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let ok1 = function Dyn (type a) ((w, x) : a ty * a) -> ignore (x : a)
let ok2 = function Dyn (type a) ((w, x) : _ * a) -> ignore (x : a)
type u = C : 'a * ('a -> 'b list) -> u
let f = function C (type a b) ((x, f) : _ * (a -> b list)) -> ignore (x : a)
(* with GADT unification *)
type _ expr =
| Int : int -> int expr
| Add : (int -> int -> int) expr
| App : ('a -> 'b) expr * 'a expr -> 'b expr
let rec eval : type t. t expr -> t = function
| Int n ->
n
| Add ->
( + )
| App (type a) ((f, x) : _ * a expr) ->
eval f (eval x : a)
(* Also allow annotations on multiary constructors *)
type ('a, 'b) pair = Pair of 'a * 'b
let f = function Pair ((x, y) : int * _) -> x + y
|
