Am 27.01.2012 17:46, schrieb Thaddy:
On 27-1-2012 17:25, Marco van de Voort wrote:
In our previous episode, Kornel Kisielewicz said:
{$apptype console}
Type
TLIST<T>=class
end;
type
Ta= TLIST<POINTER>;
TB= TLIST<POINTER>;
This may very well be a (semantics) bug in Delphi.
Did you put this to Embarcadero?
IMO a type Ta<..> should never be assignable to a type Tb<..> and
reverse when using generics. (unless with operator overloading or
similar defined)
I think this may be an unintentional "feature" in Delphi.
I now tested a "generic diamond" in Delphi XE.
Following setup:
===
unit ugendiamonddecl;
interface
type
TGeneric<T> = class
f: T;
end;
implementation
end.
===
unit ugendiamond1;
interface
uses
ugendiamonddecl;
type
TSpez1 = TGeneric<LongInt>;
implementation
end.
===
unit ugendiamond2;
interface
uses
ugendiamonddecl;
type
TSpez2 = TGeneric<LongInt>;
implementation
end.
===
program tgendiamond;
{$APPTYPE CONSOLE}
uses
// ugendiamonddecl in 'ugendiamonddecl.pas',
ugendiamond1 in 'ugendiamond1.pas',
ugendiamond2 in 'ugendiamond2.pas';
var
s1: TSpez1;
s2: TSpez2;
begin
s1 := s2;
end.
===
This compiles!
So there MUST be specific code in place in the Delphi compiler to allow
the assignment from ugendiamond2.TSpez2 to ugendiamond1.TSpez1 as those
are different definitions. Thus this can not be a bug, but must be an
intentional feature. Allowing this in FPC as well would be doable.
Now regarding Kornel's problem: we could(!) change the way the compiler
works in non-Delphi modes to what is described in the documentation (by
adding the type symbol's name to the generic's name as well), but this
will mean that we would have to define how units in Delphi and
non-Delphi modes can interact here. After that the corresponding code in
the compiler can be implemented to ensure this.
Regards,
Sven
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