1 error[E0658]: box expression syntax is experimental; you can call `Box::new` instead
2 --> $DIR/feature-gate-box-expr.rs:12:13
7 = note: see issue #49733 <https://github.com/rust-lang/rust/issues/49733> for more information
8 = help: add `#![feature(box_syntax)]` to the crate attributes to enable
10 error: aborting due to previous error
12 For more information about this error, try `rustc --explain E0658`.