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|
(* TEST
expect;
*)
type tag = [`TagA | `TagB | `TagC];;
type 'a poly =
AandBTags : [< `TagA of int | `TagB ] poly
| ATag : [< `TagA of int] poly
(* constraint 'a = [< `TagA of int | `TagB] *)
;;
let intA = function `TagA i -> i
let intB = function `TagB -> 4
;;
let intAorB = function
`TagA i -> i
| `TagB -> 4
;;
type _ wrapPoly =
WrapPoly : 'a poly -> ([< `TagA of int | `TagB] as 'a) wrapPoly
;;
let example6 : type a. a wrapPoly -> (a -> int) =
fun w ->
match w with
| WrapPoly ATag -> intA
| WrapPoly _ -> intA (* This should not be allowed *)
;;
[%%expect{|
type tag = [ `TagA | `TagB | `TagC ]
type 'a poly =
AandBTags : [< `TagA of int | `TagB ] poly
| ATag : [< `TagA of int ] poly
val intA : [< `TagA of 'a ] -> 'a = <fun>
val intB : [< `TagB ] -> int = <fun>
val intAorB : [< `TagA of int | `TagB ] -> int = <fun>
type _ wrapPoly =
WrapPoly : 'a poly -> ([< `TagA of int | `TagB ] as 'a) wrapPoly
Line 25, characters 23-27:
25 | | WrapPoly ATag -> intA
^^^^
Error: This expression has type [< `TagA of 'a ] -> 'a
but an expression was expected of type a -> int
Type [< `TagA of 'a ] is not compatible with type
a = [< `TagA of int | `TagB ]
The first variant type does not allow tag(s) `TagB
|}];;
let _ = example6 (WrapPoly AandBTags) `TagB (* This causes a seg fault *)
;;
[%%expect{|
Line 1, characters 9-17:
1 | let _ = example6 (WrapPoly AandBTags) `TagB (* This causes a seg fault *)
^^^^^^^^
Error: Unbound value example6
|}];;
|
