    |
-LL | fn test(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
-   |              ^^^^^^^^^^^^^^^^^^^
+LL | fn hashmap_not_ok(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
+   |                        ^^^^^^^^^^^^^^^^^^^
    |
    = help: consider using a set instead
 
 error: map with zero-sized value type
-  --> $DIR/zero_sized_map_values.rs:31:49
+  --> $DIR/zero_sized_map_values.rs:31:59
    |
-LL | fn test(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
-   |                                                 ^^^^^^^^^^^^^^^^^^^
+LL | fn hashmap_not_ok(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
+   |                                                           ^^^^^^^^^^^^^^^^^^^
    |
    = help: consider using a set instead
 
@@ -50,10 +50,18 @@ LL |     let _: HashMap<String, ()> = HashMap::new();
 error: map with zero-sized value type
   --> $DIR/zero_sized_map_values.rs:44:9
    |
+LL |     let _: BTreeMap<String, ()> = BTreeMap::new();
+   |         ^
+   |
+   = help: consider using a set instead
+
+error: map with zero-sized value type
+  --> $DIR/zero_sized_map_values.rs:47:9
+   |
 LL |     let _: HashMap<_, _> = std::iter::empty::<(String, ())>().collect();
    |         ^
    |
    = help: consider using a set instead
 
-error: aborting due to 7 previous errors
+error: aborting due to 8 previous errors