Mutable record field updates get lost when in partial application #10032
Description
I observed a regression when upgrading from OCaml 4.04.2 to a more recent version, after some debugging I came to the conclusion that this is related to mutable record fields and partial application, and the behavior changed from 4.05.0 to 4.06.0. Here you have a minimal example (simply ocamlopt main.ml && ./main):
type norm_env =
{ mutable k : int; }
let push_local ({k;} as env) _ =
env.k <- k + 1;
Printf.eprintf "push_local %d --> %d\n" k env.k
let pop_local ({k;} as env) _ =
env.k <- k - 1;
Printf.eprintf "pop_local %d --> %d\n" k env.k
let bug() =
let env = { k=0; } in
Printf.eprintf "BUG?\n";
List.iter (push_local env) [1; 2]; (* BUG? *)
List.iter (pop_local env) [1; 2] (* BUG? *)
let works() =
let env = { k=0; } in
Printf.eprintf "WORKS\n";
List.iter (fun x -> push_local env x) [1; 2]; (* WORKS *)
List.iter (fun x -> pop_local env x) [1; 2] (* WORKS *)
let _ =
bug();
works()
(* OCaml 4.05.0
BUG?
push_local 0 --> 1
push_local 1 --> 2
pop_local 2 --> 1
pop_local 1 --> 0
WORKS
push_local 0 --> 1
push_local 1 --> 2
pop_local 2 --> 1
pop_local 1 --> 0
*)
(* OCaml 4.06.0
BUG?
push_local 0 --> 1
push_local 0 --> 1
pop_local 1 --> 0
pop_local 1 --> 0
WORKS
push_local 0 --> 1
push_local 1 --> 2
pop_local 2 --> 1
pop_local 1 --> 0
*)