Rust Analyzer doesn't like unstable features

The failure I got from the Rust Analyzer:

error[E0554]: `#![feature]` may not be used on the stable release channel
 --> src/lib.rs:1:12
  |
1 | #![feature(iter_intersperse)]
  |            ^^^^^^^^^^^^^^^^

It’s inconsistent with the test runner - my solution passes the test suite :stuck_out_tongue:

My real issue is that since this feedback is hanging on my iteration, preventing the protein-based reviewer to come by, since they see automated feedback attached to my solution.