fix signal error message and add tests (#2118)

packages/signals/examples/errors.rs

@@ -1,75 +0,0 @@
-use dioxus::prelude::*;
-
-fn main() {
-    launch(app);
-}
-
-#[derive(Clone, Copy)]
-enum ErrorComponent {
-    Read,
-    ReadMut,
-    ReadDropped,
-}
-
-fn app() -> Element {
-    let mut error = use_signal(|| None as Option<ErrorComponent>);
-
-    rsx! {
-        match error() {
-            Some(ErrorComponent::Read) => rsx! { Read {} },
-            Some(ErrorComponent::ReadMut) => rsx! { ReadMut {} },
-            Some(ErrorComponent::ReadDropped) => rsx! { ReadDropped {} },
-            None => rsx! {
-                button { onclick: move |_| error.set(Some(ErrorComponent::Read)), "Read" }
-                button { onclick: move |_| error.set(Some(ErrorComponent::ReadMut)), "ReadMut" }
-                button { onclick: move |_| error.set(Some(ErrorComponent::ReadDropped)), "ReadDropped"}
-            }
-        }
-    }
-}
-
-#[component]
-fn Read() -> Element {
-    let signal = use_signal_sync(|| 0);
-
-    let _write = signal.write_unchecked();
-    let _read = signal.read();
-
-    unreachable!()
-}
-
-#[component]
-fn ReadMut() -> Element {
-    let signal = use_signal_sync(|| 0);
-
-    let _read = signal.read();
-    let _write = signal.write_unchecked();
-
-    unreachable!()
-}
-
-#[component]
-fn ReadDropped() -> Element {
-    let signal = use_signal_sync(|| None as Option<SyncSignal<i32>>);
-
-    if generation() < 4 {
-        needs_update();
-    }
-
-    rsx! {
-        if let Some(value) = signal() {
-            "{value:?}"
-        } else {
-            ReadDroppedSignalChild { parent_signal: signal }
-        }
-    }
-}
-
-#[component]
-fn ReadDroppedSignalChild(parent_signal: SyncSignal<Option<SyncSignal<i32>>>) -> Element {
-    let signal = use_signal_sync(|| 0);
-
-    use_hook(move || parent_signal.set(Some(signal)));
-
-    rsx! { "{signal}" }
-}