error[E0658]: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/bench.rs:3:3
   |
LL | #[bench]
   |   ^^^^^
   |
   = note: see issue #50297 <https://github.com/rust-lang/rust/issues/50297> for more information
   = help: add `#![feature(test)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: use of unstable library feature `test`: `bench` is a part of custom test frameworks which are unstable
  --> $DIR/bench.rs:6:5
   |
LL | use bench as _;
   |     ^^^^^
   |
   = note: see issue #50297 <https://github.com/rust-lang/rust/issues/50297> for more information
   = help: add `#![feature(test)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0658`.