error[E0069]: `return;` in a function whose return type is not `()`
  --> $DIR/suggest-a-value.rs:2:5
   |
LL | fn test() -> (i32,) {
   |              ------ expected `(i32,)` because of this return type
LL |     return;
   |     ^^^^^^ return type is not `()`
   |
help: give the `return` a value of the expected type
   |
LL |     return (42,);
   |            +++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0069`.