[fpc-devel] Fwd: overload question (variant vs enum subrange)

[Sergei Gorelkin]

31.03.2014 17:32, Martin Frb пишет:
> Just asking this again, as I did not get any answer yet?
>
> Is that the indented behaviour, and if so what is the reasoning for it?
>
>
This behavior is hardly intended.
To get clues about what's going on, you can compile the compiler with OPT=-dEXTDEBUG,
then use it with -vd to compile your tests.

So, in case of subrange of integer/byte, the overloaded procedures are matched as follows:

   Bar(TFoo);
    invalid
   Bar(LongInt);
    ex: 0 eq: 1 l1: 0 l2: 0 l3: 0 l4: 0 l5: 0 l6: 0 oper: 0 ord:  4.29496729300000047684E+0009
     - LongInt : equal
   Bar(Variant);
    ex: 0 eq: 0 l1: 0 l2: 0 l3: 0 l4: 0 l5: 0 l6: 0 oper: 1 ord:  0.00000000000000000000E+0000
     - Variant : convert_operator

And in case of subrange of enum, it becomes as follows:

   Bar(TFoo);
    ex: 0 eq: 0 l1: 1 l2: 0 l3: 0 l4: 0 l5: 0 l6: 0 oper: 0 ord:  0.00000000000000000000E+0000
     - TFoo : convert_l1
   Bar(LongInt);
    invalid
   Bar(Variant);
    ex: 0 eq: 0 l1: 1 l2: 0 l3: 0 l4: 0 l5: 0 l6: 0 oper: 0 ord:  0.00000000000000000000E+0000
     - Variant : convert_l1

Here Variant gets the same degree of compatibility with TFoo1 as TFoo, that's probably a bug in 
compiler (Variant should probably have same compatibility as in first case, i.e. convert_operator, 
if not incompatible at all).
Also, the subrange may receive the same treatment as in the first case, i.e. considered equal to its 
base type but with some "ordinal distance".

Regards,
Sergei

> -------- Original Message --------
> Subject: 	overload question (variant vs enum subrange)
> Date: 	Sun, 26 Jan 2014 19:48:42 +0000
> From: 	Martin Frb <lazarus at mfriebe.de>
> To: 	FPC-Pascal users discussions <fpc-pascal at lists.freepascal.org>
>
>
>
> TFoo1  is a sub range of  FFoo
>
> And it seems to match both TFoo and variant.
>> project1.lpr(24,3) Error: Can't determine which overloaded function to
>> call
>> project1.lpr(15,11) Hint: Found declaration: Bar(TFoo);
>> project1.lpr(11,11) Hint: Found declaration: Bar(Variant);
>
> No other type seems to be bothered by variant.
> Also variant is the only type, that I found that conflicts with TFoo1
>
> Why?
>
> I know I can declare
>    procedure Bar(a: TFoo1); overload;
> and it will solve it (even if I leave all the others, because it is an
> exact match).
>
> But why does a subrange of integer/byte work? Subrange of integer does
> not give the error, even so it could match both.
>
>
>
> program Project1;
> {$mode objfpc}
> {// $mode delpti}
> type
>    TFoo = (a1,a2,a3,a4,a5);
>    TFoo1 = a2..a4;
>    TFoo2 = 1..3;
>    TFoo3 = byte(1)..(3);
>
>
> procedure Bar(a: Variant); overload;
> begin   end;
> procedure Bar(a: Integer); overload;
> begin   end;
> procedure Bar(a: TFoo); overload;
> begin   end;
>
> var
>    f1: TFoo;
>    f2: TFoo1;
>    f3: TFoo2;
>    f4: TFoo3;
> begin
>    Bar(f2);
> end.
>
>
>
>
>
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