{$IFDEF trial_version}
  ShowMessage('Sorry, this function is not available in trial version');
{$ELSE}
  // do the thing
{$END}

type
  TDummy<T> = class
  public
    procedure Dummy1;
  end;

procedure TDummy<T>.Dummy1;
begin
  ...
end;

var
  FDummy1: TDummy<Integer>;
  FDummy2: TDummy<Byte>;
  FDummy3: TDummy<TButton>;
  FDummy4: TDummy<TLabel>;