Fix returns(deref | as_ref | as_deref) in tracked methods

Author: MichaReiser

tests/tracked_method_inherent_return_deref.rs

@@ -0,0 +1,31 @@
+use salsa::Database;
+
+#[salsa::input]
+struct Input {
+    number: usize,
+}
+
+#[salsa::tracked]
+impl Input {
+    #[salsa::tracked(returns(deref))]
+    fn test(self, db: &dyn salsa::Database) -> Vec<String> {
+        (0..self.number(db)).map(|i| format!("test {i}")).collect()
+    }
+}
+
+#[test]
+fn invoke() {
+    salsa::DatabaseImpl::new().attach(|db| {
+        let input = Input::new(db, 3);
+        let x: &[String] = input.test(db);
+
+        assert_eq!(
+            x,
+            &[
+                "test 0".to_string(),
+                "test 1".to_string(),
+                "test 2".to_string()
+            ]
+        );
+    })
+}