fix: do not complete builtin attributes for qualified paths

crates/ide_completion/src/completions/attribute.rs

@@ -22,7 +22,11 @@
 
 pub(crate) fn complete_attribute(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
     let attribute = ctx.attribute_under_caret.as_ref()?;
-    match (attribute.path().and_then(|p| p.as_single_name_ref()), attribute.token_tree()) {
+    let name_ref = match attribute.path() {
+        Some(p) => Some(p.as_single_name_ref()?),
+        None => None,
+    };
+    match (name_ref, attribute.token_tree()) {
         (Some(path), Some(token_tree)) => match path.text().as_str() {
             "derive" => derive::complete_derive(acc, ctx, token_tree),
             "repr" => repr::complete_repr(acc, ctx, token_tree),

crates/ide_completion/src/tests/attribute.rs

@@ -33,6 +33,18 @@ fn doesnt_complete_items() {
     )
 }
 
+#[test]
+fn doesnt_complete_qualified() {
+    check(
+        r#"
+struct Foo;
+#[foo::$0]
+use self as this;
+"#,
+        expect![[r#""#]],
+    )
+}
+
 #[test]
 fn inside_nested_attr() {
     check(r#"#[cfg($0)]"#, expect![[]])