fix: use typeid of atoms for their unique ID (#558)

packages/fermi/src/root.rs

@@ -1,11 +1,21 @@
-use std::{any::Any, cell::RefCell, collections::HashMap, rc::Rc, sync::Arc};
+use std::{
+    any::{Any, TypeId},
+    cell::RefCell,
+    collections::HashMap,
+    rc::Rc,
+    sync::Arc,
+};
 
 use dioxus_core::ScopeId;
 use im_rc::HashSet;
 
 use crate::Readable;
 
-pub type AtomId = *const ();
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct AtomId {
+    pub(crate) ptr: *const (),
+    pub(crate) type_id: TypeId,
+}
 
 pub struct AtomRoot {
     pub atoms: RefCell<HashMap<AtomId, Slot>>,
@@ -44,7 +54,15 @@ impl AtomRoot {
         // initialize the value if it's not already initialized
         if let Some(slot) = atoms.get_mut(&f.unique_id()) {
             slot.subscribers.insert(scope);
-            slot.value.clone().downcast().unwrap()
+            match slot.value.clone().downcast() {
+                Ok(res) => res,
+                Err(e) => panic!(
+                    "Downcasting atom failed: {:?}. Has typeid of {:?} but needs typeid of {:?}",
+                    f.unique_id(),
+                    e.type_id(),
+                    TypeId::of::<V>()
+                ),
+            }
         } else {
             let value = Rc::new(f.init());
             let mut subscribers = HashSet::new();