Fix unsoundness in query component access (bevyengine#1929)

Pretty much does what it says in the title lol

crates/bevy_ecs/src/lib.rs

@@ -1071,6 +1071,13 @@ mod tests {
         world.query::<(&A, &mut A)>();
     }
 
+    #[test]
+    #[should_panic]
+    fn mut_and_ref_query_panic() {
+        let mut world = World::new();
+        world.query::<(&mut A, &A)>();
+    }
+
     #[test]
     #[should_panic]
     fn mut_and_mut_query_panic() {

crates/bevy_ecs/src/query/fetch.rs

@@ -206,6 +206,10 @@ unsafe impl<T: Component> FetchState for ReadState<T> {
     }
 
     fn update_component_access(&self, access: &mut FilteredAccess<ComponentId>) {
+        if access.access().has_write(self.component_id) {
+            panic!("&{} conflicts with a previous access in this query. Shared access cannot coincide with exclusive access.",
+                std::any::type_name::<T>());
+        }
         access.add_read(self.component_id)
     }
 
@@ -656,6 +660,10 @@ unsafe impl<T: Component> FetchState for ChangeTrackersState<T> {
     }
 
     fn update_component_access(&self, access: &mut FilteredAccess<ComponentId>) {
+        if access.access().has_write(self.component_id) {
+            panic!("ChangeTrackers<{}> conflicts with a previous access in this query. Shared access cannot coincide with exclusive access.",
+                std::any::type_name::<T>());
+        }
         access.add_read(self.component_id)
     }
 

crates/bevy_ecs/src/query/filter.rs

@@ -501,6 +501,10 @@ macro_rules! impl_tick_filter {
 
             #[inline]
             fn update_component_access(&self, access: &mut FilteredAccess<ComponentId>) {
+                if access.access().has_write(self.component_id) {
+                    panic!("$state_name<{}> conflicts with a previous access in this query. Shared access cannot coincide with exclusive access.",
+                        std::any::type_name::<T>());
+                }
                 access.add_read(self.component_id);
             }