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: replace with an appropriate return type: `impl Fn() -> i32` | = 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`.