message: Split join.rs JoinResult into JoinResult & JoinItem, make easier to read
diff: @@ -24,7 +24,8 @@ pub struct Join<'a, T: 'static + Debug> {
  filter_context: Option<&'a FilterContext<'a>>,
  }
  -type JoinResult<'a, T> = Box<dyn Iterator<Item = Result<Rc<BlendContext<'a, T>>>> + 'a>;
  +type JoinItem<'a, T> = Result<Rc<BlendContext<'a, T>>>;
  +type JoinResult<'a, T> = Box<dyn Iterator<Item = JoinItem<'a, T>> + 'a>;
  macro_rules! try_iter {
  ($expr: expr) => {
  