Add test and known limitation

tests/ui/anon_trait_imports.fixed

@@ -244,3 +244,18 @@ proc_macros::with_span!(
 //     use std::any::Any::{self};
 //     "foo".type_id();
 // }
+
+// This should warn the import is unused but should not trigger anon_trait_imports
+#[warn(unused)]
+mod unused_import {
+
+}
+
+// Limitation: Suggests `use std::any::{Any as _, Any as _};`
+// mod repeated_renamed {
+//     use std::any::{Any, Any as MyAny};
+
+//     fn foo() {
+//         "foo".type_id();
+//     }
+// }

tests/ui/anon_trait_imports.rs

@@ -244,3 +244,18 @@ proc_macros::with_span!(
 //     use std::any::Any::{self};
 //     "foo".type_id();
 // }
+
+// This should warn the import is unused but should not trigger anon_trait_imports
+#[warn(unused)]
+mod unused_import {
+    use std::any::Any;
+}
+
+// Limitation: Suggests `use std::any::{Any as _, Any as _};`
+// mod repeated_renamed {
+//     use std::any::{Any, Any as MyAny};
+
+//     fn foo() {
+//         "foo".type_id();
+//     }
+// }

tests/ui/anon_trait_imports.stderr

@@ -1,3 +1,12 @@
+error: unused import: `std::any::Any`
+  --> tests/ui/anon_trait_imports.rs:251:9
+   |
+LL |     use std::any::Any;
+   |         ^^^^^^^^^^^^^
+   |
+   = note: `-D unused-imports` implied by `-D warnings`
+   = help: to override `-D warnings` add `#[allow(unused_imports)]`
+
 error: importing trait that is only used anonymously
   --> tests/ui/anon_trait_imports.rs:12:19
    |
@@ -60,5 +69,5 @@ LL |     foo!();
    |
    = note: this error originates in the macro `foo` (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 9 previous errors
+error: aborting due to 10 previous errors