Do not alias fields of tracked_struct Values when updating

Author: Veykril

src/attach.rs

@@ -41,11 +41,10 @@ impl Attached {
                     // Already attached? Assert that the database has not changed.
                     // NOTE: It's important to use `addr_eq` here because `NonNull::eq`
                     // not only compares the address but also the type's metadata.
-                    if !std::ptr::addr_eq(current_db.as_ptr(), new_db.as_ptr()) {
-                        panic!(
-                            "Cannot change database mid-query. current: {current_db:?}, new: {new_db:?}",
-                        );
-                    }
+                    assert!(
+                        std::ptr::addr_eq(current_db.as_ptr(), new_db.as_ptr()),
+                       "Cannot change database mid-query. current: {current_db:?}, new: {new_db:?}"
+                    );
 
                     Self { state: None }
                 } else {

src/input.rs

@@ -318,15 +318,18 @@ impl<C> Slot for Value<C>
 where
     C: Configuration,
 {
-    unsafe fn memos(&self, _current_revision: Revision) -> &crate::table::memo::MemoTable {
-        &self.memos
+    unsafe fn memos(
+        this: *const Self,
+        _current_revision: Revision,
+    ) -> *const crate::table::memo::MemoTable {
+        unsafe { &raw const (*this).memos }
     }
 
     fn memos_mut(&mut self) -> &mut crate::table::memo::MemoTable {
         &mut self.memos
     }
 
-    unsafe fn syncs(&self, _current_revision: Revision) -> &SyncTable {
-        &self.syncs
+    unsafe fn syncs(this: *const Self, _current_revision: Revision) -> *const SyncTable {
+        unsafe { &raw const (*this).syncs }
     }
 }

src/interned.rs

@@ -354,16 +354,19 @@ impl<C> Slot for Value<C>
 where
     C: Configuration,
 {
-    unsafe fn memos(&self, _current_revision: Revision) -> &MemoTable {
-        &self.memos
+    unsafe fn memos(
+        this: *const Self,
+        _current_revision: Revision,
+    ) -> *const crate::table::memo::MemoTable {
+        unsafe { &raw const (*this).memos }
     }
 
-    fn memos_mut(&mut self) -> &mut MemoTable {
+    fn memos_mut(&mut self) -> &mut crate::table::memo::MemoTable {
         &mut self.memos
     }
 
-    unsafe fn syncs(&self, _current_revision: Revision) -> &crate::table::sync::SyncTable {
-        &self.syncs
+    unsafe fn syncs(this: *const Self, _current_revision: Revision) -> *const SyncTable {
+        unsafe { &raw const (*this).syncs }
     }
 }
 

src/table.rs

@@ -79,7 +79,7 @@ pub(crate) trait Slot: Any + Send + Sync {
     /// # Safety condition
     ///
     /// The current revision MUST be the current revision of the database containing this slot.
-    unsafe fn memos(&self, current_revision: Revision) -> &MemoTable;
+    unsafe fn memos(slot: *const Self, current_revision: Revision) -> *const MemoTable;
 
     /// Mutably access the [`MemoTable`] for this slot.
     fn memos_mut(&mut self) -> &mut MemoTable;
@@ -89,7 +89,7 @@ pub(crate) trait Slot: Any + Send + Sync {
     /// # Safety condition
     ///
     /// The current revision MUST be the current revision of the database containing this slot.
-    unsafe fn syncs(&self, current_revision: Revision) -> &SyncTable;
+    unsafe fn syncs(slot: *const Self, current_revision: Revision) -> *const SyncTable;
 }
 
 unsafe impl<T: Slot> Send for Page<T> {}
@@ -333,15 +333,15 @@ impl<T: Slot> TablePage for Page<T> {
     }
 
     unsafe fn memos(&self, slot: SlotIndex, current_revision: Revision) -> &MemoTable {
-        unsafe { self.get(slot).memos(current_revision) }
+        unsafe { &*T::memos(self.get_raw(slot), current_revision) }
     }
 
     fn memos_mut(&mut self, slot: SlotIndex) -> &mut MemoTable {
         self.get_mut(slot).memos_mut()
     }
 
     unsafe fn syncs(&self, slot: SlotIndex, current_revision: Revision) -> &SyncTable {
-        unsafe { self.get(slot).syncs(current_revision) }
+        unsafe { &*T::syncs(self.get_raw(slot), current_revision) }
     }
 }