Re: [Caml-list] How to rename a record field

[Jacques Garrigue <garrigue@math.nagoya-u.ac.jp>]

On 2018/09/07 17:36, Alain Frisch wrote:
> 
> On 07/09/2018 01:45, Jacques Garrigue wrote:
>> Interesting idea.
>> This should be easily doable, for instance by extending the Asttypes.arg_label type.
> 
> One could also just keep the information on the value binding itself:
> 
>  val foo: ?x:int -> ?y:float-> int -> int
>     [@@ocaml.deprecated_argument x "Please use y instead!"]
>     [@@ocaml.deprecated_missing_argument x "Please pass y, it will soon be mandatory"]
> 
> 
> Or indeed allow adding attributes on (labeled?) arguments, or interpret attributes on their types.  But internally, the information could always be attached to the value binding, which should be simpler than storing it in the type.

This is not so clear. 
The binding information could be hard to bring to the application type inference, while if it is contained in the label, it is already available where it is needed.

Also, attaching  the deprecation to the binding means that we can only refer to the first optional argument with the same name. In theory, there could be several, but I agree that this is going to be extremely rare.

>> By deprecating the absence, do you mean having a warning when the argument is ommited?
>> Wouldn’t it mean having two distinct deprecation annotations for optional arguments?
> 
> Yes, of course.  "Old" attributes (that will be discarded at some point) should be reported when they are passed a value; "new" attributes (that might become non-optional) should be reported when they are omitted.  It remains to be seen what to do with applications with the ?x syntax (i.e. passing an option).


I suppose ?x should raise a warning too, since it is intended to allow both pasing and not passing, and one of the two is wrong.

Jacques

-- 
Caml-list mailing list.  Subscription management and archives:
https://sympa.inria.fr/sympa/arc/caml-list
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
Bug reports: http://caml.inria.fr/bin/caml-bugs