Debugging async generator errors in Rust

I haven't done much Async programming in Rust and I am also struggling with the error messages.

One thing I found generally useful (not with error messages) is to "typedef" some of the more complex types as it makes the code more readable. For instance using some of the long types from the article:

   type RowStream = Box<dyn Stream<Item = Row> + Send + Unpin>;
   type QueryResult = Result<RowStream,Error>;