Re: [Caml-list] Suppress warning from within Ocaml source file

[Virgile Prevosto <virgile.prevosto@m4x.org>]

2015-11-12 18:26 GMT+01:00 Daniel Bünzli <daniel.buenzli@erratique.ch>:
> Le jeudi, 12 novembre 2015 à 16:37, Leo White a écrit :
>> > This misses the point. By using `with` I can instruct the compiler that I don't want my program not to compile if I add or remove fields. In the current system I can do this with any update I want to make to a record except if for some strange reason that update happen to touch all the current fields of the record.
>>
>> I don't particularly wish to argue for or against using this warning, but I think it is worth noting
>> that this is not really any different from:
>
> […]
>
> It's quite different: you have dead code in your example.
>

But in the record case, the expr in { expr with ... } will indeed be
evaluated (thus is not dead), but its result will never be used, which
is barely better. In the (admittedly contrived) example below,
investigating the cause of the warning would save you from a runtime
exception:

type foo = { a : int; }
let rec x = lazy { a = (Lazy.force x).a }
let y = { (Lazy.force x) with a = 42 }

Now that I think of it, it is more like warning 26, with the exception
that in the present case, the expression is usually a variable and
thus already evaluated.

Best regards,
-- 
E tutto per oggi, a la prossima volta
Virgile