error[E0658]: the `#[ffi_pure]` attribute is an experimental feature --> $DIR/feature-gate-ffi_pure.rs:4:5 | LL | #[ffi_pure] | ^^^^^^^^^^^ | = note: see issue #58329 for more information = help: add `#![feature(ffi_pure)]` to the crate attributes to enable = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.