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 <https://github.com/rust-lang/rust/issues/115268> for more information
   = help: add `#![feature(proc_macro_byte_character)]` to the crate attributes to enable

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0658`.