Struct ListReorderDriver 

pub struct ListReorderDriver {
    pub can_move: Box<dyn Fn(usize, usize) -> i64>,
    pub moved: Box<dyn Fn(usize, usize)>,
}

The reorder closures the list() piece supplies (docs/list.md). Exposed to the backend as day_spec::ListReorder by [make_source]; also driven directly by list_try_reorder (the dayscript reorder step and the mock probe).

Fields

can_move: Box<dyn Fn(usize, usize) -> i64>

Consult the app’s guard: returns the accepted target index, or -1 to deny.

moved: Box<dyn Fn(usize, usize)>

Commit an accepted move: rotates the piece’s snapshot + tokens synchronously and defers the app’s on_reorder callback to the next event drain.