error[E0658]: box pattern syntax is experimental --> $DIR/feature-gate-box_patterns.rs:2:9 | LL | let box x = Box::new('c'); | ^^^^^ | = note: see issue #29641 for more information = help: add `#![feature(box_patterns)]` to the crate attributes to enable = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.