Implement DerefMut

Author: MichaReiser

src/database.rs

@@ -196,6 +196,15 @@ impl<U: UserData> std::ops::Deref for DatabaseImpl<U> {
     }
 }
 
+impl<U: UserData> std::ops::DerefMut for DatabaseImpl<U> {
+    fn deref_mut(&mut self) -> &mut U {
+        self.zalsa_mut()
+            .user_data_mut()
+            .downcast_mut::<U>()
+            .unwrap()
+    }
+}
+
 impl<U: UserData + RefUnwindSafe> RefUnwindSafe for DatabaseImpl<U> {}
 
 #[salsa_macros::db]

src/zalsa.rs

@@ -179,6 +179,10 @@ impl Zalsa {
         &*self.user_data
     }
 
+    pub(crate) fn user_data_mut(&mut self) -> &mut (dyn Any + Send + Sync) {
+        &mut *self.user_data
+    }
+
     /// Triggers a new revision. Invoked automatically when you call `zalsa_mut`
     /// and so doesn't need to be called otherwise.
     pub(crate) fn new_revision(&mut self) -> Revision {