fix(ffi): add Pop and Clear to VecDiff for sliding-sync

bindings/matrix-sdk-ffi/src/api.udl

@@ -82,9 +82,8 @@ interface SlidingSyncViewRoomsListDiff {
         u32 new_index
     );
     Push(RoomListEntry value);
-    // The following are supported by the generic VecDiff-type but
-    // in sliding sync effectively do not happen and thus aren't exposed
-    // to not pollute the API: Pop(); Clear();
+    Pop();
+    Clear();
 };
 
 callback interface SlidingSyncViewRoomListObserver {

bindings/matrix-sdk-ffi/src/sliding_sync.rs

@@ -216,6 +216,8 @@ pub enum SlidingSyncViewRoomsListDiff {
     RemoveAt { index: u32 },
     Move { old_index: u32, new_index: u32 },
     Push { value: RoomListEntry },
+    Pop,   // removes the last item
+    Clear, // clears the list
 }
 
 impl From<VecDiff<MatrixRoomEntry>> for SlidingSyncViewRoomsListDiff {
@@ -242,7 +244,8 @@ impl From<VecDiff<MatrixRoomEntry>> for SlidingSyncViewRoomsListDiff {
             VecDiff::Push { value } => {
                 SlidingSyncViewRoomsListDiff::Push { value: (&value).into() }
             }
-            _ => unimplemented!("Clear and Pop aren't provided within sliding sync"),
+            VecDiff::Pop {} => SlidingSyncViewRoomsListDiff::Pop,
+            VecDiff::Clear {} => SlidingSyncViewRoomsListDiff::Clear,
         }
     }
 }