error[E0525]: expected a closure that implements the `Fn` trait, but this closure only implements `FnOnce`
  --> $DIR/issue-26046-fn-once.rs:4:19
   |
LL |     let closure = move || {
   |                   ^^^^^^^ this closure implements `FnOnce`, not `Fn`
LL |         vec
   |         --- closure is `FnOnce` because it moves the variable `vec` out of its environment
...
LL |     Box::new(closure)
   |     ----------------- the requirement to implement `Fn` derives from here
   |
   = note: required for the cast from `Box<{closure@$DIR/issue-26046-fn-once.rs:4:19: 4:26}>` to `Box<(dyn Fn() -> Vec<u8> + 'static)>`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0525`.