add test for rust-lang#78894

Author: surechen

tests/ui/lint/use-redundant/use-redundant-issue-78894.rs

@@ -0,0 +1,14 @@
+//@ check-pass
+//@ edition:2018
+#![warn(unused_imports)]
+
+fn main ()
+{
+    bar!();
+
+    macro_rules! bar {
+        () => ();
+    }
+
+    use bar;
+}