fix: unused_trait_names FP when as name is from macro input

Author: profetia

clippy_lints/src/unused_trait_names.rs

@@ -73,6 +73,8 @@ impl<'tcx> LateLintPass<'tcx> for UnusedTraitNames {
             && let Some(snip) = snippet_opt(cx, last_segment.ident.span)
             && self.msrv.meets(cx, msrvs::UNDERSCORE_IMPORTS)
             && !is_from_proc_macro(cx, &last_segment.ident)
+            // Skip if the ident of `as` is from a macro's input
+            && !(last_segment.ident.span.from_expansion() && !ident.span.from_expansion())
         {
             let complete_span = last_segment.ident.span.to(ident.span);
             span_lint_and_sugg(

tests/ui/unused_trait_names.fixed

@@ -294,3 +294,22 @@ mod allow_lint_import {
 //         "foo".type_id();
 //     }
 // }
+
+mod issue14924 {
+    mod m {
+        pub trait Tr {
+            fn method(&self) {}
+        }
+
+        impl Tr for u8 {}
+    }
+
+    macro gen_import($Br: ident) {
+        use m::Tr as $Br;
+    }
+    gen_import!(Br);
+
+    fn do_something() {
+        0u8.method();
+    }
+}

tests/ui/unused_trait_names.rs

@@ -294,3 +294,22 @@ mod allow_lint_import {
 //         "foo".type_id();
 //     }
 // }
+
+mod issue14924 {
+    mod m {
+        pub trait Tr {
+            fn method(&self) {}
+        }
+
+        impl Tr for u8 {}
+    }
+
+    macro gen_import($Br: ident) {
+        use m::Tr as $Br;
+    }
+    gen_import!(Br);
+
+    fn do_something() {
+        0u8.method();
+    }
+}