error[E0658]: use of unstable library feature 'log_syntax': `log_syntax!` is not stable enough for use and is subject to change --> $DIR/feature-gate-log_syntax2.rs:2:22 | LL | println!("{:?}", log_syntax!()); | ^^^^^^^^^^ | = note: see issue #29598 for more information = help: add `#![feature(log_syntax)]` to the crate attributes to enable error: aborting due to previous error For more information about this error, try `rustc --explain E0658`.