[lazarus] Possible compiler bug with derived classes?

[Marc Weustink]

+ From: Chris Storah [mailto:cstorah at emis-support.demon.co.uk]

+ Just found a piece of code that may or may not clarify things:
+ (TField sample in the Delphi help)...
+
+ Problem is not limited to variables - constructors have the
+ same problem if
+ the parameters names conflict.
+
+ The compiler gets conflicts for FNAME, X anf Y, but not Value
+ - why has
+ Value got through, as it's name is re-used?

Value is private. Private parts are (supposed to be) invisible to
descendants. So you may use the name again since it is not known.

Marc

+
+ Cheers,
+ Chris.
+
+ {================================}
+ TField = class
+ private
+   X, Y, Len: Integer;
+   FName: String;
+ public
+   constructor Copy(F: TField);
+   constructor Create(FX, FY, FLen: Integer; FName: String);
+   destructor destroy; override;
+   procedure Display; virtual;
+   procedure Edit; dynamic;
+ protected
+   function GetStr: String; virtual;
+   function PutStr(S: String): Boolean; virtual;
+ private
+   procedure DisplayStr(X, Y: Integer; S: String);
+ public
+   property Name: String read GetStr write Buffer;
+ end;
+
+
+   TStrField = class(TField)
+   private
+     Value: PString;
+   public
+     constructor Create(FX, FY, FLen: Integer; FName: String);
+     destructor Destroy; override;
+   protected
+     function GetStr: String; override;
+     function PutStr(S: String): Boolean; override;
+   end;
+
+   TNumField = class(TField)
+   private
+     Value, Min, Max: Longint;
+   public
+     constructor Create(FX, FY, FLen: Integer; FName: String;
+       FMin, FMax: Longint);
+     function GetStr: String; override;
+
+     function PutStr(S: String): Boolean; override;
+     function Get: Longint;
+     procedure Put(N: Longint);
+   end;
+
+ {===================================================}
+
+
+ -----Original Message-----
+ From: Michael Van Canneyt [mailto:michael.vancanneyt at wisa.be]
+ Sent: 04 November 1999 09:32
+ To: Lazarus (E-mail)
+ Subject: Re: [lazarus] Possible compiler bug with derived classes?
+
+
+
+
+ On Thu, 4 Nov 1999, Chris Storah wrote:
+
+ > I am having problems when compiling a derived class (WinNT version).
+ > This is the code:
+ >
+ >   TVer1 = class(TObject)
+ >       protected
+ >          rec: TObject;
+ >    end;
+ >
+ >   TVer2 = class(TVer1)
+ >       protected
+ >          rec: TObject;	<=== duplicate identifier
+ >       end;
+ >
+ >
+ > The error using ppc386 is 'Error: Duplicate identifier REC'.
+
+ This IS an error; if you declare such a thing in the protected
+ part, you should rename it. How is the compiler supposed to
+ know in a descendent class which one to take ? Any decision will
+ be necessarily an arbitrary one.
+
+ > Is this a known bug?
+ > If so, anyone know how to fix it without changing the
+ identifier names
+ > (Delphi works with the above code).
+
+ Delphi has other strange quircks; Can you tell me WHICH rec it takes
+ when you refer to it ?
+
+ I agree that for the sake of compatibility, we should accept
+ this, but it is
+ simply bad programming to do this, so this is not a priority.
+
+ Michael.
+
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