I'm playing with QtD, and I tried to override a QWidget's sizeHint() function, which is declared as const QSize sizeHint(). I tried to override it by declaring my function as override const(QSize) sizeHint () . I got a compiler error that it was "not covariant" with const QSize,
http://digitalmars.com/d/2.0/const3.htmlIn that case it is a const member function which means it is not allowed to change any part of the object through the member function's this reference.