[fpc-devel] Allow record helper inheritance in Delphi mode

[Stefan Glienke]

I consider that as terribly hard to maintain code. As soon as you move around statements, refactor things everything gets messed up. No thanks.

> On 01 September 2017 at 12:15 Maciej Izak <hnb.code at gmail.com> wrote:
> 
> 
> 2017-09-01 11:41 GMT+02:00 Stefan Glienke <sglienke at dsharp.org>:
> 
> > Again you will cause unnecessary headaches because now your helper has the
> > dependency of the builtin and the third party one.
> > How would third party one and third party two implement them? They both
> > probably would extend the builtin one. Which one can you use in your code
> > then?
> > Yes, the one that comes last in the uses. What if you want to use
> > functions from both? Out of luck again.
> >
> > Inheritance regardless what form is never is the best option here. I think
> > "ancestor list" is just a misnomer in the documentation as it cannot be a
> > list but only one in case of class helper.
> 
> 
> The control of modules order in uses section can turn programmers life into
> real hell for type helpers. I think that new directive
> $EXPLICITHELPERS should help :
> 
> type
>   TH1 = record helper for string
>     procedure foo;
>     procedure foo1;
>   end;
> 
>   TH2 = record helper for string
>     procedure foo;
>     procedure foo2;
>   end;
> 
>   TH3 = record helper for string
>     procedure foo;
>     procedure foo3;
>   end;
> 
> var
>   s: string;
> begin
>   s.foo; // call TH3.foo
> 
> {$EXPLICITHELPERS TH1 for string} // scope for helpers limited only to TH1
>   s.foo; // call TH1.foo
>   s.foo3; // error
> 
> {$EXPLICITHELPERS TH2, TH1 for string}
>   s.foo; // call TH2.foo
>   s.foo1; // call TH1.foo1
> 
> {$EXPLICITHELPERS default for string}
>   s.foo; // call TH3.foo
> 
> {$EXPLICITHELPERS TH1, default for string}
>   s.foo; // TH1.foo
>   s.foo1;
>   s.foo2;
>   s.foo3;
> end.
> 
> -- 
> Best regards,
> Maciej Izak