module type Bt  = Btree
module type Bt  = Std.Btree
module type Bt  = ((Btree)[@attrIdent ][@attrParens ])
module type MyHash  =
  sig
    include module type of struct include Hashtbl end
    val replace : ('a, 'b) t -> 'a -> 'b -> unit (a:3)
  end
module type MyHash  =
  sig
    include
      ((module type of struct include Hashtbl end)[@onModTypeOf ][@onParens ])
    val replace : ('a, 'b) t -> 'a -> 'b -> unit (a:3)
  end