error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
  --> $DIR/issue-80179.rs:10:24
   |
LL | fn returns_fn_ptr() -> _ {
   |                        ^
   |                        |
   |                        not allowed in type signatures
   |                        help: replace with the correct return type: `fn() -> i32`

error[E0121]: the placeholder `_` is not allowed within types on item signatures for return types
  --> $DIR/issue-80179.rs:18:25
   |
LL | fn returns_closure() -> _ {
   |                         ^ not allowed in type signatures
   |
   = help: consider using an `Fn`, `FnMut`, or `FnOnce` trait bound
   = note: for more information on `Fn` traits and closure types, see https://doc.rust-lang.org/book/ch13-01-closures.html

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0121`.