add test cases, refactor deref

examples/stale_memo.rs

@@ -0,0 +1,36 @@
+use dioxus::prelude::*;
+
+fn main() {
+    launch_desktop(app);
+}
+
+fn app() -> Element {
+    let mut state = use_signal(|| 0);
+    let mut depth = use_signal(|| 1 as usize);
+
+    if depth() == 5 {
+        return rsx! {
+            div { "Max depth reached" }
+            button { onclick: move |_| depth -= 1, "Remove depth" }
+        };
+    }
+
+    let mut items = use_memo(move || (0..depth()).map(|f| f as _).collect::<Vec<isize>>());
+
+    rsx! {
+        button { onclick: move |_| state += 1, "Increment" }
+        button { onclick: move |_| depth += 1, "Add depth" }
+        button {
+            onclick: move |_| async move {
+                depth += 1;
+                tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+                dbg!(items.read());
+                // if depth() is 5, this will be the old since the memo hasn't been re-computed
+                // use_memos are only re-computed when the signals they capture change
+                // *and* they are used in the current render
+                // If the use_memo isn't used, it can't be re-computed!
+            },
+            "Add depth with sleep"
+        }
+    }
+}