Hijacking

[BCS]

Reply to Walter,

> kris wrote:
> 
>> There's a related problem where a public method is added to a
>> base-class A (as in your example) but where the signature is
>> *exactly* that of one existing in derived class B. If A actually
>> calls that new method internally, "bad things"tm will almost
>> certainly happen, since B never intended to effectively override the
>> newly-added method in A.
>> 
>> This is a very hard problem to isolate yet can be easily remedied by
>> the compiler. The request was first made two or three years back, and
>> once or twice since then: you make the "override" keyword *required*.
>> 
>> When "override" is required, the compiler can easily trap this
>> related type of hijacking and avoid such nasty surprises.
>> 
> That is a good point. The reason I haven't added it is because I'm not
> sure how annoying it will be to have to always add the 'override'
> keyword. It might be one of those things like exception specifications
> where everyone says it's a good idea but guiltily hate in secret <g>.
> 
> Mitigating factors are private and final methods cannot be overridden.
> 

How hard would it be to put a command line flag on the 2.0 version that would 
turn it on?