Don't complete attributes with existing expressions

crates/ide_completion/src/completions/attribute.rs

@@ -56,6 +56,7 @@ pub(crate) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext)
             _ => (),
         },
         (_, Some(_)) => (),
+        (_, None) if attribute.expr().is_some() => (),
         (_, None) => complete_new_attribute(acc, ctx, attribute),
     }
     Some(())

crates/ide_completion/src/tests/attribute.rs

@@ -40,6 +40,19 @@ struct Foo;
     )
 }
 
+#[test]
+fn proc_macros_on_comment() {
+    check(
+        r#"
+//- proc_macros: identity
+/// $0
+#[proc_macros::identity]
+struct Foo;
+"#,
+        expect![[r#""#]],
+    )
+}
+
 #[test]
 fn proc_macros_qualified() {
     check(