Hi @Yuri_Gor , this is a similar issue to that described in this thread. In short, Cursor<T> type only implements Stream if the T implements DeserializeOwned , Unpin , Send , and Sync . Because Rc is !Send and !Sync, adding the Rc makes it so the Cursor no longer implements Stream.
To work around this, we would suggest using an Arc rather than an Rc, since Arc implements Send and Sync.
Relatedly, this has come up in the past and we may be able to relax these trait bounds in the future to avoid errors like this altogether; see RUST-1358 for details.