Justin Johansson wrote:
Andrei Alexandrescu Wrote:It turns out this is a great example for NVI. In D, we could and should do the following: class Object { // Implement this private bool opEqualsImpl(Object rhs) { return false; } // Use this final bool opEquals(Object rhs) { if (this is rhs) return true; if (this is null || rhs is null) return false; return opEqualsImpl(rhs) && rhs.opEqualsImpl(this); } }"I took advantage of the fact that in a final function this may be null without an access violation." That "advantage" cannot be the general case? Surely that statement is only true when the final function is in a base class, X, (and X can only be Object in D, right?) for reason that the compiler can spot that the method is never overriden in ANY subclass of X (Object) , and therefore the method can be called directly rather than having to be dispatched through a VFT and consequently there is no VFT entry for that method/function.
Sorry, indeed I meant a "introducing final" function, not a final function. A final function that overrides one in the base class must often go through the vtable. Though if a final function (introducing or not) gets called for the static type that made it final, it needn't go through the vtable so a null this could be allowed inside of it.
Andrei
