error[E0658]: use of unstable library feature 'proc_macro_byte_character' --> $DIR/feature-gate-proc_macro_byte_character.rs:9:5 | LL | Literal::byte_character(b'a'); | ^^^^^^^^^^^^^^^^^^^^^^^ | = note: see issue #115268 for more information = help: add `#![feature(proc_macro_byte_character)]` to the crate attributes to enable = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0658`.