[fpc-devel] Bug in FPC and declaring distinct types

[Florian Klaempfl]

Yury Sidorov schrieb:
> From: "Florian Klaempfl" <florian at freepascal.org>
>> Michael Van Canneyt schrieb:
>>>
>>> On Thu, 18 Sep 2008, Graeme Geldenhuys wrote:
>>>
>>>> Hi,
>>>>
>>>> I was following a discussion in the delphi.non-technical newsgroup.
>>>> They raised an issue about distinct types. I tried the following
>>>> example under FPC and unexpectedly, FPC doesn't raise any errors!
>>>>
>>>> If you declare a distinct type as follows:
>>>>   type TMyInteger = type Integer;
>>>>
>>>> The type TMyInteger <> Integer so you are not supposed to be allowed
>>>> to assign one to the other. Yet you can. See the following program.
>>>
>>> But obviously delphi also allows it ? It compiles everything,
>>> just not as a var parameter.
>>>
>>> The whole 'Type' thing is a bit ridiculous: the only reason they did it
>>> is so they can have different type pointers in the RTTI for something 
>>> which
>>> is the same 'type' anyway. For the rest it is extremely badly 
>>> designed, and not really consistent. It serves no purpose. FPC 
>>> introduced it to be able to compile Delphi code, no other reason.
>>
>> This is not true. The main purpose is to be able to overload 
>> functions/operators:
>>
>> type
>>   TUTF8String = type ansistring;
>>
>> enables you to overload all procedure already defined for ansistrings 
>> with UTF8String functions but reusing ansistring support functionality 
>> and this is supported for years. Because nobody used this yet to make 
>> an utf-8 unit, I never took the unicode string support serious :)
> 
> Yes. But it works only partially. For example the following code is not 
> compilable:

Well, I wouldn't know either what you expect :)

> 
> //------
> type
>  TUTF8String = type ansistring;
> 
> procedure DoTest(const s: ansistring); overload;
> begin
> end;
> 
> procedure DoTest(const s: TUTF8String); overload;
> begin
> end;
> 
> begin
>  DoTest('1234');
> end.
> 
> //------
> 
> Yury Sidorov. _______________________________________________
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>