error[E0308]: mismatched types
  --> $DIR/issue-84128.rs:13:13
   |
LL |         Foo(())
   |             ^^ expected integer, found `()`
   |
note: return type inferred to be `{integer}` here
  --> $DIR/issue-84128.rs:10:20
   |
LL |             return Foo(0);
   |                    ^^^^^^

error: aborting due to previous error

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