How to merge OCaml module types (signatures) defining the same type?

Question

In OCaml, I have two module types defining a type t:

module type Asig = sig
    type t
    val a : t
end

module type Bsig = sig
    type t
             


        

Answer 1

Here is the way to do it :

module type Asig = sig
    type t
    val a : t
end

module type Bsig = sig
    type t
    val b : t
end

module type ABsig = sig
    include Asig
    include Bsig with type t := t
end

It's called "destructive substitution".