error[E0308]: `match` arms have incompatible types
  --> $DIR/issue-81839.rs:11:14
   |
LL | /     match num {
LL | |         1 => {
LL | |             cx.answer_str("hi");
   | |             --------------------
   | |             |                  |
   | |             |                  help: consider removing this semicolon
   | |             this is found to be of type `()`
LL | |         }
LL | |         _ => cx.answer_str("hi"),
   | |              ^^^^^^^^^^^^^^^^^^^ expected `()`, found future
LL | |     }
   | |_____- `match` arms have incompatible types

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0308`.