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_syntax.rs:2:5 | LL | log_syntax!() | ^^^^^^^^^^^^^ | = note: for more information, see https://github.com/rust-lang/rust/issues/29598 = 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`.