error: unreachable pattern
  --> $DIR/E0001.rs:18:9
   |
18 |         _ => {/* ... */} //~ ERROR unreachable pattern
   |         ^
   |
note: lint level defined here
  --> $DIR/E0001.rs:11:9
   |
11 | #![deny(unreachable_patterns)]
   |         ^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error