Module type Flags_intf.Flags

module type Flags = sig .. end

module type Make_arg = Flags_intf.Make_arg

module type S = Flags_intf.S

module Make: 
functor (M : Make_arg) -> S  with type t = Int63.t

We expose type t = int in the result of Flags.Make so that one can easily use flag constants as values of the flag type without having to coerce them.