fix: check if the used path is a trait

Author: woshilapin

clippy_lints/src/needless_traits_in_scope.rs

@@ -47,6 +47,14 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessTraitsInScope {
         let ItemKind::Use(use_path, UseKind::Single) = item.kind else {
             return
         };
+        // Check if it's a trait
+        if !use_path
+            .res
+            .iter()
+            .any(|res| matches!(res, def::Res::Def(def::DefKind::Trait, _)))
+        {
+            return;
+        }
         // Check if the `use` is aliased with ` as `.
         // If aliased, then do not process, it's probably for a good reason
         if item.ident != use_path.segments.last().unwrap().ident {

tests/ui/needless_traits_in_scope.fixed

@@ -22,6 +22,17 @@ pub mod trait_not_in_scope {
     }
 }
 
+pub mod is_not_a_trait {
+    mod inner {
+        pub struct Read;
+    }
+    use inner::Read;
+
+    pub fn ok() {
+        let _ = Read;
+    }
+}
+
 // FIXME: when the trait is explicitely used, the lint should not trigger
 // pub mod useful_trait_in_scope {
 //     use std::io::Read;
@@ -36,5 +47,6 @@ pub mod trait_not_in_scope {
 fn main() {
     useless_trait_in_scope::warn();
     trait_not_in_scope::ok();
+    is_not_a_trait::ok();
     // useful_trait_in_scope::ok();
 }

tests/ui/needless_traits_in_scope.rs

@@ -22,6 +22,17 @@ pub mod trait_not_in_scope {
     }
 }
 
+pub mod is_not_a_trait {
+    mod inner {
+        pub struct Read;
+    }
+    use inner::Read;
+
+    pub fn ok() {
+        let _ = Read;
+    }
+}
+
 // FIXME: when the trait is explicitely used, the lint should not trigger
 // pub mod useful_trait_in_scope {
 //     use std::io::Read;
@@ -36,5 +47,6 @@ pub mod trait_not_in_scope {
 fn main() {
     useless_trait_in_scope::warn();
     trait_not_in_scope::ok();
+    is_not_a_trait::ok();
     // useful_trait_in_scope::ok();
 }