|  | error[E0658]: the `#[optimize]` attribute is an experimental feature | 
|  | --> $DIR/feature-gate-optimize_attribute.rs:3:1 | 
|  | | | 
|  | LL | #[optimize(size)] | 
|  | | ^^^^^^^^^^^^^^^^^ | 
|  | | | 
|  | = note: see issue #54882 <https://github.com/rust-lang/rust/issues/54882> for more information | 
|  | = help: add `#![feature(optimize_attribute)]` 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|  | = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date | 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]: the `#[optimize]` attribute is an experimental feature | 
|  | --> $DIR/feature-gate-optimize_attribute.rs:6:1 | 
|  | | | 
|  | LL | #[optimize(speed)] | 
|  | | ^^^^^^^^^^^^^^^^^^ | 
|  | | | 
|  | = note: see issue #54882 <https://github.com/rust-lang/rust/issues/54882> for more information | 
|  | = help: add `#![feature(optimize_attribute)]` 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|  | = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date | 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]: the `#[optimize]` attribute is an experimental feature | 
|  | --> $DIR/feature-gate-optimize_attribute.rs:9:1 | 
|  | | | 
|  | LL | #[optimize(none)] | 
|  | | ^^^^^^^^^^^^^^^^^ | 
|  | | | 
|  | = note: see issue #54882 <https://github.com/rust-lang/rust/issues/54882> for more information | 
|  | = help: add `#![feature(optimize_attribute)]` 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|  | = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date | 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]: the `#[optimize]` attribute is an experimental feature | 
|  | --> $DIR/feature-gate-optimize_attribute.rs:12:1 | 
|  | | | 
|  | LL | #[optimize(banana)] | 
|  | | ^^^^^^^^^^^^^^^^^^^ | 
|  | | | 
|  | = note: see issue #54882 <https://github.com/rust-lang/rust/issues/54882> for more information | 
|  | = help: add `#![feature(optimize_attribute)]` 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|  | = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date | 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[E0539]: malformed `optimize` attribute input | 
|  | --> $DIR/feature-gate-optimize_attribute.rs:12:1 | 
|  | | | 
|  | LL | #[optimize(banana)] | 
|  | | ^^^^^^^^^^^------^^ | 
|  | |            | | 
|  | |            valid arguments are `size`, `speed` or `none` | 
|  | | | 
|  | help: try changing it to one of the following valid forms of the attribute | 
|  | | | 
|  | LL - #[optimize(banana)] | 
|  | LL + #[optimize(none)] | 
|  | | | 
|  | LL - #[optimize(banana)] | 
|  | LL + #[optimize(size)] | 
|  | | | 
|  | LL - #[optimize(banana)] | 
|  | LL + #[optimize(speed)] | 
|  | | | 
|  |  | 
|  | error: aborting due to 5 previous errors | 
|  |  | 
|  | Some errors have detailed explanations: E0539, E0658. | 
|  | For more information about an error, try `rustc --explain E0539`. |