(* TEST
 readonly_files = "contexts_1.ml contexts_2.ml contexts_3.ml";
 flags = "-dsource -dlambda";
 expect;
*)

#use "contexts_1.ml";;
(* Notice that (field_mut 1 input) occurs twice, it
   is evaluated once in the 'false' branch and once in the 'true'
   branch. The compiler assumes that its static knowledge about the
   first read (it cannot be a [Right] as we already matched against it
   and failed) also applies to the second read, which is unsound.
*)
[%%expect {|

#use  "contexts_1.ml";;

type u = {
  a: bool ;
  mutable b: (bool, int) Either.t };;
0
type u = { a : bool; mutable b : (bool, int) Either.t; }

let example_1 () =
  let input = { a = true; b = (Either.Left true) } in
  match input with
  | { a = false; b = _ } -> Result.Error 1
  | { a = _; b = Either.Right _ } -> Result.Error 2
  | { a = _; b = _ } when input.b <- (Either.Right 3); false ->
      Result.Error 3
  | { a = true; b = Either.Left y } -> Result.Ok y;;
(let
  (example_1/310 =
     (function param/334[int]
       (let (input/312 = (makemutable 0 (int,*) 1 [0: 1]))
         (if (field_int 0 input/312)
           (let (*match*/337 =o (field_mut 1 input/312))
             (switch* *match*/337
              case tag 0:
               (if (seq (setfield_ptr 1 input/312 [1: 3]) 0) [1: 3]
                 (let (*match*/339 =o (field_mut 1 input/312))
                   (makeblock 0 (int) (field_imm 0 *match*/339))))
              case tag 1: [1: 2]))
           [1: 1]))))
  (apply (field_mut 1 (global Toploop!)) "example_1" example_1/310))
val example_1 : unit -> (bool, int) Result.t = <fun>
|}]

#use "contexts_2.ml";;
[%%expect {|

#use  "contexts_2.ml";;

type 'a myref = {
  mutable mut: 'a };;
0
type 'a myref = { mutable mut : 'a; }

type u = {
  a: bool ;
  b: (bool, int) Either.t myref };;
0
type u = { a : bool; b : (bool, int) Either.t myref; }

let example_2 () =
  let input = { a = true; b = { mut = (Either.Left true) } } in
  match input with
  | { a = false; b = _ } -> Result.Error 1
  | { a = _; b = { mut = Either.Right _ } } -> Result.Error 2
  | { a = _; b = _ } when (input.b).mut <- (Either.Right 3); false ->
      Result.Error 3
  | { a = true; b = { mut = Either.Left y } } -> Result.Ok y;;
(let
  (example_2/346 =
     (function param/350[int]
       (let (input/348 = (makeblock 0 (int,*) 1 (makemutable 0 [0: 1])))
         (if (field_int 0 input/348)
           (let (*match*/354 =o (field_mut 0 (field_imm 1 input/348)))
             (switch* *match*/354
              case tag 0:
               (if (seq (setfield_ptr 0 (field_imm 1 input/348) [1: 3]) 0)
                 [1: 3]
                 (let (*match*/357 =o (field_mut 0 (field_imm 1 input/348)))
                   (makeblock 0 (int) (field_imm 0 *match*/357))))
              case tag 1: [1: 2]))
           [1: 1]))))
  (apply (field_mut 1 (global Toploop!)) "example_2" example_2/346))
val example_2 : unit -> (bool, int) Result.t = <fun>
|}]

#use "contexts_3.ml";;
[%%expect {|

#use  "contexts_3.ml";;

type 'a myref = {
  mutable mut: 'a };;
0
type 'a myref = { mutable mut : 'a; }

type u = (bool * (bool, int) Either.t) myref;;
0
type u = (bool * (bool, int) Either.t) myref

let example_3 () =
  let input = { mut = (true, (Either.Left true)) } in
  match input with
  | { mut = (false, _) } -> Result.Error 1
  | { mut = (_, Either.Right _) } -> Result.Error 2
  | { mut = (_, _) } when input.mut <- (true, (Either.Right 3)); false ->
      Result.Error 3
  | { mut = (true, Either.Left y) } -> Result.Ok y;;
(let
  (example_3/363 =
     (function param/367[int]
       (let (input/365 =mut [0: 1 [0: 1]] *match*/368 =o *input/365)
         (if (field_imm 0 *match*/368)
           (switch* (field_imm 1 *match*/368)
            case tag 0:
             (if (seq (assign input/365 [0: 1 [1: 3]]) 0) [1: 3]
               (makeblock 0 (int) (field_imm 0 (field_imm 1 *match*/368))))
            case tag 1: [1: 2])
           [1: 1]))))
  (apply (field_mut 1 (global Toploop!)) "example_3" example_3/363))
val example_3 : unit -> (bool, int) Result.t = <fun>
|}]