error[E0277]: expected a `FnOnce()` closure, found `{integer}` --> $DIR/closure-expected.rs:3:23 | LL | let y = x.or_else(4); | ------- ^ expected an `FnOnce()` closure, found `{integer}` | | | required by a bound introduced by this call | = help: the trait `FnOnce<()>` is not implemented for `{integer}` = note: wrap the `{integer}` in a closure with no arguments: `|| { /* code */ }` note: required by a bound in `Option::::or_else` --> $SRC_DIR/core/src/option.rs:LL:COL error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0277`.