error[E0308]: `match` arms have incompatible types
  --> $DIR/dont-highlight-diverging-arms.rs:11:18
   |
LL | /         match m {
LL | |             1 => break 'out Some(1u16),
LL | |             2 => Some(2u16),
   | |                  ---------- this is found to be of type `Option<u16>`
LL | |             3 => break 'out Some(3u16),
...  |
LL | |             _ => {}
   | |                  ^^ expected `Option<u16>`, found `()`
LL | |
LL | |         }
   | |_________- `match` arms have incompatible types
   |
   = note:   expected enum `Option<u16>`
           found unit type `()`

error: aborting due to 1 previous error

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