Fix cloned rsx double drop (#2839)

* Implement Rc generational pointers

* Clean up error handling a bit

* start adding tests

* Simplify a few types

* Separate Rc and normal generational boxes

* Add tests for rc drop and read

* Move over the pointer instead of the data in ReadOnlySignal props

* Fix panic on ref drop and release mode builds

* final rc signal cleanup

* use rc generational boxes for event handlers as well

* add a regression test for read only signal cloning

* merge main

---------

Co-authored-by: Jonathan Kelley <jkelleyrtp@gmail.com>

packages/generational-box/src/error.rs

@@ -5,7 +5,10 @@ use std::fmt::Display;
 use crate::GenerationalLocation;
 
 /// A result that can be returned from a borrow operation.
-pub type BorrowResult<T> = std::result::Result<T, BorrowError>;
+pub type BorrowResult<T = ()> = std::result::Result<T, BorrowError>;
+
+/// A result that can be returned from a borrow mut operation.
+pub type BorrowMutResult<T = ()> = std::result::Result<T, BorrowMutError>;
 
 #[derive(Debug, Clone, PartialEq)]
 /// An error that can occur when trying to borrow a value.
@@ -50,6 +53,15 @@ impl Display for BorrowMutError {
 
 impl Error for BorrowMutError {}
 
+impl From<BorrowError> for BorrowMutError {
+    fn from(error: BorrowError) -> Self {
+        match error {
+            BorrowError::Dropped(error) => BorrowMutError::Dropped(error),
+            BorrowError::AlreadyBorrowedMut(error) => BorrowMutError::AlreadyBorrowedMut(error),
+        }
+    }
+}
+
 /// An error that can occur when trying to use a value that has been dropped.
 #[derive(Debug, Copy, Clone, PartialEq)]
 pub struct ValueDroppedError {