I'm building an universal container for for pairs of a type witness and a value of the witnessed type. This I want to use for several different types, which gives me errors because the types are all named the same.

So I'm trying to rename types in the result of a functor like this:

```
module type Witness = sig type 'a key type 'a value end
module type Witnessed = sig
type 'a key
type 'a value
type t
type ('a, 'b) conv = {
key : 'c . 'c key -> 'a;
value : 'c . 'c value -> 'b;
}
val box : 'a key -> 'a value -> t
val conv : ('a, 'b) conv -> t -> ('a * 'b)
end
module MAKE(W : Witness) : Witnessed with type 'a key = 'a W.key
and type 'a value = 'a W.value = struct
include W
type t = Box : 'a key * 'a value -> t
let box k v = Box (k, v)
type ('a, 'b) conv = {
key : 'c . 'c key -> 'a;
value : 'c . 'c value -> 'b;
}
let conv conv (Box (k, v)) = (conv.key k, conv.value v)
end
type _ token
type _ attrib
module W = struct
type 'a key = 'a token
type 'a value = 'a attrib
end
module Boxed = struct
module T = MAKE(W)
type lexeme = T.t
type ('a, 'b) lexeme_conv = ('a, 'b) T.conv
include (T : module type of T with type 'a key := 'a token
and type 'a value := 'a attrib
and type t := lexeme
and type ('a, 'b) conv := ('a, 'b) lexeme_conv)
end
```

and ocaml says:

```
File "foo.ml", line 49, characters 38-80:
Error: This variant or record definition does not match that of type
('a, 'b) lexeme_conv
Their kinds differ.
```

How can the types of conv and lexeme_conv differ?