Hi,
 
I wrote a small routine to search Lazarus sources and it found about 60 places similar to this (taborderdlg.pas, line 398):  
if Assigned(LookupRoot) and (LookupRoot is TWinControl) then begin  
Should I make a patch for all occurences?
 
V.

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Yes, I think the patch would be applied.
IIRC "is" was not allowed with Nil references in old FPC versions but it was a long time ago.

BTW, a regular expression search in the Find in Files dialog would have found those cases, too.

Juha

No, "is" was always checking for nil.
Maybe some people are confused by "as", which does not check for nil.

Mattias

I am now confused, so
in FPC, it is safe to just use: if LookupRoot is TWinControl instead of
if assigned(LookupRoot) and (LookupRoot is TWinControl) then ....

is it safe to
    with LookupRoot as TWinControl do begin
        ....
    end;
or should I always
    if assigned(LookupRoot) then
      with LookupRoot as TWinControl do begin
          ....
      end;

Dennis

Yes.

is it safe to with LookupRoot as TWinControl do begin .... end;

No.

Yes.

Mattias