error: use of unstable library feature 'test': `bench` is a part of custom test frameworks which are unstable
  --> $DIR/bench.rs:1:3
   |
LL | #[bench]
   |   ^^^^^
   |
   = note: `#[deny(soft_unstable)]` on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
   = note: for more information, see issue #64266 <https://github.com/rust-lang/rust/issues/64266>

error: aborting due to previous error