Fix generation race condition with sync storage (#2638)

* Fix generation race condition with sync storage

* Document GenerationalPointer

* check generation before recycling generational box

* fix clippy

* make race_condition_regression test panic if it fails

packages/signals/src/copy_value.rs

@@ -75,16 +75,12 @@ impl<T: 'static, S: Storage<T>> CopyValue<T, S> {
 
     pub(crate) fn new_with_caller(
         value: T,
-        #[cfg(debug_assertions)] caller: &'static std::panic::Location<'static>,
+        caller: &'static std::panic::Location<'static>,
     ) -> Self {
         let owner = current_owner();
 
         Self {
-            value: owner.insert_with_caller(
-                value,
-                #[cfg(debug_assertions)]
-                caller,
-            ),
+            value: owner.insert_with_caller(value, caller),
             origin_scope: current_scope_id().expect("in a virtual dom"),
         }
     }

packages/signals/src/signal.rs

@@ -167,7 +167,6 @@ impl<T: 'static, S: Storage<SignalData<T>>> Signal<T, S> {
     ///     use_hook(move || Signal::new_with_caller(function(), caller))
     /// }
     /// ```
-    #[allow(unused)]
     pub fn new_with_caller(value: T, caller: &'static std::panic::Location<'static>) -> Self {
         Self {
             inner: CopyValue::new_with_caller(
@@ -175,7 +174,6 @@ impl<T: 'static, S: Storage<SignalData<T>>> Signal<T, S> {
                     subscribers: Default::default(),
                     value,
                 },
-                #[cfg(debug_assertions)]
                 caller,
             ),
         }