Implement dummy expansions for builtin attributes

crates/ide_completion/src/completions/qualified_path.rs

@@ -656,6 +656,32 @@ fn main() { let _ = crate::$0 }
         );
     }
 
+    #[test]
+    fn does_not_complete_non_fn_macros() {
+        check(
+            r#"
+mod m {
+    #[rustc_builtin_macro]
+    pub macro Clone {}
+}
+
+fn f() {m::$0}
+"#,
+            expect![[r#""#]],
+        );
+        check(
+            r#"
+mod m {
+    #[rustc_builtin_macro]
+    pub macro bench {}
+}
+
+fn f() {m::$0}
+"#,
+            expect![[r#""#]],
+        );
+    }
+
     #[test]
     fn completes_in_assoc_item_list() {
         check(

crates/ide_completion/src/completions/unqualified_path.rs

@@ -481,14 +481,14 @@ impl S {
         );
         check(
             r#"
-mod m {
-    #[rustc_builtin_macro]
-    pub macro Clone {}
-}
+#[rustc_builtin_macro]
+pub macro bench {}
 
-fn f() {m::$0}
+fn f() {$0}
 "#,
-            expect![[r#""#]],
+            expect![[r#"
+                fn f() fn()
+            "#]],
         );
     }