error[E0408]: variable `beta` is not bound in all patterns
  --> $DIR/issue-2848.rs:22:7
   |
22 |       alpha | beta => {} //~  ERROR variable `beta` is not bound in all patterns
   |       ^^^^^   ---- variable not in all patterns
   |       |
   |       pattern doesn't bind `beta`

error: aborting due to previous error