[fpc-devel] "Default" discussion for SmartPointers etc

[Michael Van Canneyt]

On Wed, 27 Jul 2016, Maciej Izak wrote:

> 2016-07-27 11:24 GMT+02:00 Jonas Maebe <jonas.maebe at elis.ugent.be>:
>>
>> On a more general note, I think the fact that @recordvar no longer is a
>> pointer to the record is wrong. You need a different keyword instead of
>> "record" in that case (or possibly a modifier for the "record" keyword,
>> like with "class abstract" -- but this is not a record at any more than an
>> shortstring is a record, so I don't think that's a good idea either).
>>
>> Completely changing how certain aspects of a record are treated by the
>> compiler only based on the fact that somewhere there is a "default"
>> modifier for one field is not good. You should definitely not have to go
>> through an entire declaration of a record to be able to know how it will
>> behave.
>
>
> I was thinking on additional modifier for that before. We can use something
> like this:
>
> === code begin ===
> type
>  TNullable<T: record> = record proxy to Instance
>  public type
>    PT = ^T;
>  strict private
>    Instance: ^T; // no default word anymore
>    function GetValue: T;
> === code end ===

Record proxy will not work. Proxy can be the name of a field.

So I think the modifier should be before the record, just as 'packed' or 'bitpacked' are.

And contrary to 'to instance', I prefer the default:

type
   TNullable<T: record> = proxy record
   public type
     PT = ^T;
   strict private
     Instance: ^T; default;
     function GetValue: T;
   end;

Michael.