Syntax error when with module and functor

Learning
1

I try to learn OCaml and implement tiger compiler following tiger book;
right now I meet this problem;
I implement translate.mli with the below code;

module type TRANSLATE = sig
    module Frame: Frame.FRAME
    module Temp = Frame.Temp
    type exp
    type level
    type access
    val trans_exp: unit -> exp
    val outermost: level
    val newLevel: parent:level -> name:Temp.label -> formals:bool list -> level
    val formals: level -> access list
    val allocLocal: level:level -> escapes:bool -> access
end

module F : functor(Frame: Frame.FRAME) -> TRANSLATE with module Frame = Frame

and in translate.ml I implement as belows;

module type TRANSLATE = sig

  module Frame: Frame.FRAME
  module Temp = Frame.Temp

  type exp
  type level
  type access

  val trans_exp: unit -> exp
  val outermost: level
  val newLevel: parent:level -> name:Temp.label -> formals:bool list -> level
  val formals: level -> access list
  val allocLocal: level:level -> escapes:bool -> access
end

module F = functor(Frame : Frame.FRAME) -> struct

  module Frame = Frame
  module Temp = Frame.Temp

type exp = unit

type level = Outermost  
           | Level of Frame.frame * level * unit ref

type access = level * Frame.access


let trans_exp() = ()
let outermost = Outermost

let newLevel ~parent ~name ~formals = 
  let formals = true :: formals in
  let frame = Frame.newFrame ~name ~formals in
  Level(frame, parent, ref())

let formals lvl = 
  match lvl with
  | Outermost -> assert false
  | Level(frame, _, _) -> Frame.formals frame |> List.tl_exn |> List.map ~f:(fun access -> (lvl, access))

let allocLocal ~level ~escapes = 
   match level with
   | Level(frame, _, _) -> (level, Frame.allocLocal frame escapes)
   | Outermost -> assert false

end

in visual studio code the OCaml platform inference the F’s type as below;

functor (Frame : Frame/3.FRAME) ->
  sig
    module Frame :
      sig
        type frame = Frame.frame
        type access = Frame.access
        type label = Frame.label
        module Temp = Chap6.Temp
        val newFrame : name:label -> formals:bool list -> frame
        val name : frame -> label
        val formals : frame -> access list
        val allocLocal : frame -> bool -> access
      end
    module Temp = Frame.Temp
    type exp = unit
    type level = Outermost | Level of Frame/2.frame * level * exp ref
    type access = level * Frame/2.access
    val trans_exp : exp -> exp
    val outermost : level
    val newLevel :
      parent:level -> name:Frame/2.label -> formals:bool list -> level
    val formals : level -> (level * Frame/2.access) list
    val allocLocal : level:level -> escapes:bool -> level * Frame/2.access
  end

I don’t know why the Frame’s type is Frame/3.FRAME.

And there is some compiling errors

Error: The implementation translate.pp.ml
       does not match the interface .chap6.objs/byte/chap6__Translate.cmi:
       ...
       At position module F(Frame) : <here>
       Values do not match:
         val newLevel :
           parent:level -> name:Frame.label -> formals:bool list -> level
       is not included in
         val newLevel :
           parent:level -> name:Temp.label -> formals:bool list -> level
       File "translate.mli", line 10, characters 4-79: Expected declaration
       File "translate.ml", line 35, characters 4-12: Actual declaration
2

Looking up Appel’s book, FRAME should not contain a type called label.

If you really want to keep that type, change newFrame's type to refer to the Temp’s label instead with:

val newFrame : name:Temp.label -> formals:bool list -> frame