error[E0746]: return type cannot have an unboxed trait object
  --> $DIR/issue-91801.rs:8:77
   |
LL | fn or<'a>(first: &'static Validator<'a>, second: &'static Validator<'a>) -> Validator<'a> {
   |                                                                             ^^^^^^^^^^^^^ doesn't have a size known at compile-time
   |
help: box the return type, and wrap all of the returned values in `Box::new`
   |
LL | fn or<'a>(first: &'static Validator<'a>, second: &'static Validator<'a>) -> Box<Validator<'a>> {
   |                                                                             ++++             +

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0746`.