Typechecking issue with GADTs under or-patterns #325
Description
As mentioned in an OCaml PR, this code
type _ t = A : unit t | B : bool t
let f : type a. a t -> int =
fun x -> match x with A | B -> 0is instrumented as
let f : type a. a t -> int =
fun x ->
___bisect_visit___ 2;
(match x with
| A|B as ___bisect_matched_value___ ->
((((match ___bisect_matched_value___ with
| A -> (___bisect_visit___ 0; ())
| B -> (___bisect_visit___ 1; ())
| _ -> ()))
[@ocaml.warning "-4-8-9-11-26-27-28"]);
0))rejected by the typechecker:
File "bin/main.ml", line 4, characters 28-29:
4 | fun x -> match x with A | B -> 0
^
Error: This pattern matches values of type bool t
but a pattern was expected which matches values of type unit t
Type bool is not compatible with type unit
Waiting for it to be fixed in OCaml side, maybe the instrumentation could be changed to avoid using as?
let ___bisect_matched_value___ = x in
match x with ...
I don't know how that'd interact with nested or-patterns though.