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|
(* TEST
expect;
*)
type ('a, 'b) segment =
| SegNil : ('a, 'a) segment
| SegCons : ('a * 'a, 'b) segment -> ('a, 'b) segment
let color : type a b . (a, b) segment -> int = function
| SegNil -> 0
| SegCons SegNil -> 0
| SegCons _ -> 0
[%%expect{|
type ('a, 'b) segment =
SegNil : ('a, 'a) segment
| SegCons : ('a * 'a, 'b) segment -> ('a, 'b) segment
val color : ('a, 'b) segment -> int = <fun>
|}]
(* Fail *)
let color (* : type a b . (a, b) segment -> int *) = function
| SegNil -> 0
| SegCons SegNil -> 0
| SegCons _ -> 0
[%%expect{|
Line 3, characters 12-18:
3 | | SegCons SegNil -> 0
^^^^^^
Error: This pattern matches values of type ('a * 'a, 'a * 'a) segment
but a pattern was expected which matches values of type
('a * 'a, 'a) segment
The type variable 'a occurs inside 'a * 'a
|}]
|
