error[E0767]: use of unreachable label `'a`
  --> $DIR/E0767.rs:4:26
   |
LL |     'a: loop {
   |     -- unreachable label defined here
LL |         || {
LL |             loop { break 'a; }
   |                          ^^ unreachable label `'a`
   |
   = note: labels are unreachable through functions, closures, async blocks and modules

error: aborting due to previous error

For more information about this error, try `rustc --explain E0767`.