error[E0658]: labels on blocks are unstable (see issue #48594)
  --> $DIR/feature-gate-label_break_value.rs:12:5
   |
LL |     'a: { //~ ERROR labels on blocks are unstable
   |     ^^
   |
   = help: add #![feature(label_break_value)] to the crate attributes to enable

error: aborting due to previous error

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