[Caml-list] Pattern-matching on Ocaml records

[Create Software <createsoftware@users.sourceforge.net>]

Hi all,

I'm building an old Caml Light program with OCaml, and I've come across a reluctant piece of code. Here's a a mwe:

   type t = {mutable label: int};;
   let reset {label = lbl} = lbl <- 0;;

   let test = {label = -1};;
   reset test;;
   test;;

This compiles fine in Caml Light, yielding

   Type t defined.
   reset : t -> unit = <fun>
   test : t = {label = -1}
   - : unit = ()
   - : t = {label = 0}

On the other hand, Ocaml refuses this snippet, and prints the following message:

   Characters 26-34:
     let reset {label = lbl} = lbl <- 0;;
                               ^^^^^^^^
   Error: Unbound instance variable lbl

Was this construct deprecated? If so, why?

Thanks!
Clément.


PS: I also tried

   let reset' a =
     let lbl = a.label in
     lbl <- 0
   ;;

but "The identifier lbl is not mutable.", in both OCaml and Caml Light. Why so?