Slightly cheaper get_mut

Co-authored-by: Ibraheem Ahmed <[email protected]>

Author: Veykril

src/storage.rs

@@ -1,6 +1,5 @@
 //! Public API facades for the implementation details of [`Zalsa`] and [`ZalsaLocal`].
 use std::marker::PhantomData;
-use std::mem;
 use std::panic::RefUnwindSafe;
 
 use crate::database::RawDatabase;
@@ -158,9 +157,10 @@ impl<Db: Database> Storage<Db> {
 
         let mut coordinate_lock = self.handle.coordinate.coordinate_lock.lock();
         let zalsa = loop {
-            if let Some(zalsa) = Arc::get_mut(&mut self.handle.zalsa_impl) {
-                // SAFETY: Polonius when ... https://github.com/rust-lang/rfcs/blob/master/text/2094-nll.md#problem-case-3-conditional-control-flow-across-functions
-                break unsafe { mem::transmute::<&mut Zalsa, &mut Zalsa>(zalsa) };
+            if Arc::strong_count(&self.handle.zalsa_impl) == 1 {
+                // SAFETY: The strong count is 1, and we never create any weak pointers,
+                // so we have a unique reference.
+                break unsafe { &mut *(Arc::as_ptr(&self.handle.zalsa_impl).cast_mut()) };
             }
             coordinate_lock = self.handle.coordinate.cvar.wait(coordinate_lock);
         };

src/table.rs

@@ -252,7 +252,10 @@ impl Table {
                 }
 
                 let allocated_idx = self.push_page::<T>(ingredient, memo_types.clone());
-                assert_eq!(allocated_idx, page_idx);
+                assert_eq!(
+                    allocated_idx, page_idx,
+                    "allocated index does not match requested index"
+                );
             }
         };
     }

src/views.rs

@@ -108,7 +108,11 @@ impl Views {
         &self,
         func: fn(NonNull<Concrete>) -> NonNull<DbView>,
     ) -> &DatabaseDownCaster<DbView> {
-        assert_eq!(self.source_type_id, TypeId::of::<Concrete>());
+        assert_eq!(
+            self.source_type_id,
+            TypeId::of::<Concrete>(),
+            "mismatched source type"
+        );
         let target_type_id = TypeId::of::<DbView>();
         if let Some((_, caster)) = self
             .view_casters

src/zalsa_local.rs

@@ -1173,7 +1173,7 @@ impl ActiveQueryGuard<'_> {
         unsafe {
             self.local_state.with_query_stack_unchecked_mut(|stack| {
                 #[cfg(debug_assertions)]
-                assert_eq!(stack.len(), self.push_len);
+                assert_eq!(stack.len(), self.push_len, "mismatched push and pop");
                 let frame = stack.last_mut().unwrap();
                 frame.tracked_struct_ids_mut().seed(tracked_struct_ids);
             })
@@ -1195,7 +1195,7 @@ impl ActiveQueryGuard<'_> {
         unsafe {
             self.local_state.with_query_stack_unchecked_mut(|stack| {
                 #[cfg(debug_assertions)]
-                assert_eq!(stack.len(), self.push_len);
+                assert_eq!(stack.len(), self.push_len, "mismatched push and pop");
                 let frame = stack.last_mut().unwrap();
                 frame.seed_iteration(durability, changed_at, edges, untracked_read, tracked_ids);
             })