Consider traits in lint

Author: korrat

clippy_lints/src/zero_sized_map_values.rs

@@ -46,22 +46,44 @@ impl LateLintPass<'_> for ZeroSizedMapValues {
         self.check_ty(cx, ty, local.pat.span);
     }
 
-    fn check_fn(&mut self, cx: &LateContext<'_>, _: FnKind<'_>, decl: &FnDecl<'_>, _: &Body<'_>, _: Span, _: HirId) {
-        for ty in decl.inputs {
-            self.check_hir_ty(cx, ty);
+    fn check_fn(&mut self, cx: &LateContext<'_>, _: FnKind<'_>, decl: &FnDecl<'_>, _: &Body<'_>, _: Span, id: HirId) {
+        if let Some(Node::Item(item)) = cx.tcx.hir().find(cx.tcx.hir().get_parent_item(id)) {
+            if let ItemKind::Impl { of_trait: Some(_), .. } = item.kind {
+                return;
+            }
         }
 
-        if let FnRetTy::Return(ty) = decl.output {
-            self.check_hir_ty(cx, ty);
-        }
+        self.check_fn_decl(cx, decl);
     }
 
     fn check_struct_field(&mut self, cx: &LateContext<'_>, field: &StructField<'_>) {
         self.check_hir_ty(cx, field.ty);
     }
+
+    fn check_trait_item(&mut self, cx: &LateContext<'_>, item: &TraitItem<'_>) {
+        match item.kind {
+            TraitItemKind::Const(ref ty, _) | TraitItemKind::Type(_, Some(ref ty)) => {
+                self.check_hir_ty(cx, ty);
+            },
+            TraitItemKind::Fn(ref sig, _) => {
+                self.check_fn_decl(cx, &sig.decl);
+            },
+            _ => (),
+        }
+    }
 }
 
 impl ZeroSizedMapValues {
+    fn check_fn_decl(&mut self, cx: &LateContext<'_>, decl: &FnDecl<'_>) {
+        for ty in decl.inputs {
+            self.check_hir_ty(cx, ty);
+        }
+
+        if let FnRetTy::Return(ty) = decl.output {
+            self.check_hir_ty(cx, ty);
+        }
+    }
+
     fn check_hir_ty(&mut self, cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>) {
         let ty = hir_ty_to_ty(cx.tcx, hir_ty);
         self.check_ty(cx, ty, hir_ty.span);

tests/ui/zero_sized_map_values.rs

@@ -8,6 +8,26 @@ struct Test {
     also_not_ok: Vec<HashMap<usize, ()>>,
 }
 
+trait TestTrait {
+    type Output;
+
+    fn produce_output() -> Self::Output;
+
+    fn weird_map(&self, map: HashMap<usize, ()>);
+}
+
+impl TestTrait for Test {
+    type Output = HashMap<String, ()>;
+
+    fn produce_output() -> Self::Output {
+        todo!();
+    }
+
+    fn weird_map(&self, map: HashMap<usize, ()>) {
+        todo!();
+    }
+}
+
 fn test(map: HashMap<String, ()>, key: &str) -> HashMap<String, ()> {
     todo!();
 }

tests/ui/zero_sized_map_values.stderr

@@ -16,36 +16,44 @@ LL |     also_not_ok: Vec<HashMap<usize, ()>>,
    = help: consider using a set instead
 
 error: map with zero-sized value type
-  --> $DIR/zero_sized_map_values.rs:11:14
+  --> $DIR/zero_sized_map_values.rs:16:30
+   |
+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
    |
 LL | fn test(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:11:49
+  --> $DIR/zero_sized_map_values.rs:31:49
    |
 LL | fn test(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:21:9
+  --> $DIR/zero_sized_map_values.rs:41:9
    |
 LL |     let _: HashMap<String, ()> = HashMap::new();
    |         ^
    |
    = help: consider using a set instead
 
 error: map with zero-sized value type
-  --> $DIR/zero_sized_map_values.rs:24:9
+  --> $DIR/zero_sized_map_values.rs:44:9
    |
 LL |     let _: HashMap<_, _> = std::iter::empty::<(String, ())>().collect();
    |         ^
    |
    = help: consider using a set instead
 
-error: aborting due to 6 previous errors
+error: aborting due to 7 previous errors