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type a = [ `A of int ] | |
type b = [ a | `B of int ] | |
let pair (a : a) (b : b) = ([a] :> b list) @ [b] (* works fine *) | |
module type Config = sig type t end | |
module type Box = sig | |
module C : Config | |
type t = { regions : C.t list } | |
val empty : t | |
val add : C.t -> t -> t | |
val get : t -> C.t list | |
end | |
module Box (C: Config) : Box with type C.t = C.t = struct | |
module C = C | |
type t = { regions : C.t list } | |
let empty = { regions = [] } | |
let add r box = { regions = r :: box.regions } | |
let get box = box.regions | |
end | |
module ABox = Box(struct type t = a end) | |
module BBox = Box(struct type t = b end) | |
(* Error: Type ABox.t is not a subtype of BBox.t *) | |
let join (abox : ABox.t) = BBox.get (abox :> BBox.t) |
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