error: must return Self::Output
 --> tests/ui/fail/fn-missing-output-03.rs:8:17
  |
8 |     fn bar() -> i32 {}
  |                 ^^^

error: since Output is defined here
 --> tests/ui/fail/fn-missing-output-03.rs:5:19
  |
5 |     type Output = i32;
  |                   ^^^