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|
(* TEST
* expect
*)
type _ t = I : int t;;
let f (type a) (x : a t) (y : int) =
match x, y with
| I, (_:a) -> ()
;;
[%%expect{|
type _ t = I : int t
val f : 'a t -> int -> unit = <fun>
|}]
type ('a, 'b) eq = Refl : ('a, 'a) eq;;
let ok (type a b) (x : (a, b) eq) =
match x, [] with
| Refl, [(_ : a) | (_ : b)] -> []
;;
[%%expect{|
type ('a, 'b) eq = Refl : ('a, 'a) eq
Line 4, characters 4-29:
4 | | Refl, [(_ : a) | (_ : b)] -> []
^^^^^^^^^^^^^^^^^^^^^^^^^
Error: This pattern matches values of type (a, b) eq * a list
This instance of a is ambiguous:
it would escape the scope of its equation
|}]
let fails (type a b) (x : (a, b) eq) =
match x, [] with
| Refl, [(_ : a) | (_ : b)] -> []
| Refl, [(_ : b) | (_ : a)] -> []
;;
[%%expect{|
Line 3, characters 4-29:
3 | | Refl, [(_ : a) | (_ : b)] -> []
^^^^^^^^^^^^^^^^^^^^^^^^^
Error: This pattern matches values of type (a, b) eq * a list
This instance of a is ambiguous:
it would escape the scope of its equation
|}]
(* branches must be unified! *)
let x = match [] with ["1"] -> 1 | [1.0] -> 2 | [1] -> 3 | _ -> 4;;
[%%expect{|
Line 1, characters 35-40:
1 | let x = match [] with ["1"] -> 1 | [1.0] -> 2 | [1] -> 3 | _ -> 4;;
^^^^^
Error: This pattern matches values of type float list
but a pattern was expected which matches values of type string list
Type float is not compatible with type string
|}]
|
