GenConstr.Register
module M : sig ... end
val register : ('raw, 'glb) tag -> ('raw, 'glb) M.t -> unit
val mem : (_, _) tag -> bool
val find_opt : ('raw, 'glb) tag -> ('raw, 'glb) M.t option
val get : ('raw, 'glb) tag -> ('raw, 'glb) M.t
Assert false if not present