Conditional behaviour based on concrete type for generic class

Question

Since my question from yesterday was perhaps not completely clear and I did not get the answer I wanted, I will try to formulate it in a more general way:

Is there a

Answer 1

If someone is interested how I did implement my "worst-case size with special treatment for strings"

class function RTTIUtils.GetDeepSize  (Variable : T) : Integer;
var
  StringLength          : Integer;
  Ptr                   : PInteger;
begin
if (TypeInfo (T) = TypeInfo (String)) then
  begin
  Ptr := @Variable;
  Ptr := PInteger (Ptr^);
  Dec (Ptr);
  StringLength := Ptr^;
  Result := StringLength * SizeOf (Char) + 12;
  end
else
  Result := 0;
end;

For me, this does the job at hand. Thanks to all contributors!