Re: [Caml-list] Warning for unused variables

[Gabriel Scherer <gabriel.scherer@gmail.com>]

Good point, I had not noticed the different in warning number.

  `ocamlc -warn-help` says:

 26 Suspicious unused variable: unused variable that is bound
    with "let" or "as", and doesn't start with an underscore ("_")
    character.
 27 Innocuous unused variable: unused variable that is not bound with
    "let" nor "as", and doesn't start with an underscore ("_")
    character.

I agree that the distinction is somewhat arbitrary here: arguably
variables bound in a pattern by a *let* (instead of a
pattern-matching) could be considered "suspicous" as well. But we
don't want to change the semantics of an existing pattern too much, as
it tends to annoy people, so maybe it's best left as it is.

On Wed, Feb 22, 2017 at 2:59 PM, Aymeric Fromherz
<aymeric.fromherz@ens.fr> wrote:
> Hi,
>
> Trying with OCaml 4.04 on another machine, I have the same behaviour.
> When running the ocaml interpreter with all warnings activated (-w A
> option), a warning is raised in the first case, but it is a warning 27
> instead of a warning 26.
>
> What is the difference between these two warnings? Could it be that you
> have all warnings activated by default?
>
> Thanks,
> Aymeric
>
> On 22/02/2017 20:43, Gabriel Scherer wrote:
>> This would be a bug, but I cannot reproduce it on my machine, where
>> all OCaml versions I have (including 4.02.3) raise a warning as
>> expected.
>>
>> On Wed, Feb 22, 2017 at 2:21 PM, Aymeric Fromherz
>> <aymeric.fromherz@ens.fr> wrote:
>>> Hi,
>>>
>>> Using OCaml 4.02.3, I do not have a warning for unused variables when
>>> only one of the variables in a pair is unused.
>>> For instance, the code
>>>
>>> let (a,b) = (0, 42) in b;;
>>>
>>> raises no warning, while
>>>
>>> let (a,b) = (0,42) in 1;; raises the following
>>>
>>> Warning 26: unused variable b.
>>> Warning 26: unused variable a.
>>>
>>> I would have expected a warning in the first case since a is unused.
>>>
>>> Warnings for single unused variables, such as let a = 42 in 1 are still
>>> raised.
>>>
>>> What is the reason for this? Is this behaviour intended? How are unused
>>> variables determined?
>>>
>>> Thanks in advance,
>>> Aymeric Fromherz
>>>
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>
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