Parameter Make_access.1-T
val nonempty : ('at -> ('bt, 'a, 'b) Nonempty.t) -> ('a, 'b) t -> ('at, 'bt) t
A legal implementation of this function must satisfy the following properties:
nonempty Nonempty.Accessed.return = Fn.id
Fn.compose (nonempty f) (nonempty g) = nonempty (fun at -> Nonempty.Accessed.bind (f at) ~f:g)