method returning child, doesn't overrides declared method returning parent

[Andrei Alexandrescu]

On 08/30/2011 07:13 AM, Timon Gehr wrote:
> If there already is an implementation, it overrides it, otherwise it
> implements it.

That's pretty much it. The entire purpose of the "override" keyword is 
to prevent silent bugs of two kinds:

(a) User thinks she hooks a specific method but instead introduces a new 
one.

(b) User thinks she introduces a new method but instead hooks one.

Override helps only in cases where otherwise a silent error would occur. 
If the compiler issues an error message without the help of override, 
override is unneeded and illegal. This is the case with interface and 
abstract methods - "override" is emphatically unneeded because the 
compiler/linker wouldn't allow the code anyway.


Andrei