BP question

22 Oct 2003

      BP seems to allow overriding a public method with a private one (and
vice versa). Does this seem reasonable?

What do Delphi and other compilers do?

At first sight, I'd rather forbid this in GPC (as usual, with an
exception in `--borland-pascal', but perhaps a warning even there?).

program Foo;

type
  a = object
    procedure p;
  end;

  b = object (a)
  private
    procedure p;  { ??? }
  end;

procedure a.p;
begin
end;

procedure b.p;
begin
end;

begin
end.

Oh, wait a second, it gets really strange ...

unit U;

interface

type
  a = object
    procedure p;
  end;

  b = object (a)
  private
    procedure p;
  end;

implementation

procedure a.p;
begin
  WriteLn ('a.p')
end;

procedure b.p;
begin
  WriteLn ('b.p')
end;

var
  v: b;

begin
  v.p
end.

program Foo;

uses U;

var
  v: b;

begin
  v.p
end.

Under BP, this says:

b.p
a.p

What does it mean actually? It means that `b' has *two* methods
called `p'. Within the unit, one of them shadows the other, and
outside of the unit, the first one is hidden (or non-existent
because not exported), and the second one becomes visible. That's
crazy, isn't it?

Frank

-- 
Frank Heckenbach, frank@g-n-u.de, http://fjf.gnu.de/, 7977168E
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